Opening-mode dominated crack growth along inclined interfaces: Experimental observation

This experimental study investigates the dynamic decohesion of inclined interfaces between aluminum and a polymeric material PSM-1. Two lead azide explosive charges are detonated to initiate dynamic loading in a specially designed bimaterial specimen. The dynamic loading results in crack initiation, propagation and arrest in the same experiment. Photoelasticity, in conjunction with high-speed photography, is used to observe the dynamic event. Dynamic complex stress intensity factor and the energy release rate histories are obtained using the available steady-state singular stress field equations. The dependence of the dynamic initiation and arrest toughness on the mixity under dynamic loading is also investigated. Mixity at crack initiation is controlled by the inclination of the interface. The results show that the initiation toughness is higher than the arrest toughness by about 21%. Based on the experimental observations, a dynamic fracture criterion for subsonic crack growth alongthe bimaterial interfaces is proposed. According to this criterion, the displacement at a point behind the crack tip varies exponentially with the crack-tip velocity (0 < v < c~ ; where cs is the shear wave speed of the compliant material). This criterion establishes a generalized relationship between the dynamic energy release rate and the instantaneous crack-tip velocity. © 1998 Elsevier Science Ltd. All rights reserved