Military vehicles are commonly
armour
Armour (British English
British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specificall ...
ed (or armored;
see spelling differences) to withstand the impact of
shrapnel
Shrapnel may refer to:
Military
* Shrapnel shell, explosive artillery munitions, generally for anti-personnel use
* Shrapnel (fragment), a hard loose material
Popular culture
* ''Shrapnel'' (Radical Comics)
* ''Shrapnel'', a game by Adam ...
,
bullet
A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. Bullets are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax. Bullets are made in various shapes and ...
s,
shells,
rocket
A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entire ...
s, and
missile
In military terminology, a missile is a missile guidance, guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously ...
s, protecting the personnel inside from enemy fire. Such vehicles include
armoured fighting vehicle
An armoured fighting vehicle (AFV) is an armed combat vehicle protected by armour, generally combining operational mobility with offensive and defensive capabilities. AFVs can be wheeled or tracked. Examples of AFVs are tanks, armoured ca ...
s like
tank
A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and good battlefield mobility provided by tracks and a powerful e ...
s,
aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. ...
, and
ship
A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguishe ...
s.
Civilian vehicles may also be armoured. These vehicles include cars used by
officials (e.g.,
presidential limousines),
reporters and others in conflict zones or where violent crime is common. Civilian
armoured cars are also routinely used by security firms to carry money or valuables to reduce the risk of
highway
A highway is any public or private road or other public way on land. It is used for major roads, but also includes other public roads and public tracks. In some areas of the United States, it is used as an equivalent term to controlled-access ...
robbery
Robbery is the crime of taking or attempting to take anything of value by force, threat of force, or by use of fear. According to common law, robbery is defined as taking the property of another, with the intent to permanently deprive the perso ...
or the
hijacking of the cargo.
Armour may also be used in vehicles to protect from threats other than a deliberate attack. Some
spacecraft
A spacecraft is a vehicle or machine designed to spaceflight, fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth ...
are equipped with specialised armour to protect them against impacts from
micrometeoroids or fragments of
space debris. Modern aircraft powered by
jet engine
A jet engine is a type of reaction engine discharging a fast-moving jet (fluid), jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include Rocket engine, rocket, Pump-jet, water jet, and ...
s usually have them fitted with a sort of armour in the form of an
aramid composite kevlar
Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s ...
bandage around the fan casing or debris containment walls built into the casing of their
gas turbine engines to prevent injuries or
airframe
The mechanical structure of an aircraft is known as the airframe. This structure is typically considered to include the fuselage, undercarriage, empennage and wings, and excludes the propulsion system.
Airframe design is a field of aero ...
damage should the fan, compressor, or
turbine blades break free.
The
design
A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process or the result of that plan or specification in the form of a prototype, product, or process. The verb ''to design'' ...
and purpose of the vehicle determines the amount of armour plating carried, as the plating is often very heavy and excessive amounts of armour restrict mobility. In order to decrease this problem, some new materials (
nanomaterials) and material compositions are being researched which include
buckypaper, and
aluminium foam armour plates.
Materials
Metals
Steel
''
Rolled homogeneous armour'' is strong, hard, and tough (does not shatter when struck with a fast, hard blow). Steel with these characteristics are produced by processing
cast steel billets of appropriate size and then rolling them into plates of required thickness. Rolling and forging (hammering the steel when it is red hot) irons out the grain structure in the steel, removing imperfections which would reduce the strength of the steel. Rolling also elongates the
grain structure
A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains.
Bacillite is a type of crystallite. It is rodlike with parallel longulites.
Stru ...
in the steel to form long lines, which enable the stress the steel is placed under when loaded to flow throughout the metal, and not be concentrated in one area.
Aluminium
''
Aluminium
Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...
'' is used when light weight is a necessity. It is most commonly used on
APCs and
armoured cars. While certainly not the strongest metal, it is cheap, lightweight, and tough enough that it can serve as easy armour.
Iron
Wrought ''
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
'' was used on
ironclad warship
An ironclad is a steam engine, steam-propelled warship protected by Wrought iron, iron or steel iron armor, armor plates, constructed from 1859 to the early 1890s. The ironclad was developed as a result of the vulnerability of wooden warships ...
s. Early European iron armour consisted of 10 to 12.5 cm of wrought iron backed by up to one meter of solid
wood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of ligni ...
