Mixed-mode cohesive-zone models for fracture of an adhesively bonded polymer-matrix composite

As a direct extension of previous mode-I work on the adhesion of composite joints, this paper uses a cohesive-zone approach to model the mixed-mode fracture of adhesive joints made from a polymer-matrix composite. Mode-II cohesive-zone parameters were obtained using sandwich end-notch flexure specimens. These parameters were used directly with the previously determined mode-I parameters to predict the fracture and deformation of mixed-mode geometries. It was shown that numerical simulations provided quantitative predictions for these geometries, including predictions for both the strengths of the joints and for the failure mechanisms. In conjunction with the earlier work, these results demonstrate the use of cohesive-zone approaches for the design of adhesively bonded composite joints, and indicate approaches for determining the relevant material properties to describe mixed-mode fracture.