Liquid, bullet-stopping body armor. Read that again: Liquid, bullet-stopping body armor. It’s not sci-fi, it’s real, and a team of U.K. scientists have proven it has a future in protecting soldiers from incoming rounds or shrapnel.
Liquid armor isn’t a new idea, oddly enough: As well as being a sci-fi staple (Neal Stephenson’s “sintered armor gel” from Snow Crash is a classic example) it’s been researched for decades, mainly due to the benefits that a lightweight, flexible but super-strong armored material could offer. But the team from the U.K.’s BAE company has achieved a composite liquid armor solution that they say for the first time demonstrates real battlefield-ready benefits.
The effect relies on a wild and wacky piece of physics known as non-Newtonian fluid mechanics, that is, basically every fluid you’ve encountered on a day-to-day basis–one where the viscosity is constant. In other words, as you apply more sheer strain to the liquid, the more its sheer stress rises in a predictable way. Forgetting the physics, just think of it as a liquid that reacts pretty much how you’d expect it to.
A non-Newtonian fluid, on the other hand, has no linear relationship between stress and strain–they can vary seemingly at will, or as a third factor comes into play … like time. There’s no constant of viscosity. And this means, in a common sense interpretation, that the liquid won’t behave like you expect it to. A non-Newtonian fluid (like cornstarch, Silly Putty, or custard powder, suspended in water) will easily pour from a cup, but if you hit it with a hammer it could explode into a thousand sharp shards–something water would never do. This particular type of non-Newtonian behavior is called shear-thickening, and its the principle upon which the new armor relies, though obviously the “recipe” for the liquid is being kept a closely guarded secret.
How will it work in the field? A typical bulletproof vest is heavy, awkwardly shaped and made of multiple layers of a very strong material like Kevlar. When it’s hit by a projectile (as in the left-hand image above), its enormous strength means it resists being penetrated, and as it stretches out and deforms in shape, it absorbs the energy of the bullet. You still get a thump in the chest, but all you’ll earn is a bruise. The liquid armor gel wouldn’t need as many complex layers of Kevlar, and very likely distributes the energy of an incoming projectile over a larger area: In BAE’s tests just 10 layers of Kevlar/liquid armor composite resisted the same projectiles as a 31-layer “normal” armored vest, with far less penetration through the protection (see the right-hand image). There’s no telling when and if the technology will be put to practical use, but for soldiers patrolling the scorching streets of Baghdad a lighter, safer, more flexible armor can’t arrive soon enough.
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