A US Air Force Academy cadet demonstrated that school lessons aren't just about retreading old ground, by turning a classroom exercise into a new ballistic armor made out of goo. In 2014, Cadet 1st Class Hayley Weir's assignment to combine epoxy, Kevlar and carbon fiber into an anti-ballistic substance inspired her to develop the task into a new type of flexible bullet stopper.

Composite armors aren't new and Weir's assignment was a standard one, but she wasn't satisfied with the result, which could stop a bullet but was hard and brittle. Following the suggestion of an Academy chemical adviser, she swapped out the epoxy with a shear thickening liquid.


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Again, this wasn't new. Shear thickening liquids are made of nanoparticles suspended in a polymer that looks like a plastic goo and is as flexible as a defrosted freezer gel pack under normal conditions. But if they're struck hard enough, their properties change radically and they become extremely hard and viscous.

If you want a cheap analogy to this, take a ball of Silly Putty and play with it. Molded by fingers, it's soft, saggy, and will even ooze under its own weight if left alone. But yank it or hit with a hammer and it snaps or even shatters like glass. Such fluids are already used in motorcycle leathers and military personnel armor, but Weir had stumbled on something new.

Teaming up with military and strategic studies professor Ryan Burke, Weir started developing her idea for a Kevlar, composite goo armor. When the two looked at the existing research, however, they found that no one had produced anything similar to Weir's combination.

In 2016, Weir and Burke conducted tests with the new armor as they tried to develop a mix of the three elements that was most effective. They also attempted to figure out how to layer them for the best stopping power. By December, they were ready for test shots.

What they found was that not only had they come up with a bullet stopper, but one that was more effective the larger and faster the round. A 9-mm round pierced most of the layers only to be stopped by the Kevlar fiber backing, but a .40 Smith & Wesson only got to the third Kevlar layer, and a high velocity .44 Magnum round didn't get past the first.

"The greater the force, the greater the hardening or thickening effect," says Burke.

Weir, who is graduating from the Academy, will continue her research at Clemson University in South Carolina as she and Burke work to perfect the technology. They see it as having a wide range of applications, including as personal and vehicle armor, protective tent material against bullets and shrapnel, and as quick-deploying barricades to protect civilians in mass shooting incidents.

Source: US Air Force