– Personal and equipment protection
Modern ballistic protection is often based, especially for high protection classes like e.g. SK4 personal protection, on shaped parts made of dense-sintered oxide and non-oxide ceramics in multilayer systems of ceramic-polymer composites. Despite comparatively small components sizes and high mobility, such systems are capable of absorbing the energy of an impacting projectile, and as a result guarantee maximum protection.
Reasons for the use of dense-sintered ceramic materials in such systems include the following physical properties:
- High hardness
- High compressive strength
- High bending strength
- High modulus of elasticity
- Low density
- Low mass per unit area
The material mainly used today is Al2O3 ceramic, which enables a composite system with the same protective effect but generally less than half the weight of armoured steel. The focus shifts to non-oxide ceramic materials on the basis of SiC and B4C when even lower weight has to be realized without compromising the protective function.
Both in land and water craft, and especially aircraft, and personal protection, components made of such materials are often expedient as owing to their low weight they enable increased mobility. Typical ceramic weights per unit area, e.g. for protective vests, are around 42 kg/m² for Al2O3, around 36 kg/m² for SiC and around 30 kg/m² for B4C.
The increasing requirements for armouring for ballistic protection of vehicles lead with the use of armoured steel to a corresponding and non-negligible increase in vehicle weights. The use of ceramic composite systems in such designs enables at least partial compensation of these weight increases. Particularly for the protection of aircraft, ceramic materials are extremely expedient with a view to maintaining acceptable component group weights.
One weak point in armoured vehicles are those areas that give the occupants a direct view of their environment, but on the other hand make the occupants visible to a potential attacker. These areas are conventionally protected with bullet-proof glass. Transparent Al2O3 ceramic is a mechanically strong alternative as this type of material combines the above-listed properties with high light transmission and therefore provides much higher protective effect for an equivalent design.
As a result of recent developments, transparent Al2O3 ceramic now reaches extremely high hardness with HV10 > 20 GPa. Transparent ceramics made of MgAl2O4 gets close to this level. With regard to their protective effect, it is comparable with conventional protective ceramics made of Al2O3. On account of the optically isotropic character of its crystal structure, in contrast to transparent Al2O3 ceramic, transparency is maintained even when the components have thicker walls.