A team of engineers from NASA and Massachusetts Institute of Technology (MIT) has demonstrated a new kind of ‘morphing’ aircraft 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.
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 researchers say 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.
Because the structure, comprising thousands of tiny triangles of matchstick-like struts, is made up 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.
Benjamin Jenett, a graduate student in MIT’s Center for Bits and Atoms, explains that each phase of flight — take-off and landing, cruising, manoeuvring, etc. — 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.
“We’re able to gain efficiency by matching the shape to the loads at different angles of attack,” says NASA’s Nicholas Cramer, the paper’s lead author. “We’re able to produce the exact same behaviour you would do actively, but we did it passively.”
The new wing design was tested in a NASA wind tunnel and is outlined in the Smart Materials and Structures journal.