EXAMINING HOW INSECTS’ wings and legs wear out over time may help engineers as they search for ways to make safe, more durable types of material.
Researchers at Trinity College Dublin are currently working towards a full understanding of the second-most common natural material in the world – insect cuticle.
Insects are one of the most diverse groups of animals in the world but they have one thing in common – they are all made from cuticle. Until Dr Jan-Henning Dirks, Professor David Taylor and Eoin Parle established their study, little was known about the fatigue properties of the material.
“The single biggest cause of failure in cars, aeroplanes and other mechanical structures is material fatigue,” explains lead researcher Dr Dirks. “For quite some time it has been known that this kind of fatigue behaviour easily happens in some materials, but far less in others. That’s why engineers are constantly looking for ideas to design safer, more durable types of materials.”
An insect’s exoskeleton supports them in a way bones support a human body. At the same time, the cuticle – an extremely versatile biological material – acts as a protective skin.
“If we understood how cuticle acts under repeated loads, we might be able to design more durable biomimetic materials for many kinds of applications,” continues Dr Dirks.
As a first step, the Trinity College team looked at the cuticle of the desert locust, which is capable of flying across oceans and deserts for days or weeks at a time.
Parle, who is writing a PhD thesis about the mechanical properties of insect cuticle, explains that the locusts’ wings beat hundreds of thousands a times, and their hind legs perform thousands of jumps.
To measure the fatigue properties of the cuticle, the engineers and scientists took samples of the legs and wings and mechanically simulated the repeated loading that occurs in wing beats and during jumping. The researchers were able to show that both structures can withstand hundreds of thousands of cycles, with the legs being notably more resistant to fatigue.
“Our results also show that due to their shape and fibrous material the legs are very well adapted to withstand the types of failure that might occur in jumping and kicking,” says Parle.
“For the first time, we now actually know that insect cuticle shows material fatigue after repeated loading,” adds Taylor. “These results are obviously just a first step.
“Studying insect cuticle is not only thought-provoking from the engineering point of view, where our findings might help us to develop more durable composite materials. Our results are also interesting from the biological perspective, where we can learn more about how insects evolved to become one of the most successful groups of animals.”
The study’s findings have recently been published in the Journal of Experimental Biology.
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