Projectile strength effects on the ballistic impact response of soft armor targets

Upon impact with a target panel, a portion of a projectile's striking kinetic energy is dissipated via heat loss or deformation. Typical ballistic performance determination standards require strict projectile hardness values of Rc 29 +/- 2 for consistency and repeatability, but it is of interest to examine if these required hardness values give a lower bound where the ballistic performance determination is independent of the strength of the projectile. In this study, a large range of yield strengths of metallic right-circular cylinders were used to test the effects on the ballistic response of a multi-ply soft body armor. The results show that with an increase in projectile yield strength, the ballistic limit velocity decreases. This degradation in ballistic performance of the soft armor target levels off at higher yield strengths to about 75% of the expected ballistic performance for Rc 29, indicating that there may be a minimum projectile strength after which the influence of strength is no longer significant. The degree of deformation of projectiles during impact is related to the striking velocity and the off-axis failure of the soft armor target material.