Loosely Packed Layers Offer Better Protection

Significantly enhanced impact resistance can result from how dissimilar materials are "sandwiched," say researchers at Pennsylvania State University, University Park, Pa. The researchers found that loosely attached materials worked better than tightly bonded structures. For example, penetration resistance doubled when carbon/graphite fiber-embedded epoxy (a stiff lightweight, easily penetrated composite) was lightly attached to a thin backing sheet of resin-coated Kevlar KM2 fabric (a composite highly impervious to ballistics). Lead researcher B. L. Lee, says the effect is the same as Bible wearing soldiers being protected from bullets and shrapnel. Air layers, whether between the pages of the Bible or between the sheets of carbon/graphite, act to slow the entering projectile, he adds. He believes the principle has potential for safety helmets, aircraft structural panels, automobile bodies, electronic equipment shielding panels, and military personnel armor. The research was supported in part by grants from the National Research Council, the U.S. Army, and the U.S. Air Force.