Influence of the elastic mismatch on the Hertzian cone crack path in ceramic bilayers

Contact damage is a key aspect in the structural integrity of ceramics, particularly ceramic coatings and multilayers that may have an elastic mismatch. An understanding of the critical load and trajectories of the crack produced by contact loads in such materials is valuable to characterize the damage tolerance and improve their reliability. In this work, the Hertzian cone crack initiation and propagation in brittle bilayers has been studied by FEM and verified by experimental observations. It was concluded that the elastic mismatch affects the crack initiation position and critical load for cone cracking. Critical loads are lower in bilayers than in monolithic materials. Cone crack trajectory and the corresponding fracture energy release rate are also affected by the elastic mismatch, which thus influences the damage tolerance of the system.