Skin design studies for variable camber morphing airfoils

Abstract

This paper identifies the desirable attributes of a flexible skin of a morphing wing. The study is conducted using airfoil camber morphing as an example. The ideal flex-skin would be highly anisotropic, having a low in-plane axial stiffness but a high out-of-plane flexural stiffness. Reduced skin axial stiffness allows morphing at low actuation cost. However, for some substructure and actuation designs, a lower limit on the skin's in-plane axial stiffness may be required to prevent unacceptable global camber deformation under aerodynamic loads. High flexural stiffness prevents local deformation of skin sections between supports due to aerodynamic pressure loads, and avoids buckling of skin sections under compression as the airfoil cambers under actuation force. For the camber morphing application the strain levels in the flex-skin are not expected to exceed around 2%. If the axial stiffness of the flex-skin is reduced significantly, it may be necessary to consider aerodynamic stiffness (negligible vis-à-vis structural stiffness for classical airfoils) to accurately calculate deformation under loading. The approach followed in the study can be used to identify specifications for the skin and then reverse engineer and design highly anisotropic composite skins that meet the specifications.

Fatigue Loads Mitigation on Horizontal Axis Wind Turbines Using Aerodynamic Devices. A Survey

“…Various journal articles have been published on active flow control using different aerodynamic devices. For example; micro-tabs [38][39][40][41][42][43], Rigid trailing edge flap [44,45], deformable trailing edge flap (DTEF) [14,24,[44][45][46][47][48][49][50][51][52] and morphing trailing edge [44,45,[53][54][55][56][57][58]. Upwind Offshore NREL 5MW wind turbine [59] has been used extensively to investigate reduction of load on multi megawatts turbine [14, 45, 49-52, 60, 61].…”

“…Implementation of morphing trailing edge flap on wind turbine blades is an idea that originated from the design of morphing aircraft wings and helicopter blades [26,[55][56][57][58]. The blade design is made of two portions as shown in Fig.7; detachable flexible rear part and fixed fore part.…”

Active control of strain in a composite plate using shape memory alloy actuators

“…A highly anisotropic skin is the ideal skin for a morphing aircraft according to Gandhi et al, because it will prevent skin sections between supports from undergoing local bending deformations and sections of the skin in compressive loading from undergoing buckling (Gandhi and Anusonti-Inthra 2008). It was observed that airfoil with a low skin axial stiffness is able to camber easily.…”

Smart Actuation for Helicopter Rotorblades

“…Some studies on the design of airfoils with controllable camber involve stack actuators inside a structure that convert and amplify the motion into a change of curvature of the airfoil [19,20].…”