基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙飛翔工学研究系 特任教授
- 学位
- 工学博士(1991年3月 東京大学)
- 研究者番号
- 60237419
- ORCID ID
https://orcid.org/0000-0002-2403-5780
- J-GLOBAL ID
- 202101015987830507
- researchmap会員ID
- R000025142
経歴
7-
2024年4月 - 現在
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2021年11月 - 2024年3月
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2018年4月 - 2021年10月
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2000年4月 - 2018年3月
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1994年4月 - 2000年9月
学歴
1-
1986年4月 - 1991年3月
委員歴
14-
2022年4月 - 2024年3月
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2014年4月 - 2024年3月
受賞
7論文
55-
Mathematics in Engineering, Science and Aerospace 15(3) 889-901 2024年9月 査読有り筆頭著者責任著者The interfacial stress between fibers and matrix plays an important role in the durability and damage initiation of carbon fiber reinforced composites. In this study, thermoelastic analysis was performed on a plate containing randomly distributed multiple fibers. Complex stress functions were employed with a semi-numerical method to ensure displacement continuity along the fiber/matrix interface as a boundary condition. The statistical investigation reveals that the stress concentration due to the presence of multiple fibers increases as the fiber density increases, though its deviation decreases. A numerical case study was conducted to discuss the micromechanics of the inherent scatter of material strength. The stress-strength model with Monte-Carlo simulation demonstrated the fracture probability calculation. The uncertainty obtained is partially attributed to the micromechanical stress variation around the fibers.
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AIAA Journal 62(4) 1311-1317 2024年4月 査読有りThe objective of this study is to develop a novel aircraft design approach using biomimetics as an alternative to traditional airframes. This approach is primarily inspired by the dragonfly wing, which possesses reinforcement structures composed of cross veins and longitudinal veins. These structures are assumed to regulate deformation and enhance stiffness, respectively. The cross veins were replicated using weighted centroidal Voronoi tessellation (WCVT) based on the out-of-plane displacement of the skin. In contrast, the longitudinal veins were replicated by extracting a centerline from the topology optimization (TO) results on the skin, achieved through image analysis techniques such as binarization and skeletonization. The longitudinal layout effectively reduces compliance by distributing internal loads, utilizing only essential reinforcements on the skin without increasing its mass. The WCVT layout significantly enhances the buckling resistance of the reinforced skin. As a result, the skin reinforced using both cross–longitudinal layouts from TO and WCVT exhibited a buckling load 2.7 times greater while maintaining a lower mass compared to conventional layouts.
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Composites Part A: Applied Science and Manufacturing 172 2023年9月 査読有りAn analytical approach was developed for assessing the thermal history of thermoplastic composites during tape placement for in-situ consolidation of the automated fiber placement (AFP) technique. In this study, the heat-conduction equation is developed and solved for internal energy instead of temperature because the diffusivity does not significantly change over a wide range of temperatures in the AFP process, despite the significant change in the specific heat and conductivity. The three-dimensional internal energy history is derived in an integrated form using the Green function technique. The temperature field obtained from the internal energy field agreed with the finite element solution, where the temperature-dependent thermal properties were considered. The effects of manufacturing parameters, such as the placement speed and thickness of the placed laminates, on the thermal history of laminated composites during AFP are discussed using the present approach and finite element analysiss.
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Journal of Composite Materials 57(21) 3377-3391 2023年9月 査読有りTensile tests of quasi-isotropic laminates with a circular open hole, which include a gap in the hole area, were conducted to demonstrate the effect of the gap on the strength. The test showed that the reduction in the open-hole strength owing to the gap was less significant than that in the no-hole tensile strength. A two-dimensional mechanical model of quasi-isotropic laminates with an arbitrary inclined gap was proposed and analytically solved to obtain a closed-form expression for the stress concentration. An approximate expression was provided as the sum of the global uniform stress field and the local stress field near the open hole, which was solved based on a complex variable method. The present analytical solution agrees well with the corresponding two-dimensional finite element solutions. The solution indicated that the stress increase owing to the gap is limited at the stress concentration area. The analytical results were consistent with the experimental results.
