三维机织复合材料板簧式起落架结构设计及其有限元分析

为实现直升机板簧式起落架减重和提高层间剪切性能,采用碳纤维三维机织结构整体制备复合材料起落架。针对起落架的设计要求,通过受力分析和理论计算,建立了板簧式起落架的三维力学分析模型;通过材料实验和理论计算,获得了有限元计算所需的材料工程常数;结合最大应力-应变准则,采用有限元方法对板簧进行准静态加载模拟,确定了板簧的截面和轴线几何形状,以及变截面增厚部位的长度值与厚度值。结果表明:基于斜纹2.5维机织复合材料结构,截面宽度为120 mm,厚度为24 mm的弓式圆弧形、矩形截面板簧在满足挠度的同时其应变小于材料许用应变值;基于优选截面,增厚长度为760 mm,增厚厚度为36 mm时,复合材料起落架不仅能较好满足挠度、强度等设计要求,而且在同类型航空用4340钢制成的板簧结构件基础上质量减少约30%。

Structural design and finite element analysis of landing gearwith leaf spring made of 3-D woven composite

In order to achieve the weight reduction of the helicopter leaf spring landing gear and improve the inter-layer shear performance,a carbon fiber 3-D woven structure was adopted to prepare integrally the composite landing gear.According to the design requirements of the landing gear,the 3-D mechanical analysis model of the leaf spring landing gear was established by force analysis and theoretical calculation.Through the material experiment and theoretical calculation,the material engineering constants required for the finite element calculation were obtained.Combined with the maximum stress-strain criterion,the finite element method was used to simulate the quasi-static loading of the leaf spring,the leaf spring section and axis geometry,and the length and thickness values of the variable cross-section.The results show that based on the twill 2.5-D woven composite structure,the circular arc-shaped and rectangular-section leaf spring with a section width of 120 mm and a thickness of 24 mm meets the deflection requirement while the strain is less than the allowable strain value of the material.Based on the preferred cross-section,when the thickening length is 760 mm and the thickening thickness is 36 mm,the composite landing gear not only can meet the design requirements of deflection and strength,but also the weight loss reached about 30%compared to the spring structure of 4340 steel currently used for aviation applications.