Molecular-level simulations of shock generation and propagation in polyurea

A non-equilibrium molecular dynamics method is employed in order to study various phenomena accompanying the generation and propagation of shock waves in polyurea (a micro-phase segregated elastomer). Several recent studies reported in the literature suggested that polyurea has a relatively high potential for mitigation of the effects associated with blast and ballistic impact. This behavior of polyurea is believed to be closely related to its micro-phase segregated microstructure (consisting of the so-called “hard domains” and a soft matrix) and to different phenomena/processes (e.g. inelastic-deformation and energy-dissipation) taking place at, or in the vicinity of, the shock front. The findings obtained in the present analysis are used to help elucidate the molecular-level character of these phenomena/processes. In addition, the analysis yielded the shock Hugoniot (i.e. a set of axial stress vs. density/specific-volume vs. internal energy vs. particle velocity vs. temperature vs. shock speed) material states obtained in polyurea after the passage of a shock wave. The availability of a shock Hugoniot is critical for construction of a high deformation-rate, large-strain, high pressure material models which can be used within a continuum-level computational analysis to capture the response of a polyurea-based macroscopic structure (e.g. blast-protection helmet suspension pads) to blast/ballistic impact loading.