. It has since been supplemented by steel due to steel being significantly stronger.
Titanium
Titanium
Titanium is a chemical element with the Symbol (chemistry), symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resista ...
has almost twice the density of aluminium, but can have a yield strength similar to high strength steels, giving it a high specific strength. It also has a high specific resilience and specific toughness. So, despite being more expensive, it finds an application in areas where weight is a concern, such as
personal armour and
military aviation
Military aviation comprises military aircraft and other flying machines for the purposes of conducting or enabling aerial warfare, including national airlift ( air cargo) capacity to provide logistical supply to forces stationed in a war thea ...
. Some notable examples of its use include the
USAF
The United States Air Force (USAF) is the Aerial warfare, air military branch, service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part ...
A-10 Thunderbolt II
The Fairchild Republic A-10 Thunderbolt II is a single-seat, twinjet, twin-turbofan, straight wing, straight-wing, Subsonic aircraft, subsonic attack aircraft developed by Fairchild Aircraft, Fairchild Republic for the United States Air Force ...
and the Soviet/Russian-built
Sukhoi Su-25 ground-attack aircraft, utilising a bathtub-shaped titanium enclosure for the pilot, as well as the Soviet/Russian
Mil Mi-24
The Mil Mi-24 (russian: Миль Ми-24; NATO reporting name: Hind) is a large helicopter gunship, attack helicopter and low-capacity troop transport with room for eight passengers. It is produced by Mil Moscow Helicopter Plant and has be ...
attack helicopter.
Uranium
Because of its high density,
depleted uranium
Depleted uranium (DU; also referred to in the past as Q-metal, depletalloy or D-38) is uranium with a lower content of the fissile isotope than natural uranium.: "Depleted uranium possesses only 60% of the radioactivity of natural uranium, ...
can also be used in tank armour, sandwiched between sheets of steel armour plate. For instance, some late-production
M1A1HA and M1A2 Abrams tanks built after 1998 have DU reinforcement as part of the armour plating in the front of the hull and the front of the turret, and there is a program to upgrade the rest (see
Chobham armour).
Plastic
''Plastic metal'' was a type of vehicle armour originally developed for
merchant ship
A merchant ship, merchant vessel, trading vessel, or merchantman is a watercraft that transports cargo or carries passengers for hire. This is in contrast to pleasure craft, which are used for personal recreation, and naval ships, which ar ...
s by the
British Admiralty in 1940. The original composition was described as 50% clean
granite
Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies und ...
of half-inch size, 43% of
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...
mineral, and 7% of
bitumen. It was typically applied in a layer two inches thick and backed by half an inch of
steel.
Plastic armour was highly effective at stopping
armour piercing bullet
Armour-piercing ammunition (AP) is a type of projectile designed to penetrate either body armour or vehicle armour.
From the 1860s to 1950s, a major application of armour-piercing projectiles was to defeat the thick armour carried on many wars ...
s because the hard granite particles would deflect the bullet, which would then lodge between plastic armour and the steel backing plate. Plastic armour could be applied by pouring it into a cavity formed by the steel backing plate and a temporary wooden form.
Some main battle tank (MBT) armour utilises polymers, for example polyurethane as used in the "BDD" applique armour applied to modernized
T-62 and
T-55
The T-54 and T-55 tanks are a series of Soviet main battle tanks introduced in the years following the Second World War. The first T-54 prototype was completed at Nizhny Tagil by the end of 1945.Steven Zaloga, T-54 and T-55 Main Battle T ...
.
Glass
Bulletproof glass is a colloquial term for
glass
Glass is a non-Crystallinity, crystalline, often transparency and translucency, transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most ...
that is particularly resistant to being penetrated when struck by
bullet
A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. Bullets are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax. Bullets are made in various shapes and ...
s. The industry generally refers to it as ''bullet-resistant glass'' or ''transparent armour''.
Bullet-resistant glass is usually constructed using a strong but
transparent material such as
polycarbonate thermoplastic
A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.
Most thermoplastics have a high molecular weight. The polymer chains associat ...
or by using layers of
laminated glass. The desired result is a material with the appearance and light-transmitting behaviour of standard glass, which offers varying degrees of protection from
small arms fire.
