NASA and MIT create a shape-shifting plane wing
02 April 2019
A team of engineers have built and tested a radically new kind of airplane wing, assembled from hundreds of tiny identical pieces.
The wing can change shape to control the plane’s flight, and could provide a significant boost in aircraft production, flight, and maintenance efficiency, the researchers say.
The new approach to wing construction could afford greater flexibility in the design and manufacturing of future aircraft. The new wing design was tested in a NASA wind tunnel and is described in a paper in the journal Smart Materials and Structures.
Instead of requiring separate movable surfaces such as ailerons to control the roll and pitch of the plane, as conventional wings do, the new assembly system makes it possible to deform the whole wing, or parts of it, by incorporating a mix of stiff and flexible components in its structure. The tiny subassemblies, which are bolted together to form an open, lightweight lattice framework, are then covered with a thin layer of similar polymer material as the framework.
The result is a wing that is much lighter, and thus much more energy efficient, than those with conventional designs, whether made from metal or composites, the researchers say. Because the structure, comprising thousands of tiny triangles of matchstick-like struts, is composed mostly of empty space, it forms a mechanical “metamaterial” that combines the structural stiffness of a rubber-like polymer and the extreme lightness and low density of an aerogel.
Jenett explains that for each of the phases of a flight – take-off and landing, cruising, manoeuvring and so on – each has its own, different set of optimal wing parameters, so a conventional wing is necessarily a compromise that is not optimised for any of these, and therefore sacrifices efficiency. A wing that is constantly deformable could provide a much better approximation of the best configuration for each stage.
While it would be possible to include motors and cables to produce the forces needed to deform the wings, the team has taken this a step further and designed a system that automatically responds to changes in its aerodynamic loading conditions by shifting its shape – a sort of self-adjusting, passive wing-reconfiguration process.
“We’re able to gain efficiency by matching the shape to the loads at different angles of attack,” says Cramer, the paper’s lead author. “We’re able to produce the exact same behaviour you would do actively, but we did it passively.”
This is all accomplished by the careful design of the relative positions of struts with different amounts of flexibility or stiffness, designed so that the wing, or sections of it, bend in specific ways in response to particular kinds of stresses.
The new wing was designed to be as large as could be accommodated in NASA’s high-speed wind tunnel at Langley Research Centre, where it performed even a bit better than predicted, Jenett says.
The same system could be used to make other structures as well, Jenett says, including the wing-like blades of wind turbines, where the ability to do on-site assembly could avoid the problems of transporting ever-longer blades. Similar assemblies are being developed to build space structures, and could eventually be useful for bridges and other high performance structures.
For more information, visit the MIT website.