At present, the general development trend of armor materials is toughening, lightweight, multi-functional and high-efficiency. Alumina ceramic material is an important part of bulletproof materials. It has high hardness and wear resistance, high compressive strength and excellent ballistic performance under high stress.
The ballistic resistance mechanism of alumina ceramics and metals are very different. Metals absorb the kinetic energy of projectiles due to plastic deformation, while ceramics absorb the kinetic energy of projectiles due to their rupture. Typically, ceramic armor systems consist of a single piece of ceramic or ceramic-metal composite covered with a high tensile strength organic fiber bonded nylon cloth layer.
Under the impact of the bullet, the front surface of the alumina ceramic is broken and the remaining energy is absorbed by the soft reinforcement material on the reverse side. The reverse side material must be able to support the fragments of the ceramic material and the bullet itself after the impact of the bullet. Of course, as a bulletproof ceramic, there are many properties required, including density and porosity, hardness, fracture toughness, Young's modulus, sound speed, mechanical strength, etc., none of the properties can be directly and decisively related to the overall ballistic performance. Therefore, The fracture mechanism is very complex, and the formation of cracks is caused by many factors, and the time of occurrence is very short.
The porosity of alumina bulletproof ceramics should be as low as possible to improve hardness and Young's modulus; and its hardness is very high, which should be higher than that of flying warheads; the speed of sound propagation in alumina ceramics indicates the impact surface of the ceramics On the ability to dissipate energy, the high sound velocity also indirectly indicates that the ceramic has good densification and low closed pores.
The existing bulletproof ceramics are mainly divided into two categories, namely monolithic ceramic structures and ceramic composite structures. Monolithic structural ceramics include oxide ceramics and non-oxide ceramics, as well as binary systems. In general, non-oxide ceramics have higher physical properties and relatively low densities, which are more beneficial as bulletproofs than alumina ceramics. However, most of these material manufacturing methods use expensive hot pressing, which is not easy to industrialize. But hot pressing can improve the mechanical properties of bulletproof ceramics.
Furthermore, ceramic matrix composites have high ballistic properties due to high mechanical properties, especially fracture toughness. After projectile impact, ceramic matrix composites have better integrity than monolithic ceramics. Therefore, alumina ceramics are very suitable as bulletproof ceramics.