There are basically two bulletproof mechanisms of body armor: one is to bounce off the fragments formed after fragmentation of the projectile; the other is to dissipate the kinetic energy of the warhead through the bulletproof material. The first bulletproof vests developed by the United States in the 1920s and 1930s were protected by overlapping steel plates attached to sturdy clothing. This body armor and later similar hard body armors play a bulletproof role by popping off the bullets or shrapnel, or breaking the bullets to consume and decompose their energy. For soft body armor using high-performance fiber as the main bulletproof material, its bulletproof mechanism is mainly the latter, that is, the use of high-strength fiber as the raw material to "catch" bullets or shrapnel to achieve the purpose of bulletproof.
Studies have shown that there are five ways in which soft bulletproof vests absorb energy:
(1) The deformation of the fabric: including the deformation of the bullet incident direction and the stretching deformation of the area near the incident point;
(2) Fabric destruction: including fiber fibrillation, fiber breakage, yarn structure disintegration and fabric structure disintegration;
(3) Thermal energy: energy is dissipated in the form of thermal energy through friction;
(4) Acoustic energy: the energy consumed by the sound of the bullet hitting the bulletproof layer;
(5) Deformation of the projectile. The bulletproof mechanism of the soft and hard composite body armor developed to improve the bulletproof capability can be summarized by "soft and hard". When a bullet hits the body armor, the first effect is the hard bulletproof material such as steel plate or reinforced ceramic material. During this moment of contact, both the bullet and the hard bulletproof material may deform or break, consuming most of the bullet's energy. The high-strength fiber fabric serves as the liner and second line of defense of the bulletproof vest, absorbs and diffuses the energy of the remaining part of the bullet, and acts as a buffer, thereby reducing non-penetrating damage as much as possible. In the two bulletproof processes, the previous one played the main energy absorption function, which greatly reduced the penetration of the projectile, which is the key to bulletproof.
