三种柔性蒙皮支撑结构的力学特性

Mechanical Characteristics of Three Support Structures of Flexible Skin

理论推导了U型、V型和梯形3种柔性蒙皮支撑结构面内横向无量纲化弹性模量与其平面几何参数(壁厚系数t、高度系数h、形状系数k)之间的关系:其等效弹性模量随t增大而增大,随h增大而减小,随k增大而减小。采用ANSYS软件进行了有限元模拟并通过实验对其面内力学特性进行验证。同样参数条件下,3种结构面内横向刚度从大到小依次为V型、U型和梯形。说明梯形结构具有更强的变形能力,产生同样的变形需要的能量最小。对3种结构的面法向刚度进行了有限元仿真和实验比较,其面法向刚度随几何参数的变化规律与面内等效弹性模量相似;在相同等效面法向气动载荷作用下,3种结构面法向位移大小依次为梯形、U型和V型。对3种结构拉伸前后不同载荷作用下的面法向最大位移进行实验测量,发现面法向刚度在拉伸后都有较大提升,在产生相同的面法向位移情况下,承受的压强平均提高了30%~60%。

In morphing aircraft, flexible skin bears and passes aerodynamic loads when the wing deforms, so the design of the supporting structure applied to flexible skin directly affects the performance of the morphing aircraft. Three types of cellular support structures that can be applied to the flexible telescopic sandwich skin are called V type, U type and trapezoidal shape. By analyzing the in-plane scale properties of these support structures, we obtained the relationship between the in-plane transverse dimensionless equivalent elastic modulus and the three geometric parameters (shape coefficient k, width coefficient t and height coefficient h). The equivalent elastic modulus decreased with the increase of k or h, and increased with the increase of t. We acquired finite element analysis (FEA) results using ANSYS software, and demonstrated the in-plane mechanical characteristics experimentally. Under the same parameters, the in-plane transverse stiffness of the three kinds of structures from large to small were as follows: V type, U type, and trapezoidal shape, indicating that the trapezoidal cellular type had stronger ability to transform and generated the same deformation with less energy. At the same time, we analyzed the stiffness of the three kinds of structures along surface normals with FEA simulation and compared them with the experimental results. Under the same equivalent aerodynamic load along surface normals, normal displacements of the three kinds of structures in decreasing order were trapezoidal shape, U type, and V type, indicating that the structure with better in-plane scalability had weaker load capacity along surface normals. By measuring the maximum normal displacements of the three structures before and after stretching, we showed that the stiffness of each structure type along surface normals improved greatly after drawing. In the case of generating the same normal displacement, the withstand pressure of the structures increased by an average of 30%~60%. © 2017, Editorial Department of JVMD. All right reserved.