The development course and trend of body armor

Bulletproof vests are used to protect the human body from the damage of bullets or shrapnel. The bulletproof vest is mainly composed of two parts: a jacket and a bulletproof layer. Clothing covers are often made of chemical fiber fabrics. The bulletproof layer is made of metal (special steel, aluminum alloy, titanium alloy), ceramic sheet (corundum, boron carbide, silicon carbide, alumina), glass fiber reinforced plastic, nylon (PA), Kevlar, DOYENTRONTEX Fiber, liquid protective materials and other materials , Constitute a single or composite protective structure. The bulletproof layer can absorb the kinetic energy of the bullet or shrapnel, and has obvious protective effect on the low-speed bullet or shrapnel, and can reduce the damage to the human chest and abdomen under the control of a certain depression. Bulletproof vests include infantry body armor, pilot body armor and artillery body armor. According to the appearance, it can be divided into bulletproof vests, full-protection bulletproof vests, ladies bulletproof vests and other types. Body armor refers to "a kind of clothing that can absorb and dissipate the kinetic energy of bullets and fragments, prevent penetration, and effectively protect the protected parts of the human body." From the point of view of use, body armor can be divided into two types: police and military. From the material point of view, body armor can be divided into three types: soft, hard and soft and hard composite. The material of soft body armor is mainly composed of high-performance textile fiber composite material latitude. These high-performance fibers have much higher energy absorption capacity than general materials, and endow the body armor with bulletproof function. And because this kind of body armor generally uses textiles The structure, which has considerable flexibility, is called soft body armor. Hard body armor is made of special steel plates, super aluminum alloys and other metal materials, or aluminum oxide, silicon carbide and other hard non-metallic materials as the main bulletproof materials. The body armor made from this generally does not have flexibility, and uses a plate Mainly form. The softness of the soft and hard composite body armor is between the above two types. It uses soft materials as the lining and hard materials as the panel and reinforcement material. It is a composite body armor. As a kind of protective equipment, the core performance that a body armor should have is ballistic performance. At the same time, as a kind of functional clothing, it should also have certain clothing properties. The anti-ballistic performance of the bullet-proof body armor is mainly reflected in the following three aspects: (1) Hand-robbing and step-robbing bullets: Many soft body armors can prevent hand-robbing bullets, but they must prevent step-robbing bullets or higher energy bullets. , You need to use ceramic or steel reinforced plates. (2) Bulletproof pieces. High-speed fragments produced by explosions of various explosives such as bombs, mines, artillery shells and hand-held rounds are one of the main threats on the battlefield. According to the survey, the order of the threats faced by soldiers in a battlefield is: shrapnel, bullets, explosive blast and heat. Therefore, the function of the bulletproof piece must be emphasized. (3) Non-penetrating damage prevention bullets will produce a great impact after hitting the target, and the damage produced by this impact on the human body is often fatal. This kind of injury does not show penetration, but it can cause internal injuries, and severe cases can be life-threatening. Therefore, preventing non-penetrating damage is also an important aspect of reflecting and testing the ballistic performance of body armor. Wearing performance On the one hand, the wearing performance requirements of body armor means that the body armor should be as light and comfortable as possible without affecting the bulletproof ability, and people can still perform various actions more flexibly after wearing. The other is the ability of clothing to adjust to the microclimate environment of the "clothing-human body" system. For body armor, it is hoped that after the body wears the body armor, it can still maintain the basic heat and moisture exchange state of "man-clothes", and try to avoid the accumulation of moisture on the inner surface of the body armor, which may cause discomfort such as sultry heat and humidity. Sense, reduce physical consumption. In addition, due to its special use environment, the suitability of the body armor with other weapons and equipment should also be considered. Bulletproof principle The US military was equipped with M52 nylon body armor on the Korean battlefield that year, which blocked 70% of the direct hits at that time, reduced the lethality of the chest and abdomen by 65%, and reduced the overall attrition rate by 15%. According to reports, in 1983, when five US Marines were patrolling the streets of Beirut, they were suddenly attacked by a hand-held bullet. Because they were all wearing "Kevlar" body armor, the hand-held bullet was on them. There was no death or serious injury caused by the nearby report, only minor injuries to the upper and lower limbs. The above statistics and reports strongly prove the protective effect and protective efficiency of body armor. So, what is the secret of bulletproof vests? How does "hard armor" protect against bullets? Hard material bulletproof vests such as metal, bulletproof ceramics, high-performance composite plates and composite plates of non-metal and metal or ceramics used after the early 1970s. The bulletproof mechanism is mainly that the material breaks and cracks when hit by bullets. , Plugging and delamination of multi-layer composite boards, so as to absorb a large amount of impact energy of shooting projectiles. When the hardness of the material exceeds the impact energy of the shooting object, the shooting rebound phenomenon can occur without penetration. How does "soft armor" resist seed bombs? If the bulletproof vest is made of high-performance fibers such as bulletproof nylon, aramid fiber, base fiber and other soft materials, the bulletproof mechanism is mainly that the bullet stretches and shears the fiber, and at the same time, the fiber will impact energy beyond the impact point. The energy is absorbed and the fragments or warheads are wrapped in the bulletproof layer. Tests have shown that there are five ways for soft body armor to absorb energy: ⒈Textile deformation: refers to the deformation of the bullet incident direction and the area near the incident point; ⒉The destruction of the fabric: including fiber fibrillation , Fiber breakage, yarn structure knots and disintegration of fabric structure; ⒊heat energy: bullet energy is dissipated as heat energy through friction; ⒋sound energy: energy consumed by the sound produced by seed bombs hitting the bulletproof layer; ⒌bullet Deformation of the body. How does