The function and the production of ceramic bulletproof vest

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Ceramics were first used for the protection of helicopters and individuals in the 1960s. Advances in processing technology over the past few decades have led to the use of low-cost ceramic materials. This also promotes the military and non-military applications of ceramic materials. There are many types of ceramics. At present, the main ones that can be used for personal protection are oxides, nitrides, carbides, etc.; varieties include aluminum oxide (AlO), silicon nitride (SiN), silicon carbide (SiC), boron carbide (B.C), etc. . Boron carbide has the smallest density, the highest hardness, and the best ballistic performance, but because of its high price, it is mainly used for advanced equipment; such as the American Black Hawk helicopter crew seat; hot-pressed silicon carbide has high hardness, high modulus and moderate density , used for aircraft belly, armored vehicles; alumina density is high, the ballistic resistance is medium, but the price is the lowest, and the sintering performance is good, the size is stable, widely used in armored vehicles, belly and military and police body armor. At present, a lot of progress has been made in the performance of ceramic composites. There are mainly two ways: (1) synthesis of new ceramic materials with higher performance; (2) synthesis of more suitable backing composite materials to optimize the ballistic performance of the overall structure.

Bulletproof mechanism of bulletproof ceramic composite panels

The bulletproof mechanism of bulletproof ceramic plates is completely different from that of bulletproof metals; metals mainly rely on plastic deformation to absorb energy; ceramics mainly rely on crushing and fracture energy to absorb energy.

When the bullet hits the ceramic surface, a strong compression wave is generated, which rapidly increases the internal pressure of the bullet and the ceramic plate. The warhead is deformed, passivated, or even broken due to the stress exceeding the failure limit due to the compressive stress greater than its own yield strength. The test shows that the instantaneous stress at the time of impact reaches 2800MPa; the wave velocity of the stress wave inside the metal and boron carbide is 4800m/s and 14400m/s respectively; the larger the gap between the two, the stronger the stress wave acting on the warhead.

At the same time as the warhead is deformed, circumferential and radial initial cracks are formed on the ceramic plate to absorb kinetic energy. With the continuous penetration of the bullet, the warhead will aggravate the fragments due to the abrasion with the ceramic, and the ceramic will also form continuous fragments with the expansion of the initial crack and continue to absorb energy; the bullet further penetrates, and the ceramic panel will eventually form due to tension. broken cone. Finally, the warhead fragments and ceramic fragments impinge on the backing material together. When a stress wave is launched on the backing material, the instantaneous compressive stress is converted into tensile stress, resulting in the occurrence of delamination of the backing material. The backing material absorbs the remaining energy through flexural tensile deformation, delamination, and propagation of stress waves.

Pressureless sintering process:

At present, the domestic production process of alumina bulletproof ceramics is mainly: ingredient mixing → plasticization and granulation → mold pressing → high temperature sintering.

Ingredients: industrial SiC powder, particle size 1μm (median diameter), purity ≥99%; industrial BC powder, particle size 2.5μm (median diameter), purity ≥93.4%; industrial TiC powder, particle size 3μm (median diameter), purity ≥98%; liquid water-soluble phenolic resin, polyvinyl alcohol (PVA) and dextrin are used as binders.

Mixing and granulation: weigh the proportion in the formula and add it to the ball mill together with deionized water. The ratio of ball to material is 4:1. The ball mill is made of silicon carbide. The centrifugal spray dryer is used for atomization and granulation, and the granulated material is mixed uniformly and passed through a 60-mesh sieve for use.

Pressing and sintering: Weigh the granulated material of the required weight, pour it into a steel mold and press it on a hydraulic press (molding pressure 1~2Tcm2), fully dry the formed green body, and put it into a horizontal vacuum furnace For sintering, the sintering system was set to: 2050 °C, kept for 180 min, filled with high-purity hydrogen for protection during the high temperature period, and cooled naturally after the procedure.

Equipment selection: RVS vacuum sintering furnace provided by SIMUWU is an excellent product for processing silicon carbide sintering process. SIMUWU provides a professional team of engineers who can solve various problems encountered in the production process and are committed to giving customers the most convenient and efficient experience.