Conceptual-level evaluation of a variable stiffness skin for a morphing wing leading edge

Abstract

A morphing leading edge produces a continuous aerodynamic surface that has no gaps between the moving and fixed parts. The continuous seamless shape has the potential to reduce drag, compared to conventional devices, such as slats that produce a discrete aerofoil shape change. However, the morphing leading edge has to achieve the required target shape by deforming from the baseline shape under the aerodynamic loads. In this paper, a conceptual-level method is proposed to evaluate the morphing leading edge structure. The feasibility of the skin design is validated by checking the failure index of the composite when the morphing leading edge undergoes the shape change. The stiffness of the morphing leading edge skin is spatially varied using variable lamina angles, and comparisons to the skin with constant stiffness are made to highlight its potential to reduce the actuation forces. The structural analysis is performed using a two-level structural optimisation scheme. The first level optimisation is applied to find the optimised structural properties of the leading edge skin and the associated actuation forces. The structural properties of the skin are given as a stiffness distribution, which is controlled by a B spline interpolation function. In the second level, the design solution of the skin is investigated. The skin is assumed to be made of variable stiffness composite. The stack sequence of the composite is optimised element-by-element to match the target stiffness. A failure criterion is employed to obtain the failure index when the leading edge is actuated from the baseline shape to the target shape. Test cases are given to demonstrate that the optimisation scheme is able to provide the stiffness distribution of the leading edge skin and the actuation forces can be reduced by using a spatially variable stiffness skin.

Analysis and Design of a Leading Edge with Morphing Capabilities for the Wing of a Regional Aircraft—Gapless Chord- and Camber-Increase for High-Lift Performance

“…A possible solution for such a system in a morphing CFRP structure is described in [6]. Further improvement of aerodynamic performance for morphing systems may be achieved using an integrated aerodynamic optimisation approach, which considers material limitations like the one reported in [43] together with structural optimisation algorithms, e.g., [44].…”

Leading edge redesign of dual-peak type variable inlet guide vane and its effect on aerodynamic performance

“…8 Related researches have indicated that the airfoil performance can be further improved by optimizing the leading edge portion. [9][10][11] Therefore, this paper devotes to optimize the LE geometry and reveal the flow mechanism for further improving the aerodynamic performance of this new type VIGV.…”

Morphing Wing Droop Nose with Large Deformation: Ground Tests and Lessons Learned

“…In other projects investigating morphing droop noses, a droop nose with flexible skin and kinematics was designed, manufactured and tested, with fiber optic distributed shape sensing via Rayleigh backscattering used to reconstruct the deployed shapes [20]. A conceptual numerical study on a variable stiffness skin by means of continuously variable ply angles as opposed to variable-thickness-laminates is presented in [21]. Wind tunnel tests of a flexible wing leading edge with compliant mechanisms are presented in [22,23] and additional compliant mechanism designs are presented in [24].…”