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Volume 37 (2011)
- Issue 6 Pages 203-
- Issue 5 Pages 164-
- Issue 4 Pages 121-
- Issue 3 Pages 93-
- Issue 2 Pages 46-
- Issue 1 Pages 3-
Volume 37, Issue 3
Displaying 1-3 of 3 articles from this issue
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Research paper
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Masamichi KAWAI, Yasuhiko YAGIHASHI, Hikaru HOSHI, Yutaka IWAHORI2011 Volume 37 Issue 3 Pages 93-102
Published: 2011
Released on J-STAGE: February 25, 2012
JOURNAL FREE ACCESSThe effect of water uptake on fatigue lives of a woven fabric CFRP quasi-isotropic laminate under constant amplitude loading at different stress ratios has been examined. First, constant amplitude fatigue tests are performed at room and high temperatures on the specimens immersed in hot water until saturation and on the specimens kept in a dry place. Experimental results show that the fatigue lives of wet specimens are shorter than those of dry specimens, regardless of stress ratio and test temperature. The degree of reduction in fatigue strength due to water uptake is about eleven percent at most, that is independent of stress ratio. Then, the full shapes of the constant fatigue life (CFL) diagrams for the laminate in dry and wet environments, respectively, at different temperatures are identified on the basis of the fatigue test data obtained at different stress ratios. It is demonstrated that they are characterized by asymmetry, nonlinearity and gradual change in shape. Finally, the anisomorphic CFL diagram approach for composites that was developed in the earlier study is tested on the dry and wet CFRP laminates at different temperatures. It is shown that the anisomorphic CFL diagram approach is successfully applied for predicting the CFL diagrams and thus the S-N relationships for the woven CFRP laminate, regardless of moisture content and test temperature.View full abstractDownload PDF (2240K) -
Masahito UEDA, Atsuhito HIRAGA, Tetsu NISHIMURA2011 Volume 37 Issue 3 Pages 103-110
Published: 2011
Released on J-STAGE: February 25, 2012
JOURNAL FREE ACCESSMicro-buckling characteristic of a carbon mono-fiber in matrix was studied. A fiber was modeled in matrix as a column on elastic foundation. Buckling stress of the fiber was calculated incorporating the initial fiber misalignment and non-linearity of the matrix. The effect of bending on compressive stress was also taken into considered to estimate failure initiation at fiber surface. Two processes of ultimate fiber failure were considered. First one is a compressive fracture at fiber surface due to compression and bending. Second one is a matrix-yielding initiated unstable fiber deformation. Compression test of a carbon fiber in matrix was performed by means of a four point bending test. Electrical resistance of the carbon fiber was measured during the compression test to recognize initiation of the compressive fracture. Fiber breaks at two adjacent locations were observed, which was caused by micro-buckling of the fiber. Apparent compressive strength of the fiber was measured in the experiment. Actual compressive strength of the fiber was predicted from the apparent compressive strength. Correlation between compressive strengths based on the elastic foundation model and the kink band model was discussed.View full abstractDownload PDF (1281K) -
Kazuhiro SAKATA, Naomi KISHITANI, Goichi BEN2011 Volume 37 Issue 3 Pages 111-118
Published: 2011
Released on J-STAGE: February 25, 2012
JOURNAL FREE ACCESSIsogrid structures have a higher specific strength and stiffness, they are composed of triangular grid stiffeners and a face layer. One of features in isogrid structures is the offset part which is effective for avoiding stress concentration at the cross points of grid stiffeners. These structures are being mainly used for aerospace applications. In order to produce a metal isogrid cylindrical shell, a majority of thick metal plate is milled to produce the isogrid panel and then its both ends are welded to each other. Therefore, unstable behaviors of isogrid structures are generally observed in the joint parts. However, the CFRP isogrid cylindrical shell can be simultaneously fabricated the parts of shell and grid with a filament winding method. In this study, a molding of isogrid CFRP cylindrical shells is proposed and their compression tests are also conducted to investigate the stiffening effects of isogrid CFRP cylindrical shell. Furthermore, the results of the compression tests are compared with numerical ones obtained by FEM.View full abstractDownload PDF (5953K)
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