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Tomonaga Okabe

Section

Graduate School of Engineering

Job title

Professor

Degree

博士（工学）（慶應義塾大学）

researchmap

https://researchmap.jp/tomonagaokabe

J-GLOBAL ID

200901095779580155

Research History 5

2025/04 - Present

東北大学副理事（産学連携担当）
2014/04 - Present

東北大学大学院工学研究科教授
2020/12 - 2025/03

東北大学総長特別補佐・産学連携担当
2007/04 -

東北大学大学院工学研究科准教授
2002/09 -

東北大学大学院工学研究科助教授

Education 3

慶応義塾大学大学院　理工学研究科　後期博士課程

1998/04 - 1999/09
慶応義塾大学大学院　理工学研究科　前期博士課程

1996/04 - 1998/03
慶応義塾大学　理工学部　機械工学科

1992/04 - 1996/03

Committee Memberships 44

日本航空宇宙学会　フェロー

2021/04 - Present
NEDO　経済安全保障重要技術育成プログラムプログラム・オフィサー（PO）

2023/01 - 2026/03
環境再生保全機構　プロジェクトマネージャー

2022/07 - 2026/03
科学技術振興機構　CREST領域アドバイザー

2022/05 - 2026/03
NEDO　次世代複合材創製・成形技術開発プロジェクトリーダー（PL）

2020/08 - 2026/03
経済産業省　産業構造審議会臨時委員

2023/09 - 2025/08
日本複合材料学会　代議員

2021 - 2022
NEDO　技術委員

2019/11 - 2021/03
日本複合材料学会　代議員

2019 - 2020
日本学術振興会　国際科学研究費委員会専門委員

2019/06 - 2019/11
日本学術振興会　科学研究費委員会専門委員

2018/12 - 2019/11
日本複合材料学会　理事

2017/06 - 2019/05
日本複合材料学会東北・北海道支部　支部長

2017/04 - 2019/03
NEDO　技術委員

2017/04 - 2019/03
防衛装備庁　機体構造軽量化技術の研究に関する外部評価委員会委員

2016/11 - 2018/11
日本航空宇宙学会　北部支部支部長

2017/03 - 2018/02
日本複合材料学会　理事

2015/06 - 2017/05
日本複合材料学会　支部長支部評議員

2014/04 - 2016/03
日本複合材料学会東北・北海道支部　支部監事、支部評議員

2012/04 - 2014/03
日本機械学会材料力学部門　総務委員会委員

2012/04 - 2013/03
日本機械学会　材料力学部門運営委員

2012/04 - 2013/03
日本機械学会　材料力学部門トピックス委員会委員

2012/04 - 2013/03
日本機械学会　材料力学部門第2技術委員会幹事

2012/04 - 2013/03
日本機械学会　出版センター委員

2012/04 - 2013/03
日本航空宇宙学会構造部門委員会　委員

2012/04 - 2013/03
日本機械学会材料力学部門　総務委員会委員

2012/04 - 2013/03
日本機械学会　材料力学部門運営委員

2012/04 - 2013/03
日本機械学会　材料力学部門トピックス委員会委員

2012/04 - 2013/03
日本機械学会　材料力学部門第2技術委員会幹事

2012/04 - 2013/03
日本機械学会　出版センター委員

2012/04 - 2013/03
日本航空宇宙学会構造部門委員会　委員

2012/04 - 2013/03
日本複合材料学会　理事

2011/04 - 2013/03
日本複合材料学会　評議員

2011/04 - 2013/03
日本機械学会材料力学部門　総務委員会委員

2011/04 - 2012/03
日本機械学会　出版センター委員

2011/04 - 2012/03
日本機械学会　第9技術委員会委員長

2011/04 - 2012/03
日本機械学会　材料力学部門運営委員

2011/04 - 2012/03
日本航空宇宙学会　論文編集委員会委員

2011/04 - 2012/03
日本材料学会　破壊力学部門委員会幹事

2011/04 - 2012/03
日本複合材料学会東北・北海道支部　支部幹事、支部評議員

2010/04 - 2012/03
日本機械学会　材料力学部門運営委員

2010/04 - 2011/03
日本航空宇宙学会　論文編集委員会委員

2010/04 - 2011/03
日本複合材料学会東北・北海道支部　支部幹事、支部評議員

2008/04 - 2010/03
日本複合材料学会　評議員

2007/04 - 2009/03

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Professional Memberships 4

日本材料学会
日本航空宇宙学会
日本複合材料学会
日本機械学会

Research Interests 3

破壊力学
損傷力学
連続体力学

Research Areas 1

Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Machine materials and mechanics /

Awards 15

論文賞

2021/06　日本複合材料学会　ミクロスケール解析による薄層CFRP積層板のin-situ損傷・強度特性評価
日本複合材料学会論文賞

2016/06　日本複合材料学会　粒子法を用いた熱可塑性スタンパブルシートの流動シミュレーション
日本実験力学会論文賞

2014/08　日本実験力学会
日本複合材料学会技術賞

2013/05　日本複合材料学会　熱可塑性スタンパブルシートの研究開発
新化学技術研究奨励賞

2013/05　公益社団法人新化学技術推進協会　階層的モデリングに基づく車体構造用繊維強化可塑性プラスチックの耐久性評価
文部科学大臣表彰若手科学賞

2011/04　文部科学大臣
日本複合材料学会論文賞

2010/05/25　日本複合材料学会　繊維強化プラスチックの破壊モード特性に関するマイクロメカニクス
日本機械学会論文賞

2010/04　日本機械学会
日本複合材料学会論文賞

2009/05　日本複合材料学会　一方向CFRP複合材料の引張強度予測
日本複合材料学会林賞

2008/06　日本複合材料学会　繊維強化複合材料の損傷・破壊を対象としたマイクロメカニクスに関する研究
日本複合材料学会論文賞

2007/05　日本複合材料学会　埋め込みFBGセンサを用いた有孔積層板の損傷同定に関する数値解析および実験結果への適用
日本複合材料学会論文賞

2004/05　日本複合材料学会　トランスバースクラックを有するCFRP直交積層板の引張強度
日本非破壊検査協会論文賞

2004/05　日本非破壊検査協会　ラム波伝播速度変化を利用した繊維強化プラスチックにおけるトランスバースクラックの定量モニタリングおよび位置標定精度向上
日本機械学会奨励賞

2002/04/08　日本機械学会　セラミック基複合材料の強度におけるマイクロメカニクスアプローチに関する研究
藤原賞

2000/03　慶応義塾大学理工学研究科　早期学位取得第1号に対して

Show all ︎Show 5

Papers 279

Thermal oxidative degradation of cyanate- and amine-cured epoxy resins: Experiment and ReaxFF simulation

Yoshiaki Kawagoe, Gota Kikugawa, Shohei Komori, Keiichi Shirasu, Tomonaga Okabe

Thermochimica Acta　747　179949-179949　2025/05
Publisher: Elsevier BV
DOI： 10.1016/j.tca.2025.179949 　

ISSN： 0040-6031
Monte Carlo simulation with energy-based matrix and transverse crack growth model for cross-ply ceramic matrix composites under static tensile behavior

Daichi Haruyama, Yoshiaki Kawagoe, Tomonaga Okabe

Advanced Composite Materials　1-41　2025/03/07
Publisher: Informa UK Limited
DOI： 10.1080/09243046.2025.2469961 　

ISSN： 0924-3046

eISSN： 1568-5519
Multiscale model for bottom-up prediction of failure parameters of unidirectional carbon-fiber-reinforced composite lamina from the atomic to filament-scales, and its application to failure modeling of open-hole quasi-isotropic composite laminates

Tadashi Watanabe, Yoshiaki Kawagoe, Yamato Hoshikawa, Yosuke Nakai, Kazuki Ryuzono, Tomonaga Okabe

International Journal of Solids and Structures　308　2025/02/01

DOI： 10.1016/j.ijsolstr.2024.113130 　

ISSN： 0020-7683
Prediction of laminate stiffness reduction by regression equations for damage variables obtained from the stress based Variational model

Yoshiko Nagumo, Sota Onodera, Mohammad Hajikazemi, Tomonaga Okabe

Journal of Applied Mechanics　1-26　2025/01/08
Publisher: ASME International
DOI： 10.1115/1.4067568 　

ISSN： 0021-8936

eISSN： 1528-9036

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Abstract Continuous fiber-reinforced materials exhibit reduced strength when subjected to loads perpendicular to the fiber direction, often leading to the occurrence of transverse cracks. These transverse cracks reduce the stiffness and strength of the laminates. Therefore, understanding the mechanical behavior of cracked laminates is critical, and numerous studies have addressed this issue. Notably, two key models have emerged: the continuum damage mechanics (CDM) model, which incorporates damage variables to directly account for the effects of damage modes in the constitutive law, and the stress-based variational model, which applies the principle of minimum complementary energy to develop a three-dimensional stress field in cracked laminates, thereby predicting stiffness. Although the variational model can accurately predict the stiffness degradation of a cracked laminate, it is significantly more complex than the CDM model, both in terms of the theoretical expression and the computational process. In this study, we derived explicit closed-form expressions for damage variables within the CDM framework, utilizing calculations from the variational model to estimate both the in-plane and out-of-plane thermoelastic properties of the laminate. This approach combines the simplicity of the CDM model with the accuracy of the variational method. The damage variables are explicitly expressed using normalized values, incorporating cracked ply material properties, geometrical characteristics, and adjacent ply properties. This makes the variables applicable to a wide range of laminate material. The validity of the regression equations was verified by comparing them with results from previous CDM models, finite element analysis, and experimental data.
Analytical modeling of matrix and transverse crack growth and fiber breakage for predicting the static tensile behavior of cross-ply ceramic matrix composites Peer-reviewed

Daichi Haruyama, Yoshiaki Kawagoe, Tomonaga Okabe

Materials System　42　3-20　2025

DOI： 10.34401/materialssystem.42.0_3 　
Effects of aeroelastic coupling accuracy and geometrical nonlinearity on performances of optimized composite wings

Yajun Liu, Shugo Date, Toshio Nagashima, Tomonaga Okabe, Yoshiaki Abe

Aerospace Science and Technology　109926-109926　2025/01
Publisher: Elsevier BV
DOI： 10.1016/j.ast.2024.109926 　

ISSN： 1270-9638
Finite element modeling of viscoelastic creep behavior and transverse cracking in fiber-reinforced composite materials

Yamato Hoshikawa, Kazuki Ryuzono, Sota Onodera, Yoshiaki Kawagoe, Tomonaga Okabe

International Journal of Damage Mechanics　2024/12/30
Publisher: SAGE Publications
DOI： 10.1177/10567895241302543 　

ISSN： 1056-7895

eISSN： 1530-7921

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Fiber-reinforced composites are essential in the aerospace industry, highlighting the need for an in-depth understanding of their durability. This study introduces a novel approach that integrates viscoelasticity and damage evolution based on continuum damage mechanics, employing finite element analysis. The method utilizes an anisotropic viscoelastic constitutive law to examine creep behavior under constant stress, decomposing stresses into equilibrium and non-equilibrium components. Moreover, it integrates a transverse crack damage variable associated with crack density. After solving stiffness equations, a detailed analysis of transverse crack propagation is conducted. This technique was applied to creep tests on carbon fiber-reinforced plastics and 3D woven ceramic matrix composites, resulting in strain and crack density profiles. The numerical simulations successfully reproduced experimental outcomes. The developed method offers a comprehensive tool for analyzing transverse crack propagation under viscoelastic creep conditions through finite element analysis, significantly enhancing design considerations by incorporating aspects of long-term durability.
Analytical modeling of energy-based matrix crack growth and fiber breakage in unidirectional ceramic matrix composites under static tensile behavior in the longitudinal direction

Daichi Haruyama, Yoshiaki Kawagoe, Tomonaga Okabe

Advanced Composite Materials　1-34　2024/12/18
Publisher: Informa UK Limited
DOI： 10.1080/09243046.2024.2427460 　

ISSN： 0924-3046

eISSN： 1568-5519
Recent studies on multiscale modeling of carbon fiber-reinforced composites

Tomonaga Okabe, Kazuki Ryuzono, Yoshiaki Kawagoe

Advanced Composite Materials　1-11　2024/10/21
Publisher: Informa UK Limited
DOI： 10.1080/09243046.2024.2414467 　

ISSN： 0924-3046

eISSN： 1568-5519
Finite element modeling for cohesive/adhesive failure of adhesive structures with a thermosetting resin

Yamato Hoshikawa, Yoshiaki Kawagoe, Kazuki Ryuzono, Tomonaga Okabe

Engineering Fracture Mechanics　110552-110552　2024/10
Publisher: Elsevier BV
DOI： 10.1016/j.engfracmech.2024.110552 　

ISSN： 0013-7944
Enhancing Epoxy Resin Curing: Investigating the Catalytic Role of Water as a Trace Impurity in Dense Crosslinked Network Formation Using an Advanced cat-GRRM/MC/MD Method1

Yingxiao Xi, Hironobu Fukuzawa, Gota Kikugawa, Yinbo Zhao, Yoshiaki Kawagoe, Tomonaga Okabe, Hajime Kishi, Naoki Kishimoto

Polymer　127675-127675　2024/09
Publisher: Elsevier BV
DOI： 10.1016/j.polymer.2024.127675 　

ISSN： 0032-3861
Prediction of viscoelastic effective creep compliances in cracked cross-ply composite laminates

Keiji Ogi, Shuji Yoshikawa, Tomonaga Okabe, Sota Onodera

Mechanics of Materials　105085-105085　2024/07
Publisher: Elsevier BV
DOI： 10.1016/j.mechmat.2024.105085 　

ISSN： 0167-6636
Determination of interaction parameters in a bottom-up approach employed in reactive dissipative particle dynamics simulations for thermosetting polymers

Kaiwen Li, Gota Kikugawa, Yoshiaki Kawagoe, Yinbo Zhao, Tomonaga Okabe

Soft Matter　20　(23)　4591-4607　2024/05/14

DOI： 10.1039/d3sm01743e 　

ISSN： 1744-683X

eISSN： 1744-6848
Experiment-free multiscale simulation of residual deformation in non-crimp fabric composites

Yuuki Kinugawa, Yoshiaki Kawagoe, Kota Oine, Kazuki Ryuzono, Yamato Hoshikawa, Tomonaga Okabe

Advanced Composite Materials　1-13　2024/05/07
Publisher: Informa UK Limited
DOI： 10.1080/09243046.2024.2348861 　

ISSN： 0924-3046

eISSN： 1568-5519
Fracture mechanism of carbon fiber-reinforced thermoplastic composite laminates under compression after impact

Yoshiko Nagumo, Miyu Hamanaka, Keiichi Shirasu, Kazuki Ryuzono, Akinori Yoshimura, Hironori Tohmyoh, Tomonaga Okabe

Journal of Composite Materials　2024/03/12
Publisher: SAGE Publications
DOI： 10.1177/00219983241240622 　

ISSN： 0021-9983

eISSN： 1530-793X

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Thermoplastic carbon fiber-reinforced plastics (CFRPs) are increasingly utilized in the aerospace industry owing to their beneficial properties and enhanced formability relative to thermoset CFRPs. Despite the extensive use of these materials, studies focusing on compression after impact (CAI) tests with impact energies exceeding 20 J for thermoplastic CFRPs remain scarce. This study examines CAI tests on quasi-isotropic laminates of thermoplastic CFRP, subjected to a low-velocity impact energy of 27.04 J. For comparison, quasi-isotropic laminates of thermoset CFRP were subjected to a low-velocity impact energy of 36.5 J. These tests reveal that the CAI strength of both materials is comparable, notwithstanding the lower fiber volume fraction in the thermoplastic CFRP. Further, this research incorporates a finite element (FE) analysis to investigate the damage mechanisms in thermoplastic CFRP. The FE model, integrating interlaminar damage observed during the impact tests, accurately predicted the relationship between compressive stress and strain, correlating closely with the experimental outcomes. It was observed that both interlaminar and intralaminar damage propagation were constrained until the point of maximum compressive stress. Prior to reaching this maximum, a region of elevated compressive stress in the fiber direction was noted in the 0° layer near the non-impacted side. These findings indicate that the compressive stress in the fiber direction in the 0° layer adjacent to the non-impacted side is pivotal in dictating the final failure, which determines the CAI strength of thermoplastic CFRP laminates.
Effect of inorganic material surface chemistry on structures and fracture behaviours of epoxy resin

Tomohiro Miyata, Yohei K. Sato, Yoshiaki Kawagoe, Keiichi Shirasu, Hsiao-Fang Wang, Akemi Kumagai, Sora Kinoshita, Masashi Mizukami, Kaname Yoshida, Hsin-Hui Huang, Tomonaga Okabe, Katsumi Hagita, Teruyasu Mizoguchi, Hiroshi Jinnai

Nature Communications　15　(1)　2024/03/08
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s41467-024-46138-6 　

eISSN： 2041-1723

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Abstract The mechanisms underlying the influence of the surface chemistry of inorganic materials on polymer structures and fracture behaviours near adhesive interfaces are not fully understood. This study demonstrates the first clear and direct evidence that molecular surface segregation and cross-linking of epoxy resin are driven by intermolecular forces at the inorganic surfaces alone, which can be linked directly to adhesive failure mechanisms. We prepare adhesive interfaces between epoxy resin and silicon substrates with varying surface chemistries (OH and H terminations) with a smoothness below 1 nm, which have different adhesive strengths by ~13 %. The epoxy resins within sub-nanometre distance from the surfaces with different chemistries exhibit distinct amine-to-epoxy ratios, cross-linked network structures, and adhesion energies. The OH- and H-terminated interfaces exhibit cohesive failure and interfacial delamination, respectively. The substrate surface chemistry impacts the cross-linked structures of the epoxy resins within several nanometres of the interfaces and the adsorption structures of molecules at the interfaces, which result in different fracture behaviours and adhesive strengths.
Constructing and characterizing various multi-component crosslinked epoxy resins based on molecular dynamics simulations with a curing reaction model

Yinbo Zhao, Gota Kikugawa, Keiichi Shirasu, Yoshiaki Kawagoe, Tomonaga Okabe

Polymer　297　126817-126817　2024/03
Publisher: Elsevier BV
DOI： 10.1016/j.polymer.2024.126817 　

ISSN： 0032-3861
Dissipative Particle Dynamics Simulation for Reaction-Induced Phase Separation of Thermoset/Thermoplastic Blends

Yoshiaki Kawagoe, Gota Kikugawa, Keiichi Shirasu, Yuuki Kinugawa, Tomonaga Okabe

The Journal of Physical Chemistry B　2024/02/19
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.jpcb.3c07756 　

ISSN： 1520-6106

eISSN： 1520-5207
Toward Integrated Aircraft Design with Carbon Fiber Reinforced Thermoplastic (CFRTP)

Yoshiaki Abe, Keiichi Shirasu, Shugo Date, Tomonaga Okabe, Shigeru Obayashi

Advanced Computational Methods and Design for Greener Aviation　59　229-239　2024

DOI： 10.1007/978-3-031-61109-4_15 　
Influence of Fiber Orientation on Failure of Welded Single-lap Joint with Welding Technology of Thermoset FRP Peer-reviewed

Tadashi Watanabe, Masato Honma, Mototsugu Tanaka, Keiichi Shirasu, Yoshiaki Kawagoe, Tomonaga Okabe

Materials System　41　37-45　2024

DOI： 10.34401/materialssystem.41.0_37 　
Micromechanics study of short carbon fiber-reinforced thermoplastics fabricated via 3D printing using design of experiments

Keiichi Shirasu, Yudai Yamaguchi, Yamato Hoshikawa, Gota Kikugawa, Hironori Tohmyoh, Tomonaga Okabe

Materials Science and Engineering: A　891　145971-145971　2024/01
Publisher: Elsevier BV
DOI： 10.1016/j.msea.2023.145971 　

ISSN： 0921-5093
Effects of the chain length of nonaromatic epoxy resins on thermomechanical and optical properties: experiments, and ab initio and molecular dynamics simulations

Yoshiaki Kawagoe, Yuuki Kinugawa, Keigo Matsumoto, Masashi Ohno, Naoki Kishimoto, Takahiko Kawai, Tomonaga Okabe

Physical Chemistry Chemical Physics　2024

DOI： 10.1039/d4cp02357a 　

ISSN： 1463-9076
Development of cat-GRRM/MC/MD method for the simulation of cross-linked network structure formation with molecular autocatalysis

Yingxiao Xi, Hironobu Fukuzawa, Shoji Fukunaga, Gota Kikugawa, Yinbo Zhao, Yoshiaki Kawagoe, Tomonaga Okabe, Naoki Kishimoto

Molecular Catalysis　552　113680-113680　2024/01
Publisher: Elsevier BV
DOI： 10.1016/j.mcat.2023.113680 　

ISSN： 2468-8231
Reaction-induced morphological transitions in a blend of diblock copolymers and reactive monomers: dissipative particle dynamics simulation

Yoshinori Tomiyoshi, Yutaka Oya, Toshihiro Kawakatsu, Tomonaga Okabe

Soft Matter　20　(1)　124-132　2023/12/06

DOI： 10.1039/d3sm00959a 　

ISSN： 1744-683X

eISSN： 1744-6848
In-Situ Shearing Process Observation System for Soft Materials via Transmission Electron Microscopy

Tomohiro Miyata, Hsiao-Fang Wang, Daisuke Watanabe, Yoshiaki Kawagoe, Tomonaga Okabe, Hiroshi Jinnai

Microscopy　2023/09/13
Publisher: Oxford University Press (OUP)
DOI： 10.1093/jmicro/dfad045 　

ISSN： 2050-5698

eISSN： 2050-5701

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Abstract We developed an in-situ shear test system suitable for transmission electron microscopy (TEM) observations, which enabled us to examine the shear deformation behaviours inside soft materials at nanoscale resolutions. This study was conducted on a nanoparticle-filled rubber to investigate its nanoscale deformation behaviour under a large shear strain. First, the shear deformation process of a large area in the specimen was accurately examined and proven to exhibit an almost perfect simple shear. At the nanoscale, voids grew along the maximum principal strain during shear deformation. In addition, the nanoscale regions with rubber and silica aggregates exhibited deformation behaviours similar to the global shear deformation of the specimen. Although the silica aggregates exhibited displacement along the shearing directions, rotational motions were also observed owing to the torque generated by the local shear stress. This in-situ shear deformation system for TEM enabled us to understand the nanoscale origins of the mechanical properties of soft materials, particularly polymer composites.
Multiscale model for failure prediction of carbon-fiber-reinforced composites under off-axis load

Tadashi Watanabe, Yoshiaki Kawagoe, Keiichi Shirasu, Tomonaga Okabe

International Journal of Solids and Structures　112489-112489　2023/09
Publisher: Elsevier BV
DOI： 10.1016/j.ijsolstr.2023.112489 　

ISSN： 0020-7683
Evaluations of atomic-resolution strain fields using molecular dynamics simulations combined with corrected smoothed particle hydrodynamics

Yoshiaki Kawagoe, Tomonaga Okabe

Computational Materials Science　228　112333-112333　2023/09
Publisher: Elsevier BV
DOI： 10.1016/j.commatsci.2023.112333 　

ISSN： 0927-0256
Experimental and numerical investigation of the relationship between material defects and elastoplasticity behavior of 3D-printed carbon-fiber-reinforced thermoplastics under compressive loading

Yamato Hoshikawa, Keiichi Shirasu, Ryo Higuchi, Yoshiaki Kawagoe, Hironori Tohmyoh, Tomonaga Okabe

Composites Science and Technology　110116-110116　2023/06
Publisher: Elsevier BV
DOI： 10.1016/j.compscitech.2023.110116 　

ISSN： 0266-3538
Three-dimensional analytical model for composite laminate with transverse cracks by assuming parabolic crack opening

Sota Onodera, Kazuki Ryuzono, Shigeki Yashiro, Tomonaga Okabe

Advanced Composite Materials　1-23　2023/01/16
Publisher: Informa UK Limited
DOI： 10.1080/09243046.2023.2167481 　

ISSN： 0924-3046

eISSN： 1568-5519
DELAMINATION QUANTIFICATION IN A CROSS-PLY LAMINATE BASED ON TOPOLOGY OPTIMIZATION AND LAMB WAVE PROPAGATION MECHANISMS

Kazuki Ryuzono, Shigeki Yashiro, Sota Onodera, Nobuyuki Toyama, Tomonaga Okabe

ICCM International Conferences on Composite Materials　2023
Long-term two-dimensional analysis of the flow field around a hovering flapping flat-plate wing

Tomoki YAMAZAKI, Yoshiaki ABE, Tomonaga OKABE

Journal of Fluid Science and Technology　18　(2)　JFST0026-JFST0026　2023
Publisher: Japan Society of Mechanical Engineers
DOI： 10.1299/jfst.2023jfst0026 　

eISSN： 1880-5558
Three-dimensional analytical model for composite laminate with transverse cracks by assuming parabolic crack opening

Sota Onodera, Kazuki Ryuzono, Shigeki Yashiro, Tomonaga Okabe

Advanced Composite Materials　2023

DOI： 10.1080/09243046.2023.2167481 　

ISSN： 0924-3046

eISSN： 1568-5519
Molecular-scale investigation on relationship between thermal conductivity and the structure of crosslinked epoxy resin Peer-reviewed

Yinbo Zhao, Gota Kikugawa, Yoshiaki Kawagoe, Keiichi Shirasu, Tomonaga Okabe

International Journal of Heat and Mass Transfer　198　123429-123429　2022/12
Publisher: Elsevier BV
DOI： 10.1016/j.ijheatmasstransfer.2022.123429 　

ISSN： 0017-9310
Evaluation of Notched Strength of Composite Laminates Using a Nonlinear Extended Finite Element Method

Ryo HIGUCHI, Ryoma AOKI, Tomohiro YOKOZEKI, Toshio NAGASHIMA, Tomonaga OKABE

Journal of the Japan Society for Composite Materials　48　(6)　223-235　2022/11/15
Publisher: The Japan Society for Composite Materials
DOI： 10.6089/jscm.48.223 　

ISSN： 0385-2563

eISSN： 1884-8559
Evaluation and Analysis of Thermosetting Phenolic Resins Using Multiscale Modeling that Combine Quantum Chemical Calculations and Molecular Reaction Simulations

