question: What is a bulletproof vest made of & how does that stop a massively fast bullet?
comment: To keep it as simple as possible, there are two main types of bulletproof vests; soft and hard. Soft vests are made of woven kevlar. These are tiny strands of extremely strong fabric. They're woven and layered up to create a relatively soft, flexible panel. This stops bullets by slowing them down as they impact the kevlar, losing energy as they rip through the layers of fabric. Think of it like a speeding car plowing into a bunch of buckets filled with water. These soft vests are the type typically worn by police. They're designed to stop most handgun rounds. The second type of bulletproof vest is hard armor. This is typically in the form of steel or ceramic plates. Basically these are just strong enough to withstand the impact of a bullet. Ceramic plates shatter and spread out the force of the impact much like kevlar does, but on a higher level. These type of vests are worn by military. They're designed to stop rifle rounds. Increasingly, police will carry these in their cars as well.
passages: Bulletproof vests work by dissipating the bullet's energy in another way; the vest's material, usually Aramid (Kevlar or Twaron), works by presenting a series of material layers which catch the bullet and spread its imparted force over a larger area, hopefully bringing the round to a stop before it can penetrate into the body. While the vest can prevent a bullet from penetrating, the wearer will still be affected by the kinetic energy of the bullet, which can produce serious internal injuries.
  
  Section::::See also.
  
  BULLET::::- Ballistics
  
  BULLET::::- Internal ballistics
  
  BULLET::::- External ballistics
  
  BULLET::::- Table of handgun and rifle cartridges
   Section::::Performance standards.:Backing materials for testing.
  
  Section::::Performance standards.:Backing materials for testing.:Ballistic.
   When a hand gun bullet strikes body armor, it is caught in a "web" of extremely strong fibers. These fibers absorb and disperse the impact energy that is transmitted to the bullet proof vest from the bullet causing the bullet to deform, otherwise known as a "mushroom". Additional energy is absorbed by each successive layer or material in bullet proof vests until such time as the bullet has been stopped.
   Section::::Rifle resistant armor.:Versus armor-piercing ammunition.
   These vests often have a ballistic plate inserted into the vest. Metal or ceramic plates can be used with a soft vest, providing additional protection against rifle rounds, and metallic components or tightly woven fibre layers can give soft armour resistance to stab and slash attacks from knives and similar close-quarter weapons. Soft vests are commonly worn by police forces, private citizens who are at risk of being shot (e.g., national leaders), security guards, and bodyguards, whereas hard-plate reinforced vests are mainly worn by combat soldiers, police tactical units, and hostage rescue teams.
   Due to the various types of projectile, it is often inaccurate to refer to a particular product as "bulletproof" because this implies that it will protect against any and all threats. Instead, the term bullet resistant is generally preferred.
   One of the first examples of commercially sold bulletproof armour was produced by a tailor in Dublin, Ireland in the 1840s. "The Cork Examiner" reported on his line of business in December 1847:
   Section::::History.:Postwar.
  
  During the Korean War several new vests were produced for the United States military, including the M-1951, which made use of fibre-reinforced plastic or aluminium segments woven into a nylon vest. These vests represented "a vast improvement on weight, but the armor failed to stop bullets and fragments very successfully," although officially they were claimed to be able to stop 7.62×25mm Tokarev pistol rounds at the muzzle. Developed by Natick Laboratories and introduced in 1967, T65-2 plate carriers were the first vests designed to hold hard ceramic plates, making them capable of stopping 7 mm rifle rounds.
   During the late 1920s through the early 1930s, gunmen from criminal gangs in the United States began wearing less-expensive vests made from thick layers of cotton padding and cloth. These early vests could absorb the impact of handgun rounds such as .22 Long Rifle, .25 ACP, .32 S&W Long, .32 S&W, .380 ACP, .38 Special and .45 ACP traveling at speeds of up to . To overcome these vests, law enforcement agents such as the FBI began using the newer and more powerful .38 Super, and later the .357 Magnum cartridge.
  
  Section::::History.:Second World War.
   Section::::Research.:Nanomaterials in ballistics.
  
  Currently, there are a number of methods by which nanomaterials are being implemented into body armor production. The first, developed at University of Delaware is based on nanoparticles within the suit that become rigid enough to protect the wearer as soon as a kinetic energy threshold is surpassed. These coatings have been described as shear thickening fluids. These nano-infused fabrics have been licensed by BAE systems, but as of mid-2008, no products have been released based on this technology.
   Additionally, as the hardness of the bullet core increases, so must the amount of ceramic plating used to stop penetration. Like in soft ballistics, a minimum ceramic material hardness of the bullet core is required to damage their respective hard core materials, however in armor-piercing rounds the bullet core is eroded rather than deformed.
   Vests designed for bullets offer less protection against blows from sharp implements, such as knives, arrows or ice picks, or from bullets manufactured with hardened materials, e.g., those containing a steel core instead of lead. This is because the impact force of these objects stays concentrated in a relatively small area, allowing them a better likelihood of puncturing the fiber layers of most bullet-resistant fabrics used in soft armor. By contrast, stab vests provide better protection against sharp implements, but are generally less effective against bullets. However, soft armor will still protect against most slashing attacks.
   Section::::Stab and stab-ballistic armor.
  
