Heterogeneous lightweight configuration for protection against 7.62 × 39 mm bullet impact

Abstract

Configuration of a heterogeneous lightweight material is investigated numerically and experimentally, for protection against 7.62 × 39 mm mild steel core bullet impact. The configuration consists of alumina (Al2O3) tile followed by fiber glass and polyurethane foam, all covered with kev-epoxy layer. Numerical simulations were performed using ANSYS AUTODYN. The 10-mm thick alumina completely disrupts the impacting bullet through blunting and erosion. The fiber glass and polyurethane foam disperse and absorb the propagation of shock wave, respectively. The kev-epoxy cladding seizes any scattering of brittle alumina fragments. The average impact velocity of the bullet was measured to be 710 m/s using high-speed camera. A 10-mm depth of depression spread over a wider area of 3.92 sq in of torso was recorded in blunt force trauma test, which was well within the European, German, and British standards that allow a 20–25 mm backface signature. Due to these characteristics it can be employed as body armor, vehicle armor, and for the safety and security of other critical infrastructures against this bullet and fragment impact. The residual mushroom-shaped bullet and its length of 9.3 mm in numerical simulation is in close agreement with the measured value of the 8.0 mm recovered bullet size and shape.