Ceramic armor

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Ceramic armor is armor used by armored vehicles and in personal armor to resist projectile penetration through its high hardness and compressive strength. In its most basic form, it consists of two primary components: A ceramic layer on the outer surface, called the "strike face," backed up by a ductile fiber reinforced plastic composite or metal layer. The role of the ceramic is to (1) fracture the projectile or deform the projectile nose upon impact, (2) erode and slow down the projectile remnant as it penetrates the shattered ceramic layer, and (3) distribute the impact load over a larger area, which can be absorbed by ductile polymer or metallic backings. 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, and, to a lesser extent, silicon carbide. [1] [2]

Contents

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 [3] 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 were added to pilot seats. By the following year, monolithic ceramic vests and airframe-mounted armor panels had been 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 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 either thick aluminum, multi-layered UHMWPE, para-aramid fiber, or 30% PALF + 70% epoxy composite backing. [4] 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

Unlike metals, ceramics are never used alone, as standalone materials, in armor systems; they are always combined with a ductile backing or support layer of metal or fiber reinforced plastic composite materials, and this ceramic-faced assembly is called ceramic armor. Ceramic materials, like glass, have high hardness and compressive strengths but low tensile strengths. Bonding a ceramic tile to a metallic or composite backing material, with high strength and good ductility, delays or mitigates tensile failure upon impact, and forces the ceramic to fail in compression. [2]

Ceramic armor systems defeat small arms projectiles and kinetic energy penetrators by two main mechanisms: Shattering and erosion. When a hard steel or tungsten carbide projectile hits the ceramic layer of a ceramic armor system, it is momentarily arrested, in a phenomenon known as dwell. Depending on the thickness and hardness of the ceramic layer, the projectile core is then either shattered, fractured, or blunted. The projectile's remnants continue to penetrate the comminuted ceramic tile at a reduced velocity, which erodes those remnants and reduces their energy, length, and mass. The metal or fiber reinforced plastic composite layer behind the ceramic layer then arrests the projectile's fragments or its eroded remnant, and absorbs residual kinetic energy, typically via plastic deformation. If the backing material is too thin or too weak to absorb the residual kinetic energy or if the projectile does not shatter and the eroded projectile remnant retains too much of its mass and kinetic energy penetration will occur. Both the ceramic layer and its backing layer are therefore of equal importance.

In vehicular ceramic armor, the backing material is most commonly structural steel, frequently rolled homogeneous armor, though aluminum is sometimes used. In body armor, where ceramic armor designers strive to make ceramic armor plates as light and as comfortable as possible, the backing material is typically a light-weight ultra high molecular weight polyethylene fiber composite, but may also be an aramid fiber composite and, in low-end ceramic armor plates or in plates for stationary wearers such as helicopter crews, fiberglass is sometimes used.

Against high-explosive anti-tank rounds, the ceramic elements break up the geometry of the metal jet generated by the shaped charge, greatly diminishing penetration.

Applications

Personnel

Ceramic body armor plates Craig Ballistic Plate.jpg
Ceramic body armor plates

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 use 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 Level III ceramic armor plate is 4.4 to 8 pounds (2.0 to 3.6 kg) for the typical size of 10 by 12 inches (25 by 30 cm). 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. [5] 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. [6] 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. [7]

Related Research Articles

A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.

<span class="mw-page-title-main">Shaped charge</span> Explosive with focused effect

A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Different types of shaped charges are used for various purposes such as cutting and forming metal, initiating nuclear weapons, penetrating armor, or perforating wells in the oil and gas industry.

<span class="mw-page-title-main">Kinetic energy penetrator</span> High density non-explosive projectile

A kinetic energy penetrator (KEP), also known as long-rod penetrator (LRP), is a type of ammunition designed to penetrate vehicle armour using a flechette-like, high-sectional density projectile. Like a bullet or kinetic energy weapon, this type of ammunition does not contain explosive payloads and uses purely kinetic energy to penetrate the target. Modern KEP munitions are typically of the armour-piercing fin-stabilized discarding sabot (APFSDS) type.

