Main cold weapons such as ground knives, spears, bows and arrows used in ancient wars. Soldiers wearing armor can effectively protect their bodies and reduce the damage of cold weapons. Since the emergence of guns, guns and other firearms, this situation has changed. For firearms, 30-40 kg of armor is required, which will make it difficult for soldiers to complete various combat missions. Therefore, after entering the firearms dynasty, armor was gradually eliminated.
However, people have not given up the pursuit of body protection equipment. During the First World War, it was found that most of the soldiers' casualties were caused by shells and grenades. The shrapnel caused by bombs and mines. The steel helmets born during this period proved to be effective in protecting shrapnel against the head of soldiers in actual combat. During World War I and World War II, some countries have developed and used breastplates and body armor made of steel or alloy steel. However, the infantry was practically unusable due to its heavy weight and inconvenient movement after wearing. Until the 1940s, the body armor materials considered by people had not jumped out of the circle of metal materials.
The prototype of modern body armor appeared during the Korean War in the 1950s. The US military first tested the use of soft synthetic fiber materials such as nylon to make body armor. They found that 12 layers of special nylon fiber cloth can receive a certain bulletproof effect. When the projectile hits the body armor, multiple layers of nylon fibers interlaced vertically and horizontally wrap the projectile like a net. When the projectile continues to move, the nylon fiber must be stretched. kinetic energy. Since the kinetic energy and movement speed of the shrapnel are generally much lower than that of the projectile, the protective effect of the nylon body armor on the shrapnel is more obvious.
In the 1960s, the US Army of Vietnam listed M69 nylon body armor as standard equipment. However, due to the limitation of the tensile strength of nylon fiber, nylon body armor should receive a good protective effect, and the weight needs to be more than 4.5 kg. According to the tests and analysis of relevant experts, if such a heavy body armor is inserted, the soldier's combat capability will be reduced by more than 30%. On the hot and humid Vietnam battlefield, American soldiers can hardly bear the burden and sultry sensation brought by nylon body armor. It is very dangerous in modern warfare to not wear body armor. A lot of statistical analysis shows that shrapnel is the main threat to soldiers in modern warfare. It accounts for 3/4 of the casualties and the remaining 1/4 is caused by shock waves, bullets, and burning. Therefore, after the Vietnam War, people have been looking for suitable materials for body armor. Until the 1970s, the ideal body armor material-'Kevlar' finally appeared.
'Kevlar' is a synthetic fiber developed by DuPont in the mid-1960s, and realized industrial production in 1972. Its full name is 'polyterephthalic terephthalamide fiber', and 'Kevlar' is its trade name. 'Kevlar' has extremely high tensile strength, which is more than twice that of nylon fiber. Its appearance has significantly improved the protective performance of body armor. Tests have shown that the ability of 'Kevlar' to absorb the kinetic energy of shrapnel is 1.6 times that of nylon and 2 times that of steel. The multi-layer 'Kevlar' fabric can also receive satisfactory protective effects on bullets. Because the 'Kevlar' made body armor is lighter in weight and better in elasticity than nylon body armor, it has been received by many countries' military and police Favored. At present, in addition to the United States, Germany, France, Britain, Israel, Italy have developed and equipped 'Kevlar' body armor.
Examples from several local wars in recent years have proved that 'Kevlar' body armor can indeed provide good protection for soldiers. One day in 1983, five U.S. Marines were patrolling at the joint in Beirut, Lebanon. Suddenly someone dropped a grenade. Because the American soldiers were wearing 'Kevlar' body armor at the time, the grenade exploded near them. As a result of death and serious injuries, only the upper and lower limbs not protected by body armor were slightly injured.
It is said that the Natick Research and Development and Engineering Center of the US Army Equipment Command developed a fiber called 'Spektra' in the 1990s, which has more superior performance than 'Kevlar'. Bulletproof helmets and vests made of this fiber material can reduce their weight by 1/3 while maintaining the same protective performance as 'Kevlar' products.