Thickness configuration optimization of B4C/UHMWPE composite armor under varying impact velocities and areal densities through numerical and experimental study

This study aims to optimize the ceramic-to-backing thickness ratio (R_th) of B₄C/UHMWPE composite armor to enhance the anti-penetration performance while maintaining lightweight requirements. Its primary innovation lies in systematically quantifying, through combined finite element method (FEM) and ballistic testing, the coupling mechanism of thickness ratio (R_th: 0.4-2.0), areal density (AD: 25.0-30.0 kg/m²), and impact velocity (V₀: 400.0-550.0 m/s) governing the anti-penetration performance of composite armor. The results reveal that the ballistic limit velocity (V_bl) initially increases and then decreases as R_th increases from 0.4 to 2.0, peaking at R_th = 1.4-1.6 across all AD cases. Notably, this optimal R_th range remains consistent across AD variations, with both projectile mass loss ratio (R^II_m,l) and kinetic energy loss ratio (R^II_ke,l) during the first two penetration stages peaking within this range, demonstrating robust design applicability. Furthermore, a key finding and significant contribution is the dynamic shift in the optimal R_th for minimizing projectile residual velocity (V_re) when V₀ exceeds V_bl: Under fixed AD, higher V₀ reduces the optimal R_th due to shortened projectile-armor interaction time, necessitating thicker UHMWPE laminate to prevent premature ceramic fracture failure and enhance the backing-plate energy dissipation. Conversely, under constant V₀, higher AD elevates the optimal R_th, where AD and V₀ show opposite effects on the variation of optimal R_th, and the optimal R_th converges to 1.4-1.6 as the highest V_bl corresponding to given AD approaches V₀. Critically, this study establishes a quantitative framework for V₀-AD-R_th coupling effects, providing actionable guidelines for designing lightweight composite armor against diverse ballistic threats.