Experimental and modelling evaluation on the protective performance of bulletproof plate composites for building protection

Abstract

Critical infrastructure such as police stations, military bases, and security checkpoints is increasingly exposed to armed threats, while most existing structures lack adequate ballistic protection. Conventional construction materials are generally ineffective against high-velocity projectile impacts, highlighting the need for practical, retrofit-compatible protective systems. This study aims to develop and optimize composite bulletproof panels that meet NIJ 0108.01 Level III requirements for resistance against 7.62×51 mm NATO M80 ammunition, with emphasis on structural feasibility and cost-effectiveness. An experimental program was conducted using three materials: standard structural steel (SS400), high-hardness steel (HS450), and asphalt cement (AC). These materials were configured as single-layer, double-layer, and sandwich panels. Ballistic tests were performed using 7.62×51 mm NATO projectiles at an average velocity of 847±9.1 m/s. Projectile velocities before and after impact were recorded to evaluate energy absorbed. Finite element simulations using ABAQUS were employed to validate experimental results and analyze stress-wave propagation and failure mechanisms. The results indicate that material hardness plays a more significant role than thickness in enhancing ballistic resistance. While 6 mm SS400 absorbed 35.81% of impact energy, a thinner 3 mm HS450 layer achieved 28.95%, demonstrating the efficiency of high-hardness materials. Layered configurations significantly improved performance, with SS400-6/AC25 and HS450-3/AC25 absorbing 62.39% and 78.35% of impact energy, respectively. Notably, sandwich configurations (SS400-6/AC25/SS400-6 and HS450-3/AC25/SS400-6) achieved complete projectile arrest. Numerical results confirm that a high-hardness strike face combined with a viscoelastic backing layer maximizes energy dissipation. The optimized HS450-3/AC25/SS400-6 panel provides full ballistic protection with reduced weight compared to conventional steel armor. Field validation demonstrates its applicability for retrofitting existing infrastructure. This study contributes practical design guidelines for developing cost-effective ballistic-resistant building systems in high-risk environments.