Measurement of energy release rates for dynamic interfacial fracture phenomena

First, in order to estimate a residual stress near the interfacial crack tip, the concepts of equivalent residual force and equivalent residual stress intensity factor are proposed. For a bimaterial specimen of aluminum and epoxy resin, the equivalent residual force and the equivalent residual stress intensity factor are measured. Next, dynamic interfacial fracture phenomena in the same bimaterial specimens were recorded by using a high-speed camera. The method of transmitted caustics is used to evaluate the stress intensity factors as well as the energy release rates during interfacial crack propagation. Furthermore, the separated energy release rates were also evaluated, which have the meaning of the energy flow rates into the interfacial crack tip from the individual material sides. The histories of crack velocity and energy release rate were obtained for both cases of impact and static loading. Transonic interfacial crack propagation is reported.