Effect of air gap on penetration of double-layered A3 steel shields against hemispherical-nosed projectiles

The steel plates are widely used to construct resistant structures, and a lot of literature report on the ballistic resistance of monolithic metallic target, but a few for double-layered target, especially the spaced target. Some experiments were conducted on the monolithic target, contacting double layered target, spaced double layered target with 100 mm and 6 mm gaps by using a light gas gun to launch hemispherical-nosed projectiles. Each double layered target was made of two A3 steel plates of 1mm in thickness. The initial-residual velocity curves were obtained. The experiment results show that all targets suffer from plugging, and their larger deformations occur; the combination of tearing, bending and membrane stretching absorbs the kinetic energy of the projectile; the ballistic resistance of monolithic target is higher than that of double layered plate with or without gap; the air gap size has slight effect on the ballistic limit of the spaced target; the ballistic limit of contacting layered target is close to or greater than that of the spaced layered target.