Characterization and material card calibration of PU foam under various strain rates for crash Simulation

Polyurethane (PU) foams are extensively utilized in automotive crash structures, seats, and interior components due to their exceptional capacity for energy absorption and dissipation during impact events. Specifically, PU foams in vehicle seats play a critical role in protecting occupants during crash scenarios by absorbing energy, distributing forces, and enhancing seatbelt performance, as well as providing countermeasures for head impact protection. The movement of the seat and the direction of the force during crash testing are inherently unpredictable. The material behavior of PU foam is captured using an isotropic, hyper-elasticity-based constitutive model available in LS-DYNA through *MAT_083. This model is designed to take into account the foam's compressibility, sensitivity to strain rates, low Poisson's ratio, and hysteresis. The characterization of a PU foam with a nominal density of 65 kg/m3 was performed using quasi-static compressive testing of 0.01/s and dynamic compressive testing of 1/s,13/s, 120/s, as well as a quasi-static tensile test of 0.01/s. The material response data were used to calibrate the LS-DYNA foam model MAT-FU CHANG FOAM MAT-083. Calibration of the LS-DYNA material card (*MAT_FU_CHAN_FOAM MAT-083) was performed using coupon-level test data. The goal was to accurately simulate the foam's behavior under varying strain rate conditions and extract the deformation pattern. Finally, the simulations were conducted with the same geometry and loading conditions as the experimental setup. The performance of the material card was validated by comparing simulation results with experimental data, demonstrating its ability to replicate foam behavior under crash conditions.