About effect of layering on ballistic properties of metal shields against sharp-nosed rigid projectiles

On the basis of semi-empirical model (Rosenberg Z, Dekel E. Revisiting the perforation of ductile plates by sharp-nosed rigid projectiles. Int J Solids Struct 2010; 47(22–23): 3022–3033), we present a rigorous mathematical proof of the conjecture that layering does not improve ballistic properties of ductile shields against high-speed sharp nosed impactors. Within a relatively narrow range of normalized thicknesses of a monolithic shield and of layers (ratios of thicknesses to diameter of impactor), layering does not effect ballistic properties of the shield. In other cases ballistic performance of monolithic shield is better than ballistic performance of any layered shield having the same total thickness.