High Strain Rate, High Pressure Behavior of Polyurea

Elastomeric polyurea is an important polymer for impact mitigation, but viscoelasticity, nonlinearity, pressure-effects, and the onset of the glass transition complicate analyses of experimental measurements. Ballistic impact is characterized by high pressures and high strain rates; the effects of these on material properties and their relationship to ballistic performance is not well understood. The glass transition plays an important role in rate-dependent phenomena, therefore we measured the glass transition temperature, T_g, up to pressures of 6 GPa in a diamond anvil cell. Additionally, measurements of the ballistic performance as a function of temperature are presented in order to understand polyurea’s various dissipative mechanisms, and show results from high strain rate experiments utilizing infrared thermography so that we can answer the question: where does the energy go during deformation?