Strategies for fracture toughness, strength and reliability optimisation of ceramic-ceramic laminates

Layered ceramics are, compared to conventional monolithic ceramics, a good choice for highly loaded structural applications having improved fracture toughness, strength and mechanical reliability. The use of tailored residual compressive stresses in the layers is the key parameter to adjust these properties. In this work two types of ceramics are analysed which have external (ECS-laminates) or internal (ICS-laminates) compressive stresses. The most important factors having influence on the strength and toughness of these laminates are discussed. Clear recommendations on the proper selection of a suitable mismatch strain, volume ratio of the layer materials and thickness and distribution of individual layers are given, either to achieve a high toughness and/or a high lower limit (threshold) for strength.