Morphological instability of failure fronts

Abstract

There are various observations and experiments showing that, in addition to standard shock-wave fronts, which propagate with high trans-sonic velocities, some other much slower wave fronts can propagate within substance undergoing intensive damage. These moving fronts propagate within intact substance leaving behind them intensively damaged substance. These fronts were coined as failure waves. The failure waves can be modeled differently—in this letter they are modeled as sharp interfaces separating two states: the intact and comminuted states. Several penetration experiments with transparent glasses and ceramics have shown that failure fronts have an extremely rough morphology. We suggest a simple thermodynamic theory which allows interpreting appearance of the roughness as a manifestation of morphological instability of failure fronts. For the case of isotropic phases the instability criterion is presented in explicit form.