复合材料疲劳分层的界面单元模型

Interface element model for fatigue delamination analysis of composites

提出一种三维黏聚力界面损伤模型,可以描述单调和交变载荷下层合复合材料混合型的分层损伤。损伤用界面所经历过的最大位移间断来定义,交变荷载下一个周期的加、卸载过程均考虑有损伤积累,模型还考虑了单调和疲劳损伤的门槛效应和交变载荷下裂纹的闭合效应。建立了包含该界面损伤模型的初始无厚度八节点等参界面单元,并引入加速损伤的算法,用一次计算循环代替若干次实际循环,提高计算效率。用该单元模型对某复合材料动部件疲劳分层裂纹的形成和扩展进行了模拟,得到了分层裂纹前沿界面局部损伤和结构疲劳分层的发展规律,模型预测的裂纹长度荷载循环次数对数(alogN)曲线和结构剩余刚度与试验数据吻合。

A three dimensional interfacial fatigue damage model was proposed.Mixed mode delamination of laminated composites caused by both monotonic and fatigue loads can be represented by this model.The maximum jumping displacement of interface experienced in the history was adopted as the damage indicator.For fatigue load,damage accumulation in one unloading and reloading cycle was taken into account.Damage thresholds and no interface interpenetration conditions were considered in this model.A three-dimensional eight-node isoparametric interfacial element without initial thickness was constructed to model the constitutive law of the interface.A damage accelerating arithmetic was introduced to reduce the computing time.In this arithmetic damage accumulation in several real loading cycles was represented by damage increment in one computing cycle.This element was used to simulate the initiation and growth of fatigue delamination in a laminated composite rotating component.The interfacial damage near the interface crack tip and the development of delamination in the component were obtained.The predicted a-logN curves and residual stiffness agree well with the experimental data.