Shock and spallation behavior of ultrahigh molecular weight polyethylene

We investigate dynamic compression and fracture of ultra-high molecular weight polyethylene (UHMWPE) with plate impact experiments, high-speed velocimetry, and postmortem X-ray computed tomography. The Hugoniot equation of state of UHMWPE up to peak shock stress of ∼ 2.0 GPa is obtained via reverse impact. Spall strength and corresponding tensile strain rates are determined via symmetric impact. With increasing impact velocity, spall strength is nearly a constant ( ∼ 70 MPa) up at first, and then decreases continuously as a result of competition between increasing tensile strain rate, shock heating and strain softening; the damage degree increases first and then decreases rapidly at the expense of more damage nucleation sites. The void size distributions follow a power law. The small voids are closer to spheres and voids/cracks becomes flatter as void volume increases, likely because of the rearrangement and breakage of linear polymer chains of UHMWPE.