Army scientists, engineers develop liquid body armor

Army News Service ^ | April 21, 2004 | Tonya Johnson

[O.C. - Old Cracker]

ABERDEEN PROVING GROUND, Md. (Army News Service, April 21, 2004) -- Liquid armor for Kevlar vests is one of the newest technologies being developed at the U.S. Army Research Laboratory to save Soldiers' lives.

This type of body armor is light and flexible, which allows soldiers to be more mobile and won’t hinder an individual from running or aiming his or her weapon.

The key component of liquid armor is a shear thickening fluid. STF is composed of hard particles suspended in a liquid. The liquid, polyethylene glycol, is non-toxic, and can withstand a wide range of temperatures. Hard, nano-particles of silica are the other components of STF. This combination of flowable and hard components results in a material with unusual properties.

“During normal handling, the STF is very deformable and flows like a liquid. However, once a bullet or frag hits the vest, it transitions to a rigid material, which prevents the projectile from penetrating the Soldier’s body,” said Dr. Eric Wetzel, a mechanical engineer from the Weapons and Materials Research Directorate who heads the project team.

To make liquid armor, STF is soaked into all layers of the Kevlar vest. The Kevlar fabric holds the STF in place, and also helps to stop the bullet. The saturated fabric can be soaked, draped, and sewn just like any other fabric.

Wetzel and his team have been working on this technology with Dr. Norman J. Wagner and his students from the University of Delaware for three years.

“The goal of the technology is to create a new material that is low cost and lightweight which offers equivalent or superior ballistic properties as compared to current Kevlar fabric, but has more flexibility and less thickness,” said Wetzel. “This technology has a lot of potential.”

Liquid armor is still undergoing laboratory tests, but Wetzel is enthusiastic about other applications that the technology might be applied to.

“The sky’s the limit,” said Wetzel. “We would first like to put this material in a soldier’s sleeves and pants, areas that aren’t protected by ballistic vests but need to remain flexible. We could also use this material for bomb blankets, to cover suspicious packages or unexploded ordnance. Liquid armor could even be applied to jump boots, so that they would stiffen during impact to support Soldiers' ankles.”

In addition to saving Soldiers' lives, Wetzel said liquid armor in Kevlar vests could help those who work in law enforcement.

“Prison guards and police officers could also benefit from this technology,” said Wetzel. “Liquid armor is much more stab resistant than conventional body armor. This capability is especially important for prison guards, who are most often attacked with handmade sharp weapons.”

For their work on liquid armor, Wetzel and his team were awarded the 2002 Paul A. Siple Award, the Army’s highest award for scientific achievement, at the Army Science Conference.

(Editor’s note: Tonya Johnson is a member of the Army Research Laboratory Public Affairs Office.)

[adam_az]

Liquid Armour?

[King Prout]

you should have seen the peanutbutter thread last night :)

[firewalk]

Very cool stuff
Thanks for the ping

[Shaun_MD]

Rof - Peanut butter? I won't even ask about that one...

[VadeRetro]

Even plain old water shows some of this behavior. When you dive into the water correctly, it flows around you easily. When you do a belly-flop, you slam it hard while presenting a broad surface area. It thus would have to move aside very fast to get out of your way and avoid stinging your skin. It doesn't flow that fast, everyone hears a loud "crack," and you get stung.

[King Prout]

"instant classic" FR thread, destined for moose-bites and hugh series showers.
I'll see if I can find it in the stack and send you a link.
RIOT.

[4mycountry]

Orange hair for everybody!!

[King Prout]

YEP!

http://www.freerepublic.com/focus/f-news/1122129/posts

[Shaun_MD]

I never thought about that, but you're exactly right.

[4mycountry]

Neat stuff.

[Shaun_MD]

"http://www.freerepublic.com/focus/f-news/1122129/posts"

Omg! - that was absolutely hysterical!!
In a psychotic and disturbing kind of way ;)

[King Prout]

figgered you'd dig it.

[Alex Murphy]

Never mind the obvious, unintended side effect - that the newly-armored soldier now leaves a sickly green slugtrail of "liquid armor" everywhere he goes :)

[William Terrell]

However, once a bullet or frag hits the vest, it transitions to a rigid material

But does it transition fast enough?

[4mycountry]

"DIG" it?!

And you thought Zelda games were so 90s. ;)

[Flying Circus]

Not really. Water is a fairly Newtonian fluid, ie the the shear stress is linear with the shear rate. Shear thickening is when the shear stress increases with shear rate (often at an exponential). Diving is actually a higher shear than belly flopping. If water were shear thickening, it would actually resist your diving into it more than your belly flop, and both would hurt. Also, if water were shear thickening, it wouldn't be such a miracle to walk on it!

[JerseyHighlander]

If I could pick your brain for a second, would these contigous pockets of liquid armor be without air? Do you think the paratrooper shoes would be like Asics gels with this super strong liquid armor inside?

[VadeRetro]

Shear thickening is when the shear stress increases with shear rate (often at an exponential).

Hmmm. I was envisioning the problem as sort of a critical viscosity cutoff and not appreciating the importance of the shear part of "shear thickening." That is, not only does the liquid not want to flow, it doesn't want to slide across itself.

[Flying Circus]

Yep. This is common in long chain molecules like oils and polymers (the article mentions poly-ethylene glycol) where the chains can get wound and caught in each other. The chains act like a net and pull tight against applied forces. When relaxed they slide by each other.

[SAMWolf]

T-1000 Bump.:-)