Influence of destructor case type on behaviour of fragments in military vehicles active protection system

Military vehicles active protection systems against cumulative missiles are designed to destroy the attacking missile before it hits the vehicle armour. The article presents the results of numerical studies of one of the elements of active protection system, which is the fragmentation destructor. A typical directed fragmentation warhead consists of a few parts: metallic or composite case, explosive material and fragmentation elements in the form of spheres, cylinders. The authors of this study evaluated the influence of the destructor case type – in particular material – on the effectiveness of the destructor. The effectiveness was evaluated on the basis of the maximum speed of balls. Evaluation was performed for the selected balls from each layer. Numerical calculations were performed for two materials of the case: steel and aluminum. It was assumed in simulation that the detonating material is the plastic explosive C4. The numerical analyses were based on the finite element method with the explicit time integration method implemented in the Ls-Dyna program. The interaction of solid and gaseous medium has been modelled using ALE coupling. Mechanical properties of the case were described using a simplified Johnson-Cook type material. The detonation process was described using programmed burn model approximations, and the behaviour of detonation products was described with the JWL (John, Wilkins, Lee) equation.