the composite "armor" protect against bullets? It should be pointed out that this kind of soft body armor called "soft armor" cannot prevent direct shot projectiles with sufficient energy or heavier from invading the human body. Therefore, it is necessary to add hard inserts, ceramic plates or composite plates, that is, soft The combination of hard materials and the integration of the two protection mechanisms can protect the human body and achieve the purpose of bulletproof. The bulletproof mechanism of this soft and hard composite body armor is as follows: When a bullet hits the body armor, it first contacts the bulletproof steel plate or reinforced ceramic board or composite board of the first line of defense in the body armor. At the moment of contact, Both bullets and hard bulletproof materials may deform and break, thus consuming most of the bullet's energy. The soft bulletproof material acts as the second line of defense, absorbing and dispersing the energy of the remaining part of the bullet, and acting as a buffer, thereby preventing and reducing penetrating damage. How to bulletproof body armor? Due to the irregular shape of the fragments and shrapnel produced when the hand-retained bombs and bombs explode, the edges are sharp, small in size, and light in weight. After hitting the bulletproof materials, especially the soft bulletproof materials, they will not deform, and the amount will be large and dense. , Stretch the fiber of the bulletproof fabric and make it break; the fragments also cause the interaction between the internal fibers of the fabric and the different layers of the fabric, causing the overall deformation of the fabric. When the fragments damage the bulletproof vest, it consumes its 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. Therefore, the body armor prevents damage to the chest, abdomen and even the neck (high-collar body armor) from the bullets and bomb fragments left in the hand. 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 hurt, 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 prevent low-speed hand-grabbing bullets (the projectile speed is 122 m/s), it cannot resist walking 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 become popular. 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 U.S. 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" fiberglass bulletproof vest, which weighs between 2.7 and 3.6. Between kilograms. Body armor made of nylon can provide soldiers with a certain degree of protection, but it is larger in size and weighs up to 6 kg. 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 US military took the lead in using Kevlar to make body armor, and developed two models of light and heavy. The new body armor uses 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 bulletproof vests for military forces of various countries. The success of Kevlar and the subsequent appearance of Twaron and Spectra and their application in body armor made soft body armor characterized by high-performance textile fibers become more popular, and its application range is not limited to The military, and gradually expanded to the police and political circles. However, for high-speed bullets, especially bullets fired quickly, a purely 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. In summary, there have been three generations of modern body armor development so far: 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 ballistic performance, 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 fit, and comfortable to wear. It has good comfort 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 seed shells shot by hands from 5 meters away, and will not produce secondary shrapnel, but after being hit by a bullet, it deforms greatly and can cause certain non-penetrating damage. In addition, for the bullets fired by rifle or machine gun, the 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 as the inner layer are the main development directions of body armor. The latest bulletproof vest (Instavest) developed by MKU of India is known as the fastest bulletproof vest in the world. The biggest highlight of this body armor is that it can be put on and taken off quickly. It is specially designed with a quick pull ring, as long as you pull this ring, the whole body armor can be easily taken off. According to reports, it takes only 1 second to take off the body armor, and 45 seconds to put on this body armor. Design mechanism There are basically two bulletproof mechanisms of body armor: one is to bounce off the fragments formed by fragmenting the projectile body; 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 strong clothes. This kind of body armor and later similar hard body armors play a bulletproof role by popping off the bullets or shrapnel, or breaking the bullet to consume and decompose its 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 raw material to "catch" bullets or shrapnel to achieve the purpose of bulletproof. Studies have shown that there are five ways for soft bulletproof vests to absorb energy: (1) Fabric deformation: including the deformation of the bullet incident direction and the tensile deformation of the area near the incident point; (2) Fabric destruction: including the fibril of the fiber Chemical, 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: energy consumed by the sound of bullets 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 ability 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 bullets and hard bulletproof materials 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 effect, which greatly reduced the penetration of the projectile, which is the key to bulletproof. The factors that affect the bulletproof performance of body armor can be considered from two aspects: the interacting projectile (bullet or shrapnel) and the bulletproof material. As far as the projectile is concerned, its kinetic energy, shape and material are important factors that determine its penetration. Ordinary bullets, especially lead-cored or ordinary steel-cored bullets, will deform when they come into contact with bulletproof materials. In this process, a considerable part of the kinetic energy of the bullet is consumed, thereby effectively reducing the penetration force of the bullet, which is an important aspect of the energy absorption mechanism of the bullet. For bombs, grenades, and other shrapnels or secondary fragments formed by bullets, the situation is significantly different. These shrapnels have irregular shapes, sharp edges, light weight and small size, and will not deform after hitting bulletproof materials, especially soft bulletproof materials. Generally speaking, the speed of such fragments is not high, but the amount is large and dense. The key to the energy absorption of such fragments by soft body armor lies in the fact that the fragments cut, stretch and break the yarns of the ballistic fabric, and cause the interaction between the yarns in the fabric and the different layers of the fabric to cause