Ceramic armor
Ceramic armor is armor used by armored vehicles and in personal armor to resist projectile penetration through high hardness and compressive strength. Ceramics are often used where light weight is important, as they weigh less than metal alloys for a given degree of resistance. The most common materials are alumina, boron carbide, silicon carbide, and titanium diboride.[1]
History
Tests as early as 1918 demonstrated the potential of ceramic armor; Major Neville Monroe-Hopkins found that adding a thin layer of enamel to steel greatly improved its ballistic properties. Its first operational use was not until the Vietnam war[2] in which helicopters frequently came under small arms fire. In 1965, ceramic body armor was given to helicopter crews, and ‘hard-faced composite’ armor kits added to pilot seats. By the following year, monolithic ceramic vests and airframe-mounted armor panels were deployed. In "Huey" helicopters, these improvements were estimated to have decreased fatalities by 53%, and non-fatal injuries by 27%.
Design
Ceramic armor designs range from monolithic plates to systems employing three dimensional matrices. One of the first patents of ceramic armor was filed in 1967 by the Goodyear Aerospace Corp. It embedded alumina ceramic spheres in a thin aluminum sheets, which were layered so that the spheres of each layer would fill the gaps between spheres of the surrounding layers, in a manner similar to a body-centered cubic packing structure. The entire system was held together with polyurethane foam and a thick aluminum backing.[3] This development demonstrated the effectiveness of matrix-based design, and spurred the development of other matrix-based systems. Most of these combine cylindrical, hexagonal, or spherical ceramic elements with a backing of some non-armor dedicated alloy.[1] Monolithic plate armor, by contrast, relies on 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 its ability to penetrate. Against HEAT rounds, the ceramic elements break up the geometry of the metal jet generated by the shaped charge, greatly diminishing penetration. In both cases, the hard but brittle ceramic elements are broken into pieces, which may themselves be dangerous if not confined. For this reason, ceramic materials are normally supported by a ductile backing of metal or polymer-composite materials. This backing structure also holds the ceramic elements in place so they are not merely knocked aside, but absorb the impact.
Applications
Personnel
Ceramic plates are commonly used as inserts in soft ballistic vests. Most ceramic plates used in body armor provide National Institute of Justice Type III protection, allowing them to stop rifle bullets. Ceramic plates are a form of composite armor. Insert plates may also be made of 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 (ESAPI).
The approximate weight for one NIJ Type III plate is 4 to 8 pounds (1.8–3.6 kg) 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 (maximum coverage 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.[4] 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.[5] 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.[6]
References
- ^ a b Yang, M.; Qiao, P. (2010). "High energy absorbing materials for blast resistant design". Blast Protection of Civil Infrastructures and Vehicles Using Composites. pp. 88–119. doi:10.1533/9781845698034.1.88. ISBN 978-1-84569-399-2.
- ^ J., Hazell, Paul (2015-07-29). Armour : materials, theory, and design. Boca Raton, FL. ISBN 9781482238303. OCLC 913513740.
{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: multiple names: authors list (link) - ^ Ballistic Armor System, by Goodyear Aerospace Corp, (1967, May 10). US4179979A. Accessed on Nov. 28, 2018. [Online]. Available: Google Patents
- ^ Wiley Advances in Ceramic Armor III ACS
- ^ Tencate AresShield
- ^ Foster Miller Last Armor.