Blast Mitigation Effects of Foam-Core, Composite Sandwich Structures

Abstract

Structural polymer foams have been used as core material in lightweight sandwich panels for quite some time. Traditional sandwich theory suggests that the primary function of the polymer core is to transmit shear to the thin facesheets, thereby rendering high bending stiffness and strength from a panel with a minimum weight penalty. Recent analysis of the underwater blast response of PVC foam composite sandwich panel, however, shows that in addition to the above, PVC foams have blast mitigation effects through energy absorption via plastic core crushing. Close examination of the core stresses involved during initial yield has revealed that three-dimensional core plasticity is encountered in water blasts, and plastic work dissipation of the core plays a greater role in blast mitigation. In air blast/air back cases, core yielding is primarily transverse shear, but in water blast/air back and water blast/water back cases, core yielding is due to combined transverse shear, transverse compression and/or hydrostatic pressure. Experiments have been conducted to obtain the hysteresis effects of PVC H100 subjected to combined transverse shear and compression. These have led to the development of a transversely isotropic, viscoelastic–plastic damage material model that can be adequately used to describe the behavior of foam operating in this environment.