Effects of dislocation shielding on interface crack initiation and growth in metal/ceramic layered materials

Interface crack initiation and growth in layered materials are investigated in this paper for mixed mode I and mode II loading. The dislocation plasti city in the metal layer is considered, and the energy for initial emission of a dislocation is assumed to be attained before the cleavage of the inter face crack. Superdislocation modeling is employed to obtain the critical st rain energy release rate, for crack initiation and growth. When a stress se paration law is satisfied at the interface crack tip, interface debonding o ccurs and the crack propagates with an atomically sharp tip until interacti ons with other slip sources cause arresting by a new blunting event. This p rocess repeats itself periodically, and based on this process, interface cr ack growth is simulated until a steady-state condition is reached. This mod el predicts the strong dependence of interfacial fracture toughness on mixe d mode loading. The role of the metal layer thickness and interfacial stren gth is also investigated. (C) 1999 Elsevier Science Ltd. All rights reserve d.