Dynamic Experiments and Constitutive Model Performance for Polycarbonate

Abstract

Abstract : An experimental and numerical investigation has been performed to examine material deformation of polycarbonate (PC) from low (quasi-static) to high (dynamic) strain rates. In 2012, a revised physics-based constitutive model for thermoplastics was implemented into several U.S. Department of Energy (DOE) hydrocodes at the U.S. Army Research Laboratory. This report briefly describes the Mulliken-Boyce (M-B) amorphous polymer model and reviews significant modifications in implementation for DOE hydrocodes. The original material model parameters obtained for the M-B model only considered isothermal deformations of PC, while a subsequent implementation of M-B into the finite element code LS-DYNA obtained material parameters for adiabatic heating. Observed results are used in this report for validation and to examine performance differences in the mentioned model parameter sets. Dynamic-Tensile-Extrusion is an integrated experimental technique that allows the study of material deformation at high strain rates (greater than10,000/s) and large strains (greater than 1) when subjected to dynamic tension loading conditions. This is an important complement to the more traditional Taylor cylinder impact experiment, which achieves large strain and high-strain-rate deformation but under hydrostatic compression. Additionally, model parameter sensitivity is evaluated herein by considering pressure dependence of flow strength and its influence for amorphous polymer materials subjected to hydrostatic tension or compression.