Nanoscale modeling of shock response of polyurea

This chapter summarizes our recent atomic simulations of polyurea. We used density functional theory-based quantum molecular dynamics (QMD) and force field-based classical molecular dynamics (CMD) simulations to study the shock response of polyurea and its multilayer arrangements. For example, we used QMD to predict the Hugoniot states of polyurea up to a shock pressure of 75 GPa, while providing significant insights into the shock-induced dissociation of the polymer structure. The work is important because limited experimental data for polyurea are available in the literature. Moreover, we used CMD simulations to compute the spall strength of polyurea by following two methods: (1) the indirect method (from the free surface velocity history, as commonly used in experiments) (2) direct method (from the atomic stresses in the spall region, obtainable only using MD). That study allowed us to test the validity of some approximations that are commonly used in interpreting experimental results. Finally, we present the response of ultrathin polyurea films and polyurea-based multilayer structures under ballistic impacts.