Performance requirements for ceramic bulletproof plates

- Jul 05, 2019-

Typically, a ceramic armored system consists of a single ceramic or ceramic-metal composite covered with a nylon cloth layer combined with high anti-sheet strength organic fibers (glass fibers are also available). Under the impact of the bullet (speed s 700 to 800m/s), the ceramic front is broken and the remaining energy is absorbed by the negative soft reinforcement (e.g. nylon cloth layer) material. The reverse material must be able to support the fragments of the ceramic material and the bullet itself after the impact of the bullet. Bulletproof ceramic requires more performance, such as: density and pore rate, hardness, fracture toughness, Yang's modulus, sound velocity, mechanical strength, etc. , any performance can not have a direct and decisive relationship with the overall bulletproof performance, so the fracture mechanism is very complex, crack formation is caused by many factors, and the occurrence time is very short. Bulletproof ceramic pore rate should be as low as possible to improve hardness and Yang's modulus, for Al2O3 porcelain, its pore rate should be close to zero, and the water absorption rate does not exceed 0.02%. The hardness requirement of ceramic is very high, should be higher than the hardness of the flying warhead, for Al2O3 ceramics, the hardness Hv should be more than 1220 to 1250. The speed at which sound travels in ceramics indicates the ability to consume energy on the impact surface of ceramics, hoping to have high sound velocity, and the high sound velocity also indirectly indicates that ceramics have good denseness and low closed pores. According to practical experience, Al2O3 porcelain should have a sound velocity of more than 10000m/s, preferably 10500 to 11500m/s. Ceramics have two types of bulletproof, i.e. single ceramic structure and ceramic composite structure, single-piece structure ceramics include oxide ceramics (mainly Al2O3 porcelain) and non-oxide ceramics (e.g. SiC, Si3N4, AlN and TiB2, etc.), and binary systems (e.g. B4C-TiB2 base ceramics). In general, non-oxide ceramics have higher physical properties and relatively low density (except TiB2-based ceramics), which are more beneficial as bulletproof than Al2O3 porcelain. However, these materials are manufactured with more expensive thermal pressure and are not easy to industrialization. But it is also evident that thermal pressure improves the mechanical properties of bulletproof ceramics. Ceramic-based compounds have high bullet-proof properties due to high mechanical properties, especially fracture toughness. After the projectile impact, compared with single-piece ceramic, the ceramic-based complex has better integrity. Several composite ceramics are as follows: Al2O3/SiC (w), Al2O3/SiC (f), Al2O3/C (f), TiB2/B4C (p), TiB2/SiC (p), and metal ceramics (e.g. LanxideTM), which consist of carbidgated Ni/(Al), For example, Ni/TiC and Al/B4C (p), most of these materials are thermal pressures and are therefore more expensive. Although the bullet-proof ceramic LanxideTM is not a hot-press process, it requires special processes and equipment and is therefore more expensive.