BADASS BEETLE
Secrets of unsquashable beetle revealed
Found in the desert in the southwestern USA, the diabolical ironclad beetle has an exoskeleton so strong it can survive being run over. Materials scientists at the University of California, Irvine, have discovered what makes this tiny titan so tough, and they have made composite materials with the same characteristics.
“The ironclad is a terrestrial beetle, so it’s not lightweight and fast, but built more like a little tank,” said Dr David Kisailus, principal investigator on the
study. "That's its adaptation it canot fly away, so it
just stays put and lets its specially designed armour take the abuse until the predator gives up.”
The team studied the beetles with compression tests and found that they could withstand a force 39,000 times their own body weight. That’s like a 60kg person surviving a 2,340-tonne weight.
The insect’s remarkable strength lies in its elytra.
In flying beetles, the elytra are hardened forewings that close over their hindwings s which do the flying
– and protect them from bacteria and damage. In the diabolical ironclad beetle, the elytra have fused together, forming a tough shield.
The researchers studied the elytra using microscopy and spectroscopy. They found that they are made up of a protein matrix and layers of chitin, a
fibrous material often found in insects' exoskeletons. Compared to a flying beetle, the ironclad's elytra had
about 10 per cent more protein by weight.
They also looked at how the two halves of the elytra were attached – known as the medial suture. The join looks like interlocking jigsaw pieces, but they don’t behave as you might expect.
“When you break a puzzle piece, you expect it to separate at the neck, the thinnest part,” said Kisailus. “But we don’t see that sort of catastrophic split with this species of beetle. Instead, it delaminates, providing for a more graceful failure of the structure.” That is, the layered structure of the chitin saves the day: instead of suddenly breaking, the layers slowly fracture and come apart.
Kisailus and his team have taken inspiration from these remarkable beetles to design a material with the same interlocking pieces. When they joined the material to an aluminium coupling, they found it was much stronger and tougher than standard fasteners.
The researchers hope that this could be used in aircraft to join segments together without the weak points that traditional rivets and fasteners introduce.