This conference paper was submitted for presentation at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

Thermoplastic and thermoset materials are extensively used in transportation, machinery, consumer products, and heavy-industry where material performance and high-rate impacts are crucial to characterize and design for. Using simulation driven design to predict product performance is critical to reducing design iterations, reducing time-to-market, and improving performance. Performing accurate Finite Element (FE) simulations requires testing the time-dependent behavior of thermoplastic materials due to their inherent complex viscoelasticity and viscoplasticity. In addition to changing material behavior with strain-rate, polymers exhibit stress-state dependent failure behavior, most often characterized by stress triaxiality (defined as the ratio of the pressure to the von Mises stress). Fully characterizing a material'™s behavior requires testing the material at multiple strain-rates and in multiple loading modes. The multiple loading modes are required to measure the pressure-dependence of the yield surface as well as stress-triaxiality dependent failure surface. In this work we will present the results of a study on TPO where we tested the material from quasi-static strain rates (0.001/s) to impact rates (1000/s), utilizing a drop tower for the high-rate tests. We test the material in multiple test modes to measure the pressure dependent failure behavior, including: high rate shear with samples similar to ASTM B831, modified to be smaller and appropriate for a drop tower; a dart impact test similar to ASTM D1709; and high rate notched tension tests at to measure the failure locus. The is in addition to low strain rate failure data in uniaxial tension to characterize the rate-dependence of the failure locus. We use this data to select and calibrate a rate-dependent material model for use in explicit FE simulations. We selected the SAMP-1 material model, calibrating the material model using single element FE simulations to optimize the material parameters. After calibrating the material parameters, we then perform FE simulations of the shear, dart impact tests, and notched tension tests using an inverse calibration approach to optimize the material model failure parameters. We will present the results of the simulations, showing good correlation between the material test results and FE simulations, yielding an accurate and reliable material model for use in explicit simulations that include material failure.