Reliability optimization of a large-size tubular negative Poisson’s ratio battery protection structure

The battery pack placed on the chassis of an electric vehicle is easily to be damaged in a side collision because of its large volume. Therefore, the power battery pack should comprise a protective structure that can cover the entire side. Because the traditional hollow structure has limited performance, this paper proposes a large-size tubular negative Poisson's ratio (LTNPR) protection structure. A 2D LTNPR structure that can protect the side of battery pack entirely is designed and its mechanical properties are calculated. Then, the FE model of the battery pack equipped with LTNPR structure is analyzed under side pole impact by CAE simulation, which verifies the superiority of the LTNPR structure over the traditional hollow structure. Finally, deterministic optimization and reliability optimization are applied. The study and results demonstrate that compared with traditional structure, the LTNPR structure can improve the crashworthiness of the power battery pack significantly. Furthermore, the specific energy absorption (SEA) of LTNPR structure is increased by 28.81% and the maximum acceleration of battery pack is reduced by 15.29% through deterministic optimization, while the σ level is increased from 2.8448 to 8 through reliability optimization. The passive safety of electric vehicle is improved.