May 6, 2003 on 4:30 am | In Ad Rem | 9 Comments
A British Marine Commando, Eric Walderman, was shot in the head four times and all bullets were halted by his Kevlar helmet. He was serving in Iraq and was shot at Umm Qasr. He’s uninjured and still serving with the Alpha Company.
The facts on Kevlar:
Kevlar was developed and manufactured by US firm DuPont in the mid-1960s.
Kevlar is a long chain-like molecule known as a polymer, which consists of repeating units called monomers.
Helmets made of Kevlar are 25%-40% more resistant to projectiles than their steel predecessors of equal weight.
A Kevlar fiber is an array of molecules oriented parallel to each other like a package of uncooked spaghetti. This orderly, untangled arrangement of molecules is described as a crystalline structure. Crystallinity is obtained by a manufacturing process known as spinning, which involves extruding the molten polymer solution through small holes. The crystallinity of the Kevlar polymer strands contributes significantly to Kevlar’s unique strength and rigidity.
Underwater, Kevlar is 20 times stronger than steel.
Kevlar is a polyaromatic amide. That is, it contains aromatic and amide groups. Other polymers with a high breaking strength often contain one or both of these molecular groups.
The individual polymer strands of Kevlar are held together by hydrogen bonds that form between the polar amide groups on adjacent chains.
The aromatic components of Kevlar polymers have a radial (spoke-like) orientation, which gives a high degree of symmetry and regularity to the internal structure of the fibers. This crystalline-like regularity is the largest contributing factor in the strength of Kevlar. Only with bright synchrotron radiation could the secret strength of Kevlar be revealed.
Kevlar military helmets replaced the “steel pot” helmet in the late 1970s.
Kevlar body vests and helmets have saved the lives of more than 2,700 police and prison officers in the US alone, its manufacturers claim - and they have their own Kevlar Survivors Club.
Stressed fiber optics can greatly degrade performance. Braided Kevlar is often used to surround fiber optics to ensure the tensile strength of the cable.