Contact strength of ceramic laminates

Ceramic laminates with residual stress arising from thermal mismatch, show higher strength and larger apparent fracture toughness than their monolithic counterparts. For an effective improvement under in-service conditions, such enhancement should be reflected on the blunt-contact behaviour, characterized by an inhomogeneous multiaxial stress state. The contact strength test is an interesting alternative to traditional testing methods to evaluate contact-focused resistance of brittle materials. Because of the Hertzian-like stress state, high stresses can be generated far from the surface, producing failure from the weakest part of the structure, and this is especially true in pre-stressed materials, such as the one herein studied. In this work, experimental tests on a laminated ceramic are reported together with a FE analysis, showing a noteworthy improvement, although in some cases the composite structure may fail in an inner layer, and providing general tools for designing contact-resistant structures.