Application of stress intensity to design of anisotropic/isotropic bi-materials with a wedge

Abstract

Failure in anisotropic/isotropic bi-materials starts at the interface, and the interfacial failure is of interest to some engineering fields. However, since the procedure for evaluating stress intensities at the interface corner is very complicated and time-consuming, few researchers have used it to calculate singular stress fields and stress intensities, though doing so would allow prediction of the failure strength of a structure. In this paper, a simple procedure for obtaining stress intensities is introduced in the estimation of the failure strength of anisotropic/isotropic bi-materials. The expanded Stroh formalism is used to obtain asymptotic stress and displacement fields near the anisotropic/isotropic bi-material interface corner. The procedure makes it possible to calculate singular stress fields more easily than before. To evaluate stress intensities at the interface corner, a path-independent conservative line integral derived from Betti’s reciprocal principle is used. To present a detailed description of the procedure, we describe the procedure of calculating singular stress fields and stress intensities of co-cured double lap joints with a wedge that consists of carbon fiber reinforced plastic composite and steel adherends. We found two singular terms in describing stress and displacement fields near the wedge tip, and each of them referred to a different deformation mode: mode I and II. Therefore, we needed both mode I and II stress intensities to predict the joint failure. Failure surfaces and interfaces of double lap joints were investigated, and a fracture criterion on the K I n - K II n plane is presented.