COMPARISON BETWEEN INTERNATIONAL STANDARDS UTILIZED FOR TESTING BALLISTIC HELMET PERFORMANCE

Abstract

Many existing ballistic helmets are able to withstand ballistic threats, however, the residual energy of projectiles is still too high, which leads to back-face deformation and life injuries due to loads transmitted through the helmet to the head. VPAM HVN 2009 test standard considers residual energy transferred to the head by measuring the volume of the dent formed in the head where energy transmitted to the head shall not exceed 25 joules. NIJ 0106.01 test standard considers impact transferred to the head where peak linear acceleration energy transmitted to the head shall not exceed 400 g. The aim of this study was to investigate the relation between VPAM residual energy test and NIJ impact attenuation test through experimenting ballistic helmets from the same type and size. Test results showed that an increase in the projectile velocity leads to a significant rise in the values of impact attenuation due to the increasing in the bullet energy. However, the increase in residual stress was found to be minimal. This suggests that while higher projectile velocities influence the dynamic performance of the helmet in terms of impact absorption, they have a relatively small effect on the internal stresses that remain in the material after impact. This could be due to the specific design or material properties of the helmet, which might allow for better distribution of the stresses during impact. These findings highlight the importance of considering both impact attenuation and residual stress in evaluating the performance of ballistic helmets under varying conditions.1