Naoki KISHIMOTO, Hiroki WAIZUMI, Jumpei SAKAMOTO, Tomonaga OKABE

Journal of the Japan Society for Composite Materials　48　(6)　217-222　2022/11/15
Publisher: The Japan Society for Composite Materials
DOI： 10.6089/jscm.48.217 　

ISSN： 0385-2563

eISSN： 1884-8559
Lap-shear strength and fracture behavior of CFRP/3D-printed titanium alloy adhesive joint prepared by hot-press-aided co-bonding Peer-reviewed

Keiichi Shirasu, Masayoshi Mizutani, Naoki Takano, Hajime Yoshinaga, Tsuyoshi Oguri, Ken ichi Ogawa, Tomonaga Okabe, Shigeru Obayashi

International Journal of Adhesion and Adhesives　117　2022/09

DOI： 10.1016/j.ijadhadh.2022.103169 　

ISSN： 0143-7496
Morphologies of polymer chains adsorbed on inorganic nanoparticles in a polymer composite as revealed by atomic-resolution electron microscopy

Tomohiro Miyata, Yoshiaki Kawagoe, Tomonaga Okabe, Hiroshi Jinnai

Polymer Journal　54　(11)　1297-1306　2022/08/10
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s41428-022-00690-4 　

ISSN： 0032-3896

eISSN： 1349-0540
A novel single-stroke path planning algorithm for 3D printers using continuous carbon fiber reinforced thermoplastics Peer-reviewed

Kohei Yamamoto, Jose Victorio Salazar Luces, Keiichi Shirasu, Yamato Hoshikawa, Tomonaga Okabe, Yasuhisa Hirata

Additive Manufacturing　55　102816-102816　2022/07
Publisher: Elsevier BV
DOI： 10.1016/j.addma.2022.102816 　

ISSN： 2214-8604
Multiscale modeling of process-induced residual deformation on carbon-fiber-reinforced plastic laminate from quantum calculation to laminate scale finite-element analysis Peer-reviewed

Yoshiaki Kawagoe, Kenji Kawai, Yuta Kumagai, Keiichi Shirasu, Gota Kikugawa, Tomonaga Okabe

Mechanics of Materials　170　104332-104332　2022/07
Publisher: Elsevier BV
DOI： 10.1016/j.mechmat.2022.104332 　

ISSN： 0167-6636
Generalized coordinate smoothed particle hydrodynamics with an overset method in total Lagrangian formulation Peer-reviewed

Huachao Deng, Yoshiaki Kawagoe, Yoshiaki Abe, Kenjiro Terada, Tomonaga Okabe

International Journal for Numerical Methods in Engineering　2022/06/03
Publisher: Wiley
DOI： 10.1002/nme.7043 　

ISSN： 0029-5981

eISSN： 1097-0207
Fatigue crack propagation simulation method using XFEM with variable-node element Peer-reviewed

Huachao Deng, Bo Yan, Tomonaga Okabe

Engineering Fracture Mechanics　269　108533-108533　2022/06
Publisher: Elsevier BV
DOI： 10.1016/j.engfracmech.2022.108533 　

ISSN： 0013-7944
Experimental and numerical study on open-hole tension/compression properties of carbon-fiber-reinforced thermoplastic laminates Peer-reviewed

Keiichi Shirasu, Junpei Tsuyuki, Ryo Higuchi, Sota Onodera, Tomonaga Okabe

Journal of Composite Materials　56　(14)　2211-2225　2022/06
Publisher: SAGE Publications
DOI： 10.1177/00219983221096880 　

ISSN： 0021-9983

eISSN： 1530-793X

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The stress-strain responses and damage initiation/propagation mechanisms of T700G/LM-PAEK, an open-hole carbon-fiber-reinforced thermoplastic were investigated experimentally and numerically. To obtain the mechanical properties necessary for numerical simulations, uniaxial tensile/compressive, double cantilever beam, and end notched flexure tests were conducted. T700G/LM-PAEK was found to have comparable or higher Young’s modulus, strength, and interlaminar fracture toughness relative to thermoset CFRPs with carbon fiber of a similar grade. These superior mechanical properties are mainly attributable to the higher toughness and ductility of the thermoplastic resin. The interfacial fracture toughnesses were evaluated by finite element analysis with the cohesive zone model to determine the interlaminar fracture toughnesses for crack initiation and propagation. Based on the above experimental and numerical results, the stress strain response and damage evolution of open-hole specimens were analyzed by a quasi-3D extended finite element method (XFEM) and compared with the experimental results. The computational model with the elastoplastic constitutive law provided an accurate prediction of the stress-strain response in both open-hole tension and compression (OHT and OHC, respectively), suggesting that the elastoplastic constitutive law should be considered in XFEM to guarantee the accuracy of strength prediction for both OHT and OHC. The OHT model showed that the Weibull criterion was satisfied without any delamination at the failure strain, corresponding to the brittle failure mode due to fiber breakage. For the OHC simulation, the damage initiation of 0°-ply kinking was observed at 88% of the peak stress. These predicted damage mechanisms agreed reasonably well with the experimental observations.
Effects of fiber properties on aerodynamic performance and structural sizing of composite aircraft wings Peer-reviewed

Shugo Date, Yoshiaki Abe, Tomonaga Okabe

Aerospace Science and Technology　124　107565-107565　2022/05
Publisher: Elsevier BV
DOI： 10.1016/j.ast.2022.107565 　

ISSN： 1270-9638
A new path-independent interaction integral for dynamic stress intensity factors of cracked structures Peer-reviewed

Huachao Deng, Bo Yan, Tomonaga Okabe

International Journal of Solids and Structures　243　111559-111559　2022/05
Publisher: Elsevier BV
DOI： 10.1016/j.ijsolstr.2022.111559 　

ISSN： 0020-7683
Uncovering the Mechanism of Size Effect on the Thermomechanical Properties of Highly Cross-Linked Epoxy Resins Peer-reviewed

Yinbo Zhao, Gota Kikugawa, Yoshiaki Kawagoe, Keiichi Shirasu, Naoki Kishimoto, Yingxiao Xi, Tomonaga Okabe

The Journal of Physical Chemistry B　126　(13)　2593-2607　2022/04/07
Publisher: American Chemical Society (ACS)
DOI： 10.1021/acs.jpcb.1c10827 　

ISSN： 1520-6106

eISSN： 1520-5207
Prediction of transverse crack progression based on continuum damage mechanics and its application to composite laminates and filament-wound cylindrical pressure vessels Peer-reviewed

Yoshiko Nagumo, Sota Onodera, Tomonaga Okabe

Advanced Composite Materials　1-17　2022/03/11
Publisher: Informa UK Limited
DOI： 10.1080/09243046.2022.2048452 　

ISSN： 0924-3046

eISSN： 1568-5519
Multi-fidelity progressive damage simulation of notched composite laminates with various ply thicknesses

R. Higuchi, R. Aoki, S. Onodera, X. Lu, J. Zhi, K.H. Leong, T. Yokozeki, T. Okabe, T.E. Tay

International Journal of Solids and Structures　111518-111518　2022/02
Publisher: Elsevier BV
DOI： 10.1016/j.ijsolstr.2022.111518 　

ISSN： 0020-7683
Analyzing Stochastic Features in Airport Surface Traffic Flow Using Cellular Automaton: Tokyo International Airport Peer-reviewed

Yoshiaki Kawagoe, Ryohei Chino, Satori Tsuzuki, Eri Itoh, Tomonaga Okabe

IEEE Access　10　1-1　2022
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
DOI： 10.1109/access.2022.3204819 　

eISSN： 2169-3536
Open-hole tensile properties of 3D-printed continuous carbon-fiber-reinforced thermoplastic laminates: Experimental study and multiscale analysis Peer-reviewed

Yamato Hoshikawa, Keiichi Shirasu, Kohei Yamamoto, Yasuhisa Hirata, Ryo Higuchi, Tomonaga Okabe

Journal of Thermoplastic Composite Materials　2022

DOI： 10.1177/08927057221110791 　

ISSN： 0892-7057

eISSN： 1530-7980
Density Functional Theory for Polymer Phase Separations Induced by Coupling of Chemical Reaction and Elastic Stress

Yutaka Oya, Gota Kikugawa, Tomonaga Okabe, Toshihiro Kawakatsu

Advanced Theory and Simulations　5　(1)　2100385-2100385　2022/01
Publisher: Wiley
DOI： 10.1002/adts.202100385 　

ISSN： 2513-0390

eISSN： 2513-0390
Numerical simulation for deformation of laminates combining the novel shell element with the decoupled two-scale viscoelastic analysis of FRP

Takeki Yamamoto, Tomonaga Okabe, Kenjiro Terada

International Journal of Solids and Structures　234-235　111236-111236　2022/01
Publisher: Elsevier BV
DOI： 10.1016/j.ijsolstr.2021.111236 　

ISSN： 0020-7683
Micromechanical modeling for the in-plane mechanical behavior of orthogonal three-dimensional woven ceramic matrix composites with transverse and matrix cracking

Sota Onodera, Junpei Tsuyuki, Tomonaga Okabe

International Journal of Damage Mechanics　31　(2)　105678952110260-105678952110260　2021/06/24
Publisher: SAGE Publications
DOI： 10.1177/10567895211026017 　

ISSN： 1056-7895

eISSN： 1530-7921

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Ceramic matrix composites (CMCs) are currently being considered for applications in the hot-section components of aviation gas turbines owing to their favorable characteristics. Herein, a micromechanical modeling is presented for orthogonal 3 D woven CMCs under in-plane loading. The three-dimensional effective compliance of the 3 D woven composite was derived using three-dimensional laminate theory and continuum damage mechanics. The damage variables were used to describe the stiffness reduction due to the transverse and matrix cracking in each fiber bundle. The calculation method for the transverse and matrix cracking evolutions under in-plane loading was established by introducing mixed-mode damage criteria. The stress redistribution among the fiber bundles of 3 D woven CMCs due to the fiber/matrix interfacial debonding around matrix cracking was considered to capture the interaction between the matrix and transverse crack evolutions. Additionally, a mesomechanical model comprising finite element analysis and damage mechanics was established to evaluate the stress perturbation due to the geometry of the woven structure. The edge face of the 3 D woven CMC was experimentally observed to measure the transverse and matrix cracks that occurred in each fiber bundle. The transverse and matrix crack densities predicted by the micromechanical and mesomechanical models reasonably agreed with the experimental results up to crack saturation. Furthermore, the micromechanical model reproduced the nonlinear stress–strain response under tensile and shear loading using mixed-mode damage criteria.
Experimental and numerical study on progressive damage and failure in composite laminates during open-hole compression tests

R. Higuchi, S. Warabi, A. Yoshimura, T. Nagashima, T. Yokozeki, T. Okabe

Composites Part A: Applied Science and Manufacturing　145　106300-106300　2021/06
Publisher: Elsevier BV
DOI： 10.1016/j.compositesa.2021.106300 　

ISSN： 1359-835X
Amine/epoxy stoichiometric ratio dependence of crosslinked structure and ductility in amine-cured epoxy thermosetting resins

Nobuyuki Odagiri, Keiichi Shirasu, Yoshiaki Kawagoe, Gota Kikugawa, Yutaka Oya, Naoki Kishimoto, Fumio S. Ohuchi, Tomonaga Okabe

JOURNAL OF APPLIED POLYMER SCIENCE　138　(23)　2021/06

DOI： 10.1002/app.50542 　

ISSN： 0021-8995

eISSN： 1097-4628
Cure Path Dependency in Crosslinked Structure of DGEBA/DICY/DCMU Thermosetting Resin Peer-reviewed

Nobuyuki ODAGIRI, Keiichi SHIRASU, Yoshiaki KAWAGOE, Tomonaga OKABE

Materials System　38　21-30　2021/03

DOI： 10.34401/materialssystem.38.0_21 　
A decoupling scheme for two-scale finite thermoviscoelasticity with thermal and cure-induced deformations

Risa Saito, Yosuke Yamanaka, Seishiro Matsubara, Tomonaga Okabe, Shuji Moriguchi, Kenjiro Terada

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING　122　(4)　1133-1166　2021/02

DOI： 10.1002/nme.6575 　

ISSN： 0029-5981

eISSN： 1097-0207
Thermoset resin curing simulation using quantum-chemical reaction path calculation and dissipative particle dynamics

Yoshiaki Kawagoe, Gota Kikugawa, Keiichi Shirasu, Tomonaga Okabe

Soft Matter　17　(28)　6707-6717　2021
Publisher: Royal Society of Chemistry (RSC)
DOI： 10.1039/d1sm00600b 　

ISSN： 1744-683X

eISSN： 1744-6848

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We proposed a coarse-grained curing simulation technique for thermoset resin that combines DPD with an <italic>ab initio</italic> quantum calculation. An all-atom MD system was reconstructed from the DPD system using reverse mapping to evaluate several properties.
Fluid-structural design analysis for composite aircraft wings with various fiber properties

Shugo Date, Yoshiaki Abe, Takeki Yamamoto, Tomonaga Okabe

JOURNAL OF FLUID SCIENCE AND TECHNOLOGY　16　(1)　2021

DOI： 10.1299/jfst.2021jfst0009 　

ISSN： 1880-5558
Molecular dynamics simulation of cross-linking processes and material properties for epoxy resins using first-principle calculation combined with global reaction route mapping algorithms

Yutaka Oya, Masahiro Nakazawa, Keiichi Shirasu, Yuki Hino, Kyosuke Inuyama, Gota Kikugawa, Jing Li, Riichi Kuwahara, Naoki Kishimoto, Hiroki Waizumi, Masaaki Nishikawa, Anthony Waas, Nobuyuki Odagiri, Andrew Koyanagi, Marco Salviato, Tomonaga Okabe

CHEMICAL PHYSICS LETTERS　762　2021/01

DOI： 10.1016/j.cplett.2020.138104 　

ISSN： 0009-2614

eISSN： 1873-4448
Tensile-strength-controlling factors in unidirectional carbon fiber reinforced plastic composites

Go Yamamoto, Keita Koizumi, Takahiro Nakamura, Noriyuki Hirano, Tomonaga Okabe

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　140　2021/01

DOI： 10.1016/j.compositesa.2020.106140 　

ISSN： 1359-835X

eISSN： 1878-5840
Analytical model for determining effective stiffness and mechanical behavior of polymer matrix composite laminates using continuum damage mechanics

Sota Onodera, Tomonaga Okabe

INTERNATIONAL JOURNAL OF DAMAGE MECHANICS　29　(10)　1512-1542　2020/11

DOI： 10.1177/1056789520939624 　

ISSN： 1056-7895

eISSN： 1530-7921
Evaluation of the In-situ Damage and Strength Properties of Thin-ply CFRP Laminates by Micro-scale Finite Element Analysis

Ryo Higuchi, Ryoma Aoki, Tomohiro Yokozeki, Tomonaga Okabe

Journal of the Japan Society for Composite Materials　46　(5)　212-222　2020/09/15
Publisher: The Japan Society for Composite Materials
DOI： 10.6089/jscm.46.212 　

ISSN： 0385-2563

eISSN： 1884-8559
Evaluation of the in-situ damage and strength properties of thin-ply CFRP laminates by micro-scale finite element analysis

R. Higuchi, R. Aoki, T. Yokozeki, T. Okabe

Advanced Composite Materials　29　(5)　475-493　2020/09/02
Publisher: Informa UK Limited
DOI： 10.1080/09243046.2020.1740867 　

ISSN： 0924-3046

eISSN： 1568-5519
Experimental and numerical investigations on push-out delamination in drilling of composite laminates Peer-reviewed

R. Higuchi, S. Warabi, W. Ishibashi, T. Okabe

Composites Science and Technology　198　108238-108238　2020/09
Publisher: Elsevier BV
DOI： 10.1016/j.compscitech.2020.108238 　

ISSN： 0266-3538
Gate optimization for resin transfer molding in dual-scale porous media: Numerical simulation and experiment measurement Peer-reviewed

Yutaka Oya, Tsubasa Matsumiya, Akira Ito, Ryosuke Matsuzaki, Tomonaga Okabe

Journal of Composite Materials　54　(16)　2131-2145　2020/07
Publisher: SAGE Publications
DOI： 10.1177/0021998319890122 　

ISSN： 0021-9983

eISSN： 1530-793X

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For resin transfer molding in a woven fabric, this study developed a novel framework for optimization by combining a multi-objective genetic algorithm and mold-filling simulation including a void-formation model, which gives us not only the spatial distribution of the mesoscopic and microscopic voids but also the correlations between molding characteristics such as fill time, total amount of void, weld line, and wasted resin. Our experiment observation of one-point radial injection successfully captured the anisotropic distribution of mesoscopic voids, which qualitatively validates the simulated result. As a result of multi-objective optimization for an arrangement of two injection positions, we found the trade-off relations of weld line with the other characteristics, which also have positive correlation with each other. Furthermore, visualization techniques such as self-organizing maps and parallel coordinate maps extracted the design rule of the arrangement. For example, a diagonal gate arrangement with an appropriate distance is required for reducing the both total amount of voids, fill time, and wasted resin; however, the total area of the weld line becomes relatively large. Our framework and the knowledge obtained from this study will enable us to determine the appropriate mold design for resin transfer molding.
Structure-Property Correlation Study for Organic Photovoltaic Polymer Materials Using Data Science Approach

Yue Huang, Jingtian Zhang, Edwin S. Jiang, Yutaka Oya, Akinori Saeki, Gota Kikugawa, Tomonaga Okabe, Fumio S. Ohuchi

JOURNAL OF PHYSICAL CHEMISTRY C　124　(24)　12871-12882　2020/06

DOI： 10.1021/acs.jpcc.0c00517 　

ISSN： 1932-7447

eISSN： 1932-7455
Multiscale analysis and experimental validation of crack initiation in quasi-isotropic laminates Peer-reviewed

Yuta Kumagai, Sota Onodera, Marco Salviato, Tomonaga Okabe

International Journal of Solids and Structures　193-194　172-191　2020/06
Publisher: Elsevier BV
DOI： 10.1016/j.ijsolstr.2020.02.010 　

ISSN： 0020-7683
Development of mesh-free simulation tool for the optimization of microscopic composite structure

Ryo Higuchi, Tomohiro Yokozeki, Tomonaga Okabe, Toshio Nagashima, Takahira Aoki

ECCM 2018 - 18th European Conference on Composite Materials　2020
Publisher: Applied Mechanics Laboratory
Evaluation of notched strength of thin-ply composite materials using adaptive discrete-smeared crack (A-DiSC) method

Ryo Higuchi, Ryoma Aoki, Tomohiro Yokozeki, Sota Onodera, Tomonaga Okabe, Karh Heng Leong, Jie Zhi, Xin Lu, Tong Earn Tay

Proceedings of the American Society for Composites - 35th Technical Conference, ASC 2020　1452-1465　2020
Numerical Simulation of Wake Deflection Control around NACA0012 Airfoil Using Active Morphing Flaps

Yoshiaki Abe, Takayuki Konishi, Tomonaga Okabe

Journal of Flow Control, Measurement & Visualization　08　(03)　121-133　2020
Publisher: Scientific Research Publishing, Inc.
DOI： 10.4236/jfcmv.2020.83007 　

ISSN： 2329-3322

eISSN： 2329-3330
複合材構造のCompression RTM成形における樹脂含浸時間予測 Peer-reviewed

矢代茂樹, 伊藤晃, 松宮飛翔, 辻孝鴻, 大矢豊大, 松崎亮介, 岡部朋永

日本複合材料学会誌　2020
Introducing self-organized maps (SOM) as a visualization tool for materials research and education International-coauthorship Peer-reviewed

Jimin Qian, Nam Phuong Nguyen, Yutaka Oya, Gota Kikugawa, Tomonaga Okabe, Yue Huang, Fumio S. Ohuchi

Results in Materials　4　100020　2019/12

DOI： 10.1016/j.rinma.2019.100020 　
ミクロスケール解析による薄層CFRP 積層板のin-situ損傷・強度特性評価 Peer-reviewed

樋口諒, 青木涼馬, 横関智弘, 岡部朋永

日本複合材料学会誌　46　(5)　212-222　2019/11
Three-dimensional analytical model for effective elastic constants of transversely isotropic plates with multiple cracks: Application to stiffness reduction and steady-state cracking of composite laminates

Sota Onodera, Tomonaga Okabe

ENGINEERING FRACTURE MECHANICS　219　2019/10

DOI： 10.1016/j.engfracmech.2019.106595 　

ISSN： 0013-7944

eISSN： 1873-7315
Experimental and smoothed particle hydrodynamics analysis of interfacial bonding between aluminum powder particles and aluminum substrate by cold spray technique

Abreeza Manap, Tomonaga Okabe, Kazuhiro Ogawa, Savisha Mahalingam, Huda Abdullah

International Journal of Advanced Manufacturing Technology　103　(9-12)　4519-4527　2019/08/01

DOI： 10.1007/s00170-019-03846-4 　

ISSN： 0268-3768

eISSN： 1433-3015
Data Analysis of Multi-Dimensional Thermophysical Properties of Liquid Substances Based on Clustering Approach of Machine Learning International-coauthorship Peer-reviewed

Gota Kikugawa, Yuta Nishimura, Koji Shimoyama, Taku Ohara, Tomonaga Okabe, Fumio S. Ohuchi

Chemical Physics Letters　728　109-114　2019/08

DOI： 10.1016/j.cplett.2019.04.075 　
Stiffness and permeability multi-objective optimization of carbon-fiber-reinforced plastic mesostructures using homogenization method

Ryosuke Matsuzaki, Tomohiro Ishikawa, Tomonaga Okabe, Yutaka Oya, Shigeki Yashiro

JOURNAL OF COMPOSITE MATERIALS　53　(13)　1865-1880　2019/06

DOI： 10.1177/0021998318812160 　

ISSN： 0021-9983

eISSN： 1530-793X
Considering the stress concentration of fiber surfaces in the prediction of the tensile strength of unidirectional carbon fiber-reinforced plastic composites

Go Yamamoto, Miho Onodera, Keita Koizumi, Jun Watanabe, Haruki Okuda, Fumihiko Tanaka, Tomonaga Okabe

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　121　499-509　2019/06

DOI： 10.1016/j.compositesa.2019.04.011 　

ISSN： 1359-835X

eISSN： 1878-5840
Particle simulation of dual-scale flow in resin transfer molding for process analysis

Shigeki Yashiro, Daichi Nakashima, Yutaka Oya, Tomonaga Okabe, Ryosuke Matsuzaki

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　121　283-288　2019/06

DOI： 10.1016/j.compositesa.2019.03.038 　

ISSN： 1359-835X

eISSN： 1878-5840
A multiscale model for the synthesis of thermosetting resins: From the addition reaction to cross-linked network formation Peer-reviewed

Li Jing, Jumpei Sakamoto, Waizumi Hiroki, Oya Yutaka, Huang Yue, Kishimoto Naoki, Okabe Tomonaga

CHEMICAL PHYSICS LETTERS　720　64-69　2019/04

DOI： 10.1016/j.cplett.2019.02.012 　

ISSN： 0009-2614

eISSN： 1873-4448
Numerical study for tensile strength prediction of unidirectional carbon fiber-reinforced composite considering fiber surface stress concentration

Go Yamamoto, Tomonaga Okabe

MECHANICAL ENGINEERING JOURNAL　6　(3)　2019

DOI： 10.1299/mej.19-00020 　

ISSN： 2187-9745
Analysis of structure characteristics in laminated graphene oxide nanocomposites using molecular dynamics simulation

Yutaka Oya, Kyosuke Inuyama, Tomonaga Okabe, Jun Koyanagi, Ryosuke Matsuzaki

Advanced Composite Materials　27　(4)　427-438　2018/07/04
Publisher: Taylor and Francis Ltd.
DOI： 10.1080/09243046.2017.1407278 　

ISSN： 1568-5519 0924-3046
Investigating nanostructures in carbon fibres using Raman spectroscopy Peer-reviewed

Haruki Okuda, Robert J. Young, Daniel Wolverson, Fumihiko Tanaka, Go Yamamoto, Tomonaga Okabe

Carbon　130　178-184　2018/04/01
Publisher: Elsevier Ltd
DOI： 10.1016/j.carbon.2017.12.108 　

ISSN： 0008-6223
Fracture behavior of diamondlike carbon films deposited on polymer substrates Peer-reviewed

Go Yamamoto, Tomonaga Okabe, Noriaki Ikenaga

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films　36　(2)　O2C101-1-02C101-6　2018/03/01
Publisher: AVS Science and Technology Society
DOI： 10.1116/1.5003683 　

ISSN： 1520-8559 0734-2101
Determination of full elastic constants of carbon fiber in carbon fiber reinforced plastic composites

Go Yamamoto, Shogo Kurisaki, Satoshi Atobe, Tomonaga Okabe

33rd Technical Conference of the American Society for Composites 2018　3　1508-1514　2018
Publisher: DEStech Publications Inc.
Microscale simulation of composites with various microstructures by using extended finite element method (XFEM)

Ryo Higuchi, Tomohiro Yokozeki, Tomonaga Okabe, Toshio Nagashima, Takahira Aoki

33rd Technical Conference of the American Society for Composites 2018　3　2037-2047　2018
Publisher: DEStech Publications Inc.
Changes in micro-phase separation of di-block copolymer melts induced by a circle fiber

Yutaka Oya, Naofumi Umemoto, Tomonaga Okabe

33rd Technical Conference of the American Society for Composites 2018　2　792-797　2018
Publisher: DEStech Publications Inc.
Multiscale failure analysis for prediction of matrix crack formation in polymer-matrix composites

Yuta Kumagai, Yoshiteru Aoyagi, Tomonaga Okabe

33rd Technical Conference of the American Society for Composites 2018　1　614-625　2018
Publisher: DEStech Publications Inc.
2F18 English capacity building for the first year students at research-based university: Development of a six-year engineering education system at research-based universities, Report IV.

SUTO Yuko, ANDO Akira, OKABE Tomonaga, MORIYA Hirokazu

Proceedings of Annual Conference of Japanese Society for Engineering Education　2018　336-337　2018
Publisher: Japanese Society for Engineering Education
DOI： 10.20549/jseeja.2018.0_336 　

ISSN： 2189-8928

eISSN： 2424-1458
A study of stress concentrations around fiber breaks in unidirectional CF/epoxy composites using double-fiber fragmentation tests

Watanabe, J., Tanaka, F., Higuchi, R., Matsutani, H., Okuda, H., Okabe, T.

