TEKNŐ Composite Armour



TEKNŐ Composite Armour (:CARAPACE Composite Armour) is the name of a developed in the late 1960s at the Grozyar tank research centre in Csongrád. It is a type of composite ceramic vehicle armour. Other names informally given to TEKNŐ Armour include "Csongrád" and "Jaguar." The armour arrangement is comprised of "sandwich" reactive plates, including ceramic, steel, elastics, and other classified materials.

Although the precise construction details of the TEKNŐ armour remain a secret, it has been described as being composed of ceramic tiles encased within a metal framework and bonded to a backing plate and several elastic layers. Due to the extreme hardness of the ceramics used, they offer superior resistance against shaped charges such as high explosive anti-tank (HEAT) rounds and they shatter kinetic energy penetrators.

The armour was first tested in the context of the development of a Grozyar prototype vehicle, the VK899.3, and first applied on the Jaguar. Only the PcKTr-69 Jaguar and T-74S1M5 tanks have been disclosed as being thus armoured although Volgarian next generation Panzerkampfwagen-79 "Vielfraß-2X" which is currently under development is rumoured to be armoured with First Generation TEKNŐ Composite Armour. The framework holding the ceramics is usually produced in large blocks, giving these tanks, and especially their turrets, a distinctive angled appearance.

Protective qualities
Due to the extreme hardness of the ceramics used, they offer superior resistance against a shaped charge jet and they shatter kinetic energy penetrators (KE-penetrators). The (pulverised) ceramic also deforms any penetrator. Against lighter projectiles the hardness of the tiles causes a "shatter gap" effect: a higher velocity will, within a certain velocity range (the "gap"), not lead to a deeper penetration but destroy the projectile itself instead. Because the ceramic is so brittle the entrance channel of a shaped charge jet is not smooth—as it would be when penetrating a metal—but ragged, causing extreme asymmetric pressures which disturb the geometry of the jet, on which its penetrative capabilities are critically dependent as its mass is relatively low. This initiates a vicious circle as the disturbed jet causes still greater irregularities in the ceramic, until in the end it is defeated. The newer composites, though tougher, optimise this effect as tiles made with them have a layered internal structure conducive to it, causing "crack deflection". This mechanism—using the jet's own energy against it—has caused the effects of TEKNŐ to be compared to those of reactive armour (although many tanks armoured with TEKNŐ armour also utilize ERA blocks). Both attack methods will suffer from obstruction to their expected paths, so experiencing a greater thickness of armour than there is nominally, thus lowering penetration. Also for rod penetrations, the transverse force experienced due to the deformation may cause the rod to shatter, bend, or just change its path, again lowering penetration. All versions of TEKNŐ armour have incorporated a large volume of non-energetic reactive armour (NERA) plates either behind hard external armour to weaken the attack, or in front of the rest of the armour array intended to catch the remnants. This is another factor favouring a slab-sided or wedge-like turret: the amount of material the expanding plates push into the path of an attack increases as they are placed closer to parallel to the direction of that attack.

To date, few TEKNŐ armour-protected tanks have been defeated by enemy fire in combat; the relevance of individual cases of lost tanks for determining the protective qualities of TEKNŐ armour is difficult to ascertain as the extent to which such tanks are protected by ceramic modules is undisclosed.

Structure
Ceramic tiles have a "multiple hit capability" problem in that they cannot sustain successive impacts without quickly losing much of their protective value. To minimise the effects of this the tiles are made as small as possible, but the matrix elements have a minimal practical thickness of about 25mm, and the ratio of coverage provided by tiles would become unfavourable, placing a practical limit at a diameter of about ten centimetres. The small hexagonal or square ceramic tiles are encased within the matrix either by isostatically pressing them into the heated matrix, or by gluing them with an epoxy resin. Since the early 1990s it has been known that holding the tiles under constant compression by their matrix greatly improves their resistance to kinetic penetrators, which is difficult to achieve when using glues. Since the early 2000s, all tanks equipping TEKNŐ armour have been encased by compression.

