Fully soft body armor, usually made of high-performance fibers (e.g. nylon and Kevlar). The principle of bulletproofness is that when a bullet/piece hits such a fiber layer, its huge impact force is consumed when the fiber layer is stretched and sheard, while the fiber layer will transmit the impact of the bullet/break to the area outside the impact point, thereby absorbing the impact of the bullet/break.
Full-soft body armor can withstand bullet attacks from pistols, shotguns or explosives such as grenades, as well as automatic rifle attacks over longer distances (not at close range). Reinforced/composite body armor, is a full yin body armor on the basis of metal, ceramics, high-performance composite panels and other hard materials. The bullet-proof principle of this composite body armor is that when a bullet hits, it first comes into contact with the metal plate, ceramic plate or composite plate in the body armor (equivalent to the first line of defense), and in the instant of contact, both the bullet and the hard bulletproof material plate may crack, which consumes most of the bullet's energy. Soft bulletproof material as a second line of defense, absorb and diffuse the energy of the rest of the bullet, and play a buffer, so as to achieve the purpose of bulletproof. Reinforced/composite body armor can withstand powerful weapons such as automatic rifles.
Bulletproof clothing has a variety of measures of protection, but the most common standard is the U.S. NIJ standard, which is divided into six levels by the high or low of protection capability (the higher the initial speed, the greater the warhead's weight power):
NIJ Class I: Can withstand the initial speed of about 329 m/s (bullet weight 2.6g of the warhead), or the initial speed of about 320 m/s (warhead weight 6.2g of the bullet).
NIJ IIA class: can withstand the initial speed of about 373 m/s (warhead weight 8 g bullets), or the initial speed of about 352 m/s (warhead weight 11.7g bullets), or the initial speed of about 275 m/s (warhead weight 14.9g of the bullet).
NIJ II class: can withstand the initial speed of about 398 m/s (warhead weight 8 g bullets), or the initial speed of about 436 m/s (warhead weight 10.2 g bullets). NIJ IIIA class: can withstand the initial speed of about 448 m/s (warhead weight 8.1 g bullets), or the initial speed of about 436 m/s (warhead weight 15.6g of the bullet).