Advanced Composite Materials　27　(6)　2018

DOI： 10.1080/09243046.2017.1416567 　

ISSN： 1568-5519 0924-3046
Numerical modelling of impact damage in fibre-reinforced plastic composites with smoothed particle hydrodynamics

Tomonaga Okabe, Shohei Natsui, Sota Onodera

33rd Technical Conference of the American Society for Composites 2018　3　2059-2075　2018
Prediction for stiffness reduction and progressive damage of composite laminate including ply cracks

Sota Onodera, Tomonaga Okabe

33rd Technical Conference of the American Society for Composites 2018　1　626-640　2018
Analysis of structure characteristics in laminated graphene oxide nanocomposites using molecular dynamics simulation Peer-reviewed

Yutaka OYA, Kyosuke Inuyama, Tomonaga Okabe, Jun Koyanagi, Ryosuke Matsuzaki

Advanced Composite Materials　42　(2)　1-12　2018
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.42.76 　

ISSN： 0385-2563

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Characteristics of laminated graphene oxide (LGO) nanocomposite, expected for high functional composites, are known to be related to its microstructure. In this study, we investigated influences of both hydrogen-bonding and cross-linked network structures on initial stiffness and yield stress by molecular dynamics simulations. Our results showed each structure improved the mechanical properties, and the combination of these structures made the properties stronger. Moreover, we revealed the physical origin of the enhancement is caused by cross-linked networks generate stretched polymers that connect graphene sheets. Our study is expected to give a suggestion to appropriate selection of materials for highly performance LGO nanocomposite.
Continuum damage mechanics modeling of composite laminates including transverse cracks Peer-reviewed

Tomonaga Okabe, Sota Onodera, Yuta Kumagai, Yoshiko Nagumo

International Journal of Damage Mechanics　27　(6)　877-895　2018
A study of stress concentrations around fiber breaks in unidirectional CF/epoxy composites using double-fiber fragmentation tests Peer-reviewed

J. Watanabea, F. Tanakaa, R. Higuchib, H. Matsutania, H. Okudaa, T.Okabeb

Advanced Composite Materials　42　(3)　1-13　2018
Publisher:
ISSN： 0385-2563
Multiscale modeling of free-surface effect on crack formation in unidirectional off-axis laminates Peer-reviewed

Yuta Kumagai, Sota Onodera, Yoshiko Nagumo, Tomonaga Okabe, Kenichi Yoshioka

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　98　(98)　136-146　2017/07

DOI： 10.1016/j.compositesa.2017.03.016 　

ISSN： 1359-835X

eISSN： 1878-5840
Progressive failure under high-velocity impact on composite laminates: Experiment and phenomenological mesomodeling Peer-reviewed

R. Higuchi, T. Okabe, A. Yoshimura, T. E. Tay

ENGINEERING FRACTURE MECHANICS　178　(178)　346-361　2017/06

DOI： 10.1016/j.engfracmech.2017.03.019 　

ISSN： 0013-7944

eISSN： 1873-7315
Numerical simulation of progressive damage and failure in composite laminates using XFEM/CZM coupled approach Peer-reviewed

R. Higuchi, T. Okabe, T. Nagashima

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　95　(95)　197-207　2017/04

DOI： 10.1016/j.compositesa.2016.12.026 　

ISSN： 1359-835X

eISSN： 1878-5840
Clustering Approach for Multidisciplinary Optimum Design of Cross-Linked Polymer Peer-reviewed

Yutaka Oya, Gota Kikugawa, Tomonaga Okabe

MACROMOLECULAR THEORY AND SIMULATIONS　26　(2)　1600072　2017/03

DOI： 10.1002/mats.201600072 　

ISSN： 1022-1344

eISSN： 1521-3919
Historical review of processing, microstructures, and mechanical properties of PAN-based carbon fibers

Fumihiko Tanaka, Tomonaga Okabe

Comprehensive Composite Materials II　66-85　2017/01/01
Publisher: Elsevier
DOI： 10.1016/B978-0-12-803581-8.09895-7 　
XFEM analysis of progressive damage and failure in CFRP laminates under in-plane and out-of-plane loading conditions

Ryo Higuchi, Tomonaga Okabe, Akinori Yoshimura, Toshio Nagashima

32nd Technical Conference of the American Society for Composites 2017　2　1020-1034　2017
Publisher: DEStech Publications Inc.
Transverse Cracking Behavior in Composite Laminates Based on Micromechanics Modeling

ONODERA Sota, NAGUMO Yoshiko, OKABE Tomonaga

The Proceedings of the Materials and Mechanics Conference　2017　(0)　OS1015　2017
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmemm.2017.OS1015 　

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Polymer matrix composites (PMCs) that have high specific strength and specific rigidity have been used in aerospace fields. Fiber-reinforced composite laminates exhibit specific fracture processes such as transverse cracks (cracks in a direction parallel to the fiber), delamination, and breakage of the fiber. In these fracture processes, transverse cracking occurs in the earliest stage. Therefore, it is important to clarify the mechanical behavior of laminate including transverse cracks. To evaluate the relationship between the mechanical behavior of composite laminates and transverse cracking, we formulated the continuum damage mechanics model for predicting the stiffness reduction of composite laminates including transverse cracks and the transverse cracking progression model in laminate including 90° plies. For development of the present models, stress field model, which takes into account thermal residual strain for plies including transverse cracks, was formulated based on micromechanics. Then, the damage variable in the direction normal to the fiber of a ply including transverse cracks and the energy release rate associated with transverse cracking were calculated using stress field model for plies. Finally, we compared the results obtained from present models to those of the finite element analysis (FEA) and experiment results reported in previous studies. Consequently, present models could predict the FEA results and experiment results quantitatively.
Multiscale Analysis of Free-Surface Crack Formation in Fiber-Reinforced Composites by Mesh Superposition Method

KUMAGAI Yuta, NAGUMO Yoshiko, OKABE Tomonaga

The Proceedings of The Computational Mechanics Conference　2017　(0)　270-270　2017
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmecmd.2017.30.270 　

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The effect of the stress field near the free-surface region of CFRP laminate on crack formation is investigated by multiscale analysis based on the mesh superposition method. Our multiscale approach consists of two finite-element analyses on different scale: local analysis considering microscopic structure of laminate, and global analysis assumed to be a homogeneous and anisotropic elasto-plastic body. Global analysis is performed to evaluate macroscopic deformation behavior of laminate. Local analysis is then conducted to predict crack formation in CFRP laminate, utilizing the displacement history obtained from the global analysis. Global analysis and local analysis are solved iteratively to obtain convergence results that reflect the interaction between macroscopic deformation and heterogeneity of CFRP. Our multiscale approach is applied to unidirectional CFRP laminates to evaluate the effect of the free surface on crack formation.
Multi-objective optimization for resin transfer molding process Peer-reviewed

Tomonaga Okabe, Yutaka Oya, Go Yamamoto, Junki Sato, Tsubasa Matsumiya, Ryosuke Matsuzaki, Shigeki Yashiro, Shigeru Obayashi

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　92　1-9　2017/01

DOI： 10.1016/j.compositesa.2016.09.023 　

ISSN： 1359-835X

eISSN： 1878-5840
モンテカルロ法によるCFRP直交積層板のトランスバースクラック進展解析 Peer-reviewed

Sota Onodera, Yoshiko Nagumo, Tomonaga Okabe

日本複合材料学会誌　43　(4)　124-132　2017
Publisher: The Japan Society for Composite Materials
DOI： 10.6089/jscm.43.124 　

ISSN： 0385-2563

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In this study, the prediction of the progression of transverse cracking in laminates, including 90° plies, was discussed. A refined stress field (RSF) model was formulated that takes into account the thermal residual strain for plies, including transverse cracks, and the energy release rate associated with transverse cracking was calculated using this RSF model. For comparison, the energy release rate based on a continuum damage mechanics (CDM) model was also formulated. Next, the prediction for the progression of transverse cracking in carbon fiber-reinforced plastic (CFRP) cross-ply laminates, including 90° plies, based on both stress and energy criteria was implemented using Monte Carlo methods. The results showed that the RSF and CDM models proposed in this paper can predict the experiment results for the relationship between the transverse crack density and ply strain in 90° plies. The models presented in this paper can potentially be applied to any arbitrary laminate that includes 90° plies.
Prediction for progression of transverse cracking in CFRP cross-ply laminates using Monte Carlo method Peer-reviewed

Sota Onodera, Yoshiko Nagumo, Tomonaga Okabe

ADVANCED COMPOSITE MATERIALS　26　(5)　477-491　2017

DOI： 10.1080/09243046.2017.1325076 　

ISSN： 0924-3046

eISSN： 1568-5519
Validation ofMicromechanicsModelsIncluding Imperfect Interfaces Using Injection Molded PartsofShort FiberReinforced Thermoplastics Peer-reviewed

Yoshinori INOUE, Ryuji OMOTE, Tomonaga OKABE

日本複合材料学会誌　43　(3)　81-89　2017
Publisher:
DOI： 10.6089/jscm.43.81 　

ISSN： 0385-2563
Tensile Strength Prediction of Discontinuous Carbon Fiber Reinforced Thermoplastics with an Open Circular Hole Peer-reviewed

Go YAMAMOTO, Kenji SAKAMOTO, Tomonaga OKABE, Masahiro HASHIMOTO, Noriyuki HIRANO

日本複合材料学会誌　43　(3)　104-111　2017
Publisher:
DOI： 10.6089/jscm.43.104 　

ISSN： 0385-2563
Process design for heat fusion of thermoplastic composites using molecular dynamics and a response surface method Peer-reviewed

Kento Takeuchi, Ryosuke Matsuzaki, Tomonaga Okabe, Yutaka Oya

ADVANCED COMPOSITE MATERIALS　25　33-49　2016/12

DOI： 10.1080/09243046.2016.1216726 　

ISSN： 0924-3046

eISSN： 1568-5519
短繊維強化複合材料の等価剛性予測に対する不完全接着を考慮した力学モ Peer-reviewed

井上良徳, 井川泰爾, 岡部朋永

日本複合材料学会誌　42　(6)　220-227　2016/11
Publisher: The Japan Society for Composite Materials
DOI： 10.6089/jscm.42.220 　

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Micromechanics models proposed by Nairn et al. and Hashin, which can treat imperfect bonded interfaces between fibers and matrix polymers, are evaluated to utilize the models for predicting accurate deformation of injection molded parts of short fiber reinforced thermoplastics. The treatment of the imperfect interfaces is essential to deal with a difference of the interface conditions which affect mechanical properties of the parts. In contrast, general micromechanics models, such as the Mori-Tanaka (MT) model, are not appropriate because a perfect bonded interface is assumed in the models. For the evaluation of the Nairn-Hashin (NH) models, we first compare the NH models with the MT model under the condition of the perfect interface. Elastic moduli calculated from the NH models almost agreed with that from the MT model. The NH models are then evaluated by using elastic moduli measured for randomly fiber-oriented films of short glass fiber reinforced polypropylene. By considering the imperfect interface parameters estimated from pull-out tests of a single glass fiber embedded in a polypropylene matrix, the NH models predicted the measured elastic moduli.
Tensile failure phenomena in carbon fibres Peer-reviewed

Haruki Okuda, Robert J. Young, Fumihiko Tanaka, Jun Watanabe, Tomonaga Okabe

CARBON　107　474-481　2016/10

DOI： 10.1016/j.carbon.2016.06.037 　

ISSN： 0008-6223

eISSN： 1873-3891
Effects of CNT Addition on Interlaminar Fracture Toughness of Carbon Fiber-Reinforced Plastic Composites) Peer-reviewed

Kenichi YOSHIOKA, Felix NGUYEN, Swezin THAN TUN, Go YAMAMOTO, Tomonaga OKABE

Journal of the Japan Society for Composite Materials　42　(5)　193-200　2016/09
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.42.193 　

ISSN： 0385-2563

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In this study, two types of carbon nanotube (CNT) with different types of CNT alignment are used as an interlaminar toughener for carbon fiber reinforced plastics (CFRP) preparation, and effects of CNT addition on the interlaminar fracture toughness of CFRP are investigated. The effects of the interlaminar toughening by addition of a thermoplastic resins are also investigated in addition to the above-mentioned CNT loading. It is well known that the impact resistance, i.e., interlaminar fracture toughness, is one of the most important properties for the development of CFRP. Even though the improvement in the interlaminar fracture toughness have been reported by adding thermoplastic resin between CFRP layers, further research is needed for the development of CFRP with lightweight and improved interlaminar fracture toughness. On the basis of these backgrounds, in this study, the effects of the CNT addition (unidirectionally aligned and randomly oriented CNTs), number of CNT layers (25 and 100 plies), location of CNT layer and thermoplastic resin addition on the mode I and mode II interlaminar fracture toughness are explored.
Molecular dynamics simulation of crosslinked epoxy resins: Curing and mechanical properties

Tomonaga Okabe, Yutaka Oya, Koichi Tanabe, Gota Kikugawa, Kenichi Yoshioka

EUROPEAN POLYMER JOURNAL　80　78-88　2016/07

DOI： 10.1016/j.eurpolymj.2016.04.019 　

ISSN： 0014-3057

eISSN： 1873-1945
Numerical simulation for open-hole tensile failure of lamina-based and fabric-based CFRP laminates with explicit dynamic finite element method Peer-reviewed

Kenichi YOSHIOKA, Masahiro HASHIMOTO, Ryo HIGUCHI, Kenji SAKAMOTO, Takahiko MIYACHI, Tomonaga OKABE

Journal of the Japan Society for Composite Materials　42　(4)　2016/07

DOI： 10.6089/jscm.42.125 　
Numerical simulation of damage progression and fracture in structures made of 3D woven ceramic matrix composites Peer-reviewed

R. Higuchi, T. Okabe, Y. Ohtake, T. Honda, Y. Ueda, S. Ogihara

ADVANCED COMPOSITE MATERIALS　25　(3)　209-227　2016/06

DOI： 10.1080/09243046.2015.1075672 　

ISSN： 0924-3046

eISSN： 1568-5519
A study of stress concentrations around fiber breaks in unidirectional CF/epoxy composites using double-fibers fragmentation tests Peer-reviewed

渡邉潤, 田中文彦, 樋口諒, 松谷浩明, 奥田治己, 岡部朋永

Journal of the Japan Society for Composite Materials　42　(3)　89-97　2016/05
Publisher:
DOI： 10.6089/jscm.42.89 　

ISSN： 0385-2563
Analysis of structure Characteristics in laminated graphene oxide nanocomposites using molecular dynamics simulation Peer-reviewed

大矢豊大, 犬山恭介, 岡部朋永, 小柳潤, 松崎亮介

日本複合材料学会誌　42　(2)　76-81　2016/03
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.42.76 　

ISSN： 0385-2563

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Characteristics of laminated graphene oxide (LGO) nanocomposite, expected for high functional composites, are known to be related to its microstructure. In this study, we investigated influences of both hydrogen-bonding and cross-linked network structures on initial stiffness and yield stress by molecular dynamics simulations. Our results showed each structure improved the mechanical properties, and the combination of these structures made the properties stronger. Moreover, we revealed the physical origin of the enhancement is caused by cross-linked networks generate stretched polymers that connect graphene sheets. Our study is expected to give a suggestion to appropriate selection of materials for highly performance LGO nanocomposite.
Numerical simulation of triaxial woven CFRP under tensile loading

Jun Koyanagi, Erina Imai, Ryo Higuchi, Akinori Yoshimura, Tomonaga Okabe, Satoru Yoneyama, Takahira Aoki

ECCM 2016 - Proceeding of the 17th European Conference on Composite Materials　2016
Publisher: European Conference on Composite Materials, ECCM
Optimization of heat fusion of thermoplastic resin by molecular dynamics and a response surface method

Kento Takeuchi, Ryosuke Matsuzaki, Tomonaga Okabe, Yutaka Oya

ECCM 2016 - Proceeding of the 17th European Conference on Composite Materials　2016
Publisher: European Conference on Composite Materials, ECCM
Progressive damage and failure analysis of composite laminates using XFEM/CZM coupled approach

R. Higuchi, T. Okabe, K. Yoshioka, T. Nagashima

Proceedings of the American Society for Composites - 31st Technical Conference, ASC 2016　2016
Publisher: DEStech Publications Inc.
Design Exploration of Non-crimp Fabric for Resin Transfer Molding by the GP using AIC and TOL Peer-reviewed

Tomohiro Ishikawa, Ryosuke Matsuzaki, Tomonaga Okabe, Shigeki Yashiro

DESIGN, MANUFACTURING AND APPLICATIONS OF COMPOSITES　181-186　2016
分子動力学法と応答曲面法による熱可塑性樹脂複合材料融着プロセスデザイン Peer-reviewed

竹内健都, 松崎亮介, 岡部朋永, 大矢豊大

Journal of the Japan Society for Composite Materials　42　(2)　67-75　2016
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.42.67 　

ISSN： 0385-2563

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The study worked out an efficient optimization of heat fusion conditions between thermoplastics using molecular dynamics (MD) and a response surface method. The heat fusion process between polypropylene (PP) and polyethylene (PE) and the uniaxial elongation for evaluation of the interfacial bonding strength were modeled by using coarse-grained MD simulation. To determine the optimal conditions of heat fusion, experimental points were selected on the basis of a central composite design, and a second-order polynomial response surface was created by setting temperature, pressure, and polymerization degree as explanatory variables and the strength of fused interface as the response. The obtained optimal solution under constrained conditions yielded the highest strength compared with other experimental points and random points.
Multiscale Modeling of Failure Strain Off-Axis Tensile Testing of UD-CFRP Peer-reviewed

Kenichi YOSHIOKA, Yuta KUMAGAI, Ryo HIGUCHI, Don yeon Lee

Materials system　40　(5)　227-237　2015/12/28
Torsional modulus and internal friction of polyacrylonitrile- and pitch-based carbon fibers Peer-reviewed

Masashi Ishikawa, Yasuo Kogo, Jun Koyanagi, Fumihiko Tanaka, Tomonaga Okabe

JOURNAL OF MATERIALS SCIENCE　50　(21)　7018-7025　2015/11

DOI： 10.1007/s10853-015-9254-z 　

ISSN： 0022-2461

eISSN： 1573-4803
Smoothed particle hydrodynamics in a generalized coordinate system with a finite-deformation constitutive model Peer-reviewed

Shigeki Yashiro, Tomonaga Okabe

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING　103　(11)　781-797　2015/09

DOI： 10.1002/nme.4906 　

ISSN： 0029-5981

eISSN： 1097-0207
The tensile strength of pan-based carbon fibres and nanostructure development

Haruki Okuda, Robert J. Young, Fumihiko Tanaka, Jun Watanabe, Tomonaga Okabe

ICCM International Conferences on Composite Materials　2015-　2015
Publisher: International Committee on Composite Materials
Onset of matrix cracking in fiber reinforced polymer composites: A historical review and a comparison between periodic unit cell analysis and analytic failure criteria Peer-reviewed

Tomonaga Okabe, Yuta Kumagai, Ryo Higuchi, Masaaki Nishikawa

Advanced Structured Materials　64　299-317　2015
Publisher: Springer Verlag
DOI： 10.1007/978-3-319-19440-0_13 　

ISSN： 1869-8441 1869-8433
Prediction of Tensof Tensile Strength of Unidirectional Carbon Fiber Reinforced Matrix Composite with Spring Element Model Peer-reviewed

渡邉潤, 田中文彦, 松谷浩明, 奥田治己, 津田皓正, 樋口諒, 山本剛

材料システム　2015
Experimental and numerical studies of initial cracking in CFRP cross-ply laminates Peer-reviewed

T. Okabe, H. Imamura, Y. Sato, R. Higuchi, J. Koyanagi, R. Talreja

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　68　81-89　2015/01

DOI： 10.1016/j.compositesa.2014.09.020 　

ISSN： 1359-835X

eISSN： 1878-5840
Recent studies on numerical modelling of damage progression in fibre-reinforced plastic composites Peer-reviewed

T. Okabe

Mechanical Engineering Reviews　2　(1)　1-11　2015/01/01
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/mer.14-00226 　

ISSN： 2187-9753

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This review of previous studies on the damage and mechanical modelling of fibre-reinforced composite materials, especially carbon-fibre-reinforced plastic composites, is based on the findings of recent studies conducted in conjunction with other researchers. Studies that utilized various modelling scales, ranging from macroscopic to microscopic, are considered. The modelling of impact damage, ply cracks, ultimate tensile failure, the initiation of transverse ply cracks, the micro-mechanical properties of interfaces and molecular dynamics are specifically addressed. In addition, the scope for future work in the field is described.
Tensile strength distribution of carbon fibers at short gauge lengths Peer-reviewed

J. Watanabe, F. Tanaka, H. Okuda, T. Okabe

ADVANCED COMPOSITE MATERIALS　23　(5-6)　535-550　2014/09

DOI： 10.1080/09243046.2014.915120 　

ISSN： 0924-3046

eISSN： 1568-5519
Multiscale approach to predict crack initiation in unidirectional off-axis laminates Peer-reviewed

Y. Sato, T. Okabe, R. Higuchi, K. Yoshioka

ADVANCED COMPOSITE MATERIALS　23　(5-6)　461-475　2014/09

DOI： 10.1080/09243046.2014.915100 　

ISSN： 0924-3046

eISSN： 1568-5519
Experimental and SPH study of cold spray impact between similar and dissimilar metals Peer-reviewed

A. Manap, O. Nooririnah, H. Misran, T. Okabe, K. Ogawa

SURFACE ENGINEERING　30　(5)　335-341　2014/06

DOI： 10.1179/1743294413Y.0000000237 　

ISSN： 0267-0844

eISSN： 1743-2944
Factors controlling the strength of carbon fibres in tension Peer-reviewed

Fumihiko Tanaka, Tomonaga Okabe, Haruki Okuda, Ian A. Kinloch, Robert J. Young

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　57　88-94　2014/02

DOI： 10.1016/j.compositesa.2013.11.007 　

ISSN： 1359-835X

eISSN： 1878-5840
Numerical simulation of out-of-plane impact and compression after impact test on CFRP laminates

Ryo Higuchi, Tomonaga Okabe, Kenichi Yoshioka

Proceedings of the American Society for Composites - 29th Technical Conference, ASC 2014; 16th US-Japan Conference on Composite Materials; ASTM-D30 Meeting　2014
Publisher: DEStech Publications
Flow Simulation of Thermoplastic Stampable Sheet using Particle Method Peer-reviewed

松谷浩明, 武田一朗, 橋本雅弘, 平野啓之, 岡部朋永

Journal of the Japan Society for Composite Materials　40　(5)　227-237　2014
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.40.227 　

ISSN： 0385-2563

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Flow of stampable thermoplastic sheet developed by Toray was simulated with moving particle semi-implicit method. The method was improved by introducing implicit method into velocity calculation, simplifying pressure calculation, applying parallel computing and parameterizing walls. These improvements made the present method about 80 times faster than basic MPS method. And the quaternion was introduced to calculate rotation of fiber assumed to be rigid in three dimensions. Then, compression molding of circular plate and rib was simulated with this improved MPS method. In circular plate case, computational result showed a similar tendency to experiment that the random orientation of fibers was kept through compression. And in rib case, computational results also showed a similar tendency to experiments that sheet was driven into rib keeping ply order, and that resin rich was formed depending on fiber length. The traditional computational methods such as finite element method and finite difference method are not good at these analyses of fiber orientation and resin rich (heterogeneity), and it is confirmed that the particle method is useful for these analyses.
Micromechanical simulation of tensile failure of discontinuous fiber-reinforced polymer matrix composites using Spring Element Model Peer-reviewed

Tomonaga Okabe, Toshiki Sasayama, Jun Koyanagi

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　56　64-71　2014/01

DOI： 10.1016/j.compositesa.2013.09.012 　

ISSN： 1359-835X

eISSN： 1878-5840
Numerical simulation of strain-rate dependent transition of transverse tensile failure mode in fiber-reinforced composites Peer-reviewed

Jun Koyanagi, Yukihiro Sato, Toshiki Sasayama, Tomonaga Okabe, Satoru Yoneyama

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　56　136-142　2014/01

DOI： 10.1016/j.compositesa.2013.10.002 　

ISSN： 1359-835X

eISSN： 1878-5840
Investigation of the sp3 structure of carbon fibres using UV-Raman spectroscopy Peer-reviewed

Fumihiko Tanaka, Daniel Wolverson, Tomonaga Okabe, Ian A. Kinloch, Robert J. Young

TANSO　259　(259)　1-5　2013/10/01
Publisher: THE CARBON SOCIETY OF JAPAN
DOI： 10.7209/tanso.2013.243 　

ISSN： 0371-5345

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We have used UV-Raman spectroscopy to study the sp³ structure in polyacrylonitrile- and pitch-based carbon fibres with Young's modulus values in the range of 90-830 GPa. The composite microstructure of these carbon fibres comprises an amorphous carbon phase that transfers the load to a reinforcing graphite crystalline phase. The intensity ratio of the T, D and G Raman bands showed that the low modulus polyacrylonitrile-based carbon fibres (Young's modulus=200-300 GPa) contained 10-25% sp³ carbon, whereas the stiffer polyacrylonitrile-based carbon fibres (Young's modulus >350 GPa) contained ∼5% sp³ material. This result suggests that the proportion of sp³ carbon decreases as the amorphous structure is converted into a crystalline structure during the carbonization treatment, leading to the high performance fibres. This observation is consistent with our current understanding of the relationship between structure and mechanical properties in carbon fibres.
Curing reaction of epoxy resin composed of mixed base resin and curing agent: Experiments and molecular simulation Peer-reviewed

Tomonaga Okabe, Tomohiro Takehara, Keisuke Inose, Noriyuki Hirano, Masaaki Nishikawa, Takuya Uehara

POLYMER　54　(17)　4660-4668　2013/08

DOI： 10.1016/j.polymer.2013.06.026 　

ISSN： 0032-3861

eISSN： 1873-2291
The effect of nanostructure upon the compressive strength of carbon fibres Peer-reviewed

