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Armour evolves to match the changing threat: in an age where a guerrilla armed with a recoilless grenade launcher can despatch anything from a main battle tank to a truckload of infantry, William Shakespeare's words *Now thrive the armourers* have never been more true. Armour technologies are evolving to protect everything from the tank to the foot soldier.

The traditional threat that drove the development of vehicle armour was the high-velocity, kinetic-energy projectile fired from enemy tank guns and the shaped-charge warheads fitted to anti-tank guided missiles and infantry-operated recoilless rifles and grenade launchers (RPG). However, combat experience in the counter-insurgency and peace enforcement operations that form most current military operations being conducted by armed forces has shown that armour-piercing bullets fired from rifles or machine guns have become a major threat to the lighter combat vehicles used for these roles, as have the ubiquitous improvised explosive device, or roadside bomb.

As a result, while much of the current developments in armour are aimed at protecting tanks and armoured personnel carriers, there is a growing focus on armour schemes for lighter vehicles, along with improved forms of body armour for personnel.

The most basic type of armour fitted to fighting vehicles is plate metal, usually steel. In main battle tanks, this takes the form of rolled homogeneous armour (RHA), although some lighter vehicles such as the Ml 13 armoured personnel carrier use aluminium.

Perforated steel armour uses plates drilled with a matrix of holes perpendicular to the front surface and less than half the diameter of the anticipated threat projectile. The holes reduce the weight of the armour, but with a minimum penalty in terms of ability to withstand kinetic threats.

Improved Steel

The search for better forms of steel armour continues. Improved steels allow greater protection to be provided for a given weight, or for lighter plates to be fielded while maintaining existing levels of protection.

The German company IBD Deisen-roth Engineering has worked with steel suppliers to develop a new High Strength Nitrogen steel. When tested alongside the existing Armox500Z High Hard Armour steel, this showed that protection against 7.62 x 54R calibre small arms could be achieved using plates of about 70% of the thickness necessary when using the older material.

In 2009 the British Defence Science and Technology Laboratory (DSTL), in collaboration with the Corus company, announced an advanced armour steel called Super Bainite. Manufactured using a process known as isothermal hardening, this does not require the expensive additives normally used to prevent cracking during processing. The new material is created by heating steel to 1000[degrees] C, cooling it to 250[degrees] C, then holding that temperature for eight hours before finally cooling to room temperature.

For applications where the threat forces do not have anti-armour weapons, even commercial-grade steel plate can be pressed into service. For example, Mexican drug gangs are using heavily armoured trucks fitted with steel plate intended to stop small-arms fire. Given the widespread use of'technicals' - trucks fitted with machine guns or light cannonin low-intensity conflicts within the developing world, it will be surprising if armies are not faced with similarly armoured 'technicals' in future insurgencies.

Composite

Composite armour consisting of layers of different material such as metals, plastics, ceramics or air gaps, has proved more effective than steel armour. Ceramic materials are brittle and when used on their own provide only limited protection, but when combined with other materials to create a composite construction, they have proven an effective armour for vehicles or even individual soldiers.

The first example to see widespread service was Combination K. Reported to consist of glass-reinforced plastic sandwiched between inner and outer layers of steel, this was used on the Soviet T-64, which entered service in the mid-to-late 1960s.

British-developed Chobham armour was originally tested on the British FV 4211 experimental tank. It is still classified, but is reported to consist of ceramic tiles encased within a metal matrix and bonded to a backing plate and several elastic layers. It has been used on the Challenger I and II tanks and on the Ml Abrams.

This class of technology may not be needed if the attacker does not have sophisticated anti-armour weapons. In 2004, a disgruntled American citizen fitted home-developed composite armour made from concrete sandwiched between layers of steel to a Komatsu D355 A bulldozer before going on a rampage. Tire armour was up to 300 mm thick and proved impervious to small-arms fire. It is probably only a matter of time before similar vehicles are deployed by drug gangs or insurgents.

Add-ons

Rather than equip vehicles with ever-thicker and heavier steel or aluminium-based armour, armies have adopted various forms of add-on supplementary protection.

One well-known example of add-on passive armour based on composite material is the Modular Expandable Armour System (Mexas). Developed by the German company IBD Deisenroth Engineering, it has been manufactured by Chempro. Hundreds of armour kits have been produced for tracked and wheeled armoured fighting vehicles, and wheeled trucks. Applications include the Leopard 2 tank. Ml 13 and wheeled vehicles such as the Renault 6x6 VAB and the German Fuchs.

The company has fielded its follow-on Advanced Modular Armor Protection (Amap). This is based on advanced steel alloys, aluminium-titanium alloys, nanometric steels, ceramics and nanoceramic materials.

