Behind-plate overpressure effect of steel-encased reactive material projectile impacting thin aluminum plate

Ballistic impact and sealed chamber tests were performed on the steel-encased reactive material projectile (SERMP) to understand its behind-plate overpressure effect when impacting the thin aluminum plates. The reactive material encased with a 1.5 mm thick 30CrMnSiNi2A steel shell was launched onto the initially sealed test chamber with a 3 mm thick 2024-T3 thin aluminum cover plate. Moreover, the overpressure signals in the test chamber were recorded by pressure sensors. The experimental results indicate an unusual behind-plate overpressure effect: as the density of the projectile increases from 6.43 g/cm³ to 7.58 g/cm³ by increasing the content of tungsten powder, although its total chemical energy decreases, it produces a higher behind-target overpressure at a lower impact velocity. A theoretical model is proposed to predict the reaction length of reactive material inside the projectile based on one-dimensional shock wave theory to understand this unexpected result. In addition, the deviation between the actual energy release and the theoretical calculation results, also the variation of overpressure rise time are analyzed and discussed. As the analyses show, when the SERMP successfully penetrates the cover plate, an increasing density of the reactive material inside the projectile always means that the delaying rarefaction wave effect, an increase of its internal pressure and strain rate levels. These factors lead to the increase of the overpressure limit velocity and reaction extent of the reactive material, while the overpressure rise time decreases.