Fumihiko Tanaka, Tomonaga Okabe, Haruki Okuda, Ian A. Kinloch, Robert J. Young

JOURNAL OF MATERIALS SCIENCE　48　(5)　2104-2110　2013/03

DOI： 10.1007/s10853-012-6984-z 　

ISSN： 0022-2461
The effect of nanostructure upon the deformation micromechanics of carbon fibres Peer-reviewed

Fumihiko Tanaka, Tomonaga Okabe, Haruki Okuda, Masafumi Ise, Ian A. Kinloch, Tsutomu Mori, Robert J. Young

CARBON　52　372-378　2013/02

DOI： 10.1016/j.carbon.2012.09.047 　

ISSN： 0008-6223
Initiation and progression of drilling damages on composite laminates

S. Park, M. Nishikawa, T. Okabe, N. Taked

28th Annual Technical Conference of the American Society for Composites 2013, ASC 2013　2　1038-1049　2013
Prediction of failure properties of injection-molded short glass fiber-reinforced polyamide 6,6 Peer-reviewed

Toshiki Sasayama, Tomonaga Okabe, Yoshiteru Aoyagi, Masaaki Nishikawa

Composites Part A: Applied Science and Manufacturing　52　45-54　2013

DOI： 10.1016/j.compositesa.2013.05.004 　

ISSN： 1359-835X
Numerical simulation of microscopic flow in a fiber bundle using the moving particle semi-implicit method Peer-reviewed

Tomonaga Okabe, Hiroaki Matsutani, Takashi Honda, Shigeki Yashiro

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　43　(10)　1765-1774　2012/10

DOI： 10.1016/j.compositesa.2012.05.003 　

ISSN： 1359-835X
Prediction of tensile strength of discontinuous carbon fiber/polypropylene composite with fiber orientation distribution Peer-reviewed

M. Hashimoto, T. Okabe, T. Sasayama, H. Matsutani, M. Nishikawa

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　43　(10)　1791-1799　2012/10

DOI： 10.1016/j.compositesa.2012.05.006 　

ISSN： 1359-835X
Residual Strength after Creep Loading for Open Hole CFRP Laminates

KOYANAGI Jun, YONEYAMA Satoru, OKABE Tomonaga

Journal of the Japanese Society for Experimental Mechanics　12　(2)　81-87　2012/06/25
Publisher: The Japanese Society for Experimental Mechanics
DOI： 10.11395/jjsem.12.81 　

ISSN： 1346-4930

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Residual strength after a creep loading is studied for open hole CFRP laminates. Accelerated tests are performed at the elevated temperatures. The test results show that the residual strengths are not always less than the static strength but sometimes greater than that, depending on the temperature. A digital image correlation (DIC) method is employed for the measurement of in-situ strain distribution around the open hole. DIC result implies splitting damage of loading directional layer has a role playing to enhance the residual strength after creep. Finite element analysis involving cohesive element is implemented in order to verify the splitting-induced residual strength enhancement. The cohesive element has time-dependent strength and toughness. Time-dependent internal damage propagation is thus analyzed. This study suggests the residual strength as a function of creep time once increases via stress-concentration mitigation by splitting damage and then decreases with time due to the degradation of material properties themselves.
Modeling the effect of statistical variations in length and diameter of randomly oriented CNTs on the properties of CNT reinforced nanocomposites Peer-reviewed

S. C. Chowdhury, B. Z. (Gama) Hague, T. Okabe, J. W. Gillespie

COMPOSITES PART B-ENGINEERING　43　(4)　1756-1762　2012/06

DOI： 10.1016/j.compositesb.2012.01.066 　

ISSN： 1359-8368

eISSN： 1879-1069
Damage detection in holed composite laminates using an embedded FBG sensor Peer-reviewed

T. Okabe, S. Yashiro

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　43　(3)　388-397　2012/03

DOI： 10.1016/j.compositesa.2011.12.009 　

ISSN： 1359-835X
Damage simulation of high-velocity impact of CFRP laminates

A. Yoshimura, K. Nagakura, T. Okabe, H. Kusano, T. Ogasawara, S. Ogihara

27th Annual Technical Conference of the American Society for Composites 2012, Held Jointly with 15th Joint US-Japan Conference on Composite Materials and ASTM-D30 Meeting　853-861　2012
Numerical Analysis of Interfacial Bonding of Al-Si Particle and Mild Steel Substrate by Cold Spray Technique Using the SPH Method

MANAP Abreeza, OGAWA Kazuhiro, OKABE Tomonaga

JSMME　6　(3)　241-250　2012
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jmmp.6.241 　

ISSN： 1880-9871

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The deposition mechanism of the cold spray (CS) technique is investigated numerically using the smoothed particle hydrodynamics (SPH) method. The CS process is simulated by modeling the impact of a spherical Al-Si powder particle on a mild steel substrate. In this work, the adhesive interaction between the contacting surfaces is described by intersurface forces using the cohesive zone model. Simulation results show that successful bonding is achieved above the critical velocity, but rebound was observed at high velocities. This indicates that optimum deposition is achieved only within a certain range of particle velocities. The simulated deformed particle shape evolution and estimated critical velocity from other sources were compared and good agreement was obtained. The analyses demonstrate the feasibility of the presented SPH methodology and the adhesive interaction model for simulating the deformation behavior of CS particles.
Numerical simulation of microscopic damage and strength of fiber-reinforced plastic composites Peer-reviewed

T. Okabe, T. Motani, M. Nishikawa, M. Hashimoto

ADVANCED COMPOSITE MATERIALS　21　(2)　147-163　2012

DOI： 10.1080/09243046.2012.688495 　

ISSN： 0924-3046
A periodic unit-cell simulation of fiber arrangement dependence on the transverse tensile failure in unidirectional carbon fiber reinforced composites Peer-reviewed

T. Okabe, M. Nishikawa, H. Toyoshima

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES　48　(20)　2948-2959　2011/10

DOI： 10.1016/j.ijsolstr.2011.06.012 　

ISSN： 0020-7683
Flowability of unidirectionally arrayed chopped strands in compression molding Peer-reviewed

I. Taketa, T. Okabe, H. Matsutani, A. Kitano

COMPOSITES PART B-ENGINEERING　42　(6)　1764-1769　2011/09

DOI： 10.1016/j.compositesb.2011.01.021 　

ISSN： 1359-8368
Estimation of fatigue damage in holed composite laminates using an embedded FBG sensor Peer-reviewed

S. Yashiro, T. Okabe

Composites Part A　accepted　2011/09

DOI： 10.1016/j.compositesa.2011.08.021 　
柔軟体衝突を受けるCFRP積層板の損傷解析 Peer-reviewed

駒形大輔, 岡部朋永, 矢代茂樹, 吉村彰記, 小笠原俊夫

日本複合材料学会誌　37　(5)　掲載可-171　2011/09
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.37.164 　

ISSN： 0385-2563

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The application of composite laminates to fan blade of turbofan engine is demanded in order to reduce the fuel cost and the noise of aircrafts. Bird strike is one of the most important problems in the engineering application of fan blades. However, the soft-body impact damage on the composite laminates under high-velocity impact has not been clarified sufficiently due to their complexity. Therefore, it is necessary to understand the damage process of the composite materials under the soft-body impact. The current work presented the numerical simulation for soft-body impact using the SPH method to address the large deformation problem, and discussed the change of the failure mode of the composite laminates as a function of impact velocity. Especially, in order to simulate the realistic damage process in composite laminates, a novel approach for the separation of particles was introduced to the model. We confirmed that the numerical simulation was applicable in the soft-body impact problem by the agreement of contact pressure with the experimental results. Moreover, it was shown that the catastrophic failure of the composite laminates by the soft-body impact could be also predicted using this numerical simulation.
単糸分散炭素繊維による熱可塑性プレス基材の開発とその力学特性評価 Peer-reviewed

橋本雅弘, 岡部朋永, 西川雅章

日本複合材料学会誌　37　(4)　138-146　2011/07
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.37.138 　

ISSN： 0385-2563

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We have developed a novel stampable sheet composed of discontinuous carbon mono-fibers and thermoplastic resin for press molding of composite materials. This sheet enables in-plane random orientation and dispersion of carbon fibers in composites. Therefore, complexly shaped products, such as rib structures, are easily fabricated. Moreover, composites having superior mechanical properties can be obtained because the fiber length in composite is easily controlled to be long. This study addressed the effect of fiber length on strength and fracture modes of composites made of the sheet, using tensile tests and micromechanical analyses. To investigate the influential damage for the fracture mode, our analysis utilized Duva-Curtin model for fiber breakage. We incorporated this damage model into an equivalent inclusion model combined with the Mori-Tanaka theory to predict the tensile strength of the composites. The predicted results agreed well with those of the experiments when the fiber length and orientation in the composites were appropriately considered. Our analyses also indicated that 3 mm as the lower-limit fiber length in the composite, below which the damage mode is no longer dominated by fiber breakage and superior strength of the composites cannot be obtained.
Numerical Analysis of Interfacial Bonding of Aluminum Powder Particle and Aluminum Substrate by Cold Spray Technique using the SPH Method Peer-reviewed

Abreeza Manap, Kazuhiro Ogawa, Tomonaga Okabe

Proceedings of the JSME/ASME 2011 ICMP2011　2011/06
Damage simulation of CFRP laminates under high velocity projectile impact

A. Yoshimura, T. Okabe, M. Yamada, T. Ogasawara, Y. Tanabe

ICCM International Conferences on Composite Materials　2011
A Numerical Approach for Injection Molding of Short-Fiber-Reinforced Plastics Using a Particle Method Peer-reviewed

S. Yashiro, T. Okabe, K. Matsushima

ADVANCED COMPOSITE MATERIALS　20　(6)　503-517　2011

DOI： 10.1163/092430411X584423 　

ISSN： 0924-3046
High-velocity impact damage progress in CFRP laminates Peer-reviewed

E. Oka, K. Ogi, A. Yoshimura, T. Okabe

ICCM International Conferences on Composite Materials　2011
Computer simulation of cold sprayed deposition using smoothed particle hydrodynamics Peer-reviewed

Abreeza Manap, Kazuhiro Ogawa, Tomonaga Okabe

Procedia Engineering　10　1145-1150　2011

DOI： 10.1016/j.proeng.2011.04.190 　
Damage Growth Analysis in Particle-Reinforced Composite Using Cohesive Element Peer-reviewed

Akinori Yoshimura, Tomonaga Okabe

ADVANCED COMPOSITE MATERIALS　20　(6)　569-583　2011

DOI： 10.1163/156855111X610406 　

ISSN： 0924-3046
Enhancement of strength and uniformity in unidirectionally arrayed chopped strands with angled slits

I. Taketa, N. Sato, A. Kitano, M. Nishikawa, T. Okabe

Composites Part A: Applied Science and Manufacturing　41　(11)　1639-1646　2010/11
Publisher: Elsevier BV
DOI： 10.1016/j.compositesa.2010.07.010 　

ISSN： 1359-835X
Molecular mechanics simulation of the sliding behavior between nested walls in a multi-walled carbon nanotube Peer-reviewed

Yuan Li, Ning Hu, Go Yamamoto, Zhongchang Wang, Toshiyuki Hashida, Hiroshi Asanuma, Chensong Dong, Tomonaga Okabe, Masahiro Arai, Hisao Fukunaga

CARBON　48　(10)　2934-2940　2010/08

DOI： 10.1016/j.carbon.2010.04.031 　

ISSN： 0008-6223
Prediction of Tensile Strength of Unidirectional CFRP Composites Peer-reviewed

T. Okabe, K. Ishii, M. Nishikawa, N. Takeda

ADVANCED COMPOSITE MATERIALS　19　(3)　229-241　2010/06

DOI： 10.1163/092430409X12605406698273 　

ISSN： 0924-3046
Micromechanics on the Rate-dependent Fracture of Discontinuous Fiber-reinforced Plastics Peer-reviewed

T. Okabe, M. Nishikawa, N. Takeda

INTERNATIONAL JOURNAL OF DAMAGE MECHANICS　19　(3)　339-360　2010/04

DOI： 10.1177/1056789509103649 　

ISSN： 1056-7895

eISSN： 1530-7921
Experimental characterization of high-speed impact damage behavior in a three-dimensionally woven SiC/SiC composite Peer-reviewed

Keiji Ogi, Tomonaga Okabe, Manabu Takahashi, Shigeki Yashiro, Akinori Yoshimura, Toshio Ogasawara

Composites Part A: Applied Science and Manufacturing　41　(4)　489-498　2010/04

DOI： 10.1016/j.compositesa.2009.12.005 　

ISSN： 1359-835X
Effects of Vacancy Defects on the Interfacial Shear Strength of Carbon Nanotube Reinforced Polymer Composite Peer-reviewed

Sanjib Chandra Chowdhury, Tomonaga Okabe, Masaaki Nishikawa

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY　10　(2)　739-745　2010/02

DOI： 10.1166/jnn.2010.1879 　

ISSN： 1533-4880
Microstructure-dependent fatigue damage process in short fiber reinforced plastics Peer-reviewed

M. Nishikawa, T. Okabe

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES　47　(3-4)　398-406　2010/02

DOI： 10.1016/j.ijsolstr.2009.10.002 　

ISSN： 0020-7683
Fatigue Simulation for Ti/GFRP Laminates using Cohesive Elements

T. Yamaguchi, T. Okabe, T. Kosaka

Advanced Composite Materials　19　(2)　107-122　2010/01
Publisher: Informa UK Limited
DOI： 10.1163/092430410x490428 　

ISSN： 0924-3046

eISSN： 1568-5519
Numerical simulation of the effect of interfacial properties on the strength of unidirectional CFRP Peer-reviewed

Hiroki Toyoshima, Tomonaga Okabe, Masaaki Nishikawa, Masahiro Hashimoto

Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A　76　(767)　876-883　2010
Publisher: Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.76.876 　

ISSN： 0387-5008
繊維強化プラスチックの破壊モード特性に関するマイクロメカニクス Peer-reviewed

岡部朋永, 茂谷尊, 西川雅章, 橋本雅弘

日本複合材料学会誌　35　(6)　256-265　2009/11
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.35.256 　

ISSN： 0385-2563

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Discontinuous fiber reinforced plastics have superior productivity and formability in comparison with continuous fiber reinforced plastics. However, their strengths are remarkably low. Thus there is an urgent need to establish a fundamental model in order to improve the strength of discontinuous fiber reinforced plastics. In the present work, we utilized numerical simulations that consider the microscopic damage in the composite and incorporate an individual constitutive law of thermosetting resin or thermoplastic resin. The fundamental mechanism that affected the strength and failure of the composite was investigated when the fiber length and/or matrix properties were varied from continuous glass fiber reinforced plastics to discontinuous glass fiber reinforced plastics. Our results clarified two factors that cause the strength degradation of discontinuous fiber reinforced plastics. One is the low yield stress of thermoplastic resin, which is frequently used for the matrix of discontinuous fiber reinforced plastics. As the other factor, the final failure mode is changed from fiber breaking mode to matrix cracking mode in the case of the low fiber volume fraction of discontinuous glass fiber reinforced plastics. Moreover, we investigated the relationship between fiber length and strength of carbon fiber reinforced polypropylene and the effect of thermoplastic matrix properties depending on the loading rate as well.
Numerical Simulation for Predicting Fatigue Damage Progress in Notched CFRP Laminates by Using Cohesive Elements Peer-reviewed

Tomonaga OKABE, Shigeki YASHIRO

Journal of Solid Mechanics and Materials Engineering　11　(11)　1202-1211　2009/11
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jmmp.3.1202 　

ISSN： 1880-9871

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This study proposes the cohesive zone model (CZM) for predicting fatigue damage growth in notched carbon-fiber-reinforced composite plastic (CFRP) cross-ply laminates. In this model, damage growth in the fracture process of cohesive elements due to cyclic loading is represented by the conventional damage mechanics model. We preliminarily investigated whether this model can appropriately express fatigue damage growth for a circular crack embedded in isotropic solid material. This investigation demonstrated that this model could reproduce the results with the well-established fracture mechanics model plus the Paris' law by tuning adjustable parameters. We then numerically investigated the damage process in notched CFRP cross-ply laminates under tensile cyclic loading and compared the predicted damage patterns with those in experiments reported by Spearing et al. (Compos. Sci. Technol. 1992). The predicted damage patterns agreed with the experiment results, which exhibited the extension of multiple types of damage (e.g., splits, transverse cracks and delaminations) near the notches.
Fatigue simulation for titanium/CFRP hybrid laminates using cohesive elements Peer-reviewed

T. Yamaguchi, T. Okabe, S. Yashiro

COMPOSITES SCIENCE AND TECHNOLOGY　69　(11-12)　1968-1973　2009/09

DOI： 10.1016/j.compscitech.2009.04.020 　

ISSN： 0266-3538
Strength improvement in unidirectional arrayed chopped strands with interlaminar toughening Peer-reviewed

I. Taketa, T. Okabe, A. Kitano

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　40　(8)　1174-1178　2009/08

DOI： 10.1016/j.compositesa.2009.05.006 　

ISSN： 1359-835X
結合力要素を用いたTi/GFRP 積層板の疲労損傷進展シミュレーション Peer-reviewed

山口拓真, 岡部朋永, 高坂達郎

日本複合材料学会誌　35　(4)　141-148　2009/07

DOI： 10.6089/jscm.35.141 　
一方向不連続繊維CFRPの微視損傷形態と強度特性に関する周期セルシミュレーション Peer-reviewed

西川雅章, 岡部朋永, 武田展雄

日本複合材料学会誌　35　(4)　149-156　2009/07
Publisher: The Japan Society for Composite Materials
DOI： 10.6089/jscm.35.149 　

ISSN： 0385-2563

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This paper investigated the damage transition mechanism between the fiber-breakage mode and the fiber-avoiding crack mode when the fiber-length is reduced in the unidirectional discontinuous carbon-fiber-reinforced-plastics (CFRP) composites. The critical fiber-length for the transition is a key parameter for the manufacturing of flexible and high-strength CFRP composites with thermoset resin, because below this limit, we cannot take full advantage of the superior strength properties of fibers. For this discussion, we presented a numerical model for the microscopic damage and fracture of unidirectional discontinuous fiber-reinforced plastics. The model addressed the microscopic damage generated in these composites; the matrix cracking with continuum damage mechanics model and the fiber breakage with the Weibull model for fiber strengths. With this numerical model, the damage transition behavior was discussed when the fiber length was varied. The comparison revealed that the length of discontinuous fibers in composites influences the formation and growth of the cluster of fiber-end damage, which causes the damage mode transition. Since the composite strength is significantly reduced below the critical fiber-length for the transition to fiber-avoiding crack mode, we should understand the damage mode transition appropriately with the analysis on the mechanism of the cluster growth of fiber-end damage.
結合力要素を用いた分散形複合材料の損傷進展解析 Peer-reviewed

吉村彰記, 岡部朋永

日本複合材料学会誌　35　(3)　112-119　2009/05
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.35.112 　

ISSN： 0385-2563

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The present paper proposes a simple numerical analytical method for crack extension simulation in the particle reinforced composite, and reveals the effect of crack extension on the macroscopic material properties of the particle reinforced composite. This numerical method is based on the homogenization method and Dugdale-type cohesive elements. In the present paper, we first present the formulation of the numerical model. We then verify the validity of the numerical model by comparing the simulated crack extension with the linear fracture mechanics. Finally we perform the crack extension simulation for the composite reinforced by spherical particle. We consider the inclusion crack and interfacial crack between inclusion and matrix. The analytical results reveal that the inclusion crack extends always unstably regardless of the size of initial crack, and the evolution of inclusion crack sharply decreases the apparent Young's modulus in the perpendicular direction to the crack surface and shear modulus in the out-of-plane direction of crack surface. The results also demonstrated that the interfacial crack always extends stably regardless of the size of initial crack, and the evolution of interfacial crack gradually degrades the stiffness in all direction.
Crack growth behaviour of open-hole specimens of Ti/GFRP laminates under fatigue loading Invited Peer-reviewed

Hayato Nakatani, Tatsuro Kosaka, Katsuhiko Osaka, Yoshihiro Sawada, Tomonaga Okabe

Zairyo/Journal of the Society of Materials Science, Japan　58　(5)　389-395　2009/05

DOI： 10.2472/jsms.58.389 　

ISSN： 0514-5163
Prediction of fatigue damage in holed composite laminates with embedded FBG sensors

A. Kadoya, S. Yashiro, T. Okabe

ICCM International Conferences on Composite Materials　2009
Publisher: International Committee on Composite Materials
Estimating fatigue damage in a CFRP laminate with a hole using an embedded FBG sensor

S. Yashiro, T. Okabe

12th International Conference on Fracture 2009, ICF-12　8　6160-6169　2009
Periodic-Cell Simulations for the Microscopic Damage and Strength Properties of Discontinuous Carbon Fiber-Reinforced Plastic Composites

M. Nishikawa, T. Okabe, N. Takeda

Advanced Composite Materials　18　(1)　77-93　2009/01/01
Publisher: Informa UK Limited
DOI： 10.1163/156855108x399974 　

ISSN： 0924-3046

eISSN： 1568-5519
Effect of the Microstructure on the Fracture Mode of Short-Fiber Reinforced Plastic Composites

Masaaki NISHIKAWA, Tomonaga OKABE, Nobuo TAKEDA

Journal of Solid Mechanics and Materials Engineering　3　(8)　998-1009　2009
Publisher: Japan Society of Mechanical Engineers
DOI： 10.1299/jmmp.3.998 　

ISSN： 1880-9871

eISSN： 1880-9871

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A numerical simulation was presented to discuss the microscopic damage and its influence on the strength and energy-absorbing capability of short-fiber reinforced plastic composites. The dominant damage includes matrix crack and/or interfacial debonding, when the fibers are shorter than the critical length for fiber breakage. The simulation addressed the matrix crack with a continuum damage mechanics (CDM) model and the interfacial debonding with an embedded process zone (EPZ) model. Fictitious free-edge effects on the fracture modes were successfully eliminated with the periodic-cell simulation. The advantage of our simulation was pointed out by demonstrating that the simulation with edge effects significantly overestimates the dissipative energy of the composites. We then investigated the effect of the material microstructure on the fracture modes in the composites. The simulated results clarified that the inter-fiber distance affects the breaking strain of the composites and the fiber-orientation angle affects the position of the damage initiation. These factors influence the strength and energy-absorbing capability of short fiber-reinforced composites.
Numerical Prediction of Fatigue Damage Progress in Holed CFRP Laminates Using Cohesive Elements

Shigeki YASHIRO, Tomonaga OKABE

Journal of Solid Mechanics and Materials Engineering　3　(11)　1212-1221　2009
Publisher: Japan Society of Mechanical Engineers
DOI： 10.1299/jmmp.3.1212 　

eISSN： 1880-9871
A characterization study on high speed impact damage in CFRP laminates Peer-reviewed

K. Ogi, S. Yashiro, T. Okabe, A. Yoshimura, T. Ogasawara

ICCM International Conferences on Composite Materials　2009
GLS strength prediction of glass-fiber-reinforced polypropylene Peer-reviewed

T. Okabe, M. Nishikawa

JOURNAL OF MATERIALS SCIENCE　44　(1)　331-334　2009/01

DOI： 10.1007/s10853-008-3144-6 　

ISSN： 0022-2461
Effect of cross-links on the pullout of carbon nanotubes from amorphous polymer Peer-reviewed

M. Nishikawa, T. Okabe, T. Honda

JOURNAL OF MATERIALS SCIENCE　44　(1)　339-341　2009/01

DOI： 10.1007/s10853-008-3127-7 　

ISSN： 0022-2461
Numerical simulation for predicting fatigue damage progress in notched cfrp cross-ply laminates by using cohesive elements Peer-reviewed

Tomonaga Okabe, Shigeki Yashiro

Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A　75　(751)　304-309　2009
Publisher: Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.75.304 　

ISSN： 0387-5008
Numerical prediction of fatigue damage progress in holed cfrp laminates using cohesive elements Peer-reviewed

Shigeki Yashiro, Tomonaga Okabe

Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A　75　(751)　310-315　2009
Publisher: Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.75.310 　

ISSN： 0387-5008
Effect of the microstructure on the fracture mode of short-fiber reinforced plastic composites Peer-reviewed

Masaaki Nishikawa, Tomonaga Okabe, Nobuo Takeda

Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A　75　(751)　287-295　2009
Publisher: Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.75.287 　

ISSN： 0387-5008
Estimation of statistical strength distribution of Carborundum polycrystalline SiC fiber using the single fiber composite with consideration of the matrix hardening Peer-reviewed

T. Okabe, M. Nishikawa, W. A. Curtin

COMPOSITES SCIENCE AND TECHNOLOGY　68　(15-16)　3067-3072　2008/12

DOI： 10.1016/j.compscitech.2008.06.026 　

ISSN： 0266-3538
A new compression-molding approach using unidirectionally arrayed chopped strands Peer-reviewed

I. Taketa, T. Okabe, A. Kitano

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　39　(12)　1884-1890　2008/12

DOI： 10.1016/j.compositesa.2008.09.012 　

ISSN： 1359-835X
A new cohesive model for simulating delamination propagation in composite laminates under transverse loads Peer-reviewed

N. Hu, Y. Zemba, T. Okabe, C. Yan, H. Fukunaga, A. M. Elmarakbi

MECHANICS OF MATERIALS　40　(11)　920-935　2008/11

DOI： 10.1016/j.mechmat.2008.05.003 　

ISSN： 0167-6636

eISSN： 1872-7743
Numerical modeling of progressive damage in fiber reinforced plastic cross-ply laminates Invited Peer-reviewed

T. Okabe, M. Nishikawa, N. Takeda

COMPOSITES SCIENCE AND TECHNOLOGY　68　(10-11)　2282-2289　2008/08

DOI： 10.1016/j.compscitech.2008.04.021 　

ISSN： 0266-3538
Micromechanical modeling of the microbond test to quantify the interfacial properties of fiber-reinforced composites Peer-reviewed

M. Nishikawa, T. Okabe, K. Hemmi, N. Takeda

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES　45　(14-15)　4098-4113　2008/07

DOI： 10.1016/j.ijsolstr.2008.02.021 　

ISSN： 0020-7683
Micromechanics of the fragmentation process in single-fiber composites Peer-reviewed

