Quantum and classical molecular dynamics simulations of shocked polyurea and polyurethane

We conducted density functional theory based quantum molecular dynamics (QMD) and force field based classical molecular dynamics (CMD) simulations to compute the shock Hugoniot of polyurethane and polyurea. The QMD results are in reasonable agreement with the available experimental data. However, limited experimental data for polyurea (up to a shock pressure of 30 GPa) is available in the literature. We used QMD to predict the Hugoniot states of polyurea up to a shock pressure of 75 GPa. The subsequent postmortem analysis of the shocked polymer samples provided significant insights into the shock-induced dissociation of polymer structures. Comparison of experimental and QMD derived Hugoniot states with those obtained from CMD demonstrates the limits of CMD in shock simulations. Furthermore, we conducted CMD simulations at lower shock pressures to investigate the size effects of the computed shock response.