<span class="mw-page-title-main">Armour-piercing ammunition</span> Ammunition type designed to penetrate armour

Armour-piercing ammunition (AP) is a type of projectile designed to penetrate armour protection, most often including naval armour, body armour, and vehicle armour.

<span class="mw-page-title-main">Composite armour</span> Type of vehicle armour

Composite armour is a type of vehicle armour consisting of layers of different materials such as metals, plastics, ceramics or air. Most composite armours are lighter than their all-metal equivalent, but instead occupy a larger volume for the same resistance to penetration. It is possible to design composite armour stronger, lighter and less voluminous than traditional armour, but the cost is often prohibitively high, restricting its use to especially vulnerable parts of a vehicle. Its primary purpose is to help defeat high-explosive anti-tank (HEAT) projectiles.

In materials science, a metal matrix composite (MMC) is a composite material with fibers or particles dispersed in a metallic matrix, such as copper, aluminum, or steel. The secondary phase is typically a ceramic or another metal. They are typically classified according to the type of reinforcement: short discontinuous fibers (whiskers), continuous fibers, or particulates. There is some overlap between MMCs and cermets, with the latter typically consisting of less than 20% metal by volume. When at least three materials are present, it is called a hybrid composite. MMCs can have much higher strength-to-weight ratios, stiffness, and ductility than traditional materials, so they are often used in demanding applications. MMCs typically have lower thermal and electrical conductivity and poor resistance to radiation, limiting their use in the very harshest environments.

<span class="mw-page-title-main">Bulletproof vest</span> Form of body armour that protects the torso from some projectiles

A bulletproof vest, also known as a ballistic vest or a bullet-resistant vest, is an item of body armour that helps absorb the impact and reduce or stop penetration to the torso by firearm-fired projectiles and fragmentation from explosions. The vest may come in a soft form, as worn by many police officers, prison officers, security guards, and some private citizens, used to protect against stabbing attacks or light projectiles, or hard form, using metallic or para-aramid components. Soldiers and police tactical units wear hard armour, either in conjunction with soft armour or alone, to protect against rifle ammunition or fragmentation.

<span class="mw-page-title-main">Chobham armour</span> British-designed composite tank armour

Chobham armour is the informal name of a composite armour developed in the 1960s at the Military Vehicles and Engineering Establishment, a British tank research centre on Chobham Lane in Chertsey. The name has since become the common generic term for composite ceramic vehicle armour. Other names informally given to Chobham armour include Burlington and Dorchester. Special armour is a broader informal term referring to any armour arrangement comprising sandwich reactive plates, including Chobham armour.

<span class="mw-page-title-main">Bulletproof glass</span> Projectile-resistant transparent armor

Bulletproof glass, ballistic glass, transparent armor, or bullet-resistant glass is a strong and optically transparent material that is particularly resistant to penetration by projectiles. Like any other material, it is not completely impenetrable. It is usually made from a combination of two or more types of glass, one hard and one soft. The softer layer makes the glass more elastic, so that it can flex instead of shatter. The index of refraction for all of the glasses used in the bulletproof layers must be almost the same to keep the glass transparent and allow a clear, undistorted view through the glass. Bulletproof glass varies in thickness from 34 to 3+12 inches.

A cermet is a composite material composed of ceramic and metal materials.

<span class="mw-page-title-main">Vehicle armour</span> High-strength plating used to fortify important vehicles against bullets, shells etc.

Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fighting vehicles like tanks, aircraft, and ships.

<span class="mw-page-title-main">Body armor</span> Protective clothing; armor worn on the body

Body armor, personal armor, armored suit (armoured) or coat of armor, among others, is armor for a person's body: protective clothing or close-fitting hands-free shields designed to absorb or deflect physical attacks. Historically used to protect military personnel, today it is also used by various types of police, private security guards, or bodyguards, and occasionally ordinary citizens. Today there are two main types: regular non-plated body armor for moderate to substantial protection, and hard-plate reinforced body armor for maximum protection, such as used by combatants.

