Delamination buckling in the microwedge indentation of a thin film on an elastically deformable substrate

A delamination buckling model is proposed for the assessment of the interfacial fracture toughness by the microwedge indentation delamination test on a film/substrate system. The delamination buckling model is based on Von Karman nonlinear plate theory and considers the elastic deformation in the substrate and the impression on the film. The substrate deformation is modeled by employing three-coupled springs and the effect of the impression free-surfaces is modeled by using two-coupled springs. A closed form solution is derived with the spring compliances obtained from the dimension analysis and numerical calculations. The energy release rate and the phase angle are given for a variety the elastic mismatch between the film and the substrate. The results show that in some cases, the energy release rate can be two orders in magnitude larger than that derived from the clamped end condition.