2.5维机织复合材料疲劳寿命预测方法

针对疲劳载荷作用下的2.5维机织复合材料，建立了疲劳寿命预测方法.该方法主要包括单胞模型、疲劳失效判定准则和材料性能退化方法3部分.选取单胞模型为研究对象，利用三维有限元技术进行应力分析；引入改进的三维Hashin疲劳失效准则和Mises准则作为纤维束和树脂基体的疲劳失效判据；采用刚度性能突降准则描述疲劳失效后的材料性能，采用考虑纤维体积分数影响的剩余刚度和剩余强度退化模型描述失效前材料的性能.通过疲劳寿命预测值与试验值的对比，验证了疲劳寿命预测方法的有效性.研究表明:经向拉-拉疲劳寿命随经纱纤维体积分数增大而增加，纬向拉-拉疲劳寿命受纬纱纤维体积分数影响较小. 

Fatigue life prediction method of 2.5 dimensional woven composites

A fatigue life prediction method was developed to predict fatigue life of 2.5 dimensional woven composites subjected to fatigue loading. This method consisted of unit-cell model, fatigue damage criterion and material property degradation technique. Stress analysis was performed by three dimensional finite element technology based on the unit-cell model. Modified three dimensional Hashin fatigue damage criterion and Mises criterion were adopted to identify fatigue damage separately for the yarns and matrix. The stiffness property sudden degradation rules were applied to establish the fatigue damaged material properties; the residual stiffness and strength models considering fiber volume fraction were used to establish the undamaged material properties. The coincidence of predicted fatigue life and experimental data was studied, and the comparison results validated the fatigue life prediction method. The results indicate that the tensile-tensile fatigue life in warp direction increases with the warp fiber volume fraction increasing, while weft fiber volume fraction has little effect on tensile-tensile fatigue life in weft direction.