High velocity impact conditions: A novel approach to energy analysis and stress fields in inhomogeneous materials

Abstract

A novel description of impact behavior has been developed based on a three-dimensional weighted Gaussian projection of material mass. Based on simulations and physical testing, the new mathematics may significantly improve impact-resistant designs and materials with a new description of the behavior of inhomogeneous composites. Testing consisted of a unique inhomogeneous composite; a fibrous ultra-high molecular weight polyethene semi-crystalline matrix that contained an even distribution of high-density tungsten carbide inserts. The composite was physically tested using M855A1 ERP ammunition at a velocity of 900 m/s. The composite demonstrated an unconventional failure mode that absorbed additional kinetic energy. In one case, the composite successfully halted the steel-tipped projectile. A description of the composite's failure modes was analyzed. A unique failure mode was identified as the dispersion of kinetic energy into localized stress fields surrounding the inserts. Proposed is a mathematical description to accurately represent the behavior the stress fields generated that occurred as a consequence of the resultant transverse shockwave. The composite, and descriptive mathematics display increased energy absorbance during delamination failure. The results represent a new route for designing impact resistant armors that strain harden at extreme strain rates during impact.