Mechanical Behavior of Thermosetting Polymers Undergoing High Strain-Rate Impact

A series of uniaxial and oblique flyer-plate impact experiments were conducted on fully dense, high durometer, polyurethane and epoxy formulations to investigate the high strain-rate dynamic material response. Samples were impacted at velocities ranging from 50 to 1,200 m/s at strain-rates of 105 – 106 s−1. The Hugoniot constants, yield strengths, and friction coefficients were inferred from velocity measurements taken from the back surface of the targets. Polymer Hugoniots were found to closely approximate those previously found in literature, with nonlinear curvature at low impact speeds due to viscoelastic effects. Strength behavior demonstrated pressure dependence which fit into a Mohr-Coulomb or Drucker-Prager yield surface criterion. Coefficients of friction between both epoxy and polyurethane, alongside a 7075-T6 aluminum tribological partner were quantified and results were used in conjunction with yield observations to hypothesize on the role of adhesion in high strain-rate shear of polymer-metal interfaces.