The polycarbonate layer, usually consisting of products such as Armormax,
Makroclear, Cyrolon,
Lexan or Tuffak, is often sandwiched between layers of regular glass. The use of plastic in the laminate provides impact-resistance, such as physical assault with a hammer, an axe, etc. The plastic provides little in the way of bullet-resistance. The glass, which is much harder than plastic, flattens the bullet and thereby prevents penetration. This type of bullet-resistant glass is usually 70–75 mm (2.8–3.0 in) thick.
Bullet-resistant glass constructed of laminated glass layers is built from glass sheets bonded together with
polyvinyl butyral,
polyurethane
Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethan ...
or
ethylene-vinyl acetate. This type of bullet-resistant glass has been in regular use on
combat vehicles since
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
; it is typically about 100–120 mm (3.9–4.7 in) thick and is usually extremely heavy.
Newer materials are being developed. One such,
aluminium oxynitride, is much lighter but at US$10–15 per square inch is much more costly.
Ceramic
Ceramic
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, porcelai ...
's precise mechanism for defeating
HEAT
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...
was uncovered in the 1980s. High speed photography showed that the ceramic material shatters as the HEAT round penetrates, the highly energetic fragments destroying the geometry of the metal jet generated by the
hollow charge, greatly diminishing the penetration. Ceramic layers can also be used as part of composite armour solutions. The high hardness of some ceramic materials serves as a disruptor that shatters and spreads the
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its a ...
of projectiles.
Composite
Composite armour is armour consisting of layers of two or more materials with significantly different physical properties;
steel and
ceramic
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, porcelai ...
s are the most common types of material in composite armour.
Composite armour was initially developed in the 1940s, although it did not enter service until much later and the early examples are often ignored in the face of newer armour such as
Chobham armour. Composite armour's effectiveness depends on its composition and may be effective against
kinetic energy penetrators as well as
shaped charge
A shaped charge is an explosive charge shaped to form an explosively formed penetrator (EFP) 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, init ...
munition
Ammunition (informally ammo) is the material fired, scattered, dropped, or detonated from any weapon or weapon system. Ammunition is both expendable weapons (e.g., bombs, missiles, grenades, land mines) and the component parts of other weapo ...
s;
heavy metals
upright=1.2, Crystals of lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead
Heavy metals are generally defined as metals with relatively high density, densities, atomi ...
are sometimes included specifically for protection from kinetic energy penetrators.
Composite armour used on modern Western and Israeli main battle tanks largely consists of non-explosive reactive armour (NERA) elements - a type of
Reactive armour. These elements are often a laminate consisting of two hard plates (usually high hardness steel) with some low density interlayer material between them. Upon impact, the interlayer swells and moves the plates, disrupting heat 'jets' and possibly degrading kinetic energy projectiles. Behind these elements will be some backing element designed to stop the degraded jet or projectile element, which may be of high hardness steel, or some composite of steel and ceramic or possibly uranium.
Soviet main battle tanks from the
T-64 onward utilised composite armour which often consisted of some low density filler between relatively thick steel plates or castings, for example
Combination K. For example, the T-64 turret front and cheek was originally filled with aluminum, and then ceramic balls and aluminum, whilst some models of the
T-72
The T-72 is a family of Soviet/Russian main battle tanks that entered production in 1969. The T-72 was a development of the T-64, which was troubled by high costs and its reliance on immature developmental technology. About 25,000 T-72 tanks ...
features a glass filler called "Kvartz". The tank
glacis
A glacis (; ) in military engineering is an artificial slope as part of a medieval castle or in early modern fortresses. They may be constructed of earth as a temporary structure or of stone in more permanent structure. More generally, a glaci ...
was often a sandwich of steel and some low density filler, either textolite (a
fibreglass reinforced polymer) or ceramic plates. Later T-80 and T-72 turrets contained NERA elements, similar to those discussed above.
Ships
Belt armour is a layer of armour-plating outside the
hull (watercraft)
A hull is the watertight body of a ship, boat, or flying boat. The hull may open at the top (such as a dinghy), or it may be fully or partially covered with a deck. Atop the deck may be a deckhouse and other superstructures, such as a funnel, ...
of warships, typically on
battleships,
battlecruiser
The battlecruiser (also written as battle cruiser or battle-cruiser) was a type of capital ship of the first half of the 20th century. These were similar in displacement, armament and cost to battleships, but differed in form and balance of at ...
s,
cruisers and some
aircraft carriers.
