Modeling of Ultrahigh Molecular Weight Polyethylene Single Fiber Failure Under Dynamic Multiaxial Transverse Loading

This study investigates the failure of microscale Dyneema (R) SK76 ultrahigh molecular weight polyethylene single fiber subjected to dynamic multiaxial transverse loading by three impactor geometries of radii - 200 (blunt), 20 (sharp), and 2 (razor) mu m. A 3D finite element model of the single fiber transverse impact experiments by Thomas et al. 2020 has been developed to investigate the deformation and failure mechanisms at 10 and 20 m/s impact velocities. The model predicts a transverse wave manifesting in the form of a dispersive flexural wave because of the non-negligible longitudinal shear modulus. This transverse wave reflects at the clamped boundary and travels back and forth between the impact location and the clamped end. The reflected transverse wave upon reaching the impact location induces a stepwise increase in both impactor-fiber contact force and maximum axial tensile strain. A failure criterion based on maximum axial tensile strain considering the gage length, strain rate effects, and multiaxial loading (transverse compression and transverse shear) induced degradation effects is applied to predict the fiber failure. The average tensile failure strains and strengths predicted by the model are found to agree well with the experimental results. All the impactors induce transverse compressive strain resulting in a 13.2% reduction in tensile failure strain. Transverse shear strain increases with decreasing impactor radius, with razor inducing a maximum reduction of 25%. Tensile strain concentration factors are predicted in the range of 1.5-1.6 for blunt and sharp, and 2.4-2.5 for the razor impactor.