车用复合材料螺旋弹簧的设计与优化

利用复合材料可设计性强和树脂基体轻量化的特点，并解耦“材料-结构-性能”之间的相互关联，是汽车复合材料结构件设计的难点。螺旋弹簧是汽车悬架系统的主要承载部件，工况复杂，一般采用性能极佳的弹簧钢；若用轻质复合材料替代，必须兼顾安全性与轻量化，设计难度很大。针对上述问题，提出了一种复合材料螺旋弹簧“材料-结构-性能”集成设计方法。依据弹簧受压缩载荷时，簧丝截面应力分布，确定选择±45°铺层的碳纤维复合材料（CFRP）；在满足刚度、强度和安装空间约束条件下，根据复合材料力学和弹簧刚度、强度理论模型，确定初始弹簧几何参数；再进一步利用有限元数值仿真进行校验；将正交实验设计法和有限元数值模拟结合，建立轴向压缩刚度和强度随几何参数变化的响应面模型；采用遗传算法获得满足弹簧性能要求下轻量化效果最佳的设计结果。优化后的复合材料弹簧方案比金属弹簧质量减轻34.4%，为复合材料汽车结构件设计提供了可行的整体解决方案和产品开发实例。

Design and optimization of automotive composite helical spring

A major problem in designing automotive structures is how to make full use of the flexible designability of composites and light weight of polymer matrix, and also consider the close connection among the material, structure and properties. Since the helical spring is one of the major load-bearing parts of suspension and subjected to complex loads, it is generally manufactured by spring steel with ultra-high performance. If replaced by lightweight composites, both safety and light weight should be satisfied, which makes the design of composite helical spring rather difficult. In this paper, an integrated materials-structure-performance design method of composite helical spring is proposed. According to the stress distribution on the cross section of spring under compression, carbon fiber reinforce polymer (CFRP) material with ±45° ply sequence is selected. Under the constraint conditions of stiffness, strength and installation space, the initial geometric parameters of helical spring are derived by analytical models based on spring stiffness and strength and composite material mechanics. Furthermore, the initial result is verified numerically by finite element simulation. Combining the design of orthogonal experiment with numerical simulation, the response surface model of stiffness and strength of helical spring to its geometric parameters is established. Finally, the optimal design of helical spring satisfying both required performance and weight reduction is obtained by genetic optimization algorithm. Compared with the metal helical spring, the CFRP one reduces the mass by 34.4%. As a representative product development case, it has demonstrated that the proposed method is a feasible integrated solution for design of automotive structural components with composite materials.