Bulletproof Vests

A bulletproof vest is a protective covering worn to protect the torso against bullets. Body armor fell into disguise in the sixteenth and seventeenth centuries, partly because it was ineffective against bullets. Modern body armor reappeared during World War I as a means of protecting the torso from shell fragments, but the armor was too heavy to justify the protection. World War II stimulated the development of lighter body armor that consisted of overlapping plates of steel, aluminum, or bonded fiberglass attached within a nylon garment that covered both the front and back of the wearer. These "flak jackets" were flexible enough to permit relatively free movement by the wearer while affording him adequate protection against fragments from artillery shells, mortar shells, and antiaircraft shells. They could not stop armor piercing bullets however.
In the 1960ís new types of vests were developed whose plates were made of composite layers of steel or a very hard ceramic, boron carbide. However, the discovery that numerous layers of nylon fabric could dissipate the energy of the bullet revolutionized the use of modern body armor.
The function of steel or hard plastic armor is to impervious to a bullet. The function of ceramic armor is to slow the bullet abruptly by the hardness of the ceramic and to dissipate the bulletís energy as it destroys the armor at the point of impact; the tiles or plates of ceramic bulletproof vest thus have to be replaced once they have stopped a bullet. The textile vest deforms the bullet and then dissipates its energy, entangling it in the vestís many layers.
A textile bulletproof vest is fashioned of sixteen to twenty-four layers of nylon cloth of a heavy weave, the layers stitched together like quilt. Any ordinary pistol or sub-machine gun bullet striking the garment is immediately flattened as it hits the outermost layers, and the new mushroom-shaped slug dissipates its energy as it presses against the remaining thickness of the vest, unable to penetrate its overlapping layers of coarse mesh. The wearer is usually bruised by the impact of the bullet, but without serious consequence. The more layers of nylon cloth, the better the protection of the vest.