Molecular Dynamics Simulation of Polymeric Systems Under Shock Deformation

Currently, mechanisms by which polymeric systems respond to extreme deformation conditions, in particular deformation due to shock waves, are not fully understood. This work uses molecular dynamics (MD) simulations of atomistically detailed models of both homogeneous and heterogeneous polymeric materials (with structural variations on the nanometer scale) to study the underlying physics of system response to shock waves. Simulations are performed using both equilibrium ("Hugoniostatted") and nonequilibrium MD. Semicrystalline polymers with different configurations and degrees of crystallinity are examined, with shocks applied either isotropically or directionally with respect to the crystalline-amorphous interface. The Hugoniot curves are calculated, along with shock velocity and particle velocity. Analysis of the vibrational state of the systems identifies normal modes, along with changes in the vibrational signature pre- to post-shock. This analysis enables validation against experimental results obtainable via Raman or IR spectroscopy and provides insight into deformation mechanisms.