Typically, the belt covers from the deck down someway below the
waterline
The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line (positioned amidships), that ind ...
of the ship. If built within the hull, rather than forming the outer hull, it can be fitted at an inclined angle to improve the protection.
When struck by a
shell or
torpedo
A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, s ...
, the belt armour is designed to prevent penetration, by either being too thick for the warhead to penetrate, or sloped to a degree that would deflect either projectile. Often, the main belt armour was supplemented with a
torpedo bulkhead spaced several meters behind the main belt, designed to maintain the ship's watertight integrity even if the main belt were penetrated.
The air-space between the belt and the hull also adds
buoyancy
Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...
. Several wartime vessels had belt armour that was thinner or shallower than was desirable, to speed production and conserve resources.
''Deck armour'' on aircraft carriers is usually at the
flight deck level, but on some early carriers was at the
hangar deck. (See
armoured flight deck.)
Aircraft
Armour plating is not common on aircraft, which generally rely on their speed and manoeuvrability to avoid attacks from enemy aircraft and ground fire, rather than trying to resist impacts. Additionally, any armour capable of stopping large-calibre anti-aircraft fire or missile fragments would result in an unacceptable weight penalty. So, only the vital parts of an aircraft, such as the
ejection seat and engines, are usually armoured. This is one area where titanium is used extensively as armour plating. For example, in the American
Fairchild Republic A-10 Thunderbolt II
The Fairchild Republic A-10 Thunderbolt II is a single-seat, twin-turbofan, straight-wing, subsonic attack aircraft developed by Fairchild Republic for the United States Air Force (USAF). In service since 1976, it is named for the Republic ...
and the Soviet-built
Sukhoi Su-25 ground attack aircraft, as well as the
Mil Mi-24
The Mil Mi-24 (russian: Миль Ми-24; NATO reporting name: Hind) is a large helicopter gunship, attack helicopter and low-capacity troop transport with room for eight passengers. It is produced by Mil Moscow Helicopter Plant and has be ...
Hind ground-attack helicopter, the pilot sits in a titanium enclosure known as the "bathtub" for its shape. In addition, the windscreens of larger aircraft are generally made of impact-resistant,
laminated materials, even on civilian craft, to prevent damage from
bird strike
A bird strike—sometimes called birdstrike, bird ingestion (for an engine), bird hit, or bird aircraft strike hazard (BASH)—is a collision between an airborne animal (usually a bird or bat) and a moving vehicle, usually an aircraft. The term ...
s or other debris.
Armoured fighting vehicles
The most heavily armoured vehicles today are the
main battle tank
A main battle tank (MBT), also known as a battle tank or universal tank, is a tank that fills the role of armor-protected direct fire and maneuver in many modern armies. Cold War-era development of more powerful engines, better suspension s ...
s, which are the spearhead of the ground forces, and are designed to withstand
anti-tank guided missile
An anti-tank guided missile (ATGM), anti-tank missile, anti-tank guided weapon (ATGW) or anti-armor guided weapon is a guided missile primarily designed to hit and destroy heavily armored military vehicles. ATGMs range in size from shoulder ...
s,
kinetic energy penetrators,
high-explosive anti-tank weapons,
NBC threats and in some tanks even steep-trajectory shells. The
Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
i
Merkava tanks were designed in a way that each tank component functions as added back-up armour to protect the crew. Outer armour is modular and enables quickly replacing damaged parts.
Layout
For efficiency, the heaviest armour on an
armoured fighting vehicle
An armoured fighting vehicle (AFV) is an armed combat vehicle protected by armour, generally combining operational mobility with offensive and defensive capabilities. AFVs can be wheeled or tracked. Examples of AFVs are tanks, armoured ca ...
(AFV) is placed on its front. Tank tactics require the vehicle to always face the likely direction of enemy fire as much as possible, even in
defence
Defense or defence may refer to:
Tactical, martial, and political acts or groups
* Defense (military), forces primarily intended for warfare
* Civil defense, the organizing of civilians to deal with emergencies or enemy attacks
* Defense indust ...
or
withdrawal
Withdrawal means "an act of taking out" and may refer to:
* Anchoresis (withdrawal from the world for religious or ethical reasons)
* '' Coitus interruptus'' (the withdrawal method)
* Drug withdrawal
* Social withdrawal
* Taking of money from ...
operations.
