Multiscale numerical optimisation of hybrid metal/nonwoven shields for ballistic protection

This research presents a detailed numerical study of the ballistic performance of lightweight hybrid metal/nonwoven shields for automotive applications. Several configurations, including different number of nonwoven fabrics, were analysed to find the optimal design. Impact response of the nonwoven fabric was predicted by a multiscale numerical constitutive model able to capture its complex deformation and failure mechanisms: fibre straightening, realignment and disentanglement. Special attention was paid to the interaction between layers for different air gaps in the final energy absorption capacity of the shield, and detailed analysis of the different sequences of triggered failure modes was provided. The hybrid shield outperformed the previous configurations, resulting in an absorption capacity about twice the sum of the energies dissipated by the steel plates and the nonwovens individually. Furthermore, the hybrid shield increased the energy absorption capacity of the baseline steel plates by a factor over 8, with an almost negligible increment of areal weight of 5.5%, giving the possibility to improve the ballistic performance of conventional automotive components without penalising the fuel consumption of the vehicle.