Liquid Armor: Grade-school science goes to war

By Marisa Mazart and Corey Conley

Would you trust your life to something called “bullet proof custard?” Soldiers and police of the near future may ditch most of their trusty Kevlar plates for comfy packs of liquid armor.

While the idea of liquid armor may not inspire confidence, researchers at U.K.-based BAE Systems claim their liquid armor, when mixed with Kevlar, protects better than Kevlar alone. Normal Kevlar armor can have up to thirty sheets of the stiff material, but the superior liquid blend has only ten, which represents a staggering decrease in weight and increase in comfort and mobility.

This custard works by behaving like a liquid during normal movement but shifting properties when hit with a projectile.

While the exact formulation of this super-secret concoction is a bit of a mystery, you might have encountered something similar in elementary school science class. The non-Newtonian liquid is a staple of science classes everywhere, beloved by teachers for its curious properties and simplicity.

Usually cornstarch and water, the syrupy concoction behaves normally when poured, but smack it or push against it and it effectively turns into a solid until the pressure subsides. The Internet abounds with videos of enterprising young youths walking quickly across pools of the milky white liquid. They leave ripples and turbulence behind, but rarely sink to their ankles, so long as they remain in motion. Once stopped, they sink as if in quick sand.

This “shear thickening” is the principle behind the liquid armor. When compressed, the atoms briefly lock together to create a solid, when released they flow like a liquid. In the case of the armor the bullet, not feet, would make the Kevlar-backed liquid solidify on contact, stopping the projectile cold.

What are the Benefits of Liquid Armor?

Experts predict the liquid armor could cut weight by as much as half, but that’s hardly the only benefit. Liquid armor could be far more flexible, and the liquid itself has proven far better than Kevlar alone at dissipating impact energy from a projectile. Like ripples on a lake, the kinetic energy of the bullet ripples across the entire vest, instead of transmitting its energy to the soldier’s chest.

Liquid armor will also be cooler than plate-based armor, and it’s not hard to imagine such armor fitted with a system that cools and circulates the liquid.

Of course, military tech often finds its way to the civilian world, and the possibilities for an advanced non-Newtonian liquid – one that freezes to stop a force then relaxes to dissipate the energy, are intriguing. One day our own safety equipment could incorporate similar technology, perhaps for our cars and motorcycle helmets.

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