Failure Resistance Optimisation in Layered Ceramics Designed with Strong Interfaces

Layered ceramics designed with weak interfaces favour interface delamination and provide high failure resistance, while laminates with strong interfaces show higher strength and enhanced mechanical reliability. In this paper it is proposed to combine crack bifurcation and interface delamination in a unique layered architecture with strong interfaces to optimise both failure resistance and mechanical reliability. Theoretical approaches from He and Hutchinson for delamination in bi-materials and from Lange et al. for crack bifurcation in multilayers are here employed to define an optimal design. These approaches are supported by own experimental results on an alumina-zirconia multilayer system designed with compressive stresses and strong interfaces. It is shown that a favourable condition for interface delamination occurs for bifurcated cracks if such cracks have a low inclination angle towards the next interface. The occurrence of bifurcation is triggered by the thickness of the compressive layers as well as by the compressive stresses, which also influence the bifurcation angle. Therefore, they are the key features for optimising these multilayered systems.