UAVs are taking up more and more space in aviation circles. Suong Hoa and his student co-authors describe a way for making UAV wings cheaper to construct and more efficient in flight in a recent paper published in the journal Composite Structures. For rotary-wing drones, the rotor-blades / rotor-wings rotate around a central mast, forcing air downwards and creating the vertical lift required for the aircraft to become airborne.
Hoa is a mechanical, industrial, and aerospace engineering professor at the Gina Cody School of Engineering and Computer Science. The authors conducted a feasibility analysis on the implementation of a new technology to construct adaptive compliant trailing edge (ACTE) morphing wings using a process Hoa pioneered known as 4D printing of composites. The experimental technique substitutes a hinged wing flap for one that is attached to the main wing body but can bend up to 20 degrees.
"Our work demonstrates that a UAV with this type of wing can handle a significant amount of load for small or medium-sized vehicles," adds Hoa, head of the Concordia Centre for Composites.
Using material reactions
4D printing is similar to 3D printing in that materials are changed from site to location. The distinct substance is employed because it is reactive to certain stimuli, such as water, cold, or heat. The initial printing is done on a flat surface, which is subsequently subjected to the stimuli, which chemically reacts and changes the shape of the surface. The changing configuration of the once-flat substance is referred to as the third dimension.
Composite 4D printing is more difficult. It relies on a sinewy combination of long, fine filaments held in place by a resin rather than the mushy, dough-like substance normally utilized by 3D and 4D printers. Each filament is only 10 microns thick, which is about one-tenth the diameter of a human hair. The filament-resin mixture is unrolled in ultra-thin layers at 90-degree angles from each other by the 4D composite printer. The layers are then compressed together and cured in an oven at 180 C before being chilled to 0 C, resulting in a rigid but not fragile product.
According to the scientists' article, this allows them to build a segment of material with a consistent curvature that is sandwiched between the upper and bottom sides of the wing flap. It is flexible and sturdy enough to support the wing's 20-degree deformation for flying manoeuvrability."The aim is to have a wing that can readily change shape during flight, which would be a huge advantage over fixed-wing aircraft," Hoa explains. He feels composite 4D technology has enormous potential for a wide range of applications. The transportability of its products, he claims, is a key lure."Because it is flat, it is simple to package and ship to remote locations ranging from Canada's Far North to outer space."
Because of its thermomechanical and other material qualities, 4D printing technology employs materials such as single shape memory polymers, liquid crystal elastomers, composite hydrogel, SMP composites, SMP multi-material, and other multifunctional materials. They are referred to as "Smart Materials" because of their ability to keep a temporary shape while returning to its normal shape under the influence of external factors.
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