The Influence of Velocity in Low-Velocity Impact Testing of Composites Using the Drop Weight Impact Tower

Abstract

Many structural advantages offered by composites due to their inherent tailorability await realization for lack of a clear understanding of their response under transient loading. One tool currently available for evaluation of impact response is the drop weight impact tower. In this paper, we address the influence of impact velocity in drop tower testing using woven and non-woven E-glass fabric-reinforced vinyl-ester composites fabricated by resin transfer molding (RTM). For the range of impact velocities attainable in a typical drop weight impact tower (< 7 m/s), impact energy and contact force determine the extent and type of damage. Impact velocity determines the initial loading slope and time taken to reach maximum load; however, it only marginally influences inelastic damage accumulation. Peak contact force increases linearly with impact energy and projected damage area up to the linear inelastic limit (LIL), which is described as the point where top surface penetration commences. While independent of impact velocity, LIL marks the upper limit of applicability for the well-known linear relationship between projected damage area and impact energy. Beyond LIL, these two composite systems offered no increased resistance to load application, suggesting that ultimate contact force may be an important impact metric.