As an important personal protective equipment, body armor has gone through the transition from metal armored protective panels to non-metallic synthetic materials, and from pure synthetic materials to the development of composite systems such as synthetic materials, metal armor plates, and ceramic protective sheets. The prototype of human armor can be traced back to ancient times. In order to prevent the body from being injured, primitive peoples used natural fiber braided belt as the material of the chest protector. The development of weapons has forced corresponding advances in human armor. As early as the end of the 19th century, the silk used in Japanese medieval armor was also used in body armor produced in the United States. After the assassination of President William McKinley in 1901, the body armor attracted the attention of the US Congress. Although this body armor can protect against low-speed pistol bullets (with a bullet speed of 122 m/s), it cannot protect against rifle bullets. Thus, in the First World War, a body armor made of natural fiber fabrics and steel plates appeared. Thick silk clothing was once the main component of body armor. However, silk deteriorates quickly in the trenches. This defect, coupled with the limited bulletproof capability and the high cost of silk, made silk body armors neglected by the U.S. Department of Ordnance during World War I and failed to be popularized. In World War II, the lethality of shrapnel increased by 80%, and 70% of the wounded died due to torso injuries. The participating countries, especially the United Kingdom and the United States, began to spare no effort to develop body armor.
In October 1942, the British Army first successfully developed a bulletproof vest composed of three high manganese steel plates. In 1943, there were 23 types of body armor that were trial-produced and officially adopted in the United States. The bulletproof vests of this period used special steel as the main bulletproof material. In June 1945, the U.S. Army successfully developed a bulletproof vest made of aluminum alloy and high-strength nylon. The model was M12 infantry body armor. Among them, nylon 66 (scientific name polyamide 66 fiber) is a synthetic fiber that was recently invented at that time. Its breaking strength (gf/d: gram-force/denier) is 5.9-9.5, and its initial modulus (gf/d) is 21-58. , The specific gravity is 1.14 g/(cm)3, and its strength is almost twice that of cotton fiber. During the Korean War, the US Army was equipped with a T52 full nylon body armor made of 12 layers of bullet-proof nylon, while the Marine Corps was equipped with a M1951 hard "Duolong" glass fiber reinforced plastic bulletproof vest, which weighs 2.7 to 3.6 kilograms. between. Bulletproof vests made of nylon can provide soldiers with a certain degree of protection, but they are large in size and weigh up to 6 kilograms. In the early 1970s, Kevlar, a synthetic fiber with ultra-high strength, ultra-high modulus and high temperature resistance, was successfully developed by DuPont of the United States, and it was quickly applied in the field of bulletproof. The emergence of this high-performance fiber greatly improves the performance of soft textile body armor, while also improving the comfort of the body armor to a large extent. The U.S. military took the lead in using Kevlar to make body armor, and developed two models of light and heavy.
The new body armor is made of Kevlar fiber fabric as the main material and bulletproof nylon cloth as the envelope. The lightweight body armor is composed of 6 layers of Kevlar fabric, and the medium weight is 3.83 kg. With the commercialization of Kevlar, Kevlar's excellent comprehensive performance has soon been widely used in the body armor of the military of various countries. The success of Kevlar and the subsequent emergence of Twaron and Spectra as well as their application in body armor made soft body armor characterized by high-performance textile fibers become more and more popular, and its application range is not limited to Military circles, and gradually expanded to police and political circles. However, for high-speed bullets, especially bullets fired by rifles, pure soft body armor is still incompetent. For this reason, people have developed a soft and hard composite body armor, using fiber composite materials as reinforced panels or inserts to improve the bulletproof capability of the overall body armor. To sum up, there have been three generations of modern body armor development: the first generation is a hard body armor, mainly using special steel, aluminum alloy and other metals as bulletproof materials. The characteristics of this type of bulletproof vest are: the clothing is thick and heavy, usually about 20 kilograms, it is not comfortable to wear, it has a large restriction on human activities, and has a certain degree of elasticity, but it is easy to produce secondary fragments. The second-generation body armor is a soft body armor, usually made of high-performance fiber fabrics such as multi-layer Kevlar. It is light in weight, usually only 2 to 3 kilograms, and has a relatively soft texture, good fitness, and comfortable wearing. It has good concealment when worn inside, and is especially suitable for daily wear by police and security personnel or political leaders. use. In terms of bulletproof capability, it can generally prevent bullets fired from a pistol 5 meters away, and will not produce secondary shrapnel, but it deforms greatly after being hit by a bullet, which can cause a certain amount of non-penetrating damage. In addition, for bullets fired by rifles or machine guns, soft body armor of general thickness is difficult to resist. The third-generation body armor is a composite body armor. Generally, lightweight ceramic sheets are used as the outer layer, and high-performance fiber fabrics such as Kevlar are used as the inner layer. This is the main development direction of body armor.
