In many film and television works, such a bridge often appears: after being shot at close range, the villain can still get up, shake the dust on his body and say that he is actually wearing a bulletproof vest (actually a bulletproof vest).
Is such a plot credible? Can you resist the impact of bullets with bulletproof vests?
Evolution Of Body Armor
Bulletproof vests have been updated and iterated since their birth. There is no change from the kinetic energy of the silk bullet proof clothing to that of the bullet proof clothing in the early days.
However, the protective ability of bulletproof clothing has been improved by leaps and bounds in decades. The evolution history of bulletproof clothing is also the development history of material science and technology.
Tigers can sniff roses, and silk can be bulletproof
When it comes to bulletproof vests, you have to mention “bulletproof priest” Casimir? Ziglin. The concept of “dense woven bulletproof clothing” proposed by him is still the direction of bulletproof clothing design until today.
Zygreen, a Polish engineer, was born in Ukraine in 1869. His early experience was full of twists and turns. Zieglering became a clergyman at the age of 18.
Three years later, he went to the United States to continue his religious activities.
At the peak of his religious career, zieglering served as a priest of a Polish Catholic Church in Chicago, with 40000 members, which was also the largest Polish Catholic Church in the United States at that time.
In 1893, a major event changed the fate of zieglering’s life – Chicago Mayor Carter? Harrison was assassinated. From then on, zieglering was determined to develop “sacred equipment that can protect the world” – a new type of bulletproof vest that is light and can block pistol bullets.
After experimenting with a range of materials, including cotton cloth, steel shavings and hair, he finally decided to use silk as a breakthrough.
I’m afraid most of the impressions of silk are thin like cicada wings and warm like jade. However, silk fibers actually have very high strength, silk fabrics have excellent elasticity, and are more tenacious than other natural fiber fabrics when subjected to instantaneous deformation.
The next question is how to combine silk fibers into an organic whole. In order to find a suitable weaving method, zieglering traveled across the ocean and finally developed silk fabrics in silk weaving factories in Vienna, Austria and Aachen, Germany.
Ziglin’s bulletproof material is a four layer thick silk fabric, about 3mm thick (another said that it is embedded with a 1.6mm thick steel plate), and the weight is about 250g per 0.1 square meter.
After complex weaving, this material becomes unusually thick and dense, which can successfully block the pistol bullets at that time at a very close distance.
After the success of the experiment, zieglering demonstrated the power of his new bulletproof vest on site many times throughout the United States.
For a time, zieglering became famous in the United States and even the whole western world.
The ambitious zieglering resigned from the church and devoted himself to the research, development and promotion of new bulletproof vests. However, the road of starting a business after him was full of hardships.
At first, the US military hoped to introduce his technology, but it found that the biggest problem with silk bulletproof vests was the cost. According to ziglin’s weaving method, each bulletproof vest consumes a lot of silk, and the unit price of the initial product reached US $800 (equivalent to about 90000 yuan today), which is also unable to equip a large number for the rich and powerful US military.
As a result, zieglering thought of seeking help directly from William McKinley, the then president of the United States.
After several twists and turns, the White House finally agreed to arrange for him to meet with the president. However, as President McKinley is conducting a six week national speech tour at this time, zieglering can only wait temporarily. The tragedy happened two weeks later.
On September 6, 1901, President McKinley was assassinated at the scene of the Pan American Expo in Buffalo. The killer fired two shots at him in the abdomen at close range, resulting in the president being hospitalized for emergency treatment, and then died of serious injury on September 13. In fact, the power of the revolver used by the killer was quite small. If the president was wearing zieglering’s bulletproof vest, he might have escaped.
The president’s accidental assassination dashed zieglering’s hopes for high-level government assistance. In the following ten years, zieglering and his partners continuously promoted their products to dignitaries in the western world, including Archduke Ferdinand, crown prince of Austria Hungary.
However, the tease of fate made zieglering encounter a major setback again.
On June 28, 1914, Archduke Ferdinand, dressed in zieglering bulletproof vest, was assassinated in Sarajevo (it is also said that although the Archduke had the same bulletproof vest, he was not wearing it at the time of the incident).
The murderer did not attack the part covered by the bulletproof vest, but directly shot the Archduke in the neck, which eventually led to the death of the Archduke and his wife on the spot. As you may know from later scripts, the assassination of Archduke Ferdinand directly led to the outbreak of World War I.
