Crack deflection along the interphase for fiber reinforced ceramic matrix composites (CMCs) is an important condition upon which the toughening mechanisms depend. The multilayer interphase is designed and developed to enhance this deflection mechanism. Combined with the virtual crack closure technique, a finite element model was proposed to predict the competition between crack deflection and penetration in multilayer interphase of CMCs. The model was used to analysis the propagation of primary matrix crack in a SiC_f/SiC_m composite with (PyC/SiC)_n multilayer interphase. The effects of the number of sublayers, thicknesses of sublayers and thermal residual stress (TRS) on the energy release rate and the crack deflection mechanisms were studied. Results show that the multilayer interphase increases the ability to deflect the matrix crack at interfaces between sublayers. Moreover, the number of sublayers shows a larger effect than the thicknesses of the sublayers. The influence of TRS is much complex and needs to be evaluated accordingly. The research provides an analysis tool for promoting the toughening design of CMCs.

纤维增强陶瓷基复合材料（CMC）沿界面的裂纹挠度是增韧机制所依赖的重要条件。设计和开发了多层相，以增强这种偏转机制。结合虚拟裂纹闭合技术，提出了有限元模型来预测CMCs多层相间裂纹挠度与渗透的竞争。该模型被用于分析具有（PyC / SiC）_n的SiC _f / SiC _m复合材料中初生基体裂纹的扩展。多层相。研究了子层数，子层厚度和热残余应力（TRS）对能量释放速率和裂纹偏转机理的影响。结果表明，多层相提高了偏转子层之间界面处基体裂纹的能力。而且，子层的数量显示出比子层的厚度更大的效果。TRS的影响非常复杂，需要进行相应的评估。该研究为促进CMC的强化设计提供了一种分析工具。