Dept. of Space Flight Systems

中村 俊哉

ナカムラ トシヤ  (Toshiya Nakamura)

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

論文

 54
  • Toshiya Nakamura
    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
  • Hiroki Kawabe, Yuichiro Aoki, Toshiya Nakamura
    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.
  • Hiroshi Suemasu, Yuichiro Aoki, Hikaru Hoshi, Yasutomo Tateishi, Sunao Sugimoto, Toshiya Nakamura
    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.
  • Hiroshi Suemasu, Yuichiro Aoki, Yasutomo Tateishi, Sunao Sugimoto, Toshiya Nakamura
    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.
  • Hiroshi Suemasu, Yuichiro Aoki, Sunao Sugimoto, Toshiya Nakamura
    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

 181

所属学協会

 3

共同研究・競争的資金等の研究課題

 1