You can’t crush this beetle

The diabolical ironclad beetle may be neither diabolical nor clad in iron, but it possesses material so tough that engineers envy it. God designed the tiny insect with armor that is almost impossible to crush.

The flightless beetle lives in the woods on the U.S. West Coast. Because it cannot fly, it needs toughness to survive, Max Barclay, the curator of beetles at the Natural History Museum in London, told The Guardian. Most beetles live only a few weeks, but the diabolical ironclad beetle can live up to eight years, he said. The beetle’s exoskeleton can withstand a load 39,000 times its body weight, much more than the weight of a car tire running over it on a dirt road.

Scientists studied the beetle’s load-bearing capacity with CT scans, computer simulations, and 3-D printed models. In their study, published in Nature on Oct. 21, they discovered the secret to its toughness lay in its fused wing covers, called elytra. The covering contains no minerals, only organic material. Scientists hope to imitate the protective casing to design synthetic materials.

Armor-like blades with interlocking sections like puzzle pieces make up the elytra. The pieces connect to the beetle’s shell at a line, called a suture, running the length of its abdomen. The connections are stronger and stiffer in certain areas to offer more protection to vital organs. In less sensitive areas, they act like springs to absorb energy when forces bear down on the insect, the scientists told The Guardian. This design distributes force more evenly throughout the body.

The beetle’s hard shell offers two lines of defense. The interconnecting blades lock to prevent stress from pulling them out of the suture. The suture and blades split into layers, releasing strain while keeping the elytra intact, so the exoskeleton can disperse the pressure to prevent a fatal impact at the more delicate neck.

But the entire process requires exquisite precision. Even under maximum force, if the blades interlocked too strongly or weakly, the sudden pressure would snap the beetle’s neck.

The researchers said their discovery could help solve fatigue problems in various kinds of machinery. “An active engineering challenge is joining together different materials without limiting their ability to support loads,” said David Restrepo, who helped with the research. “The diabolical ironclad beetle has strategies to circumvent these limitations.”

For example, engineers use a mechanical fastener to join metals and composite material in the gas turbines of aircraft. But the fastener adds weight and introduces stress that could cause fractures and corrosion. They also decrease performance and can require replacement. Imitating the design of the diabolical ironclad beetle could help to solve such problems, said Maryam Hosseini, another of the researchers.