Morphing aircraft can sense load and attitude in real time and adaptively deformed according to different flight environments and tasks. They can achieve excellent performance in different environments and tasks. It is one of the main hotspots in recent years. However, the torsional stiffness of deformable wing structure with flexible skin will be greatly reduced, so the wing is prone to torsion during flight, which is not conducive to flight. In this paper, a stiffness compensate device is proposed. When the wing is subjected to torque, the rotating torque is transmitted to the stiffness compensation device, which is transformed and transmitted inside the device, and finally balanced by the spring inside the device, so as to compensate for the reduced torsional stiffness of the wing due to the use of flexible skin and increase the torsional resistance of the wing.The mechanical properties of the device are studied by theoretical analysis and a case is analyzed. The ability of the device to improve the torsional stiffness of the wing and its influencing factors are analyzed in this paper. The feasibility of the device is verified. The torsion resistance of the deformable wing can be greatly enhanced by this device.
The variable camber wing can significantly improve the aerodynamic characteristics of the aircraft and is an important form of morphing aircraft. Flexible skin technology is one of the key technologies. According to the skin deformation features of the variable camber wing, a flexible skin form is proposed in this paper. The fishbone-shaped reinforcing structure (FBRS) is applied as the main component of the flexible skin to bear aerodynamic loads. Rubber material with excellent deformation ability wraps the FBRS to obtain a smooth and flat skin surface. Thorn-shaped branches on adjacent FBRSs are arranged in a staggered manner. In order to increase the out-of-plane stiffness of the flexible skin, the flexible skin needs to be used in combination with the corrugated structure. Each wave crest of the corrugated structure is connected with the FBRS of the flexible skin. By setting the wave crest of the corrugated structure into a platform shape, a stable connection between the FBRS and the corrugated structure is maintained. In this paper, the stiffness expressions of FBRS and corrugated structure are derived. The chordwise deformation capacity and out-of-plane bearing capacity of the flexible skin are verified by the method of finite element simulation. The results show that the FBRS can transmit aerodynamic loads well and maintain the smoothness and flatness of the rubber surface. Supported by a corrugated structure, this type of flexible skin has good chordwise deformation ability and high out-of-plane bearing capacity.
Morphing aircraft can change external shape in flight according to different flight environments and tasks, and improve flight performance maximumly. Among them, the morphing wing can improve the aerodynamic performance efficiently and has become one of the hot spots in recent years. One of the key technologies for morphing wing is flexible skin technique. Aiming at the conflict between in-plane deformation and out-of-plane bearing capacity of flexible skin structure design, a zero Poisson's ratio hybrid honeycomb structure was designed. The strips are added to the honeycomb structure to form a hybrid honeycomb, which increases the out-of-plane bending stiffness. Three different shapes of honeycomb grid elements were proposed, which are cruciform, square, and H-shaped. By adjusting the shape and size parameters of the three kinds of honeycomb grid elements and the height and quantity of the laying strips, the in-plane deformation mechanism of each element was analyzed by the representative volume element method, as well as the variation of mechanical properties with the element and strip shape parameters. The mechanical properties of the hybrid honeycomb structure were analyzed by finite element simulation. Considering the requirements of the variable camber trailing edge wing, a flexible skin which has capacity of out-of-plane bending resistance was constituted by covering elastic panel over the surface of zero Poisson's ratio hybrid honeycomb. The flexible skin structure has good airtightness and smooth surface. Also, it meets the requirements of in-plane unidirectional deformation along with out-of-plane bearing capacity.