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Volume 35, Issue 1
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Research paper
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Jian-Qi ZHANG, Masamichi KAWAI, Satoru SAITO, Yi XIAO, Hiroshi HATTA2009 Volume 35 Issue 1 Pages 3-14
Published: 2009
Released on J-STAGE: November 30, 2010
JOURNAL FREE ACCESSOff-axis compressive deformation behavior of a unidirectional CFRP laminate at high temperature and its strain-rate dependence in a quasi-static range are examined for various fiber orientations. By comparing the off-axis tensile and compressive behaviors at an equal loading rate, the effect of loading direction on the flow stress level, nonlinearity and rate-dependence of off-axis deformation is elucidated. The experimental results show that the compressive flow stresses for relatively larger off-axis angles 30, 45, 90° have about 50 percent larger values than in tension for the same fiber orientations, respectively. The off-axis flow stresses in tension and compression significantly depend on the rate of loading, while they exhibit similar features in fiber orientation dependence and tension-compression asymmetry of off-axis nonlinear behavior regardless of the rate of loading. Then, formulation of a phenomenological viscoplasticity model that can describe the nonlinear rate-dependent behavior as well as its tension-compression asymmetry of unidirectional composites under off-axis loading in a unified manner is attempted. It is demonstrated that the proposed viscoplasticity model succeeds in adequately predicting the fiber orientation dependence of off-axis non-linear behavior, deformation asymmetry in off-axis tension and compression, and the strain rate dependence.View full abstractDownload PDF (1021K) -
Yosuke NAGAO, Seishiro KIBE, Kanako DAIGO, Ayami HARA2009 Volume 35 Issue 1 Pages 15-26
Published: 2009
Released on J-STAGE: November 30, 2010
JOURNAL FREE ACCESSCFRP is being used as a material for primary structures in the field of spacecraft. However, a huge quantity of debris exists in the space near the earth. Since there are a lot of chances that debris collides with the composite material of a spacecraft structure, a future spacecraft design requires data on the damage development in CFRP structure. Furthermore, the collision effect on strength reduction should be known. Therefore, this study conducted hypervelocity impact tests for CFRP plates which imitated the collision of debris in the space. As a result, a specific relation between debris kinetic energy and the failure area in CFRP was obtained. Then, the residual compressive strength of a CFRP plate was investigated after a hypervelocity impact test, and a relationship between the kinetic energy and the residual strength were also clarified. Moreover, a hypervelocity impact test of a composite material was simulated by the use of commercial software, AUTODYN. In comparing simulation results with test results, a simple simulation conducted in this study demonstrated to be very effective in understanding the damage development with a hypervelocity impact.View full abstractDownload PDF (5615K) -
Akiko ODAWARA, Hiroyuki SATO, Tomohiko SUGIE, Kiyotaka MORISAKO, Tuyos ...2009 Volume 35 Issue 1 Pages 27-32
Published: 2009
Released on J-STAGE: November 30, 2010
JOURNAL FREE ACCESSThere are many traditional technologies that have much knowledge to fabricate products in Japan. Such a knowledge is so-called technical intuitions and sensitivities. The craftsmen apply the technique for regenerating some traditional products and we defined the knowledge as “implicit knowledge.” The concept of this study is to scientifically analyze the implicit knowledge of those technologies. Here, the implicit knowledge would be traced from the contemporary view point. Thus, the knowledge can be applied to the modern technology which is adaptable to the market requirements. Finally the traditional technology retailed with the advanced technology many create a new technology. Kyokabe is one of Japanese clay wall for the traditional architectures. The clay wall consists of clay, sand and straws. Straws obviously play a reinforcement, thus Kyokabe can be treated as a composite material. Straws are immersed in the mixture of clay, sand and water for some period of time. The implicit knowledge which Plasterers (masters of Kyokabe) have acquired is that increase in the straws quantity results in increase in compressive strength and increase in the time improves workability in drawing. In this study, the implicit knowledge is scientifically resolved. The effects of the quantity and the immersion time on the compressive properties and workability of Kyokabe were also investigated.View full abstractDownload PDF (1249K)
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