Stronger, Lighter, Better Body Armor

By David Hambling
Source: Aviation Week & Space Technology

Amendment II of Salt Lake City was reportedly the first to market this technology. Its material, RynoHide, is a soft armor that is lighter than Kevlar fiber but reportedly provides superior protection. RynoHide was created in partnership with the Nano Institute of the University of Utah to develop carbon nanotubes for body armor. Amendment II will not discuss details at this stage, but the company's “secret sauce” appears to involve CNTs interwoven with conventional fibers.

Others in the same field include Nanocomp Technologies of Concord, N.H., which is working with the U.S. Army's Natick (Mass.) Soldier Center. Nanocomp developed a proprietary process to make a nonwoven textile made of millimeter lengths of CNTs bonded together. A version that is 0.25 in. thick reportedly stops a 9-mm. bullet, which suggests it outperforms Kevlar. The next stage will be incorporating the material into body armor sets.

CNTs are also the key ingredient of a program to improve hard armor at Natural Resources Canada's Materials Technology Laboratory in Hamilton, Ontario. This involves mixing alumina powder, silicon carbide and boron carbide powder with CNTs and forming them into ceramic plates via hot-pressing. Previous results suggest that the nanotubes make the ceramic tougher and less brittle without affecting its strength. Plates may crack after the first hit, but a nanotube-reinforced ceramic should stop multiple rounds. It would also be more robust and less likely to be damaged during handling, which is a serious problem, as plates can break if they impact hard surfaces.

Materials science may provide simpler solutions. Auxetix Ltd. of Devon, England, has tested prototype body armor made of auxetic material. This has the seemingly paradoxical property of expanding when stretched—or as one source puts it, becoming thicker perpendicular to an applied force.

Auxetics improve materials by adding springiness to them. CEO Patrick Hook says an auxetic fabric incorporating Kevlar aramid is more ballistic-resistant than the aramid fiber by itself, and it is cheaper, since it uses as little as one-tenth of the expensive, high-tech material, with the rest being nylon. He has developed auxetic body armor, as well as blast curtains and spall liners.

Hook says auxetic material is relatively straightforward to manufacture on standard looms. An existing technique called weft insertion adds the spiral element, and the material can be engineered to adjust tension, degree of stretch and other properties.

Hook's U.S. licensee is working with Xtegra, a material he developed, to produce auxetic armor for the U.S. Navy.

While better materials may cut weight by 10%, the second approach mentioned by Mackiewicz, using appropriate armor levels, could save 30% or more. A 2012 Rand Corp. study found that troops in Iraq and Afghanistan were burdened with armor heavy enough to stop much more powerful rounds than they encountered. The threat has been shrapnel and 7.62-mm rounds. “Current body armor provides excessive overmatch against those threats,” Rand says.

The study recommends modular armor with different protection levels. Current U.S. armor varies from a 6-lb. vest, which provides basic protection that can be scaled up with front, back and side ceramic inserts totaling 32 lb. to cover more of the body (including the neck and groin).

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