M. Nishikawa, T. Okabe, N. Takeda, W. A. Curtin

MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING　16　(5)　055009　2008/07

DOI： 10.1088/0965-0393/16/5/055009 　

ISSN： 0965-0393
Determination of interface properties from experiments on the fragmentation process in single-fiber composites Peer-reviewed

M. Nishikawa, T. Okabe, N. Takeda

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　480　(1-2)　549-557　2008/05

DOI： 10.1016/j.msea.2007.07.067 　

ISSN： 0921-5093
The influence of the interfaces on the fracture strain of fiber reinforced ceramic composites Peer-reviewed

Koji Yamashita, Tomonaga Okabe

Zairyo/Journal of the Society of Materials Science, Japan　57　(5)　448-453　2008/05

DOI： 10.2472/jsms.57.448 　

ISSN： 0514-5163
Nondestructive evaluation of holed CFRP laminates by a new technique to visualize propagation of ultrasonic waves Peer-reviewed

S.Yashiro, J.Takatsubo, N.Toyama, T.Okabe, N.Takeda

Journal of Solid Mechanics and Materials Engineering　2　(3)　333-341　2008/03
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jmmp.2.333 　

ISSN： 1880-9871

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This study investigated damage detection in holed CFRP laminates by using a newly developed technique for visualizing ultrasonic waves. This technique provided a moving diagram of propagating waves with non-contact scanning by a pulsed laser. Its measurement scheme overcame the difficulties of sensitivity in conventional methods and enabled us to observe ultrasonic waves on CFRP laminates. We observed two types of ultrasonic waves propagating on the CFRP laminate in the measured snapshots. These waves were identified as the S₀ and the A₀ Lamb modes by the dispersion curves, confirming the validity of the visualization technique for composite laminates. Furthermore, ply cracks and delamination, as well as the damage during manufacturing, were observed near the hole in the loaded specimens, and we successfully visualized the Lamb waves scattered by the delamination. The region of wave scattering agreed with the damage observed by soft X-ray radiography. These inspection results demonstrated the usefulness of the visualization technique in inspecting composite laminates.
Low-velocity impact and fatigue response of Ti/GFRP laminates

Hayato Nakatani, Tatsuro Kosaka, Jun Oki, Katsuhiko Osaka, Yoshihiro Sawada, Tomonaga Okabe

Progress of Composites 2008 in Asia and Australasia - Proceedings of the 6th Asian-Australasian Conference on Composite Materials, ACCM 2008　168-171　2008
Damage extension simulation in particle reinforced composite by using cohesive element

Akinori Yoshimura, Tomonaga Okabe

Advanced Composites for Efficiency and Environment - The US-Japan Conference on Composite Materials 2008, US-Japan 2008　2008
Impact and fatigue damages of Ti/GFRP laminates

Hayato Nakatani, Tatsuro Kosaka, Jun Oki, Katsuhiko Osaka, Yoshihiro Sawada, Tomonaga Okabe

Advanced Composites for Efficiency and Environment - The US-Japan Conference on Composite Materials 2008, US-Japan 2008　2008
Effect of thermal shock on ballistic impact damage in ceramic matrix composites Peer-reviewed

Keiji Ogi, Shigeki Yashiro, Tomonaga Okabe, Akinori Yoshimura, Toshio Ogasawara

Advanced Composites for Efficiency and Environment - The US-Japan Conference on Composite Materials 2008, US-Japan 2008　2008
一方向CFRP 複合材料の引張強度予測 Peer-reviewed

岡部朋永, 石井健介, 西川雅章, 武田展雄

日本複合材料学会誌　33　(6)　205-212　2007/11

DOI： 10.6089/jscm.33.205 　
Prediction of buckling characteristics of carbon nanotubes Peer-reviewed

N. Hu, K. Nunoya, D. Pan, T. Okabe, H. Fukunaga

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES　44　(20)　6535-6550　2007/10

DOI： 10.1016/j.ijsolstr.2007.02.043 　

ISSN： 0020-7683

eISSN： 1879-2146
結合力要素を用いた単繊維複合材料中の微視的損傷に関する有限要素解析 Peer-reviewed

西川雅章, 岡部朋永, 武田展雄

日本複合材料学会誌　33　(5)　170-177　2007/09
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.33.170 　

ISSN： 0385-2563

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This paper numerically investigates the microscopic damage in a single-fiber composite (SFC). A cohesive zone model (CZM) is presented to investigate the typical microscopic damages observed in the SFC. The CZM clarifies that the behavior of interfacial debonding, which influences significantly on the axial stress recovery of the embedded fiber, is greatly affected by matrix plasticity and cracking. We conduct a Monte-Carlo simulation for the fragmentation of the embedded fiber. The Monte-Carlo simulation demonstrates that these microscopic damages are important factors in the fragmentation of the embedded fiber. These simulated results are also compared with analytical models. These discussions reveal that the fragmentation process in an embedded fiber is controlled by the cohesive parameters of the fiber/matrix interface.
Numerical simulation of interlaminar damage propagation in CFRP cross-ply laminates under transverse loading Peer-reviewed

Masaaki Nishikawa, Tomonaga Okabe, Nobuo Takeda

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES　44　(10)　3101-3113　2007/05

DOI： 10.1016/j.ijsolstr.2006.09.007 　

ISSN： 0020-7683

eISSN： 1879-2146
Damage identification in a holed CFRP laminate using a chirped fiber Bragg grating sensor Peer-reviewed

S. Yashiro, T. Okabe, N. Takeda

COMPOSITES SCIENCE AND TECHNOLOGY　67　(2)　286-295　2007/02

DOI： 10.1016/j.compscitech.2006.08.004 　

ISSN： 0266-3538
Influence of Matrix Plasticity on Local Stress Concentrations Near Loaded Fiber Breaks

Sayaka OKABE, Nobutada OHNO, Tomonaga OKABE

Journal of Solid Mechanics and Materials Engineering　1　(1)　102-113　2007
Publisher: Japan Society of Mechanical Engineers
DOI： 10.1299/jmmp.1.102 　

ISSN： 1880-9871

eISSN： 1880-9871

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This study deals with analytically evaluating the stress concentrations near loaded and initial fiber breaks in unidirectional composites with matrix yielding and interfacial sliding. To this end, by performing a detailed 3D finite element analysis, it is demonstrated that significant nonproportional straining occurs in the matrix near loaded fiber breaks in contrast to initial breaks, and that such nonproportional straining induces almost elastic developments of matrix shear stress near loaded fiber breaks. Then, the 3D shear-lag closed-form solution derived by the present authors, which is modified so as to be effective over a wide range of fiber volume fractions, is shown to be applicable to loaded, as well as initial, fiber breaks, provided the matrix shear modulus in the solution is prescribed by taking account of the nonproportional straining. It is thus demonstrated that the nonproportional straining in the matrix can lower the stress concentrations near loaded fiber breaks in the presence of matrix yielding.
Numerical study for identifying damage in open-hole composites with embedded FBG sensors and its application to experiment results

S. Yashiro, K. Murai, T. Okabe, N. Takeda

Advanced Composite Materials　16　(2)　115-134　2007/01
Publisher: Informa UK Limited
DOI： 10.1163/156855107780918946 　

ISSN： 0924-3046

eISSN： 1568-5519
Monitoring damage in holed CFRP laminates using embedded chirped FBG sensors Peer-reviewed

S. Yashiro, T. Okabe, N. Toyama, N. Takeda

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES　44　(2)　603-613　2007/01

DOI： 10.1016/j.ijsolstr.2006.05.004 　

ISSN： 0020-7683
Computer simulation of carbon nanotube pull-out from polymer by the molecular dynamics method Peer-reviewed

S. C. Chowdhury, T. Okabe

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　38　(3)　747-754　2007

DOI： 10.1016/j.compositesa.2006.09.011 　

ISSN： 1359-835X
超音波伝ぱの可視化による有孔CFRP積層板中の層間はく離検出 Peer-reviewed

矢代茂樹, 高坪純治, 遠山暢之, 岡部朋永, 武田展雄

日本機械学会論文集(A編)　72　(724)　1882-1887　2006/12
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.72.1882 　

ISSN： 0387-5008

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This study applied a newly developed technique for visualizing ultrasonic waves to damage detection in holed CFRP laminates. This technique provided a moving diagram of propagating waves with the use of a pulsed laser for generation scanning a specimen and a fixed transducer for reception. Multiple types of damage (i.e. splits, transverse cracks and delamination), as well as delamination during processing, were observed near the hole in the loaded specimens by soft X-ray radiography. The specimens were then inspected by visualizing the propagation of ultrasonic waves. The S₀ and A₀ Lamb modes were visualized on the CFRP cross-ply laminate. Furthermore, we successfully detected delamination near the hole through the appearance of scattered waves. These inspection results agreed well with that by soft X-ray radiography, and consequently confirmed the usefulness of the technique for visualizing ultrasonic waves in inspection for composite laminates.
埋め込みFBGセンサを用いた有孔積層板の損傷同定に関する数値解析および実験結果への適用 Peer-reviewed

矢代茂樹, 村井一恵, 岡部朋永, 武田展雄

日本複合材料学会誌　32　(5)　208-217　2006/10
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.32.208 　

ISSN： 0385-2563

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This study proposes two new approaches for estimating the damage patterns in a holed CFRP cross-ply laminate using an embedded fiber Bragg grating (FBG) sensor. It was experimentally confirmed that the reflection spectrum from the embedded FBG sensor drastically changed as the damage near the hole, i.e. splits, transverse cracks and delamination, extended. The damage patterns were predicted using forward analysis (a damage analysis and an optical analysis) with strain estimation and the proposed damage-identification method as well as the forward analysis only. The forward analysis with the strain estimation then to be yielding the best prediction from the viewpoint of the accuracy in estimating the damage pattern and the computational efficiency. Furthermore, the proposed damage identification achieved a significant reduction in the computational time and the equivalent accuracy compared to the conventional identification procedure, adopting the damage pattern obtained by the damage analysis as the initial estimation.
縫合CFRP積層材の引張負荷下における損傷進展挙動 Peer-reviewed

吉村彰記, 矢代茂樹, 岡部朋永, 武田展雄

日本複合材料学会誌　32　(5)　198-207　2006/10
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.32.198 　

ISSN： 0385-2563

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This study investigated the tensile damage progress in stitched laminates experimentally and numerically. Particularly, the effects of stitching on the damage progress was focused. First, it was experimentally confirmed that ply cracks and delamination appeared under loading regardless of the stitching. We then performed damage extension simulation for stitched laminate using a layer. wise finite element model with beam elements as stitch threads, in which the damage (ply cracks and delamination) was represented by cohesive elements. The detailed comparison between the observa-tion and the simulated results confirmed that stitching has few effects on the onset and the accumula-tion of the ply cracks. Furthermore, we demonstrated that the stitch threads significantly suppresses the extension of the delamination.
面外負荷を受けるCFRP直交積層板の層間はく離進展シミュレーション Peer-reviewed

西川雅章, 岡部朋永, 武田展雄

日本機械学会論文集(A編)　72　(720)　1246-1253　2006/08
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.72.1246 　

ISSN： 0387-5008

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This paper proposes a numerical simulation for the interlaminar damage propagation in FRP laminates under transverse loading, using finite element method. First, we conduct drop-weight impact tests on CFRP cross-ply laminates. A ply crack was generated at the center of the lowermost ply, and then a peanut-shaped interlaminar delamination was propagated in 90/0 ply interface. Based on these experimental observations, we present a numerical simulation for the interlaminar damage propagation, using cohenive zone model to address the energy-based criterion for damage propagation. Moreover, this simulation addresses interlaminar delamination with high accuracy by locating a fine mesh region near the damage process zone, while its computational efficiency is kept by the use of an automatic mesh generation. The simulated results of interlaminar delamination agree well with the experimental results. Moreover, we showed that the computational cost for the simulation is dramatically reduced by the proposed method.
FRP直交積層板における損傷進展を対象とした数値シミュレーション Peer-reviewed

岡部朋永, 西川雅章, 武田展雄

日本機械学会論文集(A編)　72　(720)　1254-1261　2006/08
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.72.1254 　

ISSN： 0387-5008

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This paper proposes a numerical simulation based on finite element analysis (FEA) for the tensile damage and final failure in FRP cross-ply larninates. The simulation addresses multiple damage (transverse cracks, interlaminar delaminations, fiber breaks) simultaneously for the tensile failure process of cross-ply laminates. Transverse cracks are addressed as initial damage in 90°ply of cross-ply laminates by the cohenive zone model (CZM). The interlaminar delamination at the tips of those transverse cracks are addressed by aligning cohesive elements between 0°ply and 90°ply. Moreover, the fiber breaks in 0°ply are addressed by truss elements, which represent fibers in 0°ply. The simulated results of tensile damage evolution agree well with the experimental results. Especially, our simulation could reproduce a staggered pattern of transverse cracks and interlaminar delarninations at the tips of transverse cracks in [90/0] s cross-ply laminates.
Estimation of the damage patterns in notched laminates with embedded FBG sensors Invited Peer-reviewed

N Takeda, S Yashiro, T Okabe

COMPOSITES SCIENCE AND TECHNOLOGY　66　(5)　684-693　2006/05

DOI： 10.1016/j.compscitech.2005.07.039 　

ISSN： 0266-3538
Effect of matrix hardening on the tensile strength of alumina fiber-reinforced aluminum matrix composites Peer-reviewed

T Okabe, M Nishikawa, N Takeda, H Sekine

ACTA MATERIALIA　54　(9)　2557-2566　2006/05

DOI： 10.1016/j.actamat.2006.01.044 　

ISSN： 1359-6454
Structural health monitoring of cracked aircraft panels repaired with bonded patches using fiber Bragg grating sensors Peer-reviewed

H Sekine, SE Fujimoto, T Okabe, N Takeda, T Yokobori

APPLIED COMPOSITE MATERIALS　13　(2)　87-98　2006/03

DOI： 10.1007/s10443-006-9011-1 　

ISSN： 0929-189X
Monitoring of interfacial crack growth of stiffened panel with embedded fiber Bragg grating sensors

T. Okabe, H. Sekine

Proceedings of the 3rd European Workshop - Structural Health Monitoring 2006　236-243　2006
506 Damage identification in a holed CFRP laminate under stress-free condition using an embedded chirped-FBG sensor

YASHIRO Shigeki, OKABE Tomonaga, TAKEDA Nobuo

Proceedings of the 1992 Annual Meeting of JSME/MMD　2006　269-270　2006
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2006.0_269 　
A strength reliability model of unidirectional fiber-reinforced ceramic matrix composites by Markov process Peer-reviewed

Koichi Goda, Tomonaga Okabe, Nobuo Takeda

ADVANCED COMPOSITE MATERIALS　15　(3)　263-285　2006

DOI： 10.1163/156855106778392089 　

ISSN： 0924-3046
Stiffness evaluation and damage identification in composite beam under tension using Lamb waves Invited Peer-reviewed

N Toyama, S Yashiro, J Takatsubo, T Okabe

ACTA MATERIALIA　53　(16)　4389-4397　2005/09

DOI： 10.1016/j.actamat.2005.05.043 　

ISSN： 1359-6454
[90/0]sGFRP直交積層材の損傷進展挙動 Peer-reviewed

野田淳二, 岡部朋永, 武田展雄, 清水真佐男

日本複合材料学会誌　31　(3)　112-119　2005/05
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.31.112 　

ISSN： 0385-2563

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We investigated the damage process of GFRP cross-ply laminates which have outer-ply 90° plies (e.g. [90/0]_s). While [0/90]_s laminates form symmetric cracks, staggered cracks occur in [90/0]_s laminates. To simulate the failure process of [90/0]_s laminates, we proposed a numerical model based on the finite element method. In this model, we used cohesive elements to simulate the occurrence and the propagation of ply cracks and delaminations. We found that simulated results agreed well with the experimental data. We confirmed the validity of the numerical model for the damage process of [90/0]_s laminates.
Numerical method for failure simulation of unidirectional fiber-reinforced composites with spring element model Peer-reviewed

T Okabe, H Sekine, K Ishii, M Nishikawa, N Takeda

COMPOSITES SCIENCE AND TECHNOLOGY　65　(6)　921-933　2005/05

DOI： 10.1016/j.compscitech.2004.10.030 　

ISSN： 0266-3538
個々の要素損傷をマルコフ過程で表現したセラミックス基繊維強化複合材料の強度信頼性モデル Peer-reviewed

合田公一, 岡部朋永

日本機械学会論文集（A編）　71　(706)　919-927　2005/05
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.71.919 　

ISSN： 0387-5008

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A new strength reliability model of fiber-reinforced ceramic matrix composites is proposed, in which both the processes of multiple matrix cracks and fiber breaks are taken into account, based on Markov process model. It is assumed that damages due to the cracks and breaks accumulate discretely and independently in the composite in accordance with change in transition probabilities with an increase in matrix and fiber stresses, respectively. Both the processes were finally described by simultaneous ordinary different equations, and the probabilities being in states were solved numerically. The results show that, first, the proposed reliability model can predict means and variances in fiber and matrix stresses, with an increase in strain. Next, this model predicts well strength data, obtained experimentally from various ceramic matrix composites. In addition, when the composite stress is subject to the mixed rule, the mean and variance in the composite stress can be obtained from the first-order second-moment method. The analyzed stress-strain curve of the composite can be simulated well, as been in actual behavior. According to this modeling, combination of large scatter matrix strength to small scatter fiber strength, brings an increase in strength of the composites.
切欠底の疲労強度の確率的変動に注目した高強度鋼切欠材の疲労強度特性に関する研究 Peer-reviewed

深沢剣吾, 渋谷正樹, 岡部朋永, 清水真佐男, 川嵜一博

日本機械学会論文集（A編）　71　(704)　623-629　2005/04
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.71.623 　

ISSN： 0387-5008

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This study was conducted to examine how and why a difference of fatigue strengths between unnotched and notched specimens, in terms of maximum stress amplitude at the notch bottom, depends on the change of hardness level in steel. As a result, the local fatigue strength of the notch bottom in the notched specimen became higher than that of the un-notched one with increase of notch sharpness and this was remarkable in high strength steel. This is because the transition of the fatigue fracture mode occurs from a slip induced crack initiation mode to a defect controled one with increasing hardness in steel. In addition, using a new experimental approach combined with a simulation technique based on the concept of risk competition of defects, a computer simulation was conducted on an effect of inclusion on the local fatigue strength at the notch bottom of high strength steel. It was clarified that the difference of fatigue strength between notched and un-notched specimens in high strength steel was caused by the statistical variation of the largest inclusion size contained in the critical volume at the notch bottom.
A new approach to predicting multiple damage states in composite laminates with embedded FBG sensors Peer-reviewed

S Yashiro, N Takeda, T Okabe, H Sekine

COMPOSITES SCIENCE AND TECHNOLOGY　65　(3-4)　659-667　2005/03

DOI： 10.1016/j.compscitech.2004.09.022 　

ISSN： 0266-3538
「複合材料のマイクロメカニクス・損傷解析の最新動向」の連載を始めるにあたって

岡部朋永

日本複合材料学会誌 = Journal of the Japan Society for Composite Materials　31　(1)　5-5　2005/01/15
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.31.5 　

ISSN： 0385-2563
1743 Influence of matrix plasticity on local stress concentrations near loaded fiber breaks

OKABE Sayaka, OHNO Nobutada, OKABE Tomonaga

The proceedings of the JSME annual meeting　2005　389-390　2005
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmemecjo.2005.1.0_389 　

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In this study, stress concentrations near loaded and initial fiber breaks are analyzed for unidirectional composites with matrix yielding and interfacial sliding. To this end, by performing detailed 3D finite element analysis, it is demonstrated that significant nonproportional stressing occurs in the matrix near loaded fiber breaks in contrast to initial breaks, and that the nonproportional stressing induces almost elastic shear deformation in the matrix outside the first nearest-neighbor fibers of loaded fiber breaks. Then, the 3D shear-lag analytical solution derived by the present authors is modified to be applicable to low fiber volume fractions and is employed to discuss how the nonproportional stressing in the matrix influences the stress concentrations near loaded fiber breaks. The 3D analytical solution is shown to be applicable to loaded, as well as initial, fiber breaks, if the matrix shear modulus in the solution is prescribed by taking account of the nonproportional stressing. It is thus concluded that the nonproportional stressing in the matrix may considerably lower the stress concentrations near loaded fiber breaks.
負荷後繊維破断による局所応力集中に及ぼす母材の塑性変形の影響 Invited Peer-reviewed

岡部沙也佳, 大野信忠, 岡部朋永

日本機械学会論文集（A編）　71　(710)　1340-1347　2005
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.71.1340 　

ISSN： 0387-5008

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In this study, stress concentrations near loaded and initial fiber breaks are analyzed for unidirectional composites with matrix yielding and interfacial sliding. To this end, by performing detailed 3D finite element analysis, it is demonstrated that significant nonproportional stressing occurs in the matrix near loaded fiber breaks in contrast to initial breaks, and that the nonproportional stressing induces almost elastic shear deformation in the matrix outside the first nearest-neighbor fibers of loaded fiber breaks. Then, the 3D shear-lag analytical solution derived by the present authors is modified to be applicable to low fiber volume fractions and is employed to dicuss how the nonproportional stressing in the matrix influences the stress concentrations near loaded fiber breaks. The 3D analytical solution is shown to be applicable to loaded, as well as initial, fiber breaks, if the matrix shear modulus in the solution is prescribed by taking account of the nonproportional stressing. It is thus concluded that the nonproportional stressing in the matrix may considerably lower the stress concentrations near loaded fiber breaks.
Effects of tensile strain and transverse cracks on Lamb-wave velocity in cross-ply FRP laminates Peer-reviewed

N Toyama, T Okabe

JOURNAL OF MATERIALS SCIENCE　39　(24)　7365-7367　2004/12

DOI： 10.1023/B:JMSC.0000048752.28719.3a 　

ISSN： 0022-2461
Characterization of tensile damage and strength in GFRP cross-ply laminates Peer-reviewed

T Okabe, H Sekine, J Noda, M Nishikawa, N Takeda

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　383　(2)　381-389　2004/10

DOI： 10.1016/j.msea.2004.05.060 　

ISSN： 0921-5093
GFRP直交積層材の損傷進展挙動 Peer-reviewed

野田淳二, 岡部朋永, 武田展雄, 清水真佐男

日本機械学会論文集（A編）　70　(698)　1364-1369　2004/10
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.70.1364 　

ISSN： 0387-5008

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The failure process of GFRP cross-ply laminates (up to final failure) is studied. In situ observations of ply cracks during tensile tests are carried out to obtain the damage process of the cross-ply laminates. Based on these experimental results, we propose a numerical simulation to investigate the damage process. In the present model, a ply crack is expressed by the cohesive element. Consequently, the stress-strain relationship and the density of ply cracks are simulated by choosing the strength and the critical energy release rate of the cohesive element.
Stress concentrations near a fiber break in unidirectional composites with interfacial slip and matrix yielding Peer-reviewed

N Ohno, S Okabe, T Okabe

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES　41　(16-17)　4263-4277　2004/08

DOI： 10.1016/j.ijsolstr.2004.03.018 　

ISSN： 0020-7683
繊維破断を有する一方向長繊維強化複合材における局所的応力集中に対する解析解 Peer-reviewed

岡部沙也佳, 大野信忠, 岡部朋永

日本機械学会論文集（A編）　70　(691)　464-471　2004/03
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.70.464 　

ISSN： 0387-5008

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In this study, two analytical solutions are obtained for the stress profiles in the fibers neighboring to a broken fiber in unidirectional composites. To this end, a hexagonal fiber array model containing a broken fiber is considered to derive differential equations based on a shear lag concept, in which matrix plasticity is simply taken into account by means of plastic secant modulus. It is thus shown that all affecting material parameters are consolidated into a characteristic value if a bilinear stress profile prevails in the broken fiber due to significant interfacial sliding. The governing equations are then analytically solved by assuming negligible stress concentrations in the second and third nearest neighbor fibers, respectively. The resulting two analysical solutions are verified by solving more generally the governing equations using a finite difference method. The solutions are, moreover, compared with 3D finite element analysis published in recent literatures, leading to the soundness of the present solutions and the effectiveness of the characteristic value.
Analytical solutions for stress concentration near a fiber break: evaluation based on FEM

OKABE Sayaka, SUGA Hirofumi, OHNO Nobutada, OKABE Tomonaga

Proceedings of the 1992 Annual Meeting of JSME/MMD　2004　385-386　2004
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2004.0_385 　
A new approach to identify multiple damage state around stress concentrated regions in CFRP laminates with embedded FBG sensors

OKABE Tomonaga, SEKINE Hideki, YASHIRO Shigeki, TAKEDA Nobuo

Proceedings of the 1992 Annual Meeting of JSME/MMD　2004　283-284　2004
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2004.0_283 　

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This study proposes a new approach to identify the multiple damage state around a circular hole in a composite laminate using embedded Fiber Bragg Grating (FBG) sensors. FBG sensors are sensitive to a non-uniform strain distribution along their longitudinal direction, and the effects appear in the power spectrum of the reflected light from the gage section. In this study, we propose a numerical model to predict both the damage process of the laminate and the change of the reflection spectrum from the FBG sensor. Then, we represent the damage state by some design variables, and estimate the damage state solving the mathematical optimization problem about the reflection spectrum. We found that the identified damage state from the input spectrum agreed well with the damage state corresponding to the input spectrum.
Analytical solutions for stress concentrations near a fiber break in unidirectional elastoplastic composites Peer-reviewed

S Okabe, N Ohno, T Okabe

ADVANCES IN ENGINEERING PLASTICITY AND ITS APPLICATIONS, PTS 1 AND 2　274-276　1005-1010　2004

ISSN： 1013-9826
Quantitative damage detection in CFRP composites: coupled mechanical and electrical models Peer-reviewed

Z Xia, T Okabe, JB Park, WA Curtin, N Takeda

COMPOSITES SCIENCE AND TECHNOLOGY　63　(10)　1411-1422　2003/08

DOI： 10.1016/S0266-3538903)00083-6 　

ISSN： 0266-3538
Quantitative damage detection in cross-ply laminates using Lamb wave method Peer-reviewed

