For fabrics, the bulletproof effect is related to 5 factors of fiber fabrics:
1. The fineness of the fiber
The fineness of the fibers is small, the mutual cohesion in the yarn is relatively close, and the force is relatively uniform, thus improving the strength of the yarn. At the same time, the ballistic resistance of the fine denier fiber material is also improved.
2. Physical properties such as tensile strength, modulus, elongation at break and work at break of fibers
Theoretically, materials with high tensile strength and strong elongation and deformation ability have great potential to absorb energy. But in practice, the materials used for body armor do not agree to have excessive deformation, otherwise serious non-penetrating damage will be caused. Therefore, the fiber material used for body armor must have a high elastic modulus at the same time.
3. The way of collection of fibers
Spinning yarn is an aggregate of fibers, and its breaking process is very different from that of fibers. The straightness and parallelism of the fiber arrangement, the transfer times of the inner and outer layers, and the twist of the spinning yarn have an important influence on the mechanical properties of the fabric, especially the tensile strength, elongation at break and other indicators. Therefore, the spinning yarn should be twisted with little or no twist, so that the utilization rate of the fiber can be fully improved.
4. The structure of the fabric
Theoretically, to obtain good impact resistance, UD technology materials with unidirectional and no staggered points should be adopted. Fabrics made with this technique can also be called non-weft fabrics. Most of the energy of a bullet or shrapnel can be extracted by elongation of fibers at or near the point of impact. That is to say, the non-weft fabric removes the negative effects of stress wave reflection and superposition of the cloth fabric, so that the energy of the stress wave propagates outward faster, thereby significantly improving the ballistic resistance. At the same time, the fiber structure arranged in parallel can also greatly improve the overall utilization rate of the fabric.
5. Surface features of spinning yarns
After the fibers with a completely smooth surface and low friction coefficient are impacted by the bullet, the ability to transmit energy between the fibers becomes poor, and the stress wave cannot spread rapidly, thus reducing the ability of the fabric to block the bullet. The presence of oil and moisture on the surface of the spinning yarn will also reduce the resistance of bullets or shrapnel penetrating the material. Therefore, the bulletproof material is often cleaned and dried to improve the frictional resistance of the material surface.