Damage and Energy Dissipation Mechanisms in Polymer Films Under Ballistic Impact

Abstract

Here we study the ballistic impact of millimeter- sized projectiles on films made of two different polymers: linear low- density polyethylene (LLDPE) and polydimethylsiloxane (PDMS). A single- stage gas gun (SGG), combined with a high- speed camera, was used to determine the collision dynamics and calculate the velocities before and after impact. The dissipation mechanisms and the conditions for either perforation or rebound were analyzed. We found that the collision dynamics are strongly influenced by the polymer´s architecture, and the capacity for impact energy absorption is not monotonically related to film thickness. For film thicknesses below 1 mm, LLDPE absorbs collision energy more efficiently than PDMS, owing to the larger plastic deformation involved during the collision process. In this regime, PDMS film fractures are brittle and exhibit well- defined interfaces. Critical thicknesses marking the transition from perforation to rebound were found for both materials around 0.25 mm for LLDPE and 0.66 mm for PDMS. These critical thicknesses for the perforation–rebound transition (0.25 and 0.66 mm) are distinct from the ~1 mm crossover at which the relative energy- absorption efficiency of PDMS overtakes that of LLDPE. In such cases for rebounds, LLDPE displays clear marks of indentation, while the PDMS surface remains relatively flat. Additionally, PDMS films exhibit higher energy absorption due to energy dissipation caused by material cracking.