Numerical study of mechanisms to minimize failure in a metal with soft backing under plane shock loading

In recent times, several experimental studies have reported improved ballistic penetration resistance and blast survivability of metallic structures to which an external coating of a soft elastomeric material has been applied. This work is aimed at understanding, through numerical simulations on a simple metal/elastomer flat plate geometry subjected to planar blast waves, the detailed mechanics of wave propagation, damage evolution and mitigation in a bilayer system. Void nucleation, growth and coalescence is assumed to be the damaging mechanism in the metal. A meshless technique based on smoothed particle hydrodynamics is used within the framework of large deformation elasto-viscoplasticity in the metal and nonlinear elasticity in the elastomer. We show that the thickness of the elastomer plays an important role in shielding void activity in the metal, by creating a sequence of closely spaced pulses that reflect from the interface and free surfaces to maintain non-tensile or weakly tensile states of stress. Moreover, a fictitious material that is capable of undergoing a transformation to a harder material under pressure is studied that proves to be an ideal candidate for damage mitigation.