Criteria for Fracture and Kinking of Mixed Mode Interface Crack

Abstract

Delamination of interface between dissimilar materials is one of the main causes of failure of composite materials, electronic packages and so on. The interface crack problems are primarily mixed mode and often include the residual stress. We developed a new method for the stress intensity factor analysis of an interface crack under thermal stress condition in the previous study. In this study, we focus on the mixed mode fracture toughness and the kink angle of an interface crack. We measure residual stress and perform mixed mode fracture tests for three types of interface crack. Two of them are cracks between aluminum and epoxy resin and another is an interface crack between two epoxy resins which have different stiffness. Each obtained mixed mode fracture toughness including residual stress is successfully described by stress intensity factors K_I and K_II for each interface crack. The kink angle of each interface crack also can be expected by the stress intensity factors using the modified maximum hoop stress criterion.