多层界面相陶瓷基复合材料裂纹偏转机制模拟

针对多层界面相陶瓷基复合材料(CMCs)裂纹偏转机制进行了有限元模拟。在圆柱单胞模型中,按照界面相各亚层的实际厚度建立多层界面相几何模型,然后赋予各亚层对应的组分材料参数,获取轴对称有限元模型。在此基础上,采用虚拟裂纹闭合技术(VCCT)分别计算基体裂纹在界面相处偏转与穿透两种情形的能量释放率Gd和Gp,根据断裂力学准则实现对裂纹在多层界面相内部偏转机制的分析。可以看出:各向异性界面相比各向同性界面相内部的Gd/Gp比值更大,更利于裂纹偏转的发生；总厚度相同的多层界面相与单层界面相相比,其内部的Gd/Gp比值更高,裂纹在其内部发生偏转的机会更多,且五层界面相(PyC/SiC/PyC/SiC/PyC)比三层界面相(PyC/SiC/PyC)更利于裂纹发生偏转。 

Simulation of the crack deflection mechanism for ceramic matrix composites with multilayer interphase

The crack deflection mechanism in ceramic matrix composites (CMCs) with multilayer interphase was simulated by finite element method. The sub-layers of interphase were created according to their real thickness within a cylinder unit-cell model to describe the microstructure of multilayer interphase of CMCs. The finite element method was applied to analyze the stress by defining different material properties for the interphase sub-layers. The energy release rates Gd and Gp for two cases, i.e. penetration and deflection, were calculated by the virtual crack closure technique (VCCT). After all, a simulation method for crack deflection in the multilayer interphase was developed. It can be seen that the anisotropic interface is more conducive to the occurrence of crack deflection than the isotropic interface phase as the value of Gd/Gp is higher. There is more chance for crack deflection in the multilayer interface phase than the monolayer interphase with same thickness according to the distribution of Gd/Gp in the interphase. Hence, the crack deflection is easier in the (PyC/SiC/PyC/SiC/PyC) interphase compared with the (PyC/SiC/PyC) interphase.