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.