Developing Failure Criteria for Adhesive Joints Under Complex Loading

This paper describes an investigation of the failure behavior of bonded joints under a wide range of in-plane loading. Combinations of tension, shear, and bending loads were applied to bonded joint specimens using a unique computer-controlled loading system. Failure criteria were developed for initiation of crack growth or the onset of nonlinear behavior based on a computation of energy dissipated by the failure process. Failure surfaces were constructed from these data for the range of loadings studied. A strain energy release rate formulation was developed for bonded materials which fail under shear, tension, and bending loading by interfacial crack growth. This formulation was used to analyze specimens which failed by debonding along the interface. Results of these studies were also compared with failure criteria obtained using a larger scale specimen on the basis of strain energy release rate.