Study of Various Hybrid Composite Materials and Geometries for Battery Pack Protection Undergoing Ground Impact Loading

Nowadays, electric vehicles (EV) are developed at a very fast pace. Currently, the batteries that are used in EVs are lithium-ion cells with different shapes and configurations. However, the ground impact caused by road debris can hit and penetrate the battery pack and results in a very severe fire accident. To study the ground impact accidents, a simplified finite element model of the battery pack structure using typical cylindrical 21700 cells, and floor-type architecture is analysed. Based on this model, the protection structure is improved using different core geometry and fibre metal laminate material arrangements. The evaluated criteria are battery shortening and specific energy absorption (SEA) of the protective plate. Studies are conducted to investigate the effect of different arrangements of composite layer, thickness of the composite layer, different load cases, thickness of the metal core, and different composite materials. The model is validated using the energy method. Simulation results show that adding composite backplate results in a lower battery shortening. The thinner composite layer also improves SEA while still maintaining safe battery shortening. Two load cases are also evaluated for chosen models to ensure that the protection structure is still effective. Thinner unidirectionally stiff double hull (USDH) thickness also improves SEA, up to a point where battery shortening increases significantly. Finally, changing glass fibre reinforced polymer (GFRP) material to carbon fibre reinforced polymer (CFRP) improves both battery shortening and SEA, but not in a significant way that the cost increase is justified. In this study, the most effective design for the battery pack protection structure is a USDH metal core layer with (h: w: t) = (15.87: 15.87: 1) mm and a 1.2 mm GFRP backplate layer with quasi-isotropic lay-up. Battery shortening is 51.58% better, SEA is 150.54% higher, and structure weight is 40.59% lower compared to the baseline case.