Page 53 - Plastics News April 2019

teChnoLogy

MIT and NASA engineers design lightweight polymer airplane wing

team of engineers from NASA’s Ames Research Center explains that there is a different set of optimal wing
A (Moutain View, California U.S.) and the Massachussetts parameters for each phase of flight, to provide a better
Institute of Technology have built and tested an airplane approximation of the best configuration for each stage.
wing assembled from a lattice comprising hundreds of The system is designed to automatically respond to
tiny identical polymer pieces. The wing reportedly can changes in its aerodynamic loading conditions by shifting
change shape to control the plane’s flight. The wing design its shape in specific ways. The individual parts for the
was tested in a NASA wind tunnel and is described in a previous wing were cut using a waterjet system, and it
paper in the journal Smart Materials and Structures, co- took several minutes to make each part, Jenett says. The
authored by research engineer Nicholas Cramer at NASA new system uses injection molding with polyethylene resin
Ames in California; NASA Ames engineer and MIT alumnus in a complex 3D mold, and produces each part essentially
Kenneth Cheung; MIT graduate student Benjamin Jenett a hollow cube made up of matchstick-size struts along
and eight others. Instead of requiring separate movable each edge in just 17 seconds, he says, which brings it
much closer to scalable production levels. “Now we have a
manufacturing method,” he says. While there’s an upfront
investment in tooling, once that’s done, “the parts are
cheap,” he says. “We have boxes and boxes of them, all
the same.”The resulting lattice, he says, has a density
of 5.6 kilograms per cubic meter. By way of comparison,
rubber has a density of about 1,500 kilograms per cubic
meter. “They have the same stiffness, but ours has less
than roughly one-thousandth of the density,” Jenett says.
Because the overall configuration of the wing or other
structure is built up from tiny subunits, the overall design
of the wing structure could be changed from its traditional
shape, Jenett says. Studies have shown that an integrated
body and wing structure could be far more efficient for
surfaces such as ailerons to control the roll and pitch of many applications, he says, and with this system those
the plane, as conventional wings do, the new assembly could be easily built, tested, modified and retested. The
system makes it possible to deform the whole wing, or same system could be used to make other structures as
parts of it, by incorporating a mix of stiff and flexible well, Jenett says, including the wing-like blades of wind
components in its structure. The tiny subassemblies, turbines, where the ability to do on-site assembly could
which are bolted together to form an open, lightweight avoid the problems of transporting ever-longer blades.
lattice framework, are then covered with a thin layer of Similar assemblies are being developed to build space
similar polymer material as the framework. The result structures, and could eventually be used for bridges and
is a wing that is lighter, and thus more energy-efficient, other high-performance structures.The team included
than those with conventional designs, whether made researchers at Cornell University, the University of
from metal or composites, the researchers say. Because California at Berkeley, the University of California at Santa
the structure, comprising thousands of tiny triangles of Cruz, NASA Langley Research Center, Kaunas University of
matchstick-like struts, is composed mostly of empty space, Technology in Lithuania, and Qualified Technical Services
it forms a mechanical “metamaterial” that combines Inc., in Moffett Field, Calif., U.S. The work was supported
the structural stiffness of a rubber-like polymer and the by NASA ARMD Convergent Aeronautics Solutions Program
extreme lightness and low density of an aerogel. Jenett (MADCAT Project) and the MIT Center for Bits and Atoms.

53 April 2019 Plastics News