For zieglering, a potential chance to become famous has become the talk of later generations. Zieglering’s late life is likely to be so poor that there are many statements about the exact year of his death.
However, as one of the founders of modern bulletproof clothing technology, zieglering has left his own name in history. Looking back on his slightly failed entrepreneurial experience, in addition to the fact that luck is true, there are problems with the product power of silk bulletproof clothing itself. The high cost makes it doomed to be unable to be popularized.
Steel to steel, metal bulletproof vests are a flash in the pan
After the outbreak of World War I, in order to reduce the battle damage on the front line, all countries tried different schemes of bulletproof vests. However, due to the material and technical level at that time, such bulletproof vests were basically made of metal.
Compared with the ancient conjoined armor, they have little innovation. They can be described as “stupid, big, black and thick”.
In order to resist rifle and machine gun bullets at a certain distance, they weigh more than 10kg or even 30kg, and the activity ability of the wearer is greatly limited.
On the battlefield at that time, almost only machine gunners, medical guards and pilots who did not need too much mobility would use it.
In World War II, the development of material technology greatly reduced the weight of bulletproof clothing. Some steel grades treated by special technology can play a considerable bulletproof role only with a thickness of 2mm.
Under the same protective strength, the metal bulletproof vests in World War II weighed less than one third of those in World War I. However, the weight of more than 4kg is still too heavy for the field arms that emphasize mobility.
It is urgent to realize the lightweight and high performance of bulletproof vests.
Left: German individual armor in World War I (Dragon shrimp armor) right: Soviet sn-42 individual armor in World War II, source: public domain
Although people at that time clearly knew that the dense woven bulletproof clothing similar to the zieglering scheme was the future development direction, neither silk, cotton nor nylon bulletproof materials that began to rise after World War II could gain the upper hand in the competition with contemporary firearms.
After all, while upgrading and iterating the shield, the spear is also improving day by day.
In the late stage of World War II, new guns generally enhanced the power of ammunition by adopting more efficient propelling drugs, more changeable warhead and body materials, more modern trajectory control technology and other means.
Bulletproof vests were gradually defeated in this “contradictory attack and defense”, which was not reversed until the birth of “Kevlar” in the late 1960s.
Kevlar was born, and the practical portable bulletproof vest came to the front desk
Kevlar is a kind of synthetic fiber. Its scientific name is “poly-p-phthaloyl-p-phenylenediamine”, commonly known as aramid fiber. It was first developed by DuPont company in 1965.
The tensile strength of Kevlar is about five times that of steel of the same quality. Theoretically, it only needs a fraction of the weight to achieve the similar protective performance of steel plate. Kevlar’s strong and tough performance is closely related to its structure.
The polymer monomer first forms a continuous repeated straight chain structure, and the chain is effectively connected through hydrogen bond force, so as to further strengthen the mechanical properties of the overall structure.
When attacked by a warhead, several layers of densely woven Kevlar fabric can make the kinetic energy of the warhead decay sharply as it moves forward. Warheads are usually embedded in the bulletproof layer, and the energy brought by warhead impact will be rapidly dispersed through the network of fibers and fabrics. The problem of secondary damage caused by warhead scattering in metal bulletproof clothing has been well suppressed.
In addition, it also has the characteristics of flame retardancy and self extinguishing. Kevlar will not melt like many high molecular polymers when heated, but will directly carbonize, and will not cause additional burns due to the melting of protective clothing in the fiery battlefield.
As a kind of chemical fiber, Kevlar is relatively cheap and easy to process. People have finally found an ideal material for bulletproof clothing
However, although Kevlar’s appearance brings back a city for the body armor side, it is by no means perfect. Kevlar is very sensitive to water, and its intensity decreases greatly after immersion.
Therefore, Kevlar bulletproof vests cannot be worn to wade in actual combat. Although a series of waterproof treatment processes have been developed in the later stage, so that it can cope with the situation of medium rainfall, the consequent consequence is that the permeability is completely sacrificed and the wearing comfort is quite poor.
In addition, Kevlar is also sensitive to ultraviolet rays, which greatly limits their service life. The effective service life of Kevlar bulletproof vests is often about 3-5 years.
