Effect of thermal misfit stress on crack deflection at planar interfaces in layered systems

Deflection of a crack at a planar bi-material interface in a layered system was investigated by considering the effects of the in-plane residual thermal misfit stress. A new parameter based on strains due to mismatch of thermal expansion coefficients was introduced to describe residual stress state independent of length scale. From a numerical analysis, it was predicted that introducing compressive residual stress in the stiffer intact layers of a composite laminate ahead of a growing primary crack would favour crack deflection by allowing advantageous energetic conditions, which indicates that stronger interfaces can be introduced in layered systems this way to improve overall mechanical properties. It was also predicted that the residual stress effect is negligible if the intact layer is more compliant than the cracked layer supporting a previous analysis and discussion reported elsewhere.