Velocity measuring approaches for the determination of ballistic limits of GLARE 5 fiber-metal laminate plates

Abstract

In this study, 152.4 mm by 101.6 mm (6''x4'') GLARE 5 plates with various thicknesses were impacted by a 0.22 caliber bullet-shaped projectile using a high-speed gas gun. Velocities of the projectile along the ballistic trajectory were measured at different locations throughout the test using (1) a pair of laser-beam optoelectronic paths near the gun muzzle, (2) two sets of chronographs before and after the specimen, and (3) a high speed camera for recording the trajectory history of the projectile. The high speed camera yielded the most reliable way of measuring the projectile speed and could record the projectile orientation before and after the impact. It was experimentally detected that the measured speed of the projectile at the muzzle of the barrel was less than the actual impact speed of the projectile. The phenomenon can be explained by the well-known intermediate ballistics. The incident projectile impact velocity versus the residual velocity was plotted and numerically fitted according to the classical Lambert-Jonas equation for the determination of ballistic limit velocity, V 50. The results showed that V 50 varied in a parabolic trend with respect to the metal volume fraction (MVF) and the specimen's thickness.