Armor, also known as bulletproof armor, is generally called bulletproof vest or ballistic jacket in Chinese circles, while it is called bulletproof vest in Hong Kong, Macau and Guangdong.
Similar to ancient armors, they are used as defensive weapons against attacks.
Bulletproof vests are personal protective equipment used to absorb the impact of bullets or explosive fragments fired by firearms. Different types have different operating principles. They are divided into full soft and reinforced/composite.
The bulletproof vests of hard materials such as metals, ceramics, and high-performance composite panels used after the early 1970s. The bulletproof mechanism is mainly that the material is broken, cracked, rushed and stratified when the material is hit by bullets. Phenomenon, so as to absorb a large amount of impact energy of the projectile. When the hardness of the material exceeds the impact energy of the shooting object, the shooting rebound phenomenon can occur without penetration.
If the bulletproof vest is made of soft materials such as nylon, aromatic polyamide (such as the famous Kevlar) or ultra-high molecular weight polyethylene (or Dyneema), the bulletproof mechanism is mainly the bullet Stretching and shearing, at the same time, the fiber spreads the impact energy to the area beyond the impact point, the initial velocity of the bullet is absorbed and the fragment or warhead is wrapped in the bulletproof layer.
Tests have shown that there are 5 ways for soft bulletproof vests to absorb energy:
The tensile deformation of the fiber: refers to the deformation of the bullet incident direction and the tensile deformation of the area near the incident point;
Fiber destruction: including fiber fibrillation, fiber breakage, knotting of yarn structure and disintegration of fabric structure;
Thermal energy: The energy of the bullet is dissipated as heat through friction;
Acoustic energy: the energy consumed by the sound of the bullet hitting the bulletproof layer;
Deformation of the projectile.
It should be pointed out that the soft bulletproof vest cannot prevent the direct-fire warhead with sufficient muzzle velocity or heavier from invading the human body. Therefore, it is necessary to add hard metal or ceramic, that is, a combination of soft and hard materials to integrate the two protective layers. In order to protect the human body and achieve the purpose of bulletproof. The bulletproof mechanism of this composite bulletproof vest is as follows: When a bullet hits the bulletproof vest, it first contacts the bulletproof steel plate or reinforced ceramic plate or composite plate of the first line of defense in the bulletproof vest. At the moment of contact, the bullet and Hard bulletproof materials may crack, which consumes most of the bullet's energy. The soft bulletproof material acts as the second line of defense, absorbs and diffuses the energy of the remaining part of the bullet, and acts as a buffer to prevent and reduce penetrating damage.
Due to the irregular shape of the fragments and shrapnel produced by the explosion of grenades and bombs, the edges are sharp, small in size, and light in weight. After hitting bulletproof materials, especially soft bulletproof materials, they will not deform, and the amount will be large and dense. At this time, the explosives will attack The fibers of the bulletproof fabric break; the fragments also cause the internal fibers of the fabric to interact with the different layers of the fabric, resulting in the overall deformation of the multilayer compact fibers. When the fragments damage the bulletproof vest, they consume their own energy. At the same time, a small part of the energy of the fragments is converted into heat energy through friction and into sound energy through impact. So the bulletproof vest prevents the damage of the grenades and bomb fragments to the chest, abdomen and even the neck (high-neck bulletproof vest).
Bulletproof Vest Category
Full soft bulletproof vest
Made of many layers of tightly woven aromatic polyamide or ultra-high molecular weight polyethylene, it can resist pistols, shotgun bullets or fragments from explosives such as grenades, as well as automatic rifle attacks at longer distances
The advantage is that users can move flexibly, lightly and comfortably
Reinforced/composite bulletproof vest
With metal or ceramic sheath
Can withstand close-range shooting of rifle bullets, but it is easy to crack
The advantage is that it can withstand weapons that are more powerful than pistols
Generally, law enforcement personnel or security personnel will use all-soft bulletproof vests, while soldiers on the battlefield or special policemen who need to face weapon attacks at close range often use reinforced/composite bulletproof vests.
Level of Bulletproof Vest
There are many measurement scales for the protective ability of bulletproof vests (and bulletproof plates), but the most common measurement scale is the NIJ standard of the United States, which is divided into six levels according to the level of protection——
NIJ I: can withstand the muzzle velocity of about 329m/s and the warhead weighing 2.6 grams (.22 LR Lead full lead bomb), or the muzzle velocity of about 320m/s and the warhead weight of 6.2 grams (.38 ACP FMJ full copper cover bomb).
NIJ IIA: can withstand a muzzle velocity of about 373m/s and a warhead weighing 8 grams (9×19mm Parabell FMJ copper full-coated bomb), or a warhead with a muzzle velocity of about 352m/s weighing 11.7 grams (.40 S&W FMJ copper full-coated bomb), or a warhead weighing 14.9 grams with a muzzle velocity of 275m/s (.45 ACP FMJ copper full-coated bomb).
NIJ II: Can withstand the muzzle velocity of about 398m/s and the warhead weighing 8 grams (9×19mm FMJ copper full-coated bomb), or the muzzle velocity of about 436m/s and the warhead weighing 10.2 grams (.357 Magnum JSP Soft tip bullet).
NIJ IIIA: Can withstand a muzzle velocity of about 448m/s and a warhead weighing 8.1 grams (.357 SIG FMJ copper full-coated bomb), or a muzzle velocity of about 436m/s and a warhead weighing 15.6 grams (.44 Magnum SJHP mid-air Sharp bullet).
NIJ III: It can withstand those with a muzzle velocity of about 847m/s and a warhead weighing 9.6 grams (7.62×51mm NATO M80 ordinary ammunition). This is the grade of the bulletproof board.
NIJ IVA: It can withstand those with a muzzle velocity of about 887m/s and a warhead weighing 10.8 grams (.30-06 Springfield M2 steel core armor-piercing ammunition). This is the grade of the bulletproof board.
NIJ IV: Can withstand the muzzle velocity of about 930m/s and the warhead weighing 11 grams (.300 Winchester Magnum 165grNosler). This is the grade of the bulletproof board.