<p>Mesh quality evaluation criteria.</p>

In order to improve the lightweight level of new energy vehicle battery box assembly and its design efficiency and precision, a design scheme of sheet molding compound (SMC) composite box upper plate and carbon fiber composite lower box was proposed. Based on digital twin technology and combined with an improved particle swarm-bacterial foraging (PSO-BFO) algorithm, a fiber reinforced composite layup design and multi-level twin optimization method was proposed. The SMC composite material upper panel was designed and optimized by using the morphology optimization and size optimization methods. The carbon fiber composite material lower panel layup sequence was designed and optimized by using the constructed digital twin multi-level optimization method. Comparing the performance of the battery box assembly before and after optimization, the improvement rates of battery box assembly quality and first-order modal frequency were 40.63% and 33.34% respectively. The stress improvement rates under bumpy conditions, bumpy+braking conditions/bumping+turning conditions are 83.60%; 81.01%; 84.31% respectively, and the displacement improvement rates are 62.80%, 63.21%, and 63.14% respectively. Lightweight and performance improvement The effect is remarkable. The effectiveness of the battery box assembly design scheme and carbon fiber reinforced composite material layup design optimization method proposed in this paper is demonstrated.为提升新能源汽车电池箱总成的轻量化水平及其设计效率与精度，本文提出一种片状模塑料（Sheet Molding Compound, SMC）复合材料箱上盖板与碳纤维复合材料下箱体的设计方案。基于数字孪生（digital twin）技术，结合改进的粒子群-细菌觅食（particle swarm-bacterial foraging, PSO-BFO）算法，本文提出一种纤维增强复合材料铺层设计与多级孪生优化方法。采用形貌优化与尺寸优化方法，对SMC复合材料上盖板进行设计优化；通过构建的数字孪生多级优化方法，对碳纤维复合材料下箱体的铺层顺序开展设计优化。对比优化前后电池箱总成的性能表现，优化后电池箱总成的质量与一阶模态频率的提升率分别为40.63%与33.34%；在颠簸工况、颠簸+制动工况、颠簸+转向工况下的应力提升率分别为83.60%、81.01%与84.31%，位移提升率分别为62.80%、63.21%与63.14%。轻量化与性能提升效果显著，本文提出的电池箱总成设计方案及碳纤维增强复合材料铺层设计优化方法的有效性得到验证。