Finite element analysis of interface crack in bimaterial media using cohesive force model

The intent of this paper is to investigate mixed mode interface fracture toughness J_c. Many workers have shown by experiments that the interface fracture toughness depends on the mode mixity. However, the definition of the interface stress intensity factor is not clarified and therefore the mode mixity varies with the characteristic length L of the interface stress intensity factor. To evaluate the strength of an interface, it is important to model the fracture behavior of the interface. The cohesive force model is a direct way to represent the interface nonlinear properties. Based on the internal variable theory of thermodynamics, a continuum interface constitutive relation between interface traction and interface separation has been developed. In this paper, we apply this constitutive model to the interface crack. The interface fracture toughness is analyzed for a wide range of bimaterial constant by Finite Element Method. The results show that the fracture boundary curve is elliptical shape and changes with the ratio of the Young's modulus. The interface fracture toughness is strongly influenced by the mode mixity. However, if the characteristic length L of the interface stress intensity factor is chosen suitably, the intrinsic fracture criterion can be derived.