N Toyama, J Noda, T Okabe

COMPOSITES SCIENCE AND TECHNOLOGY　63　(10)　1473-1479　2003/08

DOI： 10.1016/S0266-3538(03)00163-5 　

ISSN： 0266-3538
Lamb wave evaluation and localization of transverse cracks in cross-ply laminates Peer-reviewed

N. Toyama, T. Okabe, N. Takeda

Journal of Materials Science　38　(8)　1765-1771　2003/04/15

DOI： 10.1023/A:1023288012638 　

ISSN： 0022-2461
トランスバースクラックを有するCFRP直交積層板の引張強度 Peer-reviewed

野田淳二, 岡部朋永, 武田展雄, 清水真佐男

日本複合材料学会誌　29　(5)　177-183　2003/04

DOI： 10.6089/jscm.29.177 　
実験とシミュレーションの組合せ手法による高強度鋼の長寿命域疲労破壊特性の解明 Peer-reviewed

深沢剣吾, 岡部朋永, 小茂鳥潤, 清水真佐男

日本機械学会論文集(A編)　69　(679)　617-625　2003/03
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.69.617 　

ISSN： 0387-5008

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In order to clarify experimentally the damage process for the high strength steel in high and extremely high cycle regions and to propose a simulation model based on a new approach, rotating bending fatigue tests were performed with special focus on the effect of the role of the inclusion on the fatigue properties of high strength steel. The transition of fatigue crack initiation site from surface inclusion to internal one was observed with decreasing stress amplitude. The simulation model was proposed on the basis of the concept of a risk competition of defects, in which a virtual specimen has been constructed in the computer program and all inclusions were assumed to be equivalent to a crack origin. The results of the simulation were almost in accordance with the experimental results, and it was shown that this model could make the prediction of fatigue life of high strength steel in high and extremely high cycle regions.
New concept for modeling the electromechanical behavior of unidirectional carbon-fiber-reinforced plastic under tensile loading Peer-reviewed

JB Park, T Okabe, N Takeda

SMART MATERIALS & STRUCTURES　12　(1)　105-114　2003/02

ISSN： 0964-1726
Damage assessment of CFRP laminate with embedded FBG sensor using response surface methodology

YASHIRO Shigeki, NISHIKAWA Masaaki, OKABE Tomonaga, TAKEDA Nobuo

Proceedings of the 1992 Annual Meeting of JSME/MMD　2003　1017-1018　2003
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2003.0_1017 　

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The multiple damage state of a notched laminate was estimated with an embedded fiber Bragg grating (FBG) sensor. Reflection spectrum of the FBG sensor in a damaged laminate was numerically calculated by coupled-mode theory and damage extension analysis based on finite element method with cohesive elements. Then a database of strain distributions and reflection spectra at various damage states was obtained from the analytical results. The relationship between the damage state and the reflection spectra of the FBG sensor was expressed mathematically by response surface methodology. Then, solving the inverse problem of the relationship between damage state and reflection spectrum, we estimate typical damage state of a double-edge-notched cross-ply laminate. The estimated damage state is found to correspond well with the one obtained in the experiment.
Monitoring of damage under FRP repair patch using electrical time-domain reflectometry

URABE Kei, OKABE Tomonaga, TAKATSUBO Junji

Proceedings of the 1992 Annual Meeting of JSME/MMD　2003　1033-1034　2003
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2003.0_1033 　
Analytical solution of fiber stress profiles around a fiber breakage in unidirectional composites

OKABE Sayaka, OHNO Nobutada, OKABE Tomonaga

Proceedings of the 1992 Annual Meeting of JSME/MMD　2003　127-128　2003
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2003.0_127 　
A stochastic process model of multiple fiber breaks and matrix crackings in a ceramic matrix composite

GODA Koichi, OKABE Tomonaga

Proceedings of the 1992 Annual Meeting of JSME/MMD　2003　535-536　2003
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2003.0_535 　
Quantitative Monitoring of Transverse Crack and Improvement of Source Location Accuracy in Fiber Reinforced Plastics Using Change in Lamb Wave Velocity

TOYAMA Nobuyuki, OKABE Tomonaga, TAKATSUBO Junji, TAKEDA Nobuo

52　(1)　32-38　2003/01/01
Publisher:
ISSN： 0367-5866
Monitoring of filler distribution in resin with an electromagnetic wave transmission line Peer-reviewed

T Okabe, K Urabe

ADVANCED COMPOSITES LETTERS　12　(2)　63-68　2003

ISSN： 0963-6935
Green's function vs. shear-lag models of damage and failure in fiber composites

Z Xia, W.A Curtin, T Okabe

Composites Science and Technology　62　(10-11)　1279-1288　2002/08

DOI： 10.1016/s0266-3538(02)00073-8 　

ISSN： 0266-3538
Effect of transverse cracks on lamb wave velocity in CFRP cross-ply laminates Peer-reviewed

N Toyama, T Okabe, N Takeda, T Kishi

JOURNAL OF MATERIALS SCIENCE LETTERS　21　(4)　271-273　2002/02

DOI： 10.1023/A:1017925315239 　

ISSN： 0261-8028
FRP repair patch monitoring mechanical damage

URABE Kei, OKABE Tomonaga

Proceedings of the 1992 Annual Meeting of JSME/MMD　2002　343-344　2002
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2002.0_343 　
Effect of hardness on the fatigue strength of notched specimen

FUKAZAWA Kengo, SHIBUYA Masaki, OKABE Tomonaga, SHIMIZU Masao

Proceedings of the 1992 Annual Meeting of JSME/MMD　2002　565-566　2002
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2002.0_565 　

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Fatigue strength and life tend to decrease due to the stress concentration. To examine notch effect quantitatively, it has been paid attention to the relationship between maximum stress at the notch bottom and stress gradient. However, effective critical volume might be a main factor for inclusion induced fatigue failure in the case of high strength steel whose failure dominated by inclusions. The aim of the present study is to experimentally investigate the difference of fatigue strength between un-notched specimen and notched specimen in high strength steel.
A Study of the Damage Process in Conductive Thin Film on High Polymer Film

TOYODA Takao, OKABE Tomonaga, YANAKA Masaaki, TAKEDA Nobuo, SHIMIZU Masao

The proceedings of the JSME annual meeting　2002　455-456　2002
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmemecjo.2002.2.0_455 　

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The present paper investigates the relationship between crack phenomena and electric resistance of an ITO thin film on polymer film. The electrical conductivity of ITO film was decreases due to the multiple film cracking. In order to predict the variation of electrical conductivity of ITO film with applied strain, we conducted the Monte Carlo simulation with a finite element analysis. This numerical procedure can easily and accurately calculate the stress distribution in the film on the elastic-plastic substrate. The predictions are found to have good agreements with the experimental results.
Monitoring of resin flow and cure with an electromagnetic wave transmission line using carbon fiber as conductive elements Peer-reviewed

K Urabe, T Okabe, H Tsuda

COMPOSITES SCIENCE AND TECHNOLOGY　62　(6)　791-797　2002

DOI： 10.1016/S0266-3538(02)00047-7 　

ISSN： 0266-3538
Shear-lag versus finite element models for stress transfer in fiber-reinforced composites Peer-reviewed

Z Xia, T Okabe, WA Curtin

COMPOSITES SCIENCE AND TECHNOLOGY　62　(9)　1141-1149　2002

DOI： 10.1016/S0266-3538(02)00072-6 　

ISSN： 0266-3538
Size effect on tensile strength of unidirectional CFRP composites - experiment and simulation Peer-reviewed

T Okabe, N Takeda

COMPOSITES SCIENCE AND TECHNOLOGY　62　(15)　2053-2064　2002

DOI： 10.1016/S0266-3538(02)00146-X 　

ISSN： 0266-3538
Effect of matrix yield properties on fragmentation behavior of single fiber composites Peer-reviewed

FM Zhao, T Okabe, N Takeda

COMPOSITE INTERFACES　9　(3)　289-308　2002

DOI： 10.1163/156855402320257366 　

ISSN： 0927-6440
Electromechanical modeling of unidirectional CFRP composites under tensile loading condition Peer-reviewed

JB Park, T Okabe, N Takeda, WA Curtin

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　33　(2)　267-275　2002

DOI： 10.1016/S1359-835X(01)00097-5 　

ISSN： 1359-835X
Elastoplastic shear-lag analysis of single-fiber composites and strength prediction of unidirectional multi-fiber composites Peer-reviewed

T Okabe, N Takeda

COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING　33　(10)　1327-1335　2002

DOI： 10.1016/S1359-835X(02)00170-7 　

ISSN： 1359-835X
Statistical analysis of multiple cracking phenomenon of a SiOx thin film on a polymer substrate Peer-reviewed

M. Yanaka, Y. Tsukahara, T. Okabe, N. Takeda

Journal of Applied Physics　90　(2)　713-719　2001/07/05

DOI： 10.1063/1.1379355 　

ISSN： 0021-8979
Improved Surface Treatment of SMA Foils and Damage Suppression of SMA-Foil Embedded CFRP Laminates

Toshimichi Ogisu, Norio Ando, Junji Takaki, Tomonaga Okabe, Nobuo Takeda

Journal of Intelligent Material Systems and Structures　12　(4)　265-270　2001/04
Publisher: SAGE Publications
DOI： 10.1106/9apu-q5ec-44ty-ff0v 　

ISSN： 1045-389X

eISSN： 1530-8138

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The authors have been conducting research and development studies on some applications of embedded SMA foil actuators in CFRP laminates for weight reduction and improvement of reliability for next generation aircraft. The goal of this research is to develop a method for the suppression of damage growth in CFRP laminates. It is certified that one of the key technologies is bonding properties between SMA foils and CFRP laminates. In this paper, improvement of bonding properties between SMA foils and CFRP and confirmation of suppression effects of damage growth are described. Some surface treatments (sol-gel method, anodic-oxidation method and spattering method) were performed on SMA foils. Then, peel resistance and single lap shear strength tests were performed using surface treated SMA foils. It was found that treatment by 10%NaOH is the most effective treatment for improvement of bonding properties. The treated surface was found porous and rough, which is supposed to provide anchoring effects of SMA/CFRP interfaces. Then, quasi-static load-unload tests were performed using the optimum treatment as mentioned above to investigate the damage behavior of quasi-isotropic CFRP laminates with embedded SMA foils. Micromechanisms of fracture behavior and the correlation between the crack density and the residual strain were discussed. The recovery stress of the SMA foil generated at over Af temperature showed capability of suppression for onset of transverse cracks in quasi-isotropic CFRP laminates with embedded SMA foils.
305 Effect for Fatigue Fracture Properties of Steel in Extremely High Fatigue Region

KANAMORI Daisuke, FUKAZAWA Kengo, OKABE Tomonaga, KOMOTORI Jun, SHIMIZU Masao

Proceedings of the 1992 Annual Meeting of JSME/MMD　2001　237-238　2001
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmezairiki.2001.0_237 　

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To clarify the effect of hardness on fatigue characteristics of structural steel in an Extremely High Cycle Fatigue(EHCF) regime, rotational bending fatigue tests were carried out for two types of specimen with different hardness of microstructure. Fracture surfaces were observed using a Scanning Electron Microscope to examine the fracture mechanisms. Two types of fracture modes, surface fracture and internal fracture, were observed for high-strength steel. In middle strength steel, however, surface fracture mode alone was observed instead of fatigue crack started at nonmetallic inclusion. Computer simulation was also performed to discuss the fatigue properties in EHCF regime. The proposed model was possible to predict fatigue properties of both high-and middle-strength steel and showed that the possibility of internal failure (fish-eye failure) in EHCF of middle-strength steel.
K-0521 Fracture Mode Transition of high strength notched specimen in high and extremely high cycle fatigue regions

FUKAZAWA Kengo, OKABE Tomonaga, KOMOTORI Jun, SHIMIZU Masao

The proceedings of the JSME annual meeting　1　167-168　2001
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmemecjo.I.01.1.0_167 　

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The objectives of the present study are to experimentally examine the fatigue damage process and to propose a simulation model for the fatigue fracture process of notched specimen in high cycle fatigue regions. The origins of fatigue cracks of the un-notched specimen are surface inclusion or internal inclusion. On the other hand, those of the notched specimen are surface inclusion. The inclusion sizes of the origins of fatigue cracks in notched specimen are smaller than those of the unnotched specimen. This is partly because the critical zone of the notched specimen is smaller than that of the un-notched specimen.
Estimation of strength distribution for a fiber embedded in a single-fiber composite: experiments and statistical simulation based on the elasto-plastic shear-lag approach Peer-reviewed

T Okabe, N Takeda

COMPOSITES SCIENCE AND TECHNOLOGY　61　(12)　1789-1800　2001

DOI： 10.1016/S0266-3538(01)00080-X 　

ISSN： 0266-3538
A 3D shear-lag model considering micro-damage and statistical strength prediction of unidirectional fiber-reinforced composites Peer-reviewed

T Okabe, N Takeda, Y Kamoshida, M Shimizu, WA Curtin

COMPOSITES SCIENCE AND TECHNOLOGY　61　(12)　1773-1787　2001

DOI： 10.1016/S0266-3538(01)00079-3 　

ISSN： 0266-3538
Strength Evaluation of TiN Thin Film due to Monte Carlo Simulation

MISAWA Kazunori, OKABE Tomonaga, YANAKA Masaaki, TAKEDA Nobuo, SHIMIZU Masao

The proceedings of the JSME annual meeting　2000　241-242　2000
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmemecjo.2000.3.0_241 　

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The damage process of TiN thin film has been studied and the elastplastic shear-lag approach which consider the plasticity of substrate is proposed to evaluate the damages under the monotonic loading. In order to assert the validity of the present approach, we conducted the elastoplastic FEM analysis based on the strain increamental theory. The present results have good agreements with FEM results. The strength properties of TiN film were obtained with the Monte Carlo simulation using the present approach.
Monte-Carlo Simulation for Fatigue Fracture Properties of High Strength Steel

FUKAZAWA Kengo, OKABE Tomonaga, SHIMIZU Masao

The proceedings of the JSME annual meeting　2000　255-256　2000
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/jsmemecjo.2000.3.0_255 　

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A Monte-Carlo simulation was developed in order to propose a new model for the fracture process of high strength steel in high and extremely high cycles fatigue regions. The analysis results of the proposed model were almost accordance with the experiment result, and it was shown that this model could make the prediction of fatigue life of high strength steel. And it was shown that the fish-eye failure could be appeared even for the low and middle strength steel in an extremely high cycles fatigue region.
The estimation of statistical fiber strength by fragmentation tests of single-fiber composites Peer-reviewed

FM Zhao, T Okabe, N Takeda

COMPOSITES SCIENCE AND TECHNOLOGY　60　(10)　1965-1974　2000

DOI： 10.1016/S0266-3538(00)00084-1 　

ISSN： 0266-3538
A new fracture mechanics model for multiple matrix cracks of SiC fiber reinforced brittle-matrix composites Peer-reviewed

T. Okabe, N. Takeda, J. Komotori, M. Shimizu, W. A. Curtin

Acta Materialia　47　(17)　4299-4309　1999/11/26
Publisher: Elsevier Ltd
DOI： 10.1016/S1359-6454(99)00309-2 　

ISSN： 1359-6454
Mechanical behavior of SiC fiber reinforced brittle-matrix composites Peer-reviewed

T Okabe, J Komotori, M Shimizu, N Takeda

JOURNAL OF MATERIALS SCIENCE　34　(14)　3405-3412　1999/07

DOI： 10.1023/A:1004637300310 　

ISSN： 0022-2461
SiC繊維強化耐熱ガラス基直交積層板における損傷進展過程 Peer-reviewed

岡部朋永, 武田展雄, 今井克広, 小茂鳥潤, 清水真佐男, 今井義一

日本機械学会論文集(A編)　65　(631)　621-627　1999/03/01
Publisher: The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.65.621 　

ISSN： 0387-5008

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The damage process of fiber reinforced glass composites were studied under tensile loading. The tensile damage initiation and growth in BN-coated HI-NICALON SiC fiber reinforced glass matrix cross-ply laminates were experimentally clarified by replica observations, An improved shear-lag model with two major cracks, which penetrate both 0 degree and 90 degree plies, were used to predict the stress-strain behavior and reasonably well predicted the stress-strain curve until matrix cracks in the 0 degree ply saturate. Ultimate tensile strength (UTS) could be predicted by using a probabilistic fracture model based on the strength distribution data of fibers extracted from fabricated composites. Difference between the experimental strength and the predicted one was attributed to a difference in the strength distribution data of fibers and the one of fibers in the real composites. Then, UTS was compared with the prediction using the modified strength distribution data of fibers.
Tensile matrix cracking behavior of Hi-Nicalon fiber glass matrix cross-ply laminate composites Peer-reviewed

T Okabe, N Takeda, J Komotori, M Shimizu, K Imai, Y Imai

HIGH TEMPERATURE CERAMIC MATRIX COMPOSITES III　164-1　221-224　1999

ISSN： 1013-9826
一方向SiC繊維強化耐熱ガラス基複合材料における損傷進展過程 Peer-reviewed

岡部朋永, 武田展雄, 今井克広, 小茂鳥潤, 清水真佐男, 今井義一

日本機械学会論文集(A編)　64　2931-2937　1998/12/01

DOI： 10.1299/kikaia.64.2931 　
Damage process of unidirectional SiC fiber reinforced glass-matrix composites Peer-reviewed

T Okabe, N Takeda, J Komotori, M Shimizu, K Imai, Y Imai

CERAMIC MATERIAL SYSTEMS WITH COMPOSITE STRUCTURES　99　371-379　1998

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Misc. 91

Viscoelastic damage mechanics analysis of CFRP laminates with transverse cracking

黄木景二, 吉川周二, 岡部朋永, 小野寺壮太

日本複合材料合同会議(Web)　14th　2023
繊維強化複合材料の損傷を考慮した力学解析(4)3次元織物セラミック基複合材料の非線形挙動予測

小野寺壮太, 南雲佳子, 岡部朋永

機械の研究 = Science of machine　74　(9)　696-710　2022/09

ISSN： 0368-5713
繊維強化複合材料の損傷を考慮した力学解析(3)積層板におけるクラック発生予測

南雲佳子, 小野寺壮太, 岡部朋永

機械の研究 = Science of machine　74　(8)　607-618　2022/08

ISSN： 0368-5713
繊維強化複合材料の損傷を考慮した力学解析(2)面内引張圧縮,面外負荷下における損傷進展

南雲佳子, 小野寺壮太, 岡部朋永

機械の研究 = Science of machine　74　(7)　524-534　2022/07

ISSN： 0368-5713
繊維強化複合材料の損傷を考慮した力学解析(1)損傷を含む積層板の剛性低下

南雲佳子, 小野寺壮太, 岡部朋永

機械の研究 = Science of machine　74　(6)　431-440　2022/06

ISSN： 0368-5713
非線形拡張有限要素法による複合材料の有孔強度評価

樋口諒, 青木涼馬, 横関智弘, 長嶋利夫, 岡部朋永

日本複合材料学会誌　48　2022
3D造形した連続繊維熱可塑性CFRPの圧縮特性に関する実験的評価

干川大和, 白須圭一, 岡部朋永

日本複合材料学会誌　48　(4)　142-148　2022
シアネート硬化エポキシ樹脂の熱機械特性に関する実験的評価と分子動力学シミュレーション

Yoshiaki Kawagoe, Shohei Komori, Gota Kikugawa, Keiichi Shirasu, Tomonaga Okabe

Journal of the Japan Society for Composite Materials　48　(4)　134-141　2022
Publisher: The Japan Society for Composite Materials
DOI： 10.6089/jscm.48.134 　

ISSN： 0385-2563

eISSN： 1884-8559
Experimental and Numerical Evaluation of Open Hole Tensile Properties of 3D Printed Continuous Carbon Fiber Reinforced Thermoplastics

HOSHIKAWA Yamato, SHIRASU Keiichi, TSUYUKI Junpei, OKABE Tomonaga, HIGUCHI Ryo, YAMAMOTO Kohei, HIRATA Yasuhisa

Materials System　38　2021

ISSN： 2435-1520
Molecular Dynamics Simulation with Reaction Model Based on Accurate Quantum Chemical Calculation for Cross-Linking Process of Epoxy Resins and its Comparison to Experimental Measurement

Yutaka Oya, Yuki Hino, Kyosuke Inuyama, Gota Kikugawa, Jing Li, Riichi Kuwahara, Naoki Kishimoto, Hiroki Waizumi, Masaaki Nishikawa, Anthony Waas, Nobuyuki Odagiri, Andrew Koyanagi, Marco Salviato, Tomonaga Okabe

2019/07/16

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We propose a new simulation procedure for the curing reaction of epoxy resin by coupling quantum chemical (QC) calculations with molecular dynamics (MD) simulations. A polymer network formation composed of base resin and curing agent is investigated using the present simulation. Relationships between the atomistic structures in the system and their material properties derived from the simulations are also studied. The polymer network formation includes the reaction between epoxy resin and curing agents. Accurate activation energy and heat of formation are required for simulating the reaction. In this study, we introduce the ab initio QC calculation to the MD simulation to determine out the reaction pathways. To validate our proposed simulation, we experimentally measured densities, thermal characteristics and mechanical properties. The simulated results agree with experiments. The simulated results also indicate that branching structures of monomers causes the coarsening of the network formation of epoxy resin, so that the glass transition temperature (i.e. Tg) tends to increase. In contrast with Tg, the densities and Young's modulus are dominated mainly by the backbone structure of monomers and the degree of conversions.
From addition reactions to cross-linked network formation

Jing Li, Sakamoto Jumpei, Hiroki Wizumi, Yue Huang, Naoki Kishimoto, Yutaka Oya, Tomonaga Okabe

33rd Technical Conference of the American Society for Composites 2018　2　769-779　2018/01/01
Multiscale Modeling for Initial Crack Prediction of Fiber-Reinforced Composites by Mesh Superposition Method

22　6p　2017/05
Publisher: 日本計算工学会
Progressive Damage Analysis of Composite Laminates under In-Plane/Out-of-Plane Loadings Using Quasi-3D XFEM

22　6p　2017/05
Publisher: 日本計算工学会
Effect of Macroscopic Nonlinear Behavior and Microscopic Failure Criteria on Prediction of Initial Matrix Cracking in CFRP Laminates

35　19-27　2017
Publisher: 金沢工業大学材料システム研究所
ISSN： 0286-6013
An application of SPH method to axial crash simulation of composites

21　6p　2016/05
Publisher: 日本計算工学会
Numerical simulation of Progressive Damage and Failure in Composite Laminates using X-FEM

21　6p　2016/05
Publisher: 日本計算工学会
PS0004-173 Extraction of design guidelines of CFRP meso structure by multi-objective optimization using the homogenization method

ISHIKAWA Tomohiro, MATSUZAKI Ryosuke, Okabe Tomonaga, YASHIRO Shigeki

2015　"PS0004-173-1"-"PS0004-173-3"　2015/11/21
Publisher: The Japan Society of Mechanical Engineers

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Dry textiles are usually incorporated into the RTM method as a fibrous reinforcing material. The architecture of the textile material affects both the permeability and material properties of the final product. We optimized the textile architecture to improve manufacturing efficiency and product quality. In this optimization, in-plane stiffness, in-plane permeability, out-of-plane stiffness, and out-of-plane permeability were calculated via the homogenization method in the liquid and solid phases as objective functions. We use a multi-objective genetic algorithm as an optimization technique. A self-organizing map was used as a visualization tool. As a result, we obtained a Pareto solutions group, which is significant in designing the architecture of the textile. We demonstrated the design rules and knowledge of fabric structure by analyzing the Pareto solutions.
Mechanical properties of fiber/matrix interface in polymer matrix composites

Jun Koyanagi, Shinji Ogihara, Hayato Nakatani, Tomonaga Okabe, Satoru Yoneyama

ADVANCED COMPOSITE MATERIALS　23　(5-6)　551-570　2014/09

DOI： 10.1080/09243046.2014.915125 　

ISSN： 0924-3046

eISSN： 1568-5519
Preface

Tomonaga Okabe, Mototsugu Tanaka, Jun Koyanagi

ADVANCED COMPOSITE MATERIALS　23　(5-6)　389-389　2014/09

ISSN： 0924-3046

eISSN： 1568-5519
分子シミュレーション研究会

松崎亮介, 小柳潤, 岡部朋永

日本複合材料学会誌　40　(5)　238-243　2014
Publisher: 日本複合材料学会
ISSN： 0385-2563
1423 Evaluation of Material Properties on Crystalline Polymer Based on Multiscale Modeling

AOYAGI Yoshiteru, SASAYAMA Toshiki, INOUE Yoshinori, YAMAMOTO Satoru, OKABE Tomonaga

The Computational Mechanics Conference　2013　(26)　"1423-1"-"1423-2"　2013/11/02
Publisher: The Japan Society of Mechanical Engineers
ISSN： 1348-026X
OS2005 Micromechanics for the strength properties of discontinuous carbon fiber-reinforced plastic composites

OKABE Tomonaga

2013　"OS2005-1"-"OS2005-2"　2013/10/12
Publisher: The Japan Society of Mechanical Engineers

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We utilized a unit cell model that considers microscopic damage including matrix cracking and fiber breaking, and incorporates constitutive laws of thermosetting resin or thermoplastic resin for the matrix. The tensile damage and strength of the composite were investigated for various fiber lengths and/or matrix properties. We compared the simulated strengths with experiments for carbon fiber-reinforced polypropylene.
5・4・1 複合材料の力学(5・4 界面・複合材料,5.材料力学,<特集>機械工学年鑑)

岡部朋永

日本機械学會誌　116　(1137)　528-528　2013/08/05
Publisher: 一般社団法人日本機械学会
ISSN： 0021-4728
炭素繊維強化プラスチックを利用した輸送機の軽量化

岡部朋永

日本機械学會誌 = Journal of the Society of Mechanical Engineers　116　(1132)　201-201　2013/03/05
Publisher: 一般社団法人日本機械学会
ISSN： 0021-4728
Strain-Rate Dependence of Transverse Tensile Failure of CFRP

(13)　195-198　2013
Publisher: 日本実験力学会
ISSN： 1346-4922
繊維強化プラスチックにおける変形・損傷・破壊に関する数値シミュレーション

岡部朋永

未来材料　12　(1)　12-19　2012/01
Publisher: エヌ・ティー・エス
ISSN： 1346-0986
Numerical Simulation of Initial Damage in a Transverse Ply of CFRP Laminates

