Dynamic failure analysis along interfaces in composite materials

Several features of an interface crack dynamically propagating in composite materials are investigated and their results are presented in this paper. First, the stress intensity factors for a dynamic interface crack are accurately extracted from finite element field solutions using a conservation integral. This integral is based on the steady state solution for a dynamically propagating interface crack in an orthotropic bimaterial. It extracts the Mode I and II contributions of the mixed-mode crack tip field. The ratio of the mixed-mode factors, or the phase angle is an essential parameter in defining the fracture resistance of dynamic interface cracks. A new toughness formula is applied to the simulation of crack propagation using an iterative procedure. The iterative procedure is an effective method which can be used to interpret experimental data. The analysis of an interface crack along two isotropic materials shows that the resulting velocity history agrees well with the experimental record when appropriate parameters are chosen for the proposed toughness criterion. A computational analysis is also carried out for a propagating interface crack in differently oriented transversely isotropic materials. The computed results demonstrate that the energy release rate and the phase angle of a propagating crack depend greatly on the orientation of the orthotropic solid on the either side of the crack.