Analysis based on the energy release rate criterion of a dynamically growing crack approaching an interface

A problem of a dynamically growing crack, which is approaching an interface between the two elastic isotropic materials at an arbitrary angle, is considered in this paper. That crack could behave in three ways: (i) it can arrest at contact with the interface, (ii) it can deflect into the interface and continue to propagate along it or (iii) the crack can penetrate the interface and continue to propagate in the material across it. The competition between the latter two cases can be estimated by considering the ratio of the energy release rates necessary for the crack penetrating the interface and for the crack deflecting into the interface. A concept that the criterion for the dynamic crack growth in homogeneous solids could be based on the static stress field, with addition of the stress intensity factor dependent on time, is used here to explain the behavior of the crack approaching the interface in dynamic loading conditions. Obtained results enable comparison of the interface dynamic fracture toughness to the fracture toughness of the base material (without the interface), to determine whether the incoming crack would deflect into or would penetrate the interface. If the ratio between the dynamic fracture toughness of the interface and the dynamic fracture toughness of the material into which the crack continues to propagate was less than the ratio of the dynamic release rates for the deflecting and penetrating crack, the incoming crack would deflect into the interface. If the case was reversed, the crack would cross the interface and continue to propagate in the material across it. Comparison of results for the load phase angle dependence on the crack tip propagation speed and on the approaching angle, obtained by this criterion and by the maximum stress direction criterion, proves the validity of the energy release rate concept adopted in this analysis.