30　5-10　2012
Publisher: 金沢工業大学材料システム研究所
ISSN： 0286-6013
Numerical simulation of drilling thrust damage in CFRP laminates using elasto-plastic FEM Peer-reviewed

S.C. Park, M. Nishikawa, T. Okabe, N. Takeda

27th Annual Technical Conference of the American Society for Composites 2012, Held Jointly with 15th Joint US-Japan Conference on Composite Materials and ASTM-D30 Meeting　1506-1515　2012
繊維強化プラスチックの変形・破壊・プロセッシングに関する数値シミュレーション

岡部朋永

宇宙構造・材料シンポジウム : 講演集録　27　10p　2011/12/08
Publisher: 宇宙航空研究開発機構宇宙科学研究所
Numerical modeling of mechanical damage in short fiber reinforced thermoplastic composites Peer-reviewed

T. Okabe, M. Nishikawa, M. Hashimoto

Conference Program for the 3rd International Conference on Heterogeneous Materials Mechanics, ICHMM 2011　861-864　2011
(4)短繊維強化プラスチックの破壊モードに及ぼす材料微視構造の影響(論文,日本機械学会賞〔2009年度(平成21年度)審査経過報告〕)

西川雅章, 岡部朋永, 武田展雄

日本機械学會誌　113　(1098)　315-316　2010/05/05
Publisher: 一般社団法人日本機械学会
ISSN： 0021-4728
Numerical simulations for the transverse tensile failure of fiber reinforced plastics considering the constitutive law of ductile polymer

15　(2)　659-662　2010/05
Publisher: 日本計算工学会
ISSN： 1342-145X
A Numerical Approach for Injection Molding of Short-fiber Reinforced Plastics by Using a Particle Method

YASHIRO Shigeki, OKABE Tomonaga, MATSUSHIMA Kisa

Journal of the Japan Society for Composite Materials　36　(1)　11-18　2010/01/15
Publisher: The Japan Society for Composite Materials
DOI： 10.6089/jscm.36.11 　

ISSN： 0385-2563

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This paper proposes a numerical approach for predicting the injection-molding process of short-fiber-reinforced plastics using the Moving Particle Semi-implicit (MPS) particle-simulation method. Unlike conventional methods, this approach represents all of the fibers and the resin as particles and automatically analyzes the interaction between the fiber and the resin and the interaction between the fibers. This method can also follow the flow of a specific fiber. The injection molding of short-fiber-reinforced plastics was simulated assuming the thermoplastic resin to be an incompressible viscous fluid and the fibers to be rigid bodies. The numerical result demonstrated that the molding material was unidirectionally reinforced by short fibers since the fibers were rotated and aligned parallel to the flow direction due to the velocity gradient near the boundary. Moreover, the resin was predicted to accumulate at a corner. These results agreed well with previous studies, and the present approach was confirmed. Furthermore, we predicted the accumulation of fibers near a wall due to the velocity gradient, which could not be represented by conventional simulation methods.
Effect of matrix hardening on tensile strength of alumina-fiber reinforced aluminum matrix composites

T. Okabe, M. Nishikawa, N. Takeda, H. Sekine

Key Engineering Materials　430　83-99　2010/01/01

DOI： 10.4028/www.scientific.net/KEM.430.83 　

ISSN： 1013-9826

eISSN： 1662-9795
Characterization of the influence on thermomechanical behavior of shape memory polymer due to fiber reinforcement

N. Nishikawa, K. Wakatsuki, T. Okabe, N. Takeda

24th Annual Technical Conference of the American Society for Composites 2009 and 1st Joint Canadian-American Technical Conference on Composites　3　1688-1700　2009/12/01
Numerical Prediction of Fatigue Damage Progress in Holed CFRP Laminates Using Cohesive Elements

Shigeki YASHIRO, Tomonaga OKABE

Journal of Solid Mechanics and Materials Engineering　3　(11)　1212-1221　2009
Publisher: Japan Society of Mechanical Engineers
DOI： 10.1299/jmmp.3.1212 　

ISSN： 1880-9871

eISSN： 1880-9871
Periodic-Cell Simulations for the Microscopic Damage and Strength Properties of Discontinuous Carbon Fiber-Reinforced Plastic Composites

M. Nishikawa, T. Okabe, N. Takeda

Advanced Composite Materials　18　(1)　77-93　2009/01/01
Publisher: Informa UK Limited
DOI： 10.1163/156855108x399974 　

ISSN： 0924-3046

eISSN： 1568-5519
Numerical simulation for the microscopic damage and its influence on the macroscopic fracture properties in short-fiber reinforced plastic composites

M. Nishikawa, T. Okabe, N. Takeda

Advanced Composites for Efficiency and Environment - The US-Japan Conference on Composite Materials 2008, US-Japan 2008　2008/12/01
OS0409 Molecular simulation of a Ni/Ni_3Al interface

YAMADA Mitsuru, OKABE Tomonaga, SUZUKI Ken

2008　"OS0409-1"-"OS0409-2"　2008/09/16
Publisher: The Japan Society of Mechanical Engineers
OS0403 Molecular simulation of interfacial characteristics of carbon nanotube-polymer composites

HONDA Takashi, OKABE Tomonaga, NISHIKAWA Masaaki

2008　"OS0403-1"-"OS0403-2"　2008/09/16
Publisher: The Japan Society of Mechanical Engineers
OS0613 Numerical evaluation of fatigue damage process in holed CFRP laminates

YASHIRO Shigeki, OKABE Tomonaga, OGI Keiji

2008　"OS0613-1"-"OS0613-2"　2008/09/16
Publisher: The Japan Society of Mechanical Engineers
Micromechanics-based simulation for the fracture of composite materials with cohesive/volumetric finite-element schemes

M. Nishikawa, T. Okabe, N. Takeda

American Society for Composites - 22nd Technical Conference of the American Society for Composites 2007 - Composites: Enabling a New Era in Civil Aviation　1　39-58　2007/12/01
Mechanics of fiber fragmentation in single-fiber composite

Masaaki Nishikawa, Tomonaga Okabe, Nobuo Takeda

ICCM International Conferences on Composite Materials　2007/12/01
Characterization of tensile damage progress in stitched CFRP laminates

Akinori Yoshimura, Shigeki Yashiro, Tomonaga Okabe, Nobuo Takeda

ADVANCED COMPOSITE MATERIALS　16　(3)　223-244　2007/06

DOI： 10.1163/156855107781393740 　

ISSN： 0924-3046
繊維強化複合材料の損傷・破壊を対象とした数値シミュレーション

岡部朋永

計算数理工学レビュー　2007　(1)　25-34　2007/03
Publisher: 日本計算数理工学会
ISSN： 1348-7353
Numerical study for identifying damage in open-hole composites with embedded FBG sensors and its application to experiment results

S. Yashiro, K. Murai, K. Murai, T. Okabe, N. Takeda

Advanced Composite Materials: The Official Journal of the Japan Society of Composite Materials　16　115-134　2007/03/01

DOI： 10.1163/156855107780918946 　

ISSN： 0924-3046
Prediction of tensile strength of unidirectional CFRP composites

OKABE T.

Journal of the Japan Society for Composite Materials　33　205-212　2007
Characterization of fiber fragmentation in a single-fiber composite in relation to matrix failure and interfacial debonding

M. Nishikawa, T. Okabe, N. Takeda

Proceedings of the 12th U.S.-Japan Conference on Composite Materials　774-792　2006/12/01
365 Effect of Interface on Matrix Craking in Fiber Reinforced Ceramics

YAMASHITA Koji, OKABE Tomonaga

The Computational Mechanics Conference　2006　(19)　679-680　2006/11/02
Publisher: The Japan Society of Mechanical Engineers
ISSN： 1348-026X
Tensile strength of CFRP cross-ply laminates containing transverse cracks

Junji Noda, Tomonaga Okabe, Nobuo Takeda, Masao Shimizu

Advanced Composite Materials: The Official Journal of the Japan Society of Composite Materials　15　81-93　2006/07/10

DOI： 10.1163/156855106776829338 　

ISSN： 0924-3046
Damage monitoring of CFRP laminates with open holes using chirped FBG sensors

S. Yashiro, T. Okabe, N. Takeda

20th Technical Conference of the American Society for Composites 2005　3　1522-1535　2005/12/01
繊維強化複合材料内部に発生する複数損傷を対象とした数値シミュレーション

岡部朋永

日本複合材料学会誌　31　(4)　147-159　2005/07
Publisher: JAPAN SOCIETY FOR COMPOSITE MATERIALS
DOI： 10.6089/jscm.31.147 　

ISSN： 0385-2563
Damage identification in CFRP cross-ply laminates containing an open hole using an embedded FBG sensor

Murai K., Shimizu M., Okabe T., Takeda N.

Symposium on Evaluation and Diagnosis　2004　(3)　82-85　2004/12/15
Publisher: The Japan Society of Mechanical Engineers

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In this study, we estimated the damage pattern in a CFRP cross-ply laminate containing an open hole using an embedded Fiber Bragg Gratings (FBG) sensor. The damage pattern near the hole was investigated by finite element an alysis with cohesive elements, and the reflection spectrum of the embedded FBG sensor was analyzed from the strain distribution obtained in the damage analysis. Based on the above analysis, the damage pattern expressed by the residual strength distribution of the cohesive elements was optimized as an inverse problem, while the spectrum shape was adopted as the objective function. The damage pattern estimated from the measured spectrum agreed with the observation.
Numerical simulation of transverse cracking in fiber reinforced cross-ply laminates with higher-order plate theory

OKABE Tomonaga, SHOKINJI Takeo, SEKINE Hideki

2004　31-32　2004/05/24
Damage Evolution of GFRP Cross-ply Laminates

NODA Junji, OKABE Tomonaga, TAKEDA Nobuo, SHIMIZU Masao

2004　37-38　2004/05/24
Damage Process of the Three Dimensional Woven Composite Under Uniaxial Tensile Load

YOSHIMURA Akinori, OKABE Tomonaga, TAKEDA Nobuo

2004　29-30　2004/05/24
Damage monitoring near stress concentrations in CFRP laminate using embedded FBG sensor

YASHIRO Shigeki, OKABE Tomonaga, TAKEDA Nobuo, SEKINE Hideki

2004　121-122　2004/05/24
Health Monitoring of CFRP Laminates with Interlaminar Delamination under Compression

NISHIKAWA Masaaki, OKABE Tomonaga, TAKEDA Nobuo

2004　123-124　2004/05/24
Inverse analysis for damage identification in CFRP laminates with embedded FBG sensors

Shigeki Yashirol, Tomonaga Okabe, Nobuo Takeda

Composites Technologies For 2020　993-998　2004/01/01
Analytical solutions for local stress concentrations in long fiber reinforced unidirectional composites with a fiber breakage

OKABE Sayaka, OHNO Nobutada, OKABE Tomonaga

28　119-120　2003/10/23
Analysis of Multiple Cracking Process in Transparent Conducitve Film on Polymer Substrate

YANAKA Masaaki, IHASHI Noritaka, TOYODA Takao, OKABE Tomonaga, TAKEDA Nobuo, SHIMIZU Masao

Materials and processing conference　2003　(11)　253-254　2003/10/17
Publisher: The Japan Society of Mechanical Engineers

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The progress of multiple cracking and the change of electric resistance in an indium-tin-oxide (ITO) film deposited onto a polyethylene terephtalate substrate were measured simultaneously during the tensile test. The proportionality relation between the crack density and the electric resistance was obtained. The Monte Carlo simulation was conducted to predict the increase both of the crack density and the electric resistance. In the simulation, stress distributions in film fragments were properly calculated by the elastic-plastic finite element analysis. The predictions showed good agreements with experiments.
Health monitoring of CFRP lamintes under compression using an embedded FBG sensor

NISHIKAWA Masaaki, OKABE Tomonaga, TAKEDA Nobuo

Materials and processing conference　2003　(11)　91-92　2003/10/17
Publisher: The Japan Society of Mechanical Engineers

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We examined the deformation behavior of CFRP laminates with delaminations by the buckling analysis based on nonlinear FEM. First, the buckling mode is estimated by linearlized eigenvalue buckling analysis. The result shows that local buckling is generated due to the existing interlaminar delamination in CFRP laminates under compression. Next, we calculated the reflection spectra of FBG sensors embedded at the delaminated region in the laminate, using post-buckling analysis and coupled-mode theory. From the result, we confirmed that the local buckling can be detected by reflection spectrum of the embedded FBG sensor.
OS9(5)-22(OS09W0168) Health Monitoring with Electromagnetic Wave Transmission Line

Urabe Kei, Okabe Tomonaga

Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics　2003　256-256　2003/09/09
Publisher: The Japan Society of Mechanical Engineers
Damage Simulation of GFRP Cross-ply Laminate

NODA Junji, OKABE Tomonaga, TAKEDA Nobuo, SHIMIZU Masao

2003　149-150　2003/05/01
Lamb Wave Evaluation of Mechanical Damages in FRP Cross-ply Laminates

OKABE Tomonaga, TOYAMA Nobuyuki, SEKINE Hideki

2003　(38)　188-189　2003/03/15
Publisher: The Japan Society of Mechanical Engineers
Damage Analysis of 3D Woven Composites Using the Finite Element Method

YOSHIMURA Akinori, OKABE Tomonaga, TAKEDA Nobuo

2003　(9)　183-184　2003/03/13
Publisher: The Japan Society of Mechanical Engineers

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Fracture process of three dimensional woven composites was analyzed using the Finite Element Method. Special emphasis was put on the influences that microscopic damage gives to macroscopic property. There are three types of microscopic damages in the three dimensional woven composites : tow fracturing, transverse crack and delamination. In order to simulate these damages, the three dimensional woven composite was modeled by combination of three types of elements : brick elements, truss elements and cohesive elements. Truss elements express the rigidity in the fiber direction of tow. The rigidity of the truss element was dropped to zero when the tow was fractured. Brick elements express the property of matrix. Cohesive elements are introduced along the boundaries of the inner layers and inside the transverse plies to simulate the spontaneous initiation and propagation of transverse cracks and delaminations.
Analytical Solution of Fiber Stress Profiles around Fiber Break in Unidirectional Composites

OKABE Sayaka, OHNO Nobutada, OKABE Tomonaga

2003　(52)　247-248　2003/03/01
Publisher: The Japan Society of Mechanical Engineers
Damage process of ceramic matrix composites

OKABE Tomonaga

2003　127-130　2003
Publisher: 日本機械学会

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The present paper introduces our recent works for the damage process of ceramic matrix composites. Especially, the microscopic damage in composites are reported. Based on the experimental data and observations, analytical models are presented. We introduce some ideas to compare with the experimental data. The predicted results agrees well with experimental data.
Health Monitoring with Electromagnetic Wave Transmission Line

URABE Kei, OKABE Tomonaga

27　239-240　2002/10/09
Evaluation of the measurement method for the electrical resistance change of unidirectional CFRP composites using electrical potential theory

PARK Jae Beom, TAKEDA Nobuo, OKABE Tomonaga

27　101-102　2002/10/09
電磁気法 (非破壊検査特集)

卜部啓, 岡部朋永

強化プラスチックス　48　(8)　321-328　2002/08
Publisher: 強化プラスチックス協会
ISSN： 0452-9685
(2)セラミック基複合材料の強度におけるマイクロメカニクスアプローチに関する研究

岡部朋永

日本機械学會誌　105　(1002)　306-306　2002/05/05
Publisher: 一般社団法人日本機械学会
ISSN： 0021-4728
Monitoring of Manufacturing Process of Resin Composites with High-frequency Electromagnetic Wave Transmission Characteristics

URABE Kei, OKABE Tomonaga

51　(5)　269-274　2002/05/01
Publisher: 日本非破壊検査協会
ISSN： 0367-5866
Non-linear behavior on the Stress-strain curve of GFRP cross-ply laminates

NODA Junji, UENO Yuki, OKABE Tomonaga, TAKEDA Nobuo, SHIMIZU Masao

2002　117-118　2002/05/01
Evaluation of the internal damage of CFRP composite using the electrical anisotropic characteristics

PARK Jaebeom, YOSHIMURA Akinori, OKABE Tomonaga, TAKEDA Nobuo

2002　91-92　2002/05/01
Percolation study on electrical resistanceof CFRP composites

2002　(8)　235-236　2002/03/14
Publisher: The Japan Society of Mechanical Engineers

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Electrical resistance in CFRP composite have been already shown to be sensitive for the internal damage. Then, in order to quantify the variation of electrical conductivity of CFRP composite, a new numerical model is proposed. The present model couple the electrical resistance network model with the 3D shear-lag model. The free parameter xx in the previous GLS model is determined as a function of internal fiber to fiber contact by the numerical simulation.
213 Prediction of the Whole Stress-strain Curve and Final Composite Strength of GFRP Cross-ply Laminates

Noda Junji, Okabe Tomonaga, Takeda Nobuo, Shimizu Masao

JSME Materials and Processing Conference (M&P)　10　(1)　441-444　2002
Publisher: The Japan Society of Mechanical Engineers

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The strength prediction of the composite laminates is necessary for the engineering application. In predicting the strength of the arbitrary lay-up laminates, the interaction between the fiber failure and the ply cracks is critical. Therefore, the advanced micro-mechanical models considering the ply cracks and the fiber failures should be established. The present study investigates experimentally the microscopic damage evolution of glass fiber reinforced polymer (GFRP) cross-ply laminates and predicts the stress-strain relation up to failure using the statistical simulation. Especially, a new numerical model based on the finite element method and the Monte Carlo simulation is proposed and the fiber breakage is coupled with the matrix cracks in the 90-degree plies in this model. Concerning the matrix cracks, the present model utilizes the experimental results obtained from the replica observations. The simulated results have a good agreement with the experimental results and it is found that the present model can predict the micro mechanical damage process of GFRP.
126 Analysis of Electrically Conductive Internal Network in CFRP Composites Using Anisotropy of Electrical Conductivity

Park Jae Beom, Okabe Tomonaga, Yoshimura Akinori, Takeda Nobuo

JSME Materials and Processing Conference (M&P)　10　(1)　428-431　2002
Publisher: The Japan Society of Mechanical Engineers

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As shown by previous research results, the internal electrically conductive network, which is constructed by the contacts between conductive carbon fibers, is very important in correlating the measured electrical resistance change of CFRP composites under tensile loading to the mechanical damage state. In this study, the internal conductive network in CFRP is investigated experimentally and analytically. The anisotropy characteristics of the electrical conductivity in CFRP are measured for various carbon fiber volume fractions using DC 4 and 6 probe methods. The electrical ineffective length, which represents the internal conducting path due to the fiber contacts, is also estimated using the resistance change curve obtained by mechanical tensile tests. For the analytical investigation, Kirchhoff's rule for DC network circuit analysis is combined with the Monte Carlo simulation for the contact point distribution. By comparing the analytical and experimental results, the distribution configuration and the number of contact points, which constitute the internal electrically conductive network of CFRP composites, can be evaluated quantitatively.
Monitoring of resin cure with eletromagnetic wave transmission line

Okabe Tomonaga, Urabe Kei

2002　86-87　2002
Publisher: 日本機械学会

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The authors previously suggested the potentiality of using the characteristics of a high-frequency electromagnetic wave transmission line constructed inside a structure or material as a new tool for in-situ cure monitoring in the manufacturing process of resin composites. The advantage of using a high-frequency electromagnetic wave is the possibility of obtaining information on the position of the discontinuity or distribution of material properties because of its short wavelength. This paper experimentally investigates the time domain response to a step input signal of a model transmission line filled with epoxy resin having inclusions.
Quantitative evaluation of the electrically conductive internal network in CFRP composites

Jae Beom Park, Tomonaga Okabe, Akinori Yoshimura, Nobuo Takeda, William A. Curtin

Proceedings of SPIE - The International Society for Optical Engineering　4704　40-50　2002/01/01

DOI： 10.1117/12.470734 　

ISSN： 0277-786X
A study for inner damage process of CFRP cross-ply laminates

NODA Junji, OKABE Tomonaga, TAKEDA Nobuo, SHIMIZU Masao

26　89-90　2001/11
In-situ health monitoring of CFRP composites using electrical characteristics

Jae Beom Park, Tomonaga Okabe, Dong Yeul Song, Nobuo Takeda, Akihiko Kitano

Proceedings of SPIE - The International Society for Optical Engineering　4328　323-331　2001/08/06

DOI： 10.1117/12.435535 　

ISSN： 0277-786X
A theory for multi damage evaluation of TiN thin film

Kazunori Misawa, Tomonaga Okabe, Masaaki Yanaka, Masao Shimizu, Nobuo Takeda

Materials Research Society Symposium-Proceedings　653　2001/01/01

ISSN： 0272-9172
Durability and defect distribution of SiOx film on polymer substrate analyzed by a statistical approach

M. Yanaka, Y. Tsukahara, T. Okabe, N. Takeda

Proceedings, Annual Technical Conference - Society of Vacuum Coaters　487-491　2001/01/01

ISSN： 0737-5921
Development of damage suppression system using embedded SMA foil in CFRP laminates

Toshimichi Ogisu, Masato Nomura, Norio Ando, Junji Takaki, Masakazu Kobayashi, Tomonaga Okabe, Nobuo Takeda

Proceedings of SPIE - The International Society for Optical Engineering　4333　387-398　2001/01/01

DOI： 10.1117/12.432778 　

ISSN： 0277-786X
209 The mechanical behavior analysis of the unidirectional GFRP composite using 3D Monte Carlo simulation

KAMOSHIDA Yoshimasa, OKABE Tomonaga, TAKEDA Nobuo, SHIMIZU Masao

Materials and processing conference　2000　(8)　65-66　2000/11/24
Publisher: The Japan Society of Mechanical Engineers

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The present paper proposes a new numerical model for predicting the mechanical behavior of unidirectional composites, based on a 3D shear lag model. The present model considers the micro-damage including interfacial yielding. In order to confirm the validity of the present model, the simulated the ultimate tensile strength (UTS) is compared with the experimental result. Then, the damage process is researched by calculating the stress concentration factor (SCF) at the final failure plane.
210 The mechanical behavior analysis of the CFRP cross-ply laminates

NODA Junji, OKABE Tomonaga, TAKEDA Nobuo, SHIMZU Masao

Materials and processing conference　2000　(8)　67-68　2000/11/24
Publisher: The Japan Society of Mechanical Engineers

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The present paper proposes a new numerical model for predicting the mechanical behavior of the CFRP cross-ply laminates(T800H/3631), based on a 3D shear lag model. In order to confirm the validity of the present model, the simulated the ultimate tensile strength (UTS) is compared with the experimental result Then, the effect of the stress concentration on the tip of Transverse Crack is researched by reproducting the inner damages numerically at the crack plane.
222 Damage Evaluation of Unidirectional CFRP Composites Using Carbon Fiber's Electrical Characteristics

Park Jae Beom, Okabe Tomonaga, Song Dong Yeul, Takeda Nobuo

Materials and processing conference　2000　(8)　219-220　2000/11/24
Publisher: The Japan Society of Mechanical Engineers

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The present paper addresses the correlation between the mechanical damage behavior and the change of electrical resistance of CFRP under tensile loading. The linear relation between the strain and the electrical resistance of carbon fiber is obtained experimentally and the CFRP's electrical behavior under tensile loading is investigated. The mechanical damage evolution process is studied using the Global Load Sharing (GLS) model and correlated to the electrical behavior. These investigations leads to a new concept of electrical ineffective length and the electrical model using the DC series circuit with equally spaced discrete parallel cells is proposed to apply the electrical circuit theory to real composites. The predicted results using this model explain the experimental results very well.
Damage Growth Prediction of Unidirectional CFRP Composites Using Discrete Electrical Resistance Models

PARK Jae Beom, OKABE Tomonaga, SONG Dong Yeul, TAKEDA Nobuo

25　73-74　2000/10
Theory for ultimate tensile strength of Ceramics Matrix Composites

OKABE Tomonaga, TAKEDA Nobuo

2000　39-40　2000
An Analysis of Multiple Matrix Crack of Ceramics Matrix Composites

OKABE Tomonaga, TAKEDA Nobuo, KOMOTORI Jun, SHIMIZU Masao

1999　75-76　1999/04/27

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Books and Other Publications 5

応用解析からはじめる弾性力学入門

岡部, 朋永

コロナ社　2021/06

ISBN: 9784339046731
テンソル解析からはじめる応用固体力学

Tomonaga Okabe

コロナ社　2015/06/12

ISBN: 9784339046410
複合材料の力学

岡部朋永, 矢代茂樹

共立出版　2015/05/25

ISBN: 9784320081994
ベクトル解析からはじめる固体力学入門

岡部朋永

2013/03
入門複合材料の力学

末益博志編著

2009/09/07

Presentations 6

Multiscale Modeling of Carbon Fiber-Reinforced Composites from Molecule to Structure Invited

South East Asia-Japan Conference on Composite Materials 2024　2024/08/13
先進複合材料におけるマルチスケールモデリング（分子から機体設計まで）

第12回日本複合材料会議(JCCM-12)
Numerical Modelling of Prograssive Failure in Carbon Fibre Reinforced Plastic Composites

17th US-Japan Conference on Composite Materials
Multiscale modeling of fiber reinforced plastic composites International-presentation

UK-Japan Workshop on Composites　2013/03/24
Numerical modeling of fiber reinforced plastic composites International-presentation

Seminar in Mechanical Engineering of EPFL　2012/12/05
Multi-scale Modering of Fiber-reinforced Plastic Composites International-presentation

TEXAS A&M ENGINEERING Seminar　2012/10/03

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Industrial Property Rights 2

