MIT and NASA engineers demonstrate a new kind of airplane wing. Assembled from tiny identical pieces, the wing could enable lighter, more energy-efficient aircraft designs.
Researchers in the US have designed, built and tested a radical new lightweight wing design that can change shape mid-flight to enhance performance and boost efficiency.
The wing is made from thousands of triangular components with matchstick-like struts, bolted together in a lattice framework. This lattice is then covered in a thin layer of polymer material similar to the struts. The resulting wing structure is comprised mostly of empty space, forming a mechanical metamaterial that combines the stiffness of a rubber-like polymer with the lightness and low density of an aerogel. According to the researchers, the wing has a density of just 5.6kg per cubic meter.
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 — takeoff and landing, cruising, maneuvering and so on — each has its own, different set of optimal wing parameters, so a conventional wing is necessarily a compromise that is not optimized 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.
The research is presented in the journal Smart Materials and Structures.
While this version was hand-assembled by a team of graduate students, the repetitive process is designed to be easily accomplished by a swarm of small, simple autonomous assembly robots. The design and testing of the robotic assembly system is the subject of an upcoming paper, Jenett says.
A 1m version of the wing was developed a few years ago to validate the underlying principle, with a waterjet used to fabricate the individual components. This latest research saw the team develop a 5m prototype, using injection moulding to significantly speed up the manufacturing process. The struts still had to be put together by hand, but the team believes this step could be automated using assembly robots, and this is the subject of an upcoming research project. As the wing is made from thousands of sub-units, it also opens up the possibility of entirely new aircraft designs.
The individual parts for the previous wing were cut using a waterjet system, and it took several minutes to make each part, Jenett says. The new system uses injection molding with polyethylene resin in a complex 3-D mold, and produces each part — essentially a hollow cube made up of matchstick-size struts along each edge — in just 17 seconds, he says, which brings it a long way closer to scalable production levels.
Studies have shown that an integrated body and wing structure could be far more efficient for many applications, he says, and with this system those could be easily built, tested, modified, and retested.
The new wing was designed to be as large as could be accommodated in NASA’s high-speed wind tunnel at Langley Research Center, where it performed even a bit better than predicted, Jenett says.
The team included researchers at Cornell University, the University of California at Berkeley at Santa Cruz, NASA Langley Research Center, Kaunas University of Technology in Lithuania, and Qualified Technical Services, Inc., in Moffett Field, California. The work was supported by NASA ARMD Convergent Aeronautics Solutions Program (MADCAT Project), and the MIT Center for Bits and Atoms.