Since ancient times, spears and shields have corresponded to each other, and war and the development of new materials are catalysts for both. The development of protective equipment can be divided into three stages in modern times.
In the first stage, with the outbreak of the second war in the last century, firearms and protective equipment have been rapidly developed, especially protective equipment. More and more soldiers find that the protective equipment mainly made of iron plate, steel plate and other metal materials on the body and on the head restricts their movement. Because of the heavy weight of the material, it increases the burden of the soldiers when moving. At the same time, when crawling, jumping, and running fast, the movement is affected by the weight of the material, cutting corners, and so on, which brings uncomfortable wearing experience. Therefore, it can also be seen in some documentary films that most of the soldiers in the Second World War did not have physical protective measures. Because of the simple manufacturing process and easy access to materials, the helmet basically realized one helmet for each hand.
     In the second stage, at the beginning of the 1970s, an American female engineer's unexpected discovery brought the groundbreaking high strength and high modulus fiber - Kevlar (i.e. aramid). The appearance of this kind of material introduced the concept of lightweight and comfort into protective equipment for the first time. Since then, Kevlar has been used in a variety of protective equipment, such as helmets, bulletproof vests, armor, fire and heat resistant clothing and other fields. Due to Kevlar's sensitivity to light, and in the 1990s, the preparation process of ultra-high molecular weight polyethylene (UHMWPE) became more and more mature. UHMWPE with millions of molecular weight has the characteristics of high strength and high modulus, and the preparation cost is low. Therefore, UHMWPE has also been introduced into the manufacturing of helmets, bullet-proof vests and other products, with lower surface density. Of course, the latter is not resistant to high temperature. The bulletproof equipment in the second stage has initially solved the problems of heavy weight, uncomfortable carrying and inconvenient movement of bulletproof equipment, and brought about the problems of insufficient protection level, limited service life and limited application environment.
     In the third stage, since the beginning of the new century, on the one hand, helmets have basically replaced helmets with high-strength aramid or PE or PBO or CF and other fiber composites. Judging from the recent Russian-Uzbekistan war, some soldiers in Russia are still steel helmets and some are composite helmets. On the other hand, with the rapid development of various industries, ceramic composite high-strength fiber has become the mainstream of body bulletproof at present. That is, silicon carbide/boron carbide/aluminum oxide with high hardness is used as the anti-bomb layer to resist and consume bullet energy. Composite PE or aramid is responsible for absorbing energy, dissipating the remaining kinetic energy of the bullet, and reducing the depression value as much as possible. The bulletproof equipment in the third stage solved the problems of insufficient protection level and limited use environment in the second stage. The existing problems are limited service life, relatively large weight and relatively insufficient flexibility, which still need the continuous efforts of the majority of bulletproof equipment workers.
     Above, the development process and current development trend of human body bulletproof equipment are briefly introduced. In the beginning, the continuous development of spear is also forcing the updating and upgrading of shield. Therefore, as a research and development personnel of human body protective equipment, we need to have greater enthusiasm, passion and feelings to invest in the development of new products and new processes, and strive to realize our own value, and hope to contribute to the progress and development of human body bulletproof equipment in China.
     So far, the end of this article, and the opening content of the next article: "Popular Science of Bullet-proof Equipment Level".