導電薄膜の導電性測定装置

特許第4107382号

Property Type: Patent
補修・補強状況検知方法

特許第3704559号

Property Type: Patent

Research Projects 33

株式会社メニコン×東北大学みる未来のための共創研究所

伊藤恵利、岡部朋永、高田昌樹、白須圭一、鈴木研、菊川豪太、川越吉晃

Offer Organization: メニコン

System: 共創研究所

Institution: 東北大学

2024/04 - 2027/03
次世代コンタクトレンズ及びコンタクトレンズの流通・製造に関する基盤技術構

岡部朋永, 高田昌樹, 白須圭一, 鈴木研, 菊川豪太, 川越吉晃

Offer Organization: メニコン・東京大学

Category: 共同研究

Institution: 東北大学

2024/04 - 2027/03
次世代ETB(Ethanol to Butadiene)触媒の共同開発

岡部朋永、鈴木研、川越吉晃

Offer Organization: 日揮ホールディングス

Category: 共同研究

Institution: 東北大学

2024/04 - 2027/03
ｾｲｺｰｴﾌﾟｿﾝ株式会社×東北大学ｻｽﾃｨﾅﾌﾞﾙ材料共創研究所

間ケ部明、岡部朋永、高田昌樹、白須圭一、高山裕貴、川越吉晃

Offer Organization: セイコーエプソン

System: 共創研究所

Institution: 東北大学

2023/08 - 2027/03
次世代航空機の開発／航空機複合材構造の設計歪向上の研究

岡部朋永、白須圭一、川越吉晃、南雲佳子

Offer Organization: 三菱重工（NEDO）

System: グリーンイノベーション基金事業

Category: 共同研究

Institution: 東北大学

2023/04 - 2027/03
Study for mechanical properties of carbon fiber-reinforced composite materials with phase-separated structures

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2023/04/01 - 2026/03/31
Study for mechanical properties of carbon fiber-reinforced composite materials with phase-separated structures

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2023/04/01 - 2026/03/31
CFRP用MIシステム開発（CoSMIC）

岡部朋永、川越吉晃

Offer Organization: 三菱ケミカル

Category: 共同研究

Institution: 東北大学

2021/08 - 2025/07
バイオマス(再生)プラとドライファイバーセルロースの複合化基礎技術開発

岡部朋永, 高田昌樹, 白須圭一, 高山裕貴, 川越吉晃

Offer Organization: セイコーエプソン

Category: 共同研究

Institution: 東北大学

2023/06 - 2025/05
ＣＭＣミクロ解析技術の開発

岡部朋永

Offer Organization: IHI

Category: 共同研究

Institution: 東北大学

2024/05 - 2025/03
航空エンジン用部品の接着継手構造評価に関する研究

岡部朋永

Offer Organization: IHI

Category: 共同研究

Institution: 東北大学

2024/04 - 2025/03
高分子用MIシステム開発（CoSMIC）

岡部朋永、川越吉晃

Offer Organization: 東亞合成

Category: 共同研究

Institution: 東北大学

2023/06 - 2025/03
CFRP用MIシステム開発（CoSMIC）

岡部朋永、川越吉晃

Offer Organization: 帝人

Category: 共同研究

Institution: 東北大学

2023/04 - 2025/03
CoSMICを応用した材料開発用ＭＩシステム開発

岡部朋永, 川越吉晃

Offer Organization: 矢崎総業

Category: 共同研究

Institution: 東北大学

2023/04 - 2025/03
一方向CFRPの引張破壊メカニズムと解析技術の開発

岡部朋永、川越吉晃

Offer Organization: 豊田自動織機

Category: 共同研究

Institution: 東北大学

2023/04 - 2025/03
CFRPマルチマテリアル系構造の機体用途への適合性評価／マルチマテリアル系接合部の信頼性保証

岡部朋永、白須圭一、川越吉晃、南雲佳子、阿部圭晃

Offer Organization: 東レ（NEDO）

Category: 共同研究

Institution: 東北大学

2020/11 - 2025/03
複合材時代の理想機体構造を実現する機体設計技術の開発

大林茂, 岡部朋永, 服部裕司, 河合宗司, 下山幸治, 廣田真, 水谷正義, 白須圭一, 焼野藍子, 阿部圭晃, 久谷雄一

Offer Organization: 新エネルギー・産業技術総合開発機構

Category: 受託研究

Institution: 東北大学

2020/06 - 2025/03
CFRP用MIシステム開発（CoSMIC）

岡部朋永、白須圭一、川越吉晃、龍薗一樹

Offer Organization: CoSMIC-DX

Category: 共同研究

Institution: 東北大学

2024/01 - 2025/01
OI機構・多元・陣内浩司「計測・計算融合によるAtom To Tire A2Tの実現」

陣内浩司、岡部朋永、宮田智衆、川越吉晃、熊谷明美、小林祥子

Offer Organization: ブリヂストン

Category: 共同研究

Institution: 東北大学

2023/12 - 2024/12
繊維強化複合材料のマルチスケールシミュレーション技術の開発

岡部朋永, 川越吉晃

Offer Organization: 東レ

Category: 共同研究

Institution: 東北大学

2023/10 - 2024/09
風車ブレードの保守判定に向けたブレード損傷量・破壊リスク評価法に関する研究

岡部朋永、阿部圭晃、龍薗一樹

Offer Organization: 東芝エネルギーシステムズ

Category: 共同研究

Institution: 東北大学

2023/05 - 2024/09
Quantum-Annealing Assisted Innovative Material Informatics Infrastructure

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (A)

Institution: Tohoku University

2019/04/01 - 2023/03/31
Establishment of multiscale modeling for the CFRP and its application to the structural design

OKABE Tomonaga

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (C)

Institution: Tohoku University

2015/04/01 - 2018/03/31

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Recently, instead of conventional metal, carbon fiber reinforced plastic (CFRP) composites are applied to the main structural members in the transport aircrafts. For example, 50% volume percent of the main body of Boeing 787 consists of CFRP. It is well known that the design approach of metal aircrafts cannot be applied to CFRP aircrafts because the damage and failure process of CFRP is quite unique owing to the hierarchical microstructure. However, in the real design, the strain criterion which is used in the design of metal aircrafts has been applied to the development of new transport aircrafts. This approach cannot cover with the several problems including edge delamination, impact damage, transverse cracks and micro damages seen in the CFRP structures. Based on these backgrounds, multiscale modeling which addresses plural damages and systematically organizes the models has been presented in this study.
Multiscale modeling of manufacturing process for the advanced composite materials

OKABE Tomonaga, NISHIKAWA Masaaki

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2010 - 2012

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This study addressed the development of the production of the composite material by considering the resin flow and atomic structures. The contents done in this study are as follows; (1) Molecular dynamics simulation of interface between fiber and matrix, (2) Development of particle modeling for the resin transfer molding, (3) Resin transfer molding simulation for the modeled unit cell structures, (4) Micro mechanical simulation for the interface between fiber and matrix using the cohesive zone model, (5) Experimental study for the modeled unit cell structures, (7) Experimental evaluation of interface between fiber and matrix.
Highly accurate evaluation of mechanical and electrical properties of nanocomposites based on multi-scale analysis

HU Ning, FUKUNAGA Hisao, OKABE Tomonaga, WATANABE Tomonori

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Chiba University

2010 - 2012

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To enhance the properties of high-performance and multi-functional nanocomposites, it isimportant to accurately predict the macroscopic mechanical and electrical properties of the nanocomposites based on the information of nano- and micro-scale material structures. In this research, based on the construction of highly accurate sequential multi-scale numerical models for prediction of the mechanical and electrical properties of the nanocomposites, we uncovered the mechanisms of enhancement of matrix's mechanical and electrical properties due to addition of nanofillers. Moreover, experimental measurements of the mechanical and electrical properties of the nanocomposites were carried out for validating the proposed multi-scale numerical models. The design guidelines of the nanocomposites were provided by these multi-scale numerical models, which finally were used to successfully enhance the the mechanical and electrical properties of the nanocomposites.
Real-time Damage Monitoring of Aerospace CFRP Structures Based on Exper imental Impact Force Identification

FUKUNAGA Hisao, HU Ning, OKABE Tomonaga, KAMEYAMA Masaki

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2008 - 2010

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In the present research, a real-time identification method on impact location and force is established for foreign object impact of CFRP laminated plates, stiffened panels and FW tanks with piezoelectric sensors, based on the experimental impact force identification method. Further, a damage monitoring technique to monitor impact damages in real-time is developed by using the identified maximum impact force.
Research on highly accurate structural health monitoring based on the Lamb wave propagation analysis for composites structures

HU Ning, FUKUNAGA Hisao, OKABE Tomonaga, KAMEYAMA Masaki

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2007 - 2009

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In this research, for smart metallic and composite structures with sensor and actuator network in operating aircrafts and high speed vehicles, a highly accurate numerical simulation method of Lamb wave propagation and a signal processing method have been developed. Based on detailed investigations of interactions between Lamb wave and various damages, the mechanism of reflected and transmitted waves, and the characteristics of these reflected and transmitted waves have been studied. Then, the identification accuracy and reliability of damage location in metallic and composite structures has been improved, moreover, quantitative evaluation methods of damage size have been built up.
Experimental characterization of thermal shock and ballistic impact damages in 3D-woven CMC

OGI Keiji, OKABE Tomonaga, TAKAHASHI Manabu

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Ehime University

2006 - 2008
CFRPにおける繊維・マトリックス界面の力学的特性評価

岡部朋永

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 若手研究(B)

Institution: 東北大学

2006 - 2007

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単繊維複合材料による繊維・界面の評価結合力要素を組み込んだ有限要素解析を用い、SFCにおける微視的損傷を解析し、以下の結論を得た.繊維破断から発生する母材のき裂および界面の剥がれの発生・進展を解析した。剥がれの進展は、母材のき裂の進展によって大きく抑制される。従って、界面の剥がれは、母材のき裂を考慮して評価する必要がある。繊維破断部近傍の損傷形態に及ぼす母材の塑性変形の影響について調べた。界面の剥がれの進展は、母材の塑性変形によって遅延する。この結果から、弾性モデルを用いた解析方法は、実験結果を説明できる破壊靱性値を高く見積もるため、適切でないことが分かった。また、SFCにおける埋め込まれた繊維の破断過程に対するモンテカルロシミュレーションを行なった。界面の剥がれが繊維破断近傍の支配的な損傷である場合、破断数は飽和する。この場合、Huiらの理論モデルで繊維強度の推定が行える。一方、母材のき裂が繊維破断近傍で発生する場合、剥がれの発生は抑制され、破断数が飽和しない。この場合、本シミュレーション結果は、弾塑性シアラグモデルを用いたモンテカルロシミュレーション結果と良く一致することが示された。微視的モデルに基づく繊維強化複合材料の強度予測実験にて求めた構成材料の機械的性質・強度を基に、一方向CFRP複合材料の引張強度予測を行った。本予測手法を用いれば、構成材料(繊維・マトリックス)の特性をデータベース化しておくことで、設計に幅広く利用することができる。具体的には、ばね要素モデルの結果とサイズスケーリング手法を組み合わせて、一方向CFRP複合材料の引張強度の予測を行ったところ、概ね予測することができた。一方、通常のワイブル分布を用いた場合の予測結果は実験と比べ、極めて高い値となった。つまり、一方向CFRP複合材料の引張強度を予測する上で、合成ワイブルモデルは必要不可欠な考え方である。
IMPACT DAMAGE MONITORING OF AIRCRAFT COMPOSITE STRUCTURES WITH PIEZOELECTRIC SENSORS

FUKUNAGA Hisao, HU Ning, OKABE Tomonaga, KAMEYAMA Masaki

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2005 - 2007

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In the present research, we have developed a real-time and automatic health monitoring method for smart composite structures with strain sensors, in order to improve the reliability and safety of composite structures. The conclusions obtained by the present study are summarized as follows: 1. We have proposed a force identification method using an experimental transfer matrix, and identified the location and history of impact force from dynamic strain responses in composite laminates. The validity of the present method is verified through an impact test of CFRP stiffened panels with impulse hummer, and the location and history of impact force can be identified precisely in a few seconds after impact. 2. A real-time damage monitoring method has been developed using the identified impact force history. It is shown that the damage occurrence can be predicted easily from the shape of the identified force history, where the shape of force history is smooth without damage while that has a sharp oscillation with damage. 3. The experimental relationships between the impact energy and the maximum force, and between the maximum force and the damage size have been obtained in drop-weight test, which have a good agreement with predicted ones based on the finite element analysis. Delamination size predicted by the finite element analysis has also a good agreement with that observed experimentally by the ultrasonic C-scan image.
REAL-TIME HEALTH MONITORING OF COMPOSITE STRUCTURES BASED ON ACTIVE SENSING

FUKUNAGA Hisao, HU Ning, OKABE Tomonaga, KAMEYAMA Masaki, SUZUKI Hiroshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: TOHOKU UNIVERSITY

2003 - 2004

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In the present research, we have developed a real-time and automatic health monitoring method for smart composite structures with piezoelectric sensors, in order to improve the reliability and safety of composite structures. The conclusions obtained by the present study are summarized as follows : 1.We proposed a force identification method to estimate the location and history of impact force using dynamic responses of piezoelectric sensors embedded in composite laminates. The validity of the present method is verified through an impact experiment of CFRP laminated plates using impulse hummer, and it is shown that the location and history of impact force can be identified precisely in a few seconds after impact. A real-time damage monitoring method under impact force is also developed by using damage growth analysis. 2.We proposed a damage monitoring method of laminated composites based on an active sensing using piezoelectric actuators and sensors. The density of matrix cracking of cross-ply laminates under extension is identified effectively from the velocity variation of Lamb waves in laminated composites with and without damage. 3.Highly effective spectral analysis is developed to analyze the wave motion in laminated composites with matrix cracking or delamination.
繊維強化プラスチックの損傷力学的評価とヘルスモニタリング技術開発

岡部朋永

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 若手研究(B)

Institution: 東北大学

2002 - 2003

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電気抵抗変化によるヘルスモニタリング炭素繊維強化複合材料においては繊維が導電性を有するため、その破断は電気抵抗変化の形でモニタリングすることが可能である。そこで、数値解析および損傷力学モデルを併用することで、引張荷重下の損傷のモニタリングを試みた。特に材料内部の繊維の状況を等価電気回路に置き換えた数値解析手法は世界でも類を見ないものである。実験結果は予測結果と良く一致しており、有効なヘルスモニタリング手法であることが示された。損傷力学モデリング複合材内部に発生するき裂が引き起こす剛性の低下を、損傷力学モデルによって評価した。このとき、従来では損傷テンソルの導出が曖昧であり、得られた結果を現象と結びつけることが出来なかった。そこで、き裂近傍の変位場を解析的に解くことによって、損傷テンソルの導出を行った。数多くの先行研究における実験結果と比較検討を行ったところ、様々な積層構成を有する積層板に適用が可能であることがわかり、妥当な結果を得ることが出来た。また、この定式化を利用した有限要素法による数値破壊シミュレーションを確立した。ラム波を用いたヘルスモニタリング近年、注目を集めているラム波を用いたヘルスモニタリングを先に述べた損傷力学を利用することで行った。複合材中を伝播する波の速度は損傷量が増えるにつれ低下し、解析結果は実験結果と良く一致した。また、この技術をもとに、機械的ひずみの増大に伴う剛性の上昇を加味した新しいヘルスモニタリング手法を確立した。
Structural Health Monitoring of CFRP Laminates : Development of 90-degree Crack Detection and Suppression System

TAKEDA Nobuo, OKABE Tomonaga, OKABE Yoji

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: The University of Tokyo

2001 - 2002

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The purpose of the present study is to develop a structural health monitoring system to detect and suppress transverse cracks in a90-degree layer which generate at the early stage of loading. Transverse crack detection was made with a small-diameter (40 μm in coating diameter, 52 μm in coating diameter) Fiber Bragg Grating (FBG) sensor embedded in the CFRP lamina neighboring to the 90-degree layer. Transverse cracks generated in the gage section of the FBG sensor induce non-uniform strain distribution in the same section and change in the reflection spectrum of the sensor. This phenomenon can be used for the detection of transverse cracks. The experiments for the transverse crack detection were successfully conducted for cross-ply laminates as well as quasi-isotropic laminates. The experimental results were also reasonably explained by the theoretical analysis of the non-uniform strain distribution and the fiber optic theory. Transverse crack suppression was made with a 40-μn thick pre-strained shape memory alloy (SMA) foil embedded in the interlaminar region. When the pre-strained SMA is heated, the SMA shrinks and the recovery stress is generated, which retards the strain level of crack initiation and reduces the crack multiplication rate. The experiments for the transverse crack suppression were successfully conducted for cross-ply laminates at different temperatures. These experimental results were also reasonably explained by the theoretical analysis based on both the modified Brinson model for SMA constitutive equation and the shear-lag analysis. Then the optimum condition was determined for the SMA location, pre-strain level and applied temperature. Then, both detection and suppression systems were implemented in the same CFRP laminate to demonstrate the simultaneous damage detection and suppression system. The damage suppression system was successfully operated after the damage detection system detected the transverse cracks in the 90-degree ply.

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Teaching Experience 3

力学と物理数学　東北大学
弾性力学　東北大学
固体力学　東北大学

Social Activities 9

仙台市立青陵中等教育学校講演会

2017/09/19 -

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1年生とそのPTA向けの講演
金沢工業大学特別講義

2017/06/10 -

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複合材料の設計について講義を行う
土木学会東北地区応用力学フォーラム

2016/10/04 -

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講師
ダッソー・システムズ・バイオビア株式会社講演会

2016/06/15 -

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マルチスケール・シミュレーション・プロジェクトに関わる研究成果について講演
株式会社インテリジェント・コスモス研究機構第四回ＣＦＲＰ研究会講演会

2016/01/13 -

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講師
青森県立弘前南高等学校出前講義

2015/07/09 -

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青森県立弘前南高等学校生徒への講義を行う
サイエンスカフェ第85回

2012/10/26 -

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講演「次世代航空機への挑戦～航空機開発の最前線～」
河北新報「次世代航空機開発へ」

2012/04/03 -
中日新聞

2012/04 -

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「次世代航空機研究センター発足」

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Media Coverage 1

河北新報「科学の泉」

2014/04

Type: Newspaper, magazine

Other 63

CFRPの低コスト製造プロセスに関するマルチスケールシミュレーション技術開発

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分子シミュレーションに基づく高性能かつ高生産性を有する樹脂の開発
異種材料接着における分子・マクロ計算の連係法の調査研究

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分子動力学法と有限要素法を連結し、異種材料界面の破壊を再現する手法を確立する
CMC損傷評価技術の開発

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CMC損傷評価に関する解析手法および評価技術の開発
次世代複合材民間旅客機体設計ツールの開発

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東北大学の空力・構造同時多目的最適化設計ツールを用い、複合材旅客機体設計の技術課題を抽出する。
繊維強化複合材料のマルチスケールシミュレーション技術の開発

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繊維強化複合材料の力学特性を抜本的に向上させ、航空機構造用の軽量化を推進するための新しい材料設計の方法論を創出する。
炭素繊維複合材の切削加工の技術開発

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次世代構造部材創製・加工技術開発（航空機用難削材高速切削加工技術）の開発
CMC損傷評価技術の開発

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CMC損傷評価に関する解析手法および評価技術の開発
異種材料接着における分子・マクロ計算の連係法の調査研究

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分子動力学法と有限要素法を連結し、異種材料界面の破壊を再現する手法を確立する
複合材料の破壊解析とシミュレーションによる検証

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実験の破壊を再現するモデルを作成する
繊維強化複合材料のマルチスケールシミュレーション技術の開発

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繊維強化複合材料の力学特性を抜本的に向上させ、航空機構造用の軽量化を推進するための新しい材料設計の方法論を創出する。
CMC損傷評価技術の開発

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CMC損傷評価に関する解析手法および評価技術の開発
航空機用構造設計シミュレーション技術開発

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次世代構造部材創製・加工技術開発（航空機用難削材高速切削加工技術）の開発
CFRP接着における分子・マクロ計算の連携法の調査研究

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分子・マクロ計算間で計算条件や材料物性を相互にやりとりする方法論の調査研究
異種材料接着における分子・マクロ計算の連係法の調査研究

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分子動力学法と有限要素法を連結し、異種材料界面の破壊を再現する手法を確立する
複合材料の破壊解析とシミュレーションによる検証

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実験の破壊を再現するモデルを作成する
炭素繊維複合材の切削加工の技術開発

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次世代構造部材創製・加工技術開発（航空機用難削材高速切削加工技術）の開発
繊維強化複合材料のマルチスケールシミュレーション技術の開発

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繊維強化複合材料の力学特性を抜本的に向上させ、航空機構造用の軽量化を推進するための新しい材料設計の方法論を創出する。
CFRPの低コスト製造プロセスに関するマルチスケールシミュレーション技術開発

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分子シミュレーションに基づく高性能かつ高生産性を有する樹脂の開発
軽量耐熱複合材（CMC）の損傷評価技術の開発

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CMC損傷評価に関する解析手法および評価技術の開発
複合材料の破壊解析とシミュレーションによる検証

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実験の破壊を再現するモデルを作成する
熱可塑性CFRPの開発及び構造設計・加工基盤技術の開発

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熱可塑性CFRPの開発及び構造設計・加工基盤技術の開発
繊維強化複合材料のマルチスケールシミュレーション技術の開発

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繊維強化複合材料の力学特性を抜本的に向上させ、航空機構造用の軽量化を推進するための新しい材料設計の方法論を創出する。
等方性CFRTPの材料・構造マルチスケール解析技術の研究

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等方性CFRTPの長期耐久性評価モデルを構築し、寿命予測シミュレーション手法を確立する。
軽量耐熱複合材（CMC）の損傷評価技術の開発

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CMC損傷評価に関する解析手法および評価技術の開発
CFRPに対するマルチスケール構造解析・設計手法の研究

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CFRP構造に対する新規構造解析手法（マルチスケール解析）の開発
高分子の大変形過程の可視化

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結晶性高分子の大変形時に内部で起こる現象を表すためのモデル開発と検証
炭素繊維複合材の切削加工技術開発

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次世代構造部材創製・加工技術開発（航空機用難削材高速切削加工技術）の開発
繊維強化複合材料のマルチスケールシミュレーション技術の開発

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繊維強化複合材料の力学特性を抜本的に向上させ、航空機構造用の軽量化を推進するための新しい材料設計の方法論を創出する。
CFRPに対するマルチスケール構造解析・設計手法の研究

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CFRP構造に対する新規構造解析手法（マルチスケール解析）の開発
軽量耐熱複合材（CMC）の損傷評価技術の開発

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CMC損傷評価に関する解析手法および評価技術の開発
新規等方性短繊維CFRTPのミクロ構造解析技術の研究

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新規等方性短繊維CFRTPのミクロ構造解析技術の研究
熱硬化性樹脂の硬化反応特性に関する数値シミュレーション技術の開発

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熱硬化性樹脂の主剤と硬化剤との組み合わせに依存する硬化時間並びに架橋形成を予測する数値シミュレーション技術の開発
ガラス繊維強化熱可塑性樹脂の各種特性に関する数値シミュレーション

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ガラス繊維の径や長さ、強化熱可塑性樹脂との界面密着状態等をパラメータとしたシミュレーションプログラムを開発する。
CFRPに対するマルチスケール構造解析・設計手法の研究

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CFRP構造に対する新規構造解析手法（マルチスケール解析）の開発
軽量耐熱複合材（CMC）の損傷評価技術の開発

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CMC損傷評価に関する解析手法および評価技術の開発
奨学研究費

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研究助成の為
複合材料研究センター助成金

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研究助成の為
新規等方性短繊維CFRTPのミクロ構造解析技術の研究

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新規等方性短繊維CFRTPのミクロ構造解析技術の研究
熱硬化性樹脂の硬化反応特性に関する数値シミュレーション技術の開発

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熱硬化性樹脂の主剤と硬化剤との組み合わせに依存する硬化時間並びに架橋形成を予測する数値シミュレーション技術の開発
Development Of An Analytical Tool For Damage Evolution Of Cracked Particle Reinforced Rubber Composite(PRC)

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Development Of An Analytical Tool For Damage Evolution Of Cracked Particle Reinforced Rubber Composite(PRC)
奨学研究費

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研究助成の為
新規等方性短繊維CFRTPのミクロ構造解析技術の研究

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新規等方性短繊維CFRTPのミクロ構造解析技術の研究
一方向CFRPの界面特性が破壊強度に与える影響に関する数値シミュレーション

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一方向CFRPの界面特性が破壊強度に与える影響に関する数値シミュレーション
複合材料研究センター助成金

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研究助成の為
CFRP積層板へのソフトボディ衝突時の損傷進展解析技術の研究

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界面強度と破壊靱性値の影響を考慮するために繊維－樹脂界面に結合力要素を導入した数値シミュレーション手法を構築し、一方向CFRPの破壊形態や強度に及ぼす影響を明らかにすると共に強度向上のための指針について検討する。
CFRP積層板の高速衝撃挙動の予測技術の研究

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複合材ファンシステムの衝撃損傷問題に関する解析面からの取組を行うものであり、ファンシステムにおける衝撃現象高速衝撃による複合材料の損傷・破壊現象のモデル化とシミュレーション手法の研究開発を行う。
2009年度＿研究助成のため

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岡部朋永准教授に対する研究助成
新規等方性短繊維CFRTPのミクロ構造解析技術の研究

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新規等方性短繊維CFRTPの強度解析
研究助成

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岡部朋永准教授に対する研究助成
研究助成

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岡部朋永准教授に対する研究助成
数値解析によるCFRP積層板の高速衝撃損傷の予測に関する研究

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数値解析によるCFRP積層板の高速衝撃損傷の予測を行う
2008年度＿研究助成のため

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岡部朋永准教授に対する研究助成
新規等方性短繊維CFRTPのミクロ構造解析技術の研究

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新規等方性短繊維CFRTPの強度解析をおこなう。
研究助成

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岡部朋永准教授に対する研究助成
研究助成のため

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岡部朋永准教授に対する研究助成
CFRP積層板の高速衝突損傷解析に関する研究

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CFRP積層板の高速衝突損傷解析を行う
２００７年度研究助成

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岡部朋永准教授に対する研究助成
２００７年度研究助成のため

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岡部朋永准教授に対する研究助成
２００７年度研究助成

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岡部朋永准教授に対する研究助成
２００７年度＿研究助成

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岡部朋永准教授に対する研究助成
２００６年度研究助成

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岡部朋永准教授に対する研究助成
構造ヘルスモニタリングシステムにおけるセンシング最適化に関する委託研究

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構造ヘルスモニタリングシステムにおけるセンシング最適化を行う
熱焼反応流中における先進セラミック基複合材料の曝露試験法の提案

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熱焼反応流中における先進セラミック基複合材料の曝露試験法の提案sしている

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