Finite Element Analysis of the Crack Deflection in Fiber Reinforced Ceramic Matrix Composites with Multilayer Interphase Using Virtual Crack Closure Technique

Abstract

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 SiCf/SiCm 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.