关键词: 复合材料, 弹性, 周期结构, 预应力蒙皮, 变体, 机翼

Abstract:

A variable chord wing based on composite material elastic periodic structure and flexible skin is designed using NACA0014 profile. According to the requirement of structure stiffness， the concept of pre-morphing is introduced. The non-mechanical high variable chord length is realized， while ensuring the structure strength and stiffness. The disadvantages of heavy weight and complex drive of traditional morphing mechanism are avoided. A finite element model of the wing is built， and the maximum chord morphing amplitude is given based on static strength analysis. An aerodynamic analysis model of the wing is established， and the aerodynamic performance of the wing is calculated at different morphing states. The pre-morphing analysis is done according to stiffness requirement in the normal direction. The strength， stiffness and stability of the morphing wing structure are checked in the heavy load case and economical cruise case. The initial damage mode and ultimate load factor of the wing structure are predicted through overload calculation. The normal mode analysis and transient analysis of the morphing wing are completed， and the basic dynamic performance is given. It is shown that the variable chord wing based on symmetrical double ripple elastic periodic structure has simple structure and activation mechanism. During chord morphing， the streamline and smooth wing surface are maintained， and the strength， stiffness and stability of the morphing wing meet the design requirements. The maximum stretch amplitude of the elastic periodic structure is 140 mm， which is 58.33% of the initial chord length of periodic structure and 23.33% of the initial wing chord length. The maximum safety angle of attack and the optimum angle of attack of the initial and maximum morphing states of the wing is 12° and 8°， respectively. The lift of the maximum morphing state is higher than that of the initial states by 22.89%. The stiffness issue in Y direction is satisfied through the pre-stressed silicon rubber skin with the pre-chord-morphing of 16 mm. The initial damage of the periodic structure occurs when the aerodynamic load increases up to 1.96 times of the static strength heavy load， and the damage mode is fiber tensile failure. The first and second order normal modes of the maximum morphing state are vertical and horizontal bending， respectively. The displacement kinetic convergence of the morphing wing occurs in 2 s when gust load is encountered during level flight.

Key words: composite material, elasticity, periodic structure, pre-stressed skin, morphing, wing