  Section::::Stab and stab-ballistic armor.:Early "ice pick" test.
   Section::::Vest sizing, carriers and encapsulation.
  
  In order for ballistic protection to be wearable the ballistic panels and hard rifle-resistant plates are fitted inside a special carrier. The carrier is the visible part of a ballistic vest. The most basic carrier includes pockets which hold the ballistic panels and straps for mounting the carrier on the user. There are two major types of carriers: military or tactical carriers that are worn over the shirt, and covert law enforcement type carriers that are worn under the shirt.
  
  Section::::Vest sizing, carriers and encapsulation.:Military carriers.
   While a vest can prevent bullet penetration, the vest and wearer still absorb the bullet's impulse. Even without penetration, heavy bullets deal enough force to cause blunt force trauma under the impact point. Vest specifications will typically include both penetration resistance requirements and limits on the amount of impact force that is delivered to the body.
  
  On the other side, some bullets can penetrate the vest, but still deal low damage to its wearer because of speed loss or their small mass/form.
   The military type of carrier, English police waistcoat carrier, or police tactical carrier most typically has a series of webbing, hook and loop, and snap type connectors on the front and back face. This permits the wearer to mount various gear to the carrier in many different configurations. This load carriage feature is an important part of uniform and operational design for police weapons teams and the military.
   In recent years, advances in material science have opened the door to the idea of a literal "bulletproof vest" able to stop handgun and rifle bullets with a soft textile vest, without the assistance of additional metal or ceramic plating. However, progress is moving at a slower rate compared to other technical disciplines. The most recent offering from Kevlar, Protera, was released in 1996. Current soft body armor can stop most handgun rounds (which has been the case for roughly 15 years ), but armor plates are needed to stop rifle rounds and steel-core handgun rounds such as 7.62×25mm. The para-aramids have not progressed beyond the limit of 23 grams per denier in fiber tenacity.
   Bulletproof vest
  
  A ballistic vest or bullet-resistant vest, often called a bulletproof vest, is an item of personal armor that helps absorb the impact and reduce or stop penetration to the body from firearm-fired projectiles and shrapnel from explosions, and is worn on the torso. Soft vests are made of many layers of woven or laminated fibres and can protect the wearer from small-calibre handgun and shotgun projectiles, and small fragments from explosives such as hand grenades.
   Section::::Stab and stab-ballistic armor.:Stab and spike vests.
   Textile vests may be augmented with metal (steel or titanium), ceramic or polyethylene plates that provide extra protection to vital areas. These hard armor plates have proven effective against all handgun bullets and a range of rifles. These upgraded ballistic vests have become standard in military use, as soft body armor vests are ineffective against military rifle rounds. Prison guards and police often wear vests which are designed specifically against bladed weapons and sharp objects. These vests may incorporate coated and laminated para-aramid textiles or metallic components.
  
  Section::::History.
  
  Section::::History.:Early modern era.
   Cercom, now BAE systems, CoorsTek, Ceradyne, TenCate Advanced Composites, Honeywell, DSM, Pinnacle Armor and a number of other engineering companies develop and manufacture the materials for composite ceramic rifle armor.
  
  Section::::Explosive protection.
   There are various mandatory tests which items must pass before they can be classified as bullet-resistant. These tests specify the detailed characteristics of bullets which the material or object must be resistant to. For example, the U.S. National Institute of Justice standard 0104.04 for bullet-resistant vests specifies that a Type II vest must not deform clay representing the wearer's body when hit by an 8.0 g (124 gr) 9 mm caliber round nosed full-metal jacket bullet travelling at up to 358 m/s (1175 ft/s); but a Type IIIA vest is needed for protection against the same bullet travelling at up to 427 m/s (1400 ft/s). In both cases, the vest is not required to protect against a second hit within 51 mm (2 inches) of the first.
   Body armor may combine a ballistic vest with other items of protective clothing, such as a combat helmet. Vests intended for police and military use may also include ballistic shoulder and side protection armor components, and bomb disposal officers wear heavy armour and helmets with face visors and spine protection.
   Bullet-resistant materials (also called ballistic materials or, equivalently, anti-ballistic materials) are usually rigid, but may be supple. They may be complex, such as Kevlar, UHMWPE, Lexan, or carbon fiber composite materials, or they may be basic and simple, such as steel or titanium. Bullet resistant materials are often used in law enforcement and military applications, to protect personnel from death or serious injuries. In 2018, the US military began conducting research into the feasibility of using artificial silk as body armor.
  
  Section::::Classification.
   One important factor in test backing for armor is its hardness. Armor is more easily penetrated in testing when backed by harder materials, and therefore harder materials, such as Roma clay, represent more conservative test methods.
  
  Section::::Performance standards.:Backing materials for testing.:Stab.
  
  Stab and spike armor standards have been developed using 3 different backing materials. The Draft EU norm calls out Roma clay, The California DOC called out 60% ballistic gelatin and the current standard for NIJ and HOSDB calls out a multi-part foam and rubber backing material.
  