Correspondence Between Energy Release Rates and Critical Shear Stresses Due to Interfacial Debonding in a Hybrid Composite

Two criteria for the propagation of a debond crack in a carbon-glass–epoxy hybrid unidirectional composite material are investigated comparatively. The first criterion is based on the fracture mechanics notion of a critical energy release rate. The second criterion is based on a critical interfacial shear stress threshold. In the case of simple microbonding test both the criteria have been shown in the literature to be consistent, i.e. a unique critical energy release rate and a unique critical shear stress threshold both characterize the debond crack propagation. Contrary to this observation, it is presently shown using finite element analysis that the two criteria predict inconsistent debond crack propagation in a hybrid composite.