An efficient stiffness analysis model based on shear deformation theory for flexible skin shear variable-sweep wing

Fixed-wing aircraft cannot maintain optimal aerodynamic performance at different flight speeds.As a type of morphing aircraft,the shear variable-sweep wing(SVSW)can dramatically improve its aerodynamic performance by altering its shape to adapt to various flight conditions.In order to achieve smooth continuous shear deformation,SVSW’s skin adopts a flexible composite skin design instead of traditional aluminum alloy materials.However,this also brings about the non-linear difficulty in stiffness modeling and calculation.In this research,a new SVSW design and efficient stiffness modeling method are proposed.Based on shear deformation theory,the flexible composite skin is equivalently modeled as diagonally arranged nonlinear springs,simulating the elastic force interaction between the skin and the mechanism.By shear loading tests of flexible composite skin,the accuracy of this flexible composite skin modeling method is verified.The SVSW stiffness model was established,and its accuracy was verified through static loading tests.The effects of root connection,sweep angles,and flexible composite skin on the SVSW stiffness are analyzed.Finally,considering three typical flight conditions of SVSW:low-speed flow(Ma=0.3,Re=5.8210^(6)),transonic flow(Ma=0.9,Re=3.4410^(6)),and supersonic flow(Ma=3,Re=7.5110^(6)),the stiffness characteristics of SVSW under flight conditions were evaluated.The calculated results guide the application of SVSW.

Nonlinear Out-of-Plane Mechanical Behaviours of Rectangular Woven Composite Flexible Skin Under Uniform Normal Pressure

This paper seeks to investigate nonlinear out-of-plane mechanical behaviours of woven composite flexible skin(WCFS)through experimental and theoretical methods.Firstly,quasi-static experiments are carried out on rectangular WCFSs with different aspect ratios under uniform normal pressure to measure out-of-plane deformation and failure loads.Afterwards,a new three-parameter geometric model is presented to describe 3D geometry of pressurized WCFS,and thus,a nonlinear mechanical model is deduced for depicting the relationship between pressure and out-of-plane displacement.The application of the aforementioned models for experimental results shows that the new models have adequately and logically depicted deformation geometry and nonlinear mechanical characteristics.