Study on Fatigue of Carbon-Epoxy Composites

研究了碳-环氧层压板的疲劳机理。对不同层合板的平片进行了拉-拉疲劳试验和压-压疲劳试验。两种试验都表明，疲劳损伤的基本过程是从试件自由边缘开始的分层扩展。基于有限元计算得到的各层界面应变能释放率预测的分层位置与实验结果吻合较好。验证了断裂力学对复合材料分层的适用性。在高温、高相对湿度条件下对试件进行了拉伸强度测试。结果表明，温度和湿度的环境效应对碳/环氧复合材料的力学性能有重要影响，方形层合板在后屈曲剪切载荷作用下发生疲劳循环。疲劳强度几乎没有降低，这说明复合材料层合板具有后屈曲重复加载能力。

Mechanism of fatigue of carbon-epoxy laminates was investigated. Tension-tension fatigue test on plain coupons of various laminates was conducted together with compressioncompression fatigue test. Both tests showed that the basic fatigue damage process is the growth of delamination initiated at the free edges of the specimens. The locations of delaminations predicted by the strain energy release rate at each interface of layers based on the finite element calculations were in good agreement with the experimental results. Thus the applicability of the fracture mechanics to the delamination of composites was verified.Tensile strength was tested on coupons at high temperature and high relative humidity. It was shown that the environmental effects of temperature and moisture play important role on the mechanical properties of carbon-epoxy composites.And square laminated panels were fatigue cycled under shear loading in post-buckling range. The fact that little reduction of strength due to fatigue was detected reveals the post-buckling repeated loading capacity of composite laminates.