The main means of protecting personnel from bullets and shrapnel is currently body armor. Over the past decades, it has gone a long way of evolution, but in the end, only three versions of its design, to some extent interconnected with each other, were most widespread. So, body armor based on metal plates, Kevlar and combined, in which Kevlar sheets are interspersed with plates of the corresponding metal are used. Attempts are regularly made to adapt ancient developments, such as, for example, lamellar armor, to protection against bullets, but so far no particular success has been achieved in this field.
The main problem of modern body armor is the ratio "weight - quality of protection". In other words, a more reliable body armor turns out to be heavy, and one that has an acceptable weight has a too low protection class. By the way, this is exactly the problem that Kevlar was supposed to solve. In the 70s of the last century, in the course of research, it was found that Kevlar fabric of dense weave, laid in several layers, effectively dissipates the energy of the bullet over its entire surface, so that the bullet cannot penetrate the entire Kevlar bag. In combination with a plate made of a suitable metal (for example, titanium), this property of Kevlar fabric made it possible to create relatively light bulletproof vests that have the same protective properties as all-metal ones.
However, the Kevlar-metal body armor has its drawbacks. In particular, it still has significant weight and considerable thickness. In the case of the combat work of a soldier, this can be of great importance: the fighter is forced to carry additional weight on his shoulders, which could be used in order to take more cartridges or provisions. But in this case, you have to choose between payload and health, if not life. So the choice is clear. Scientists all over the world have been struggling to solve this problem for more than a dozen years, and there are already certain successes. In 2009, there was almost sensational news. A group of British scientists led by R. Palmer has developed a special gel called D3O. Its peculiarity lies in the fact that upon impact of considerable force, the gel becomes harder, while maintaining its relatively low weight. In the absence of any impact, the gel bag remained soft and flexible. D3O gel was proposed to be used in body armor, special modules for protecting vehicles, and even as a soft lining for soldiers' helmets. The last point looks particularly interesting. According to Palmer, a helmet with such a lining will become bulletproof. Does he really not know what price the soldiers of the First World War paid for the bulletproof helmets? Nevertheless, the British Department of Defense became interested in the gel and allocated a grant of 100 thousand pounds to Palmer's laboratory. In the three years that have passed since then, news on the progress of work has regularly appeared, photo and video materials from the tests of the next version of the gel, but the finished helmet or vest with D3O has not yet been demonstrated.
A little later, a similar gel was demonstrated to representatives of the DARPA agency. The American counterpart D3O was developed by Armor Holdings. It works on exactly the same principle. Both gels are essentially what physics calls a non-Newtonian fluid. The main feature of such fluids is the nature of their viscosity. In most cases, these are liquid solutions of solids with relatively large molecules. Due to this property, a non-Newtonian fluid has a viscosity that directly depends on the velocity gradient. In other words, if a body interacts with it at a low speed, then it will simply drown. If the body hits a non-Newtonian fluid at a sufficiently high speed, then it will be inhibited or even thrown away due to the viscosity and elasticity of the solution. A similar liquid can be made even at home from plain water and starch. Such properties of some solutions have been known for a very long time, but relatively recently they reached the use of non-Newtonian fluids in protection against bullets and shrapnel.
The latest successful "liquid armor" project to date was created by the British branch of BAE Systems. Their composition Shear Thickening Liquid (tentatively called bulletproof cream) appeared in 2010 and is planned to be used not on its own, but in combination with Kevlar sheets. BAE Systems do not disclose the composition of their non-Newtonian liquid for body armor for obvious reasons, however, knowing the physics, certain conclusions can be drawn. Most likely, it is an aqueous solution of some substance (substances) that has the most suitable viscosity characteristics for strong impacts. In the Shear Thickening Liquid project, it finally came to creating a full-fledged body armor, albeit an experienced one. With the same thickness as the 30-layer Kevlar vest, the "liquid" one has three times less number of layers of synthetic fabric and half the weight. In terms of protection, the STL Gel Liquid Body Armor has almost the same protection as the 30-ply Kevlar. The difference in the number of sheets of fabric is compensated by special polymer bags with non-Newtonian gel. Back in 2010, testing of a ready-made prototype gel-based body armor began. For this, experimental and control samples were fired upon. 9-mm bullets of the 9x19 mm Luger cartridge were fired from a special pneumatic cannon with a muzzle velocity of about 300 m / s, which is somewhat similar to most types of firearms chambered for this cartridge. The protection characteristics of the experimental and control body armor were approximately the same.
However, liquid-protected body armor has a number of disadvantages. The most obvious one lies in the fluidity of the gel under normal conditions: it can leak out through the bullet hole and the level of protection of the vest will be significantly reduced. In addition, a non-Newtonian liquid or gel cannot completely absorb or dissipate all of the bullet's energy. Accordingly, a significant improvement in performance is possible only with the simultaneous use of Kevlar, liquid bags, and metal plates. Obviously, in this case, there may not be a trace of weight advantages, of course, if you compare such a vest with only Kevlar. At the same time, a slight increase in weight can be considered a quite adequate price for improving the protective properties.
Unfortunately, so far not a single piece of body armor or other protection using the principles of non-Newtonian fluid has left the stage of laboratory tests. All research organizations dealing with this problem are primarily working to increase the effectiveness of the protection of liquids / gels and reduce their density in order to reduce the overall weight of the body armor or helmet. From time to time, unverified information appears that this or that sample is about to go to British or American units for trial operation, but so far there has been no official confirmation of this. Perhaps the security forces of foreign countries are simply afraid to trust the lives of fighters in a new and, frankly, not yet looking reliable technology.
