陶瓷基复合材料低循环拉—拉疲劳寿命预测

Low Cycle Tensile-Tensile Fatigue Life Prediction of Ceramic Matrix Composites

采用细观力学方法建立预测纤维增强陶瓷基复合材料低循环拉—拉疲劳寿命的模型。该模型考虑初始加载到疲劳峰值应力时,基体出现裂纹,纤维/基体界面发生脱粘,部分纤维将发生断裂,并采用统计方法得到初始加载到峰值应力时的纤维失效体积分数;在后续循环过程中,考虑纤维相对基体在界面脱粘区滑移造成界面切应力下降,纤维失效模型与Evans界面磨损模型相结合,得到循环过程中纤维失效体积分数与界面切应力、循环数之间的关系;当纤维失效导致剩余强度下降,并小于疲劳峰值应力时,判断材料失效。采用剩余强度方法对陶瓷基复合材料的S-N曲线进行预测,并将预测的S-N曲线与试验数据进行对比,结果吻合较好。

A micro mechanics approach to predict low cycle tensile-tensile fatigue life of fiber reinforced ceramic matrix composites is presented. When first loading to fatigue maximum stress, matrix cracking, fiber/matrix interface de-bonding occur, and partial fibers fracture. The statistical approach is used to determine the percentage of fracture fibers. Upon cycling, fiber slips relative to matrix in the interface de-bonding region, which makes interface shear stress decreased. By combing fiber failure model and interface wear model, the relationship between the percentage of fiber failure and interface, or cycles, is determined. Residual strength of ceramic matrix composites decreases as fiber failure. When residual strength is lower than fatigue maximum stress, the material fails. The residual strength approach is used to predict the S-N curve of ceramic matrix composites, the S-N curve agrees well with experiment data.