New armour design draws inspiration from the sea

Tuesday, 7 February 2017
New armour design takes inspiration from the sea.

Fish-inspired armour could provide industrial workers with increased protection from piercing, after researchers at McGill University spent two years studying the properties and mechanics of fish scale.

Natural armours such as fish scales or osteoderms combine plates of hard material with a softer substrate, creating a protective system that is simultaneously hard to puncture and flexible.

While humans have made segmented armours for a long time, the protective and flexible properties of these armours have been hampered by a limited understanding of the mechanics and optimal design, as well as by challenges of cost-efficient manufacturing.

The team, led by François Barthelat, who teaches in the Department of Mechanical Engineering at McGill University, wanted to take inspiration from animal scales, and use modern analytical and manufacturing technology to create an updated type of segmented armour, creating protective glves that exhibit both increased resistance to piercing, but still flexible enough for factory workers to work in.

The researchers started with striped bass, puncturing or fracturing hundreds of fish scales under the microscope, but the solution came when they started looking more closely at the scales of an alligator gar.

"Nature has been finding solutions to 'engineering problems' over millions of years of evolution," said Barthelat about the team's approach.

"For a long time biologists and engineers largely ignored each other, but this is now changing. Biologists are using more and more engineering tools and methods, and engineers are revisiting old engineering problems using bioinspiration. Biologists and engineers are now talking to each other more than ever before, which is very stimulating and makes it is a very exciting time to be working in this field."

The team used a series of experiments to identify a critical set of mechanisms in the way natural fish scales deform, interact and fracture. They also developed a new manufacturing technique, combining laser engraving with a stretch-and-release method, allowing them to fine-tune the size and overlap of the scales, and cover large surfaces with a shell of overlapping ceramic tiles. They used computer modelling to determine the optimal size, shape, arrangement and overlap to make protective gloves that are much more resistant to piercing than those currently in use.

"There's an optimum size for the scales so they can resist puncture. There is an optimum geometry that governs how the scales interact, there's an optimum arrangement," Barthelat explained.

According to Roberto Martini, a post-doctoral fellow and the lead author of the paper that the team published about their work, smaller scales are more difficult to pierce than larger ones, and the team used engineering analysis to fully explain why. The team also learned that the scales are the toughest collagen-based material known.