Mother of pearl inspires mother of all armours
Researchers develop a plastic that’s much tougher than steel.
US researchers have mimicked the outer coating of pearls to create a plastic they say is 14 times stronger and eight times lighter than steel – and thus ideal for absorbing the impact of bullets and other projectiles.
The work by a team from the University of Buffalo, and published in the journal ACS Applied Polymer Materials, was, perhaps not surprisingly, funded by the US Army Research Office.
"The material is stiff, strong and tough," says lead author Shenqiang Ren, a professor in the Department of Mechanical and Aerospace Engineering.
"It could be applicable to vests, helmets and other types of body armour, as well as protective armour for ships, helicopters and other vehicles."
The bulk of it is ultrahigh molecular weight polyethylene (UHMWPE) – essentially a souped-up version of the most common plastic, polyethylene, which is used to make everything from artificial hips to guitar picks.
However, when designing it, Ren and colleagues first studied nacre – better known as mother of pearl – which molluscs create by arranging a form of calcium carbonate into a structure that resembles interlocking bricks.
It is found in nature as an inner shell layer, as well as the outer coating of pearls.
Mother of pearl has an extremely tough outer shell with a more flexible inner backing that's capable of deforming and absorbing projectiles – and that’s the approach the researchers took.
The potential is in the material’s flexibility as well as its strength, they say. It would be easier to cast or mould into complex shapes than steel, or even woven materials that are used to create so-called soft armour.
In addition, it has high thermal conductivity, and this ability to rapidly dissipate heat further helps it absorb the energy of bullets and other projectiles.
The team also experimented by adding silica nanoparticles to its UHMWPE, finding that tiny bits of the chemical could enhance the material's properties and potentially create stronger armour.