Scientists from the above-mentioned DSTL have developed a ceramic add-on protection system which could be attached to vehicles. Commercially developed as Camac EFP by NP Aerospace in Britain, this has already been fielded in Afghanistan.

The system uses small thimble-sized hexagonal segments of ceramic the size, geometry and arrangement into an array I of which were researched by DSTL. The j individual segments are held together by a moulding resin and packaged in a com posite material with high ballistic per formance, j

The use of add-on panels of explosive reactive armour (ERA) to protect vehicles is well known, but the detonation of such panels can stress the vehicle and pose a risk to nearby infantry. As its name suggests, self-limiting explosive reactive armour (Slera) limits the propagation of the explosive effects, but pays a penalty in slightly reduced performance. It uses a material that can be classified as passive, but which is not as effective as fully delonable explosives. Nevertheless Slera can provide protection against multiple hits.

Non-Explosive Reactive Armour takes this concept a stage further by being passive, offering a similar level of protection: as Slera, and good multiple-hit capability against hollow-charge warheads. Non-Energetic Reactive Armour comes further down the performance scale when attacked by shaped-charge warheads.

Electrics

The most recent development in armour technology for fighting vehicles is active armour based on electrical technology. One form is Spaced Electromagnetic Armour (SEA). This takes the form of two metal plates connected to opposite terminals of a capacitor storage system. If an incoming hollow-charge warhead is detected, the plates are energised, creating a strong electromagnetic field in the gap between the two. When the round strikes, and its detonation creates a plasma penctrator, this is warped and distorted by the electromagnetic field, reducing its effectiveness.

In May 2011 the US Navy was awarded a patent for an armour system consisting of a strain-rate-sensitivity-hardening elastomeric laver sandwiched between two rigid electrically conductive plates. The latter are connected to the opposite outputs of an electrical power supply in order to form an electrical open circuit.

When the armour is struck by a projectile, the circuit between the plates is closed cither by the body of the projectile or by a conductive plasma sheath created in the elastomeric layer by friction of the entering projectile. The elastomeric layer causes * decrease in the projectile's speed and/or change of the projectile's direction and/or degradation of the projectile says the patent. These effects increase the time during which at least a portion of the projectile is situated between the first plate and the second plate, closing the electrical circuit. The resulting electrification further degrades the projectile's performance.

One new concept currently under study is 'smart armour in which transducers embedded within plates of armour would monitor the real-time health of each plate, indicating if a plate was in a satisfactory condition, receiving hostile fire or was damaged. This data would be reported to the vehicle's crew or transmitted back to base so that maintenance crews could get ready to replace the damaged sections upon the vehicle's return.

A team from the US Army's Tank Automotive Research, Development and Engineering Center (Tardec) is planning to take the concept a stage further, by using the data from the transducers to determine the type of projectile striking the plate, or even the direction from which the hostile fire came.

Applied to future form of ERA, embedded sensors could allow a microprocessor-controlled firing mechanism to determine the optimum moment to initiate the armour.

Premature Triggering

Spaced armour uses solid skirts or a network of slats or bars positioned at a stand-off distance from of a vehicle's main armour. These are intended to prematurely initiate the fuze of an incoming Heat warhead. They are also effective against Hesh projectiles. Given the widespread use of weapons in the class of the RPG-7 grenade launcher and its more modern descendants in recent insurgencies, spaced armour is in widespread use in areas such as Afghanistan.

Although relatively light in comparison with a vehicle's primary armour, bar or slat armour increases the vehicle's overall dimensions and degrades mobility and load-capacity. To get around this problem, the British company Amsafe has developed Tarian cloth add-on armour. This takes the form of fabric panels. Similar in effect to slat or bar armour, but between 50 and 85% lighter than metal equivalents, it has been trialled in Afghanistan by the British armed forces. The results persuaded Britain to order 30 kits for further evaluation.

If part of the slats or bars is missing as a result of combat or accidental damage, the main armour is exposed to potential attack. Earlier this year, British units operating in Afghanistan were issued with a solution to this problem in the form of Tarian Quickshield. This takes the form of a flexible mesh that can be unfolded. and then mounted in position over damaged bar armour as a field repair.

The idea that a net can protect a vehicle from RPG-7 fire is not new. During f the Vietnam War, American forces used a net-based RPG screen to protect tanks and armoured personnel carriers. A 1976 US Army document explained the principle: * The nose fuse of the [RPG-7] round can pass through the wire [mesh] without striking a wire strand, but this will bend [the] metal ogive on the warhead against the inner cone. This cone carries the firing signal from the nose fuse to the base detonator and shorts when the ogive touches the cone.[much greater than] This would happen to about 50% of the grenades that strike the mesh, the report stated.

