Effects of the thermal residual stress field on the crack propagation in graded alumina/zirconia ceramics

A numerical approach to study the crack propagation in symmetric step-wise graded Alumina/Zirconia composites subjected to a residual stress field is presented in this work. The finite element method is used to calculate the stress intensity factor for cracks developing from the surface and to determine the effects of the thermal residual stresses. The results show that a suitably conceived stacking sequence induces in the laminate a residual stress field able to provide increased toughness and reliability of the structure by making the crack propagation stable below a given threshold stress. Moreover a lower bound on stress, below which no crack propagation occurs, can be identified.