Morphing skins

Abstract

A review of morphing concepts with a strong focus on morphing skins is presented. Morphing technology on aircraft has found increased interest over the last decade because it is likely to enhance performance and efficiency over a wider range of flight conditions. For example, a radical change in configuration, i.e. wing geometry in flight may improve overall flight performance when cruise and dash are important considerations. Although many morphing aircraft concepts have been elaborated only a few deal with the problems relating to a smooth and continuous cover that simultaneously deforms and carries loads. It is found that anisotropic and variable stiffness structures offer potential for shape change and small area increase on aircraft wings. Concepts herein focus on those structures where primary loads are transmitted in the spanwise direction and a morphing function is achieved via chordwise flexibility. To meet desirable shape changes, stiffnesses can either be tailored or actively controlled to guarantee flexibility in the chordwise (or spanwise) direction with tailored actuation forces. Hence, corrugated structures, segmented structures, reinforced elastomers or flexible matrix composite tubes embedded in a low modulus membrane are all possible structures for morphing skins. For large wing area changes a particularly attractive solution could adopt deployable structures as no internal stresses are generated when their surface area is increased.

Passive load alleviation bi-stable morphing concept

“…The idea of morphing has attracted much attention from researchers within the aerospace community given the potential performance gains offered and, in particular, in view of augmented optimal operation in a wide range of conditions. 2 Similarly, gains in terms of reduced inspection costs, lighter actuation systems, and particularly, extended fatigue life can be achieved implementing morphing in wind turbine blades allowing for upscaling to higher more efficient ratings. Most studies have concentrated on actively actuated morphing control surfaces for load alleviation in wind turbines.…”

Passive Control of Viscous Flow via Elastic Snap-Through

“…While viscous flow control is readily applicable to microfluidics, the passive control and rapid transition capabilities of elastic materials is increasingly being exploited more broadly, e.g. in soft robotics and morphing skins [16,29]. Developing theoretical models that provide intuition and facilitate device optimization will be critical in these burgeoning fields of technology.…”

A drone with insect-inspired folding wings

“…The results are fragile and poorly scalable foldable structures, that often require multiple manipulations to deploy, which is time consuming and can lead to errors. Other drones, equipped with inflatable or continuously deformable wings [6], can autonomously deploy without human intervention. Inflatable wings are composed of a series of longitudinal pressurized tubes approximating the desired wing shape, however the requirement of a high-pressure distribution system generates additional weight, thus reducing payload and flight autonomy.…”