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Composite Structures 306 2023年2月15日 査読有りCompression tests of quasi-isotropic laminates with embedded gaps were conducted to reveal the effect of the gap(s) on their compressive strength. Specimens were prepared such that the gaps are located at designated relative positions on a free side edge of the gage section. An analytical solution for a two-dimensional mechanical model of quasi-isotropic laminates with an arbitrary inclined gap is used to estimate the stress changes at the free edge owing to inclined gaps in the arbitrary relative locations. The relative reductions in the compressive strengths of the specimens with different gap arrangements were consistent with the analytically estimated increases in stress. The present results indicate that the significant reduction in compressive strength is caused not only by the waviness of the laminas at the gaps but also by the stress concentration at the free boundary due to the gap ends. Moreover, it is found that the standardized compression test may not be adequate to investigate the effect of the defect introduced by automated-fiber-placement method on the strength of the laminates because the sizes of the gage section of the compression test specimens specified by standard test methods are small compared to the gap spacing.
MISC
28講演・口頭発表等
190-
Asia-Pacific Conference on Fracture and Strength
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18th Japan International SAMPE Symposium and Exhibition 2023年11月
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36th Technical Conference of the American Society for Composites 2021: Composites Ingenuity Taking on Challenges in Environment-Energy-Economy, ASC 2021 2021年The aim of this study is to establish a novel aircraft design approach replacing the conventional airframe by utilizing biomimetics. This design approach particularly focused on the dragonfly wing, whose reinforcement structures are composed of cross-veins and longitudinal veins. The cross-veins have been emulated by weighted Centroidal Voronoi Tessellation (WCVT) following the out-of-plane displacement on the skin, while the longitudinal veins have been emulated by extracting a centerline from the topology optimization result on the skin to be reinforced, through image analysis of binarization and skeletonization. The longitudinal layout can reduce the compliance distributing the inner load with only essential reinforcement on the skin without increasing the mass. The weighted CVT layout can improve the effectiveness of the reinforced skin against buckling drastically. Thus, the skin reinforced along the cross-longitudinal layout by the topology optimization and weighted CVT pattern increased buckling load 2.7 times higher even with less mass than the conventional layout.
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Proceedings of the American Society for Composites - 35th Technical Conference, ASC 2020 2020年The aim of this study is to establish a novel aircraft design approach combining structural optimized biomimetics. The intention of utilizing biomimetics lies in acquiring an efficient and novel composites airframe structural concept replacing the “black metal structure.” A typical macroscopic structural layout on a dragonfly wing, called Voronoi patterns, was applied to the reinforcement structures on a part of an aircraft wing. This design approach significantly contributed to structural weight reduction. The manufacturability of more complex structure is also confirmed by producing prototypes, evaluating quality of created models and identifying an effective sectional shape in In-Situ Consolidation process. Furthermore, this application has advanced to a novel design methodology defining reinforcement layout not as some feature extracted from dragonfly wings but as theoretical and mathematical disposition. This methodology allows composites cover to acquire excellent properties, namely lightness and stiffness combining themselves properly. Bionic structure with Voronoi patterns has potential for weight reduction replacing conventional composites aircraft structures.
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Proceedings of the American Society for Composites - 35th Technical Conference, ASC 2020 2020年The aim of present study is to establish the optimization design approach for light weight composites aircraft structure. A composite panel with a large cut-out representing a part of lower wing panel is optimally designed with the curved fiber orientation based on principal load path. The optimum curved fiber orientation is directly defined by the principal stress direction derived from finite element analysis result. Only the fiber orientation in 0 degree layers are steered based on principal load path. Three different types of the optimum panel with different staggering strategies are precisely manufactured by Automated Fiber Placement (AFP) with tow-steering layup technique. The optimum panels are evaluated by testing under tensile load. The results show that the initial failure load of the optimum panels with curved fiber orientation is 6% higher than that of the conventional panel with straight fiber orientation with the same weight, and the panel stiffness of the optimum panel is 3% higher than that of the conventional panel. The maximum strain level around the cut-out of the optimum panel is 8% smaller than that of the conventional panel. These results indicate that the optimum panel is capable of sustaining larger load than the conventional panel, and imply the potential of structural weight reduction for load path tailored composite panel. Those improvements in the testing correspond well with the numerical prediction which is used for the panel design.
共同研究・競争的資金等の研究課題
1-
日本学術振興会 科学研究費助成事業 1999年 - 2001年