Ballistic penetration of bi-layer structures with water container and fiber composite: Effects of the container position

Bi-layer structures with a water container and a fiber composite were designed for constructing explosion-proof equipment. The effects of the water position on the anti-fragment performance were explored by performing ballistic impact tests on bare water containers, bare fiber panels, water/fiber structures and fiber/water structures. For both UHMWPE and aramid fiber panels, the water/fiber structure exhibited a lager ballistic limit than the fiber/water structure, whose ballistic limit was even smaller than that of the corresponding bare fiber panel. Numerical models for the impacts of these targets with a UHMWPE panel were established and verified by the experimental results. The numerical results demonstrated that, for the UHMWPE/ water structure, the rear water weakened the ballistic performance of the UHMWPE panel mainly via enhancing the tensile stress in fiber direction, and thereby caused premature fiber fracture that was also observed in the experiments. For the water/UHMWPE structure, the ballistic performance of the rear UHMWPE panel was promoted compared with the bare UHMWPE panel at a high impact velocity, consistent with the experimental observation. It is because the water pre-accelerated the UHMWPE panel prior to projectile impact and thereby reduced the relative velocity between the projectile and the panel when it was penetrated.