Oct 22, 2020 - Science

How studying a nearly indestructible beetle could improve aircraft construction

Beetles.
Phloeodes diabolicus, the diabolical ironclad beetle. Photo: David Kisailus/University of California, Irvine

The diabolical ironclad beetle can withstand enormous forces, protecting it from predators — and potentially providing scientists with new designs for materials.

Why it matters: Details of the beetle's architecture reported by researchers this week could lead to improved ways to join together materials like plastics and metals that are key for constructing airplanes and buildings but can break unpredictably.

Details: The forewings, called elytra, in the flightless Phloeodes diabolicus are fused together into a hard exoskeleton that likely evolved to protect the insect from predators.

  • Jesus Rivera of the University of California, Riverside and his colleagues report the beetle can survive being run over by a car and withstand forces up to 39,000 times greater than its body weight — equivalent to a 150-pound person supporting about 240 school buses.

How it works: Using scanning electron microscopy and CT scans, the researchers found the beetle's strength and toughness are due to two key features.

  1. Three different types of supports on the sides of the beetle, where the elytra and the shell on the insect's underside meet, allow the beetle to be compliant so it can squeeze into rocks without crushing its organs, says David Kisailus, a materials scientist who is Rivera's adviser. Other beetles have these lateral supports, but only one kind of them across the length of their body.
  2. The two elytra on the beetle's back interlock like jigsaw puzzle pieces, giving the exoskeleton strength. If the load on the beetle is great enough to disconnect those pieces, the layers of tissue within them separate and slide past each other, slowly deforming the exoskeleton and dissipating the stress.

When Rivera mimicked the beetle's exoskeleton with a carbon-fiber plastic material and compared it to standard fasteners used in aviation today, he found the beetle-inspired design was slightly stronger, significantly tougher and broke in a more predictable way, the authors report in the journal Nature.

The big idea: As organisms adapt over millions of years to various environments and stresses, nature sometimes converges on what are probably the best designs, says Kisailus. Identifying those designs in plants and animals could provide a set of rules for creating new materials.

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