Originally published in the ebook A Passion for Science: Stories of Discovery and Invention.
by Suze Kundu
In 2001, a police lieutenant, David Spicer, was recovering in hospital after being shot in the chest and arms at point blank range. Spicer was alive to tell the tale, thanks to the Kevlar body armour that he was wearing at the time.
Kevlar thread is strong because it is made of plastic fibres in which matchstick-like molecules line up and stick to one another, giving it a specific tensile strength of over eight times that of steel wire. Kevlar fabric is even stronger because these fibres are then woven tightly together and are very difficult to prise apart. This is why Kevlar is used for body armour: the amount of energy required to break apart multiple layers of Kevlar fabric is greater compared to the energy that a bullet or a knife can impart. The bullet, knife or other weapon is slowed down and deformed by each layer until it is stopped in its tracks within the body a...
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