Development and Testing of an Unconventional Morphing Wing Concept with Variable Chord and Camber

Driven by the need to improve the performance and energy-efficiency of aircraft, current research in the field of morphing wings is growing in significance. The most recently developed concepts typically adjust only one characteristic of the wing. Within this paper a new concept for morphing wings is developed and tested, enabling large changes of the chord length and camber simultaneously. By changing two characteristics of the wing instead of one, the range of flight missions can be extended more effectively. To achieve these large shape changes, highly adaptable leading and trailing sections are mounted onto a rigid wingbox. A thin polymer film is encompassing these three sections. By adjusting the length of this film, the outline of the wing can be changed significantly. A prototype has been designed and manufactured for wind tunnel tests. The leading and trailing sections are made of polyurethane foam, which can be compressed to 10 percent of its original volume. Different polyurethane foams are tested for optimal stiffness to withstand the aerodynamic loads acting on the wing, while being soft enough to accommodate the large deformations. The film encompassing the sections is retracted into the wingbox to achieve the desired shapes of the airfoil. On the one hand, this film needs to be very thin to fit into the wingbox, while on the other hand it needs to be stiff enough to withstand the pressure exerted by the foam. The manufactured prototype enables changes of the chord length by 30 percent and the camber by 10 percent of the chord length. These deformations were achieved without any significant kinking or buckling. Three different asymmetric airfoil shapes and two symmetric shapes with different chord lengths were tested in a series of wind tunnel tests. All five airfoil shapes deformed very little under wind loads. The lift and drag results were compared to generate values and matched very closely. The prototype fulfils all predefined requirements and performs very well over a wide range of airfoil shapes and wind speeds.