An efficient stiffness analysis model based on shear deformation theory for flexible skin shear variable-sweep wing

Fixed-wing aircraft cannot maintain optimal aerodynamic performance at different flight speeds. As a type of morphing aircraft, the shear variable-sweep wing (SVSW) can dramatically improve its aerodynamic performance by altering its shape to adapt to various flight conditions. In order to achieve smooth continuous shear deformation, SVSW's skin adopts a flexible composite skin design instead of traditional aluminum alloy materials. However, this also brings about the non-linear difficulty in stiffness modeling and calculation. In this research, a new SVSW design and efficient stiffness modeling method are proposed. Based on shear deformation theory, the flexible composite skin is equivalently modeled as diagonally arranged nonlinear springs, simulating the elastic force interaction between the skin and the mechanism. By shear loading tests of flexible composite skin, the accuracy of this flexible composite skin modeling method is verified. The SVSW stiffness model was established, and its accuracy was verified through static loading tests. The effects of root connection, sweep angles, and flexible composite skin on the SVSW stiffness are analyzed. Finally, considering three typical flight conditions of SVSW: low-speed flow (Ma=0.3, Re=5.82 ×106), transonic flow (Ma=0.9, Re=3.44 ×106), and supersonic flow (Ma=3, Re=7.51 ×106), the stiffness characteristics of SVSW under flight conditions were evaluated. The calculated results guide the application of SVSW.