Today’s aeroplane wings are designed to have a single fixed shape. This means the design is a compromise between the most fuel-efficient shape for different flying conditions, and since it is a compromise, it increases fuel burn in all conditions. They also use hinged surfaces like ailerons and flaps to control the plane, which have gaps and sharp changes in shape that cause the airflow to separate, leading to a substantial increase in drag and noise. In contrast, avians like hawks and eagles can fly silently and efficiently, because they have flexible wings that allow them to change the wing shape smoothly and continuously, to keep the airflow attached, and therefore reduce drag and noise.In order to help bridge this divide between flexible natural fliers and our modern rigid aircraft, this research shows a flexible morphing wing inspired by the fish skeleton called the Fish Bone Active Camber (FishBAC). The FishBAC can change the wing shape every second smoothly and continuously to keep the wing shape optimal, and the flow attached like avian wings, therefore reducing drag, noise and fuel consumption. This morphing concept has shown an increase of lift-to-drag ratio for about 25% compared to a conventional control surface.Compliance-based morphing structures need to be soft enough to deform, but stiff enough to withstand aerodynamic forces. This reality leads to compromise - The FishBAC is currently both stiffer than desired in terms of actuation energy and softer than desired for aeroelastic effects. This research aims to remove those compromises by introducing a novel material that can actively change its stiffness. The new concept is based on the ability of granular materials to act as either a soft “liquid” or a solid depending on how tightly the grains are squeezed together.The novel approach is to fill aircraft wings with coffee grinds, which can be squeezed together under vacuum pressure to make a stiff aircraft wing. When the vacuum is turned off, the grains unlock, and the wing becomes soft enough to be deformed into a new shape. This allows the wing to immediately adapt its shape to changing operating conditions – reducing noise, drag and therefore fuel burned. The research includes detailed mechanical modelling and experimental testing of the complex and highly non-linear behaviour of granular media, and the design, manufacturing, and testing of prototype demonstrators, which show the concept can achieve outstanding levels of stiffness adaptation.

A Smart Wing Based on Vacuum-Packed Particles

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2021/volume/85499

ASME 2021 Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2021)

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