(ORDO NEWS) — The American beetle Nosoderma diabolicum will not be crushed even by a passing car: the insect’s rigid elytra can withstand enormous loads due to unusual structures that resemble the connection of puzzle pieces.
The Nosoderma diabolicum beetles and their relatives are called “armadillos” for a reason: the unusually thick and durable shell allows them to withstand loads of up to 150 Newtons – about 15 kilograms, about 39 thousand times their own weight. It is not surprising that these insects have lost the ability to fly, but they survive the collision of a car wheel without any problems. For their natural opponents – birds, rodents and lizards – they represent a tough nut, which is almost impossible to gnaw.
Teams Pablo Zavattieri of Purdue University and David Kisailus of the University of California Irvine investigated the strength secrets of these coleoptera by observing the behavior of the carapace under high loads under a microscope and using computed tomography, and then printing on a 3D printer and having experienced similar structures. Their article was published in the journal Nature.
The authors note that common beetles are unable to withstand even half of the load that Nosoderma diabolicum tolerates. The secret of their durability lies in the structure of the elytra, thanks to which they have turned from ordinary “covers” for the wings into a powerful protection for all internal organs. First, the outer layers of the carapace are reinforced with structural proteins for added strength. According to scientists, the protein content here is about 10 percent higher than in the rest of the beetle.
Second, the centerline junction of both elytra is reinforced with structures resembling puzzle pieces. If the pressure is too high, even for such a reinforced exoskeleton, the elytral joints will deform and slowly pull apart, like a zip fastened. This process requires a lot of effort, effectively dissipating the applied energy and keeping the carapace from breaking.
In this case, the surfaces of the protrusions and depressions entering into each other are covered with elastic proteins, which increase the strength of their connection and do not allow them to collapse when they separate. Scientists have 3D printed such structures and tested them under stress, confirming that they provide increased strength. The authors of the study are confident that their find will be another idea that can be borrowed from nature and applied in engineering, creating more durable structures from metals and composites.
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