BULLET PROOF KEVLAR
“Kevlar” is synonymous with “bullet proof.” Woven bullet resistant Kevlar cloth gives bullet-proof vests their bullet resistance. The Kevlar-based fiberglass helmets that the U.S. Army began issuing active service soldiers in the 1980s have saved countless lives in the battlefield. Like “Band-aid,” “Kleenex,” and “Xerox,” Kevlar is just one player in a crowded field, but its prominence in movies and news stories has made it the default term for “bullet resistant fibers.”
THE BIRTH OF KEVLAR
First developed in 1965 by DuPont, Kevlar was originally used to replace the steel and cloth belts in race car tires. The material itself is a woven synthetic para-aramid fiber (similar to nylon). DuPont had already been successful in bringing several related aramid synthetic fibers into the market, including Nomex (which is still used to produce fire-resistant garments for firefighters and test pilots). Kevlar shares Nomex’s lack of a melting point and near complete fire-resistance under normal oxygen levels. But in contrast to Nomex or nylon, when Kevlar forms into fibers, its molecules naturally align themselves into long, unbroken chains along the fiber’s entire length. Subsequently, in addition to its fire-resistance, Kevlar is also highly resistant to abrasion and shows incredible tensile strength–making it perfect for stopping bullets.
Today many different companies produce para-aramid fiberglass cloth comparable to DuPont’s Kevlar. Such cloth is the basis of the fiberglass panels used in banks, convenience stores, and other sites to make walls and counter tops “bullet proof.”
KEVLAR IN ACTION
Bullet resistant fiberglass panels are made by saturating a synthetic fiber mesh made from a Kevlar-like material with resin. Flat layers of this resin-soaked mesh are squeezed and baked by an industrial press. The result is a hard, dense, rigid panel. A speeding bullet, striking such a panel, deforms, loosing much of its forward momentum. Meanwhile, the layers of hard resin-caked mesh separate, unfolding like an accordion’s bellows. This absorbs even more of the bullet’s energy. The practically unbreakable strands of Kevlar running through the panel can then act like the net walls of a batting cage, easily catching and deflecting the bullet.
These ballistically rated fiberglass bullet resistant panels are often called opaque armor or “Kevlar panels.”