As many people have heard, new types of "liquid body armor" have been developed abroad; This new body armor is actually aimed at traditional Kevlar and other high-strength fiber body armor, using special liquid materials (known as "shear thickening liquid", short for STF) enhanced products, the appearance and traditional soft body armor is no different. If you're really looking for a liquid body armor, or a bulletproof vest made of a water sac structure, you'll certainly not find it. The exact principle of STF is still unclear, and several possible theories are very boring and obscure to explain. Broadly speaking, STF is actually very common, with starch and water can be made; The most common practice of sFFs that can really be used for bulletproof, is generally composed of a large number of 20-50 nm diameter silicon dioxide (one of the main components of glass) solid particles, mixed with polyglycol. The principle of traditional soft body armor is to use the high-strength fiber break, deformation, extraction process, the consumption of the warhead's kinetic energy, and finally the warhead lost the ability to further invade. This capability is not provided by a separate layer of fiber fabric, but by a multi-layer edgy structure overlay.
And the application of STF in bulletproof clothing, in addition to its own consumption of bullet kinetic energy, it is also very effective in strengthening the fiber between, between fiber bundles, fabric layers of inter-relationship; For example, the application of STF can be required by the same level of protection, the original need for 15 layers of Kevlar material body armor, as long as 10 layers can meet the target. Although the STF itself brings a certain amount of weight, the reduction in the weight and the thickness of the body armor by 5 layers of Kevlar material has resulted in a more flexible and fatigue-prone movement of those wearing protective clothing. In the specific process, simply applying STF to the bulletproof fabric material is also feasible, but in a large number of comparative studies confirmed that the effect is not good.
The current mainstream approach is to dilute the STF with solvents (e.g. ethanol, or alcohol) and thoroughly impregnate the bulletproof fabric, and then dry it with vacuum or low temperatures (e.g. 80 degrees). At present, the application of STF in bulletproof equipment is still in a very early stage, many problems have not been perfectly solved. But in lower-level protective settings, such as skiing, motorcycle clothing and other sports protective equipment, or impact helmets and other police riot gear, STF enhancement products have been successfully commercialized. Some athletes in the United States and Canada, for example, have already started using match equipment containing D30 materials at previous Winter Olympics.