X-Message-Number: 24016
From: "Mark Plus" <>
Subject: Liquid body armor
Date: Thu, 29 Apr 2004 14:47:02 -0700

This has obvious applications to the problem of reducing the risk of death 
by misadventure [Mark Plus]:

http://www.foxnews.com/story/0,2933,118577,00.html

Thursday, April 29, 2004

BALTIMORE   Army scientists are working on a liquid body armor for clothing 
that stays flexible during normal use but can harden to stop a projectile 
when hit suddenly.

Researchers hope the liquid could be used in sleeves and pants, areas not 
protected by ballistic vests because they must stay flexible.

The liquid, hard particles suspended in a fluid, is soaked into layers of 
Kevlar, which holds it in place. Scientists recently had an archer shoot 
arrows at it to see how well the liquid boosted the strength of a Kevlar 
vest (search).

"Instead of the arrow going through the Kevlar, it is completely stopped by 
the Kevlar vest and sometimes just bounces right off," said Norman Wagner, a 
University of Delaware chemical engineering professor who is working on the 
project.

Vests treated with the liquid have also blocked stabs from an ice pick, and 
researchers are doing more tests to see if it can stop bullets or shrapnel, 
too.

The project, which has been under way for about three years, is a joint 
venture between the U.S. Army Research Laboratory (search) and the 
University of Delaware's Center for Composite Materials (search).

Eric Wetzel, a mechanical engineer who heads the project team for the Army 
lab, said a "shear thickening fluid" is a key component of the liquid armor. 
Hard particles are suspended in the liquid, polyethylene glycol. At low 
strain rates, the particles flow with the fluid, enabling clothing to stay 
flexible. But when heavily strained, the particles become rigid.

"If it's impacted suddenly by a projectile or a knife, say, it rigidifies 
and somehow restricts the ability of the fabric to move," Wetzel said.

The transition happens very quickly, a millisecond or quicker.

Wetzel and Wagner are optimistic the liquid body armor will be useful to 
local police and prison guards and perhaps it could one day protect people 
in automobile and airplane crashes.

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