The past and present of bulletproof vests

 After World War I, bulletproof vests made of multiple layers of cotton or cloth gradually became the main character.  Compared with silk bulletproof vests, cotton and cloth bulletproof vests are slightly less protective, but they are cheaper. 
  Later, with the development of science and technology, especially the emergence of manganese steel, metal bulletproof materials have returned.  This is because manganese steel not only has the advantages of "hard" and "light", but also is cheap. 
  In the 1970s, Kevlar, an even better material for body armor, appeared.  This material is five times stronger than steel of the same quality and only 1/5 denser.  The bulletproof vest made of it wears on the body, which is soft and close-fitting, flexible and flexible, and has strong bulletproof ability.  Not only that, but the bulletproof vest made of Kevlar can also resist acid and alkali corrosion, and has strong heat resistance and flame retardancy, coupled with antistatic characteristics, it is a more ideal wearable "shield". 
  The success of Kevlar and the subsequent emergence and application of Teflon and Specter fibers have made soft bulletproof vests made of high-performance textile fibers increasingly popular. 
  At the same time, in the face of bullets with higher and higher firing rates, people have developed soft and hard composite bulletproof vests, and fiber composite materials are used as inserts to enhance the protective capabilities of such bulletproof vests again. 
  At present, with the emergence of more related new materials and new technologies, the footsteps of countries around the world looking for "the strongest personal shield" have not stopped.  All efforts are made only to make soldiers safer and more likely to win on the battlefield. 

  Bulletproof vest also pays attention to its strengths 
  Put on armor and go to battle, courage increases by three points. 
  On the battlefield, soldiers wearing bulletproof vests effectively resist attacks from various light weapons, and actual combat proves the important role of bulletproof vests. 
  However, it would be a mistake to think that wearing a bulletproof vest means entering a "safe".  Because, there is no bulletproof vest in the world is impeccable, they more or less have their own "cover door." 
  The material used in bulletproof vests objectively determines its limited effect.  Even the best bulletproof vest can only protect against some smaller caliber bullets at a certain distance.  For larger caliber armor-piercing bullets, grenades, etc., it is more than enough. 
  Soldiers wearing body armor have the probability of being shot repeatedly on the battlefield, and there is often no time to change the body armor or bulletproof plate in time under battlefield conditions.  Some soft bulletproof vests withstand the first blow, and the fibers in the corresponding parts will be strongly stretched or even broken. 
  Soft bulletproof vests also couldn't withstand sharp weapons.  The effectiveness of soft bulletproof vest comes from its protective material using a laminated structure, and the piercing of sharp weapons is precisely "immune" to this structure.  For example, daggers could penetrate all kinds of soft protective materials and deal a fatal blow to the user. 
  Therefore, for soldiers wearing soft bulletproof vests, first, they should make full use of terrain features or shelters to minimize the probability of being hit.  Second, we must maintain a certain distance from our opponents so as to avoid "soft spots" being attacked. 
  In the face of such repeated attacks, composite bulletproof vests are also difficult to "straighten the back".  After all, it also has its own "hood."  Bulletproof plate fragmentation is the main way to absorb the energy of incoming projectiles. After a hit, it will cause a large area of damage to the corresponding parts, greatly reducing the protection performance.  Even if it does not shatter, the ballistic panel will usually shift under repeated impact, and this change will endanger the safety of the user to some extent. 
  Therefore, in order to give full play to the role of this type of bulletproof vest in combat, once the user is hit, he must quickly adjust his position to reduce the probability of being hit again. 
  In addition to projectiles, bulletproof vests have other "natural enemies."  In 2003, there was an incident in the United States where a certain body armor was easily "broken".  This bulletproof vest is made of Zelon material and is not supposed to be easily penetrated.  However, subsequent investigations showed that the protective capacity of the body armor was reduced by about 30% compared with the prescribed standard, due to the aging of the Zelon fiber due to the early production date. 
  It can be seen that bulletproof vest is actually a relatively delicate equipment.  Whether it is Kevlar or Zelon, this synthetic chemical fiber will naturally age due to light, moisture, mildew and other reasons during use. 
  Among them, the biggest influence is light.  Under direct sunlight, processes like fiber aging are greatly accelerated. 
  Therefore, bulletproof vests, which are used as self-defense, should be eliminated and updated in time.  In daily combat readiness training, officers and soldiers should take sufficient time to maintain bulletproof vests and keep them in optimal condition. 
  Tougher, lighter and more considerate is the direction of development 

  In recent years, with the continuous development of military science and technology, especially material science, more and more new bulletproof materials have been used in the development of bulletproof vests. 
  BAE Systems, a British company, uses a liquid called shear thickening fluid in the design and manufacture of body armor.  Many special particles are freely suspended in this liquid.  When a bullet hits the liquid at high speed, particles in the "shear thickening fluid" absorb the impact energy and quickly harden, acting as a barrier to the bullet. 
  It is reported that Russia has also made new progress in the development of new bulletproof materials.  The country's researchers have developed ultra-high molecular weight polyethylene fiber, and plans to use this new material for "100-man long" individual equipment, more effective defense against submachine gun bullets.