Two-dimensional dynamic damage accumulation in engineered brittle materials

Abstract

This paper details the dynamic materials testing of three advanced ceramics (CoorsTek Engineered Ceramics AD85 and AD995 alumina and a silicon carbide) and a cermet (Luminant TitanMade®) and discusses the observations of damage accumulation in these materials as they were strained to failure. Through the use of a Kolsky bar in conjunction with a Shimadzu HPV-X2 ultra-high-speed camera and Correlated Solutions VIC-2D digital image correlation software, stress, axial strain, and lateral strain could all be measured independently from each other and at high speeds. This independent measurement allowed for the evolution of the apparent elastic properties of stiffness and Poisson’s ratio to be tracked. With both of these variables tracked, damage metrics were extended from the stiffness to the Poisson’s ratio, giving another degree of freedom with which to measure damage accumulation in brittle materials before complete failure. The combination of new experimental observations and damage expression resulted in trends and insights not reported on before. It was found that stiffness damage did not need to be monotonic, and Poisson’s ratio changes were far more significant to the evolution of behavior than stiffness changes for advanced ceramics. These observations and insights have implications for models and simulations of brittle material under dynamic loading conditions.