The influence of an interphase on the deflection of a matrix crack in a ceramic-matrix composite

The main purpose of this paper is to develop a criterion which is able to predict a particular mechanism of matrix crack deflection which often occurs in brittle-matrix composites: an interface debonding ahead of the matrix crack. The problem is solved with the help of an energetic approach which couples an asymptotic and a numerical analysis. It is further extended by taking into account the presence of an interphase introduced between the fibre and the matrix. Numerical results are then used to describe a crack deflection mechanism within a model bi-material (consisting of two dense alumina substrates separated by a porous alumina interlayer) and a SiC/SiC composite.