Research On Key Technologies Of Morphing Wing Structures

For flight performance,the wing is the most important structural component in aircraft,it supports the aircraft mission in each condition: take-off,landing,cruise,maneuver,climb… Furthermore,the aircraft may travel at full or almost empty weight,at high or low altitude,at high or low speed,into very different environmental conditions.Yet,in the process of aircraft design and development,wing shape is a compromise that allows the aircraft to fly at a range of flight conditions,but the performance of most flight condition is suboptimal.Morphing aircraft has the potential to significantly improve the aerodynamic characteristics of an aircraft over its flight envelope and expand its flight capability to allow it to perform dramatically different missions.It is one of the main directions to resolve this problem.The technique of a wing surface to change its geometry(Morphing Wing)during flight has fascinated researchers and designers over the years as this reduces the design compromises required,enables the aircraft can automatically adjust its wing shape according to the flight state.Existing morphing wing solutions always led to penalties in terms of cost,complexity and weight,although in certain circumstances,these were overcome by system-level benefits.With the progress of technology,recent developments in advanced structural design technology and smart materials may overcome the limitations of traditional morphing technology and enhance the total benefits from existing design solutions.This thesis mainly takes adaptive wing variable camber trailing edge as the thread,focuses on the the large deformation skin design,the active compliant trailing edge(ACTE)design based on the concept of “distributed compliance” and adaptive shock control bump(ASCB)design based on shape memory alloy.The main content of the thesis includes:1?With the object of the design of morphing wing skin,the design and preparation methods for fiber reinforced elastomer skin is studied.According to the theory of nonlinear deformable-body dynamics,the applicable condition of large deformable flexible skin is given,that is,the in-plane force of the skin cannot be compressive.Based on the background of the variable camber wing,a novel flexible skin with 0 Poisson's ratio is proposed which has an ability of unidirectional deformation in one-dimension prepared by the method of fiber reinforced elastomer.Then,study has been taken to analyses the nonlinear mechanical properties of the skin by using incremental relation methon,and a mechanical model of the flexible skin was established.The results show that the deformation of the skin is greater than 50% which good uniaxial tensile deformation properties.Based on the background of the flexible shear deformation wing,a flexible skin designed for shear morphing wing is constructed.The flexible skin is comprised of a coarse fiber reinforced layer and a deformable two-dimensional grid layer,which is advantageous for enabling its large shear deformation.The experimental results demonstrate that the bearing capacity of the skin can be notably improved by employing the coarse fiber to reinforce the effect.Compared with the non-fiber reinforced skin,the load carrying capacity of this skin is increased by 60%,and meanwhile,the influence on the deformation driving force on the skin can be neglected.2? Smart material and structure based actuators using hydraulic linear motor of piezoelectric pump,two-way shape memory alloy(TWSMA)wires and TWSMA stripes are analyzed for the application to variable camber trailing edge.Experiments are carried out to test the mechanical properties of the smart materials and structures.The results show that the hydraulic linear motor of piezoelectric pump and TWSMA wires can be used in the deformation actuators,and the TWSMA stripes can be applied in the control of flow field,together with the trailing edge.Based on that,different aircraft wing loads are analyzed to search for the appropriate driving mode for the specified aircrafts.3?Based on the background of low wing load aircraft,a novel Morphing Wing structure known as the Active Compliant Trailing Edge(ACTE)is proposed.ACTE structures were designed using the concept of “distributed compliance” and wing skins of ACTE were fabricated from high-strength fiberglass composites laminates.Through the relative sliding between upper and lower wing skins which were connected by a linear guide pairs,the wing is able to achieve a large continuous deformation.The pseudo-rigid-body model is used to simplify the active compliant trailing edge,and a platform for optimization design of trailing edge structure is established based on the simplified model.By optimizing the layout of the structure,internal hinges on the trailing edge structure are greatly reduced and the system reliability is improved.Then the ACTE structure using multi pulley drive scheme is researched and the configuration parameters are optimized.According to the optimization,an experimental prototype of the ACTE is developed and the corresponding test platform has been builted.The results show that the design of ACTE is able to bear the out-of-plane loads,which can satisfy the requirement of low wing load aircraft.4?Based on the background of high wing load aircraft,a realizable design of continuous trailing edge variable camber adaptive wing(Active Compliant Trailing Edge,ACTE)is proposed.The feasibility of the design scheme is validated through the analysis of structural finite element simulation and CFD simulation.Active Compliant trailing edge is a distributed compliant mechanism,and the multi-segment wing rib covered with traditional glass fiber composite material as the skin material can realize the continuous deformation of trailing edge variable camber.CFD simulation results show that the aerodynamic performance of the airfoil can be optimized by changing the deflection displacement and deflection mode of the trailing edge wing.After the application of Active compliant trailing edge,the aerodynamic performance under high lift coefficient is improved,and the maximum lift-to-drag ratio has raised by 7.96% as the velocity is less than drag divergence Mach number(Ma=0.6).When the velocity is in the vicinity of divergence Mach number,the application of variable camber trailing edge can improve the lift-drag performance in high lift coefficient,while the improvement of maximum lift-to-drag ratio is not obvious.5?ACTE deflection will increase the shock wave intensity while the velocity located near the drag divergence Mach number,which leads to the increase of wave drag and reduction in aerodynamic benefit.In order to reduce the wave drag in different flow fields,the shock control bump is studied in this thesis,and a design of two-dimensional adaptive shock control bump(ASCB)based on two-way shape memory alloy is proposed.Shock wave in different flow conditions can be controlled by adjusting the deflection of two-way SMA bump in different temperatures.An ACTE-ASCB optimization platform consisting of a genetic algorithm optimizer,a NURBS curve module and a CFD simulation module is developed,which can optimize the ASCB configuration in different trailing edge deflection conditions.The results demonstrate that the optimized bump configuration can reduce the wave drag of the airfoil greatly,improve the aerodynamic benefits of ACTE,increase the maximum lift-drag ratio,and improve the lift-drag characteristics under high lift conditions.Compared with the wing morphing mode only using the active flexible trailing edge,the maximum lift-to-drag ratio is increased by about 5.4% while using ASCB.