Ceramic armor is armor used by armored vehicles and in personal armor for its attenuative properties. Ceramics provide projectile resistance through their high hardness and compressive strength and are often used in applications where weight is a limiting factor due to their lightweight nature relative to metals commonly used in armors. Most commonly alumina, boron carbide, silicon carbide, and titanium diboride ceramics are used in armor but other ceramics are used.
History
Ceramic armor has been in use by the US military since the Vietnam war although the first testing that demonstrated the potential ceramics had was in 1918. Major Neville Monroe-Hopkins found that by adding a thin layer of enamel, the ballistic properties of steel were greatly increased. Helicopters frequently came under small arms fire from small scale assaults which put the crews in greater danger. In 1965, ceramic body armor was given to the crews as well as ‘hard-faced composite’ armor kits placed within the pilot seats to offer better protection. Building off of this, the following year, monolithic ceramic vests and airframe-mounted armor panels were employed. These improvements are estimated to have decreased fatalities by 53% and the incident of non-fatal injuries by 27% in "Huey" helicopters. This was the first battle use of ceramic armor by any military.
Design
Ceramic armor comes in a variety of designs ranging from monolithic plating to systems employing three dimensional matrices. One of the first patents of ceramic armor was filed in 1967 by the Goodyear Aerospace Corp. It consisted of alumina ceramic spheres embedded into a thin aluminum sheets. These sheets were layered atop each other such that the spheres of other layers would fall within the spaces between spheres of the surrounding layers in a manner similar to a body-centered cubic packing structure. The remaining gaps were then filled with a polyurethane foam and the entire system was then given a thick aluminum backing to hold it together. This development demonstrated the effectiveness of matrix based design and thus spurred the development of other matrix based systems. Other matrix based designs can be included however, the main theme among the designs is the use of a ceramic based system with a backing composed of some non-armor dedicated alloy. Many of these designs can include systems employing cylindrical, hexagonal, or spherical ceramic pieces. Monolithic plate armor is also available. These come in the form of single plates of an advanced ceramic slipped into a traditional ballistic vest in place of a steel plate.
Mechanism
Hard ceramic materials defeat the kinetic energy projectile by shattering it into pieces, decreasing the penetration ability of projectile. In case of HEAT rounds the shattered ceramic fragments destroy the geometry of the metal jet generated by the shaped charge, greatly diminishing the penetration. Ceramic materials cannot be used as a stand alone for armour applications because of its shattering effect due to their inherent nature of brittleness. Therefore, in order to prevent the shattered ceramic and projectile pieces from further damaging the protected system, ceramic materials should always be supported by a ductile backing with metallic or polymeric composite materials. Another advantage of using backing material is to improve the ballistic performance of ceramics by preventing its premature failure.
Applications
Personnel
s are commonly used as inserts in soft ballistic vests. Most ceramic plates used in body armor provide National Institute of JusticeType III protection, allowing them to stop rifle bullets. Ceramic plates are a form of composite armor. Insert plates may also be manufactured from steel or ultra high molecular weight polyethylene. A ceramic plate is usually slipped into the outer layer of a soft armor vest. There may be two plates, one in the front and one in the back, or one universal plate on either front or back. Some vests permit the usage of small plates on the sides for additional protection. Ceramic plates issued by the United States military are called Enhanced Small Arms Protective Inserts. The approximate weight for one NIJ Type III plate is 4 to 8 pounds for the typical size of 10" by 12". There are other types of plates that come in different sizes and offer different levels of protection. For example, the MC-Plate offers 19% more coverage than a standard ceramic plate. Ceramic materials, materials processing and progress in ceramic penetration mechanics are significant areas of academic and industrial activity. This combined field of ceramics armor research is broad and is perhaps summarized best by The American Ceramics Society. ACerS has run an annual armor conference for a number of years and compiled a proceedings 2004–2007. An area of special activity pertaining to vests is the emerging use of small ceramic components. Large torso sized ceramic plates are complex to manufacture and are subject to cracking in use. Monolithic plates also have limited multi hit capacity as a result of their large impact fracture zone These are the motivations for new types of armor plate. These new designs use two and three dimensional arrays of ceramic elements that can be rigid, flexible or semi-flexible. Dragon Skin body armor is one these systems, although it has failed numerous tests performed by the US Army, and has been rejected. European developments in spherical and hexagonal arrays have resulted in products that have some flex and multi-hit performance. The manufacture of array type systems with flex, consistent ballistic performance at edges of ceramic elements is an active area of research. In addition advanced ceramic processing techniques arrays require adhesive assembly methods. One novel approach is use of hook and loop fasteners to assemble the ceramic arrays.