While Kevlar is emerging, people have successively developed a series of high polymer man-made fibers. These include tevalen with similar structure to Kevlar, and ultra high molecular weight polyethylene (UHPE) represented by dinima and spectra.
The molecular weight of ordinary polyethylene is only hundreds of thousands, while the molecular weight of UHPE can reach nearly 10 million. UHPE material has better impact resistance and wear resistance than Kevlar, will not deteriorate in water absorption, and can float on the water surface.
But the disadvantage is that UHPE material will melt in the environment of about 135 degrees.
The appearance of various polymer fibers adds a lot of flexibility to the selection of bulletproof clothing materials.
By the end of the last century, the polymer bulletproof vest with Kevlar as the representative material could resist the continuous shooting of most modern pistol bullets at a relatively short distance (provided that there was a certain distance between the firing points).
Moreover, compared with the bulky predecessors, the polymer bulletproof clothing has revolutionized its lightness and comfort.
How to tap the potential of bulletproof materials in the post Kevlar Era
However, the technical upgrading of bulletproof vests is far from the time to call it quits. First, polymers such as Kevlar alone cannot effectively resist rifle bullets at close range. Compared with pistol bullets, rifle bullets are longer, charge more, and have greater muzzle velocity and kinetic energy.
At the same time, with the help of the ballistic stability brought by the long barrel, the warhead can be processed into a more sharp shape, which greatly increases the penetration performance.
In addition, in the 1980s and 1990s, affected by the large-scale export of weapons from the Soviet Union to the Middle East and the turmoil in Eastern Europe after the disintegration of the Soviet Union, some Russian made pistol shells and corresponding pistols and guns with large charge gradually flowed into the hands of criminals all over the world.
This kind of pistol bullet is extremely powerful and can easily penetrate the light bulletproof vests commonly equipped by the police of various countries. American slang even directly refers to this kind of bullet as “cop killer”.
Therefore, since the 1990s, western countries have launched a new generation of bulletproof vests with stronger defense.
Most of these products enhance their protective ability by arranging hard protective plates on the outer layer of traditional polymer bulletproof clothing. This kind of polymer has high thermal penetration resistance and high pressure forming resistance.
Ceramic protective plates are not only lighter than metal, but also have higher hardness, which makes them more strongly deform the warhead when they collide with the warhead, so as to reduce its kinetic energy.
However, ceramics have inherent brittleness. Once attacked by shotguns and other weapons with multiple bullet points, they are likely to break instantly due to stress concentration.
The metal protection plate is mainly made of steel, titanium alloy and high-strength aluminum alloy.
Its advantage is that the natural high plasticity of metals can avoid the occurrence of embrittlement similar to ceramics, and give them higher continuous impact resistance.
However, due to the relatively low ratio of hardness to ceramic, the ability to resist penetration is limited. In addition, for metal, bouncing bullets and fragments must be paid attention to, so there is often a layer of fabric on the surface of the metal guard to prevent the warhead from splashing.
Polymer guard board can be divided into hot pressing type and fiber braiding type. It has the advantages of light weight, good energy absorption, easy molding and high specific strength.
Although the protective plate sacrifices a certain mobility, it gives the bulletproof vest the ability to resist some rifle armor piercing bullets at close range.
This is already the upper limit of the current protective capacity of bulletproof clothing.
What will bulletproof vests look like in the future?
What kind of materials will bulletproof vests be made of in the future?
At present, many new technologies and materials, such as spider silk fiber, graphene and shear rheological materials, are temporarily exposed in the laboratory. Considering the cost and comprehensive performance and other factors, polymer chemical fiber is still the first choice of bulletproof materials. After all, the above materials may have outstanding experimental values in terms of specific strength and local energy absorption characteristics, but there is still a long way to go to achieve large-scale production.
Considering that simply increasing the ammunition capacity and gun size will damage the mobility of guns, it is not practical, and the enhancement of bullet power has almost reached the bottleneck. Nowadays, the duel between bulletproof vests and bullets seems to be equal for the time being.
Under the selected test conditions, bulletproof vests have been able to well resist the attack of bullets of the corresponding level.
However, the development of human science and technology is endless.
The next generation of portable high kinetic energy weapons and laser weapons are likely to return today’s bulletproof clothing technology to the level of primitive society.
How will the bulletproof clothing technology be upgraded at that time?
The confrontation will continue. However, what we want most is a world where none of these protections can be used.