Sloping and curving armour can both increase its protection. Given a fixed thickness of armour plate, a projectile striking at an
angle
In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the '' vertex'' of the angle.
Angles formed by two rays lie in the plane that contains the rays. Angles ...
must penetrate more armour than one impacting
perpendicular
In elementary geometry, two geometric objects are perpendicular if they intersect at a right angle (90 degrees or π/2 radians). The condition of perpendicularity may be represented graphically using the ''perpendicular symbol'', ⟂. It can ...
ly. An angled surface also increases the chance of deflecting a projectile. This can be seen on
v-hull designs, which direct the force of an
Improvised explosive device
An improvised explosive device (IED) is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery shell, attached to a detonating mecha ...
or
landmine away from the crew compartment, increasing crew
survivability.
Spall liners
Beginning during the Cold War, many AFVs have ''spall liners'' inside of the armour, designed to protect crew and equipment inside from fragmentation (spalling) released from the impact of enemy shells, especially
high-explosive squash head warheads. Spall liners are made of
Kevlar
Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s ...
,
Dyneema,
Spectra Shield, or similar materials.
Appliqué
Appliqué armour, or add-on armour, consists of extra plates mounted onto the hull or turret of an AFV. The plates can be made of any material and are designed to be retrofitted to an AFV to withstand weapons that can penetrate the original armour of the vehicle.
An advantage of appliqué armour is the possibility to tailor a vehicle's protection level to a specific threat scenario.
Improvised
Vehicle armour is sometimes improvised in the midst of an armed conflict by vehicle crews or individual units. In
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, British, Canadian and Polish tank crews welded spare strips of tank track to the hulls of their
Sherman tanks.
[Moran, Michael]
"Frantically, the Army tries to armour Humvees: Soft-skinned workhorses turning into death traps,"
''MSNBC'', April 15, 2004. U.S. tank crews often added sand bags in the hull and turrets on Sherman tanks, often in an elaborate cage made of girders. Some Sherman tanks were up-armoured in the field with glacis plates and other armour cut from knocked-out tanks to create ''Improvised Jumbos'', named after the heavily armoured
M4A3E2
}
The M4 Sherman, officially Medium Tank, M4, was the most widely used medium tank by the United States and Western Allies in World War II. The M4 Sherman proved to be reliable, relatively cheap to produce, and available in great numbers. I ...
assault tank. In the
Vietnam War
The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...
, U.S. "
gun trucks" were armoured with sandbags and locally fabricated
steel armour plate.
[Gardiner, Paul S]
"Gun Trucks: Genuine Examples of American Ingenuity,"
''Army Logistician'', PB 700-03-4, Vol. 35, No. 4, July–August 2003, Army Combined Arms Support Command, Fort Lee, Virginia. More recently,
U.S. troops in Iraq armoured
Humvees and various military transport vehicles with scrap materials: this came to be known as "
hillbilly armour" or "haji armour" by the Americans.
Moreover, there was the
Killdozer incident, with the modified bulldozer being armoured with steel and concrete composite, which proved to be highly resistant to small arms.
Spaced
Armour with two or more plates spaced a distance apart, called spaced armour, has been in use since the
First World War
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fig ...
, where it was used on the
Schneider CA1 and
Saint-Chamond tanks. Spaced armour can be advantageous in several situations. For example, it can reduce the effectiveness of
kinetic energy penetrators because the interaction with each plate can cause the round to tumble, deflect, deform, or disintegrate. This effect can be enhanced when the armour is
sloped. Spaced armour can also offer increased protection against
HEAT
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...
projectiles. This occurs because the
shaped charge
A shaped charge is an explosive charge shaped to form an explosively formed penetrator (EFP) 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, init ...
warhead can detonate prematurely (at the first surface), so that the metal jet that is produced loses its coherence before reaching the main armour and impacting over a broader area. Sometimes the interior surfaces of these hollow cavities are sloped, presenting angles to the anticipated path of the shaped charge's jet in order to further dissipate its power. Taken to the extreme, relatively thin armour plates, metal mesh, or
slatted plates, much lighter than fully protective armour, can be attached as side skirts or turret skirts to provide additional protection against such weapons. This can be seen in
middle and late-World War II German tanks, as well as many modern
AFVs. Taken as a whole, spaced armour can provide significantly increased protection while saving weight.