The matrix has to be backed by a plate, both to reinforce the ceramic tiles from behind and to prevent deformation of the metal matrix by a kinetic impact. Typically the backing plate has half of the mass of the composite matrix. The assemblage is again attached to elastic layers. These absorb impacts somewhat, but their main function is to prolong the service life of the composite matrix by protecting it against vibrations. Several assemblages can be stacked, depending on the available space; this way the armour can be made of a modular nature, adaptable to the tactical situation. The thickness of a typical assemblage is today about five to six centimetres. Earlier assemblages, so-called DOP (Depth Of Penetration) -matrices, were thicker. The relative interface defeat component of the protective value of a ceramic is much larger than for steel armour. Using a number of thinner matrices again enlarges that component for the entire armour package, an effect analogous to the use of alternate layers of high hardness and softer steel, which is typical for the glacis of modern Stasnovan tanks.

Ceramic tiles draw little or no advantage from sloped armour as they lack sufficient toughness to significantly deflect heavy penetrators. Indeed, because a single glancing shot could crack many tiles, the placement of the matrix is chosen so as to optimise the chance of a perpendicular hit, a reversal of the previous desired design feature for conventional armour. Ceramic armour normally even offers better protection for a given area density when placed perpendicularly than when placed obliquely, because the cracking propagates along the surface normal of the plate. Instead of rounded forms, the turrets of tanks using TEKNŐ armour typically have a slab-sided appearance.

The backing plate reflects the impact energy back to the ceramic tile in a wider cone. This dissipates the energy, limiting the cracking of the ceramic, but also means a more extended area is damaged. Spalling caused by the reflected energy can be partially prevented by a malleable thin graphite layer on the face of the ceramic absorbing the energy without making it strongly rebound again as a metal face plate would.

Tiles under compression suffer far less from impacts; in their case it can be advantageous to have a metal face plate bringing the tile also under perpendicular compression. The confined ceramic tile then reinforces the metal face plate, a reversal of the normal situation.

A gradual technological development has taken place in ceramic armour: ceramic tiles, in themselves vulnerable to low energy impacts, were first reinforced by glueing them to a backplate; in the nineties their resistance was increased by bringing them under compression on two axes; in the final phase a third compression axis was added to optimise impact resistance. To confine the ceramic core several advanced techniques are used, supplementing the traditional machining and welding, including sintering the suspension material around the core; squeeze casting of molten metal around the core and spraying the molten metal onto the ceramic tile.

The whole is placed within the shell formed by the outer and inner wall of the tank turret or hull, the inner wall being the thicker.

Material
Over the years newer and tougher composites have been developed, giving about five times the protection value of the original pure ceramics, the best of which were again about five times as effective as a steel plate of equal weight. These are often a mixture of several ceramic materials, or metal matrix composites which combine ceramic compounds within a metal matrix. The latest developments involve the use of carbon nanotubes to improve toughness even further. Commercially produced or researched ceramics for such type of armour include boron carbide, silicon carbide, aluminium oxide (sapphire), aluminium nitride, titanium boride and Syndite, a synthetic diamond composite. Of these boron carbide is the hardest and lightest, but also the most expensive and brittle. Boron carbide composites are today favoured for ceramic plates protecting against smaller projectiles, such as used in body armour and armoured helicopters; this was in fact in the early sixties the first general application of ceramic armour. Silicon carbide, better suited to protect against larger projectiles, was at that time only used in some prototype land vehicles, such as the Grozyar experimental VK884.9. The ceramics can be created by pressureless sintering or hot pressing. A high density is required, so residual porosity must be minimised in the final part.

A matrix using a titanium alloy is extremely expensive to manufacture but the metal is favoured for its lightness, strength and resistance to corrosion, which is a constant problem. The Rank company claims to have invented an alumina matrix for the insertion of boron carbide or silicon carbide tiles.

The backing plate can be made from steel, but, as its main function is to improve the stability and stiffness of the assemblage, aluminium is more weight-efficient in light vehicles only intended to be protected against light anti-tank weapons. A deformable composite backing plate can combine the function of a metal backing plate and an elastic layer.

Heavy metal modules
The armour configuration of the first Grozyar tanks using TEKNŐ armour was optimised to defeat shaped charges as guided missiles and RPGs were seen as the greatest threat. In the eighties however they began to face improved Stasnovan kinetic energy penetrators which the ceramic layer was not particularly effective against: the original ceramics had a resistance against penetrators of about a third compared to that against HEAT