<span class="mw-page-title-main">Bulletproofing</span> Provision for resisting fired bullets

Bulletproofing is the process of making an object capable of stopping a bullet or similar high velocity projectiles. The term bullet resistance is often preferred because few, if any, practical materials provide complete protection against all types of bullets, or multiple hits in the same location, or simply sufficient kinetic (movement) energy to overcome it.

<span class="mw-page-title-main">Small Arms Protective Insert</span> American military ballistic protection system

The Small Arms Protective Insert (SAPI) is a ceramic ballistic plate used by the United States Armed Forces. It was first used in the Ranger Body Armor and Interceptor Body Armor, both are ballistic vests. It is now also used in the Improved Outer Tactical Vest as well as the Modular Tactical Vest, in addition to commercially available "plate carriers". The Kevlar Interceptor vest itself is designed to stop projectiles up to and including 9×19mm Parabellum submachine gun rounds, in addition to fragmentation. To protect against higher-velocity rifle rounds, SAPI plates are needed.

<span class="mw-page-title-main">Ballistic plate</span> Protective armoured plate

A ballistic plate, also known as an armour plate, is a protective armoured plate inserted into a carrier or bulletproof vest, that can be used stand-alone, or in conjunction with other armour. "Hard armour" usually denotes armour that uses ballistic plates.

<span class="mw-page-title-main">Spaced armour</span> Armour with plates spaced a distance apart

Armour with two or more plates spaced a distance apart falls under the category of spaced armour. Spaced armour can be sloped or unsloped. When sloped, it reduces the penetrating power of bullets and solid shot, as after penetrating each plate projectiles tend to tumble, deflect, deform, or disintegrate; spaced armour that is not sloped is generally designed to provide protection from explosive projectiles, which detonate before reaching the primary armour. Spaced armour is used on military vehicles such as tanks and combat bulldozers. In a less common application, it is used in some spacecraft that use Whipple shields.

<span class="mw-page-title-main">Ceramic engineering</span> Science and technology of creating objects from inorganic, non-metallic materials

Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties.

<span class="mw-page-title-main">Improved Outer Tactical Vest</span> US Army body armor

The Improved Outer Tactical Vest (IOTV) is an enhanced version of, and a replacement for, the older Outer Tactical Vest (OTV) component of the Interceptor multi-threat body armor system, as fielded by the United States Army beginning in the mid-2000s. The IOTV is compatible with the Deltoid and Axillary Protector System (DAPS) components, ESAPI, Enhanced Side Ballistic Inserts (ESBI), as well as the OTV's groin protector. A flame-resistant standalone shirt, the Army Combat Shirt (ACS), was designed in the late 2000s specifically for use with the IOTV.

<span class="mw-page-title-main">Solid</span> State of matter

Solid is one of the four fundamental states of matter along with liquid, gas, and plasma. The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural rigidity and resistance to a force applied to the surface. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire available volume like a gas. The atoms in a solid are bound to each other, either in a regular geometric lattice, or irregularly. Solids cannot be compressed with little pressure whereas gases can be compressed with little pressure because the molecules in a gas are loosely packed.

References

  1. 1 2 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.
  2. 1 2 "Ballistic Armor Glossary - Common Terms, Threats, and Materials". Adept Armor. May 3, 2021. Retrieved May 11, 2022.
  3. Hazell, Paul J. (July 29, 2015). Armour: materials, theory, and design. Boca Raton, FL: CRC Press. ISBN   9781482238303. OCLC   913513740.
  4. Ballistic Armor System, by Goodyear Aerospace Corp, (1967, May 10). US4179979A. Accessed on Nov. 28, 2018. [Online]. Available: Google Patents
  5. Wiley Advances in Ceramic Armor III ACS
  6. Tencate AresShield
  7. Foster Miller Last Armor.