The analogous
Whipple shield uses the principle of spaced armour to protect spacecraft from the impacts of very fast
micrometeoroids. The impact with the first wall melts or breaks up the incoming particle, causing fragments to be spread over a wider area when striking the subsequent walls.
Sloped
Sloped armour is armour that is mounted at a non-vertical and non-horizontal angle, typically on tanks and other armoured fighting vehicles. For a given normal to the surface of the armour, its plate thickness, increasing armour slope improves the armour's level of protection by increasing the thickness measured on a horizontal plane, while for a given area density of the armour the protection can be either increased or reduced by other sloping effects, depending on the armour materials used and the qualities of the projectile hitting it. The increased protection caused by increasing the slope while keeping the plate thickness constant, is due to a proportional increase of area density and thus mass, and thus offers no weight benefit. Therefore, the other possible effects of sloping, such as deflection, deforming and ricochet of a projectile, have been the reasons to apply sloped armour in armoured vehicles design. Another motive is the fact that sloping armour is a more efficient way of covering the necessary equipment since it encloses less volume with less material. The sharpest angles are usually seen on the frontal glacis plate, both as it is the hull side most likely to be hit and because there is more room to slope in the longitudinal direction of a vehicle.
Reactive
''Explosive reactive armour'', initially developed by German researcher Manfred Held while working in Israel, uses layers of
high explosive
An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An e ...
sandwiched between steel plates. When a shaped-charge warhead hits, the explosive
detonates and pushes the steel plates into the warhead, disrupting the flow of the charge's liquid metal penetrator (usually
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...
at around 500 degrees Celsius; it can be made to flow like water by sufficient pressure). Traditional "light" ERA is less effective against kinetic penetrators. "Heavy" reactive armour, however, offers better protection. The only example currently in widespread service is Russian
Kontakt-5. Explosive reactive armour poses a threat to friendly troops near the vehicle.
''Non-explosive reactive armour'' is an advanced spaced armour which uses materials which change their geometry so as to increase protection under the stress of impact.
''
Active protection systems'' use a sensor to detect an incoming projectile and explosively launch a counter-projectile into its path.
Slat
Slat armour is designed to protect against
anti-tank rocket and missile attacks, where the warhead is a
shaped charge
A shaped charge is an explosive charge shaped to form an explosively formed penetrator (EFP) 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, init ...
. The slats are spaced so that the warhead is either partially deformed before detonating, or the fuzing mechanism is damaged, thereby preventing detonation entirely. As shaped charges rely on very specific structure to create a jet of hot metal, any disruption to this structure greatly reduces the effectiveness of the warhead.
Slat armour can be defeated by
tandem-charge designs such as the
RPG-27 and
RPG-29.
Electric armour
Electric armour is a recent development in the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
by the
Defence Science and Technology Laboratory.
A vehicle is fitted with two thin shells, separated by insulating material. The outer shell holds an enormous
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respecti ...
, while the inner shell is at ground. If an incoming HEAT jet penetrates the outer shell and forms a bridge between the shells, the electrical energy discharges through the jet, disrupting it. Trials have so far been extremely promising, and it is hoped that improved systems could protect against KE penetrators. The developers of the
Future Rapid Effect System (FRES) series of armoured vehicles are considering this technology.
See also
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Active protection system
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Armoured fighting vehicle
An armoured fighting vehicle (AFV) is an armed combat vehicle protected by armour, generally combining operational mobility with offensive and defensive capabilities. AFVs can be wheeled or tracked. Examples of AFVs are tanks, armoured ca ...
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Armoured forces
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Main battle tank
A main battle tank (MBT), also known as a battle tank or universal tank, is a tank that fills the role of armor-protected direct fire and maneuver in many modern armies. Cold War-era development of more powerful engines, better suspension s ...
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Non-military armoured vehicles
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Personal armour
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Plastic armour
References
External links
Electrically charged armourModern armoured vehicles
{{DEFAULTSORT:Vehicle armour
Armoured warfare
History of the tank