The Mechanochemistry of Damage and Terminal Ballistics

The asymmetric radial crack patterns that occur in brittle targets when impacted by high velocity projectiles are explained using a Phenomenological Mechanochemistry of Damage (PMD) engineering model. The developed model, which constitutes a simplification of the generalized PMD framework, reveals an energy instability during failure of brittle materials configured in a purely symmetric geometry and impact configuration. The underlying cause of the instability is due to the competition between stored elastic energy and the energy associated with new surface creation through broken chemical bonds. The instability manifests itself in the form of asymmetric radial cracking in the brittle target. The model is built upon the general PMD framework and assumes the target material is sufficiently brittle that strains are small and linear elasticity is applicable. Furthermore, the impact geometry is assumed to be purely symmetric, which leads to a reduction of the geometry to a one-dimensional radial configuration. The model is not restricted to any ballistic impact speed regime, provided the target material remains in the solid phase.