Hugoniot and dynamic strength in polyurea

Abstract

Polyurea is of interest for blast mitigation of structures, which requires a good understanding of the dynamic properties including the shock Hugoniot and dynamic spall and shear strength. In this study, reverse impact experiments were used to determine the shock Hugoniot, direct impact experiments were used to determine the spall strength, and lateral manganin gauge experiments were used to determine the dynamic shear strength. Reverse impact experiments revealed that the Hugoniot has a linear fit at low pressures and appears to be undergoing a reaction at higher pressures. The spall strength experiments in this study in combination with the literature data showed that the spall strength increases as a function of pressure, which is unusual in polymers and may be attributed to polyurea transforming to a glassy phase. In the shear strength experiments, the shear stress was shown to increase with increasing longitudinal stress in polyurea, similar to estane, another elastomer.

Shock compression of semiflexible polymers

“…A linear correlation between compression and shock velocity, as illustrated in eqn (3), was found to be applicable at low to moderate compression velocities for various systems such as polyethylene, epoxy, polycarbonate, polyimide, polysulfone, poly(tetrafluoroethylene), poly(methylmethacrylate), poly(vinylchloride), polybutadiene, polypropylene, and others. 4,[16][17][18][19][20][21][22] Generally, at higher compression speeds, a deviation from linearity is observed in most systems. This can be attributed, among other factors, to pressure-induced breaking and re-formation of covalent bonds.…”

State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure–Properties Relationship, and Nanocomposites for Ballistic Protection Applications

“…However, there is a relatively small number of published papers that explore the behavior of polyurea-coated metallic substrates subjected to localized loads generated from bullet impact. When subjected to high-velocity impact, polyurea coatings could improve the penetration/fragmentation resistance of the underlying substrate, depending on the following parameters: thickness of the polyurea coating [24], number of layers and configuration of the composite, dissipation of the localized shock wave (Scheme 3) through multiple reflections as it traverses the composite [25], T g and a viscoelastic transition of the elastomer to its glassy state due to the localized loading resulting from the impact of a high-speed projectile [23], dynamics of hard/soft segments and hydrogen bonding [26,27], etc. Relatively recent studies [21,22] sustain that the explosion shock wave determines a reordering at a molecular level; thus, the molecular rearrangement and neutralization appear to be events dominated by energy dissipation during impact.…”