平織ＣＦＲＰ擬似等方積層板の疲労挙動に及ぼす湿熱環境の影響と非相似形等寿命線図の適用性

Abstract

The 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.