The Role Of Bulletproof Materials in Stab-proof Body Armor

In terms of bulletproof materials, in order to meet the requirements of stab-proof body armor to absorb the kinetic energy of bullets and other projectiles to a great extent, bulletproof materials must have high strength, good toughness, and strong energy absorption capabilities. The materials currently used in stab-proof body armor, especially soft body armor, are mainly high-performance fibers. These high-performance fibers are characterized by high strength and high modulus. Although some high-performance fibers such as carbon fiber or boron fiber have high strength, they are basically not suitable for body armor due to poor flexibility, small work of fracture, difficulty in textile processing, and high price. Specifically, for bulletproof fabrics, its bulletproof effect mainly depends on the following aspects: tensile strength of fibers, elongation at break and work at break of fibers, modulus of fibers, degree of orientation of fibers and velocity of stress wave transmission, fiber The fineness of fiber, the way of fiber collection, the weight of fiber per unit area, the structure and surface characteristics of yarn, the structure of fabric, the thickness of fiber net layer, the number of layers of net layer or fabric layer, etc. The performance of fiber materials used for impact resistance depends on the fracture energy of fibers and the speed of stress wave transmission. The stress wave needs to spread as quickly as possible, and the fracture energy of the fiber under high-speed impact should be increased as much as possible. The tensile work of a material is the energy possessed by the material to resist external force damage, and it is a function related to the tensile strength and elongation deformation. Therefore, in theory, the higher the tensile strength, the stronger the elongation and deformation ability of the material, the greater the potential for energy absorption. But in practice, the material used for body armor does not allow excessive deformation, so the fiber used for body armor must also have a high ability to resist deformation, that is, a high modulus. The influence of the structure of the yarn on the bulletproof ability is due to the difference in the utilization rate of single fiber strength and the overall elongation and deformation ability of the yarn caused by different yarn fabrics. The breaking process of the yarn depends on the breaking process of the fiber first, but because it is an aggregate, there are great differences in the breaking mechanism. If the fineness of the fiber is fine, the mutual cohesion in the yarn is relatively close, and the force is also relatively uniform, thus improving the strength of the yarn. In addition, the straightening parallelism of the fiber arrangement in the yarn, the number of inner and outer layer transfers, and the twist of the yarn all have important effects on the mechanical properties of the yarn, especially the tensile strength and elongation at break. In addition, due to the interaction between yarns and yarns and between yarns and elastic bodies during the impact process, the surface characteristics of the yarns will either strengthen or weaken the above two effects. The presence of oil and moisture on the surface of the yarn will reduce the resistance of bullets or shrapnel to penetrate the material, so people often have to clean and dry the material and seek ways to increase the penetration resistance. Synthetic fibers with high tensile strength and high modulus are usually highly oriented, so the fiber surface is smooth and the coefficient of friction is low. When these fibers are used in bulletproof fabrics, the energy transfer ability between fibers is poor after being hit by bullets, and the stress wave cannot spread rapidly, thus reducing the ability of the fabric to block bullets. Ordinary methods to increase the surface friction coefficient, such as napping and corona finishing, will reduce the strength of the fibers, while the method of fabric coating will easily cause "welding" between fibers, resulting in bullet shock waves in the yarn Lateral reflection occurs, causing premature fiber breakage.