Next generation armor inspired by animal scales

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3D-printed scales introduced onto a soft substrate cause the material to become tougher (Photo: Matthew Modoono)

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We've seen scientists examine everything from the structure of sea sponges to the clubbing ability of mantis shrimps in the search for next generation lightweight armor systems. Researchers at Northeastern University’s College of Engineering believe that fish scales could hold the key to creating armor that's both impervious and lightweight. They eventually aim to combine the properties of fish, snake and butterfly scales into a single protective armor system.

Fish scales have been studied extensively because of their ability to protect the body while still allowing movement. However most of these studies have focused on the material of the scales and how their plasticity or elasticity alters their protective qualities. Ranajay Ghosh, an associate research sci­entist, and his colleagues explored a different track. They took a soft substrate and examined how adding scales of a certain size, laid out geometrically, would affect its properties.

"We found that as long as the scale material is at least an order of magnitude stiffer than the skin material, perceptible benefits can begin to accrue," Ghosh told Gizmag.

Adding 3D-printed scales to the soft substrate caused the material to stiffen up and become less penetrable. Combining geometry with scale interaction allowed the team to achieve a "structural stiffening" which is believed to be key. Simple scales used in specific arrangements that stiffen up could help to create better armor, the researchers say, given how nature seems to achieve multiple functions quite well without using the kind of high-strength materials that humans do.

"Many scales are optimized for different and often distinct purposes – protection (e.g. some fishes), mobility (snakes) or coloration (butterfly) depending on maximizing the probability of survival and replication," Ghosh tells us. "In principle, we can have a protective system which combines the protective functions of a fish scale with the mobility advantage of snake scale with the optical properties of butterfly scales."

The team aims to tweak various materials and use both 3D printing and nano-fabrication to combine these different properties into one. Challenges include fabricating and testing scales and modifying them to withstand the high energies and temperatures associated with impacts. Going forward the team hopes to gain more insights into the fundamental principles that combine geometry with scale interaction to help design better armor.

"Modern armor would be more successful if we have an easier handle on different properties from as few design variables as possible,", says Ghosh. "This reduction is possible when we discover a deeper underlying principle which makes natural dermal scale modifications so widespread and ancient."

A paper on the work so far has been published in the journal Applied Physics Letters.

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