A protective net intended to counter low-intensity threats such as rocket-propelled grenades has been developed by the Netherlands' TNO Defence, Security and Safety laboratory. Made from high-strength synthetic fibres. Constrictor is intended to emulate the Vietnam-era system by damaging the grenade's nose-mounted fuzing system, and preventing the shaped charge from firing.

Personnel

Combat experience in Iraq and Afghanistan has shown that conventional body-armour vests are of limited use when personnel inside vehicles are attacked by RPGs and roadside bombs. While the protection that they offer may allow the soldier to survive an explosion, it leaves the wearer's arms and legs exposed, making limb amputation more common than before the availability of torso armour.

This is a particular problem for commanders surveying the tactical situation from an open cupola hatch, or gunners manning the 0.50-calibre machine guns mounted on vehicle cupolas. In both cases the soldier's arms are exposed to blast effects.

In May 2011 the US Army patented a protective shield that could be mounted around the cupola of a gunner of commander. This would consist of a series of outward-canted panels, each incorporating a ballistic glass window.

These panels would be made from RHA Steel, High Hard Steel aluminium, titanium or composite laminate, while the windows would be made from laminated annealed glass, polycarbonate, poly-urethane, polyvinyl butyral and/or ceramics. Each window would be positioned in front of one of the vehicle's existing observation periscopes so that the latter can still be used when the vehicles are closed, while the outward cant (typically about 25 degrees) is intended to provide additional protection against close threats.

In 2005 Sandia filed a patent for a garment incorporating protective sleeves made of a ballistic fabric and two or more rigid armour inserts that cover the upper and lower arm and protect against high-velocitv projectiles, shrapnel and spall.

The plate protecting the lower arm is designed to cover the hand up to the knuckles, but could be shorter, ending at the wrist to allow a greater range of motion for the hand but leaving the entire hand unprotected.

In 2004 the US Army revealed that it was investigating the use of liquid-filled panels as a new form of armour. These would be filled with a shear thickening fluid (STF) composed of hard particles suspended in a liquid. Polyethylene glycol was seen as a potential liquid, while nano-particles of silica were investigated as the hard component.

To make a practical form of body armour, the STF would be soaked into all the layers of a Kevlar vest. These layers would hold the compound in place, while still serving their normal role as part of the armour-The saturated fabric can be draped and sewn just like normal Kevlar-based material. The resulting panel is light and flexible, preserving the soldier's mobility.

* During normal handling, the STF is very deformable and flows like a liquid, [much greater than] said Dr. Eric Wetzel, a mechanical engineer from the Weapons and Materials Research Directorate. * However, once a bullet or fragment hits the vest, it transitions to a rigid material, which prevents the projectile from penetrating the soldier's body.[much greater than] The material could also protect soldiers or law-enforcement personnel from stab wounds.

A likely first application would be the soldier's arms and legs, which are not protected by ballistic vests. Another is for bomb blankets used to cover suspicious packages or unexploded ordnance. One novel application might be jump boots that stiffen automatically to support the soldier's ankles during potentially damaging impacts.

In 2006 Armor Holdings announced that it had been selected as an exclusive licensee for STF, and in the following year it was acquired by BAE Systems and renamed BAE Systems Mobility & Protection Systems.

Could ERA be used as a body armour for soldiers? The idea seems far-fetched, but in 2002 the Southwest Research Institute of San Antonio, Texas patented what it described as, * A reactive armor system that is effective against armor-piercing projectiles and lightweight enough to be worn by humans[much greater than].

According to the patent, the proposed armour would consist of an outer laver backed by a reactive layer. When the latter explodes in response to a projectile strike, the explosive material is intended to provide sufficient pressure against the back surface of the outer layer to counteract the loading created by the threat projectile, maintaining the outer layer's integrity long enough to delay or preferably prevent fracture of the outer layer by the projectile.

* Delaying fracture of the outer layer results in increasing the amount of time the projectile dwells on the outer layer, thus losing its kinetic energy, and allowing the outer layer to either completely defeat the projectile or cause considerable damage to the incoming projectile, [much greater than] said the patent text. * If the projectile does penetrate the outer layer, it has been reduced in size through erosion and it does so at reduced velocity, making it easier for subsequent layers to stop the projectile.[much greater than]

It's an intriguing concept, but perhaps no one will be willing to give the soldier who is wearing such an armour a pat on the back to indicate "job well done'.
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Title Annotation:Armour technology
Author:Richardson, Doug
Publication:Armada International
Date:Oct 1, 2011
Words:2617
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