ARTICLE

August 2004

Army Researchers Optimistic About ‘Liquid Armor’

by Sandra I. Erwin

After two decades of research, Army engineers may be getting closer to developing “liquid armor,” which one day could be used to make military bulletproof garments.

By combining a liquid composite substance—known as shear thickening fluid—with Kevlar fabric, Army researchers have created a stab resistant material, although it is not yet robust enough to halt bullets.

Engineers hope, however, that this liquid armor eventually will be bulletproof, said Eric Wetzel, who heads the project at the Army Research Laboratory.

The novel composite material could provide a more flexible and less bulky alternative to Kevlar fabrics, Wetzel told National Defense.

Although this material has been investigated academically for a couple of decades, it is only now getting renewed attention as the Army struggles to come up with alternatives to heavy ceramic body armor, which adds 17 to 24 pounds of extra weight to the average soldier’s load. About two years ago, the Army enlisted University of Delaware researchers to help with the project.

In its current state, the liquid armor combined with four layers of Kevlar fabric cans top an ice pick puncture, Wetzel said. That would make the material potentially useful for prison guards who get stabbed with handmade sharp instruments, for example, Wetzel said.

If this technology ever succeeds as an alternative to conventional armor, the Army would use it to protect soldiers’ extremities. Currently, soldiers’ arms and legs go unprotected because conventional body armor, with ceramic tile inserts, is too bulky and stiff for extremities. The liquid armor could change that, although any breakthroughs are, according to Wetzel, “a few years down the road.”

The shear thickening liquid is a polyethylene glycol that is “very deformable,” he noted. When intense pressure is applied, it transitions to a rigid material, which would in theory prevent a bullet from penetrating it.

To make liquid armor, the material is soaked into the layers of a Kevlar vest, then handled just like any other fabric.

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