Effects of membrane pre-stress on the aerodynamic characteristics of an elasto-flexible morphing wing

This paper considers the experimental investigation of a morphing wing concept for subsonic UAV application, which is made up of an elasto-flexible membrane spanned over an articulated structure to allow large variations of the planform geometry. Due to its large flexibility, the wing surface deforms when subjected to aerodynamic loads and the wing camber depends passively on the flow conditions. In this context, the present study focuses on the potential of a variation of the membrane pre-stress to influence its deflection and control the wing camber. Based on a baseline version of the wind tunnel model, the pre-stress modification is achieved by moving the trailing-edge spar. The results of force and deformation measurements performed at several dynamic pressures indicate that varying the pre-stress effectively allows to influence the passive deformation of the wing surface and adjust the wing camber within a certain range at a given flow condition. This in turn can be used to adjust the aerodynamic performance and improve the lift-to-drag ratio compared to the baseline model where the pre-stress is constant.