Thermally induced failure of multilayer ceramic structures

In this work, a methodology is proposed to predict the fracture behaviour o f multilayer ceramic systems subjected to thermal shock conditions. The sta tistical variability exhibited by the fracture behaviour of three-layer str uctures used in solid oxide fuel cells under transient thermal stresses is determined. The dominant fracture mode was found to be unstable crack propa gation from existing interfacial defects oriented normal to the plane of th e layers. Finite-element analyses and a weight function method are relied u pon to obtain analytical solutions for the interfacial crack driving force in two- and three-layer ceramic structures subjected to inhomogeneous in-pl ane temperature distributions. Failure diagrams are constructed in terms of geometric and loading variables which allow fail-safe regions to be identi fied. The effect of the elastic property mismatch between the ceramic layer s on the maximum interfacial crack driving force is also discussed.