The Methods For Analysis And Preventing The Wrinkles In Flexible Skin Based On The Corrugated Structure

Morphing aircraft,which can change their aerodynamic layouts according to external flight environments and missions,is the main development direction for the future spacecraft.To adapt the requirements of wide speed range and multi-mission flight modes with optimal performance,the key component of the morphing aircraft is the morphing wing with continuous large deformability.The wing skins are required to have the ability of large deformation in the direction of deformation and meet the requirements of a small force to drive deformation.At the same time,the skins should have sufficient stiffness in the non-deformation direction to bear the external aerodynamic load and maintain their aerodynamic shape.Besides,the skins must maintain a smooth and continuous surface during the deformation process.Traditional materials and structures are difficult to meet the above requirements.Based on the current research progress of morphing aircraft,a composite flexible skin structure with elastic panel and corrugated core is proposed to further study the stiffness characteristics and deformation wrinkles in the skin.The main research contents of this article are as follows:Firstly,the Mooney-Rivlin model was employed to describe the constitutive relationship for the silicone rubber panel.MATLAB software was used to fit the silicone rubber material test data.The effects of corrugated configuration and core geometric parameters on structure stiffness were discussed through the finite element model and theoretical derivation,respectively.The structure dimensions were considered to research the wrinkle problem of flexible skin with the elastic panel under the bending load.Based on the above research results,the dimensions of the flexible skin structure were determined.Secondly,the metal matched-mold is designed and processed to prepare the trapezoidal composite corrugated core.The separately cured core and the elastic panel were bonded into a sandwich structure.The effects of adhesives and interface chopped fiber toughening on the bonding performance were studied to solve the debonding phenomenon between the elastic panel and the corrugated core during the deformation process.The experimental results show that the epoxy resin combined with aramid chopped fibers can greatly improve the interface adhesion between the elastic panel and the core.The finite element simulation results agreed well with the experimental results for bending stiffness of the flexible skin with interface toughening.Finally,two methods,the inner support structure,and the special-shaped silicone rubber panel were proposed to prevent the wrinkling phenomenon of the composite flexible skin during the deformation process.The effects of preventing wrinkles were investigated by changing the key parameters such as the shape,material modulus,and sizes of the support structure.For the other preventing method,two factors of panel shape and size were explored.The advantages and disadvantages of the two preventing methods are discussed comprehensively on the skin deformation driving force,overall skin mass,method feasibility,and skin wrinkle preventing effect.The research results will provide a theoretical and experimental basis for the design,manufacture,and performance evaluation of the flexible skin in the morphing aircraft.