Geometrical factors govern ballistic energy dissipation of polymeric nanoscale thin films

The design of materials with enhanced resistance to impact and shock deformation is critical for numerous technological applications. This work investigates energy dissipation mechanisms in ballistic impacts on nanoscale polymer thin films through molecular dynamics simulations and theoretical modeling. Using a pseudo-continuous model for polymer chain generation followed by Kremer-Grest potential relaxation, we systematically study the effects of impact velocity, projectile radius, and film thickness for various polymer chain lengths. Our findings reveal that traditional kinetic impact models are insufficient to describe the observed energy dissipation. We propose an improved model incorporating an energy dissipation term that scales with the cylindrical hole area created during impact, characterized by a single fitting parameter β, that encapsulates shear-dependent deformation and failure mechanisms. This model accurately predicts energy dissipation across both low and high-velocity regimes and shows that energy dissipation scales linearly with film thickness at the nanoscale.