Mechanical properties of rigid and flexible polyurethane foam in-situ foamed Nomex honeycomb

To enhance the mechanical properties of Nomex honeycomb, the honeycomb was foamed in-situ using rigid polyurethane (PU) foam and flexible polyurethane foam (NHRPU, NHFPU, collectively NHPU). Mechanical properties were studied based on tests, theoretical and finite element (FE) methods, respectively. The results showed that NHRPU and NHFPU improve the energy absorption by 85.25% and 47.27% compared to the sum of PU and honeycomb alone. The specific energy absorption (SEA) of NHRPU is improved by 21.76%, while the SEA of NHFPU decreases, NHRPU significantly improves in terms of the honeycomb energy absorption performance, while NHFPU enhances the resilience of the honeycomb. The mesoscale FE model and equivalent FE model were constructed to achieve better prediction of NHPU. 75.6% energy absorption and 19.8% SEA can be improved by NHPU as a core-filled thin-walled tube compared with empty tube, and the passive safety protection capability is significantly improved by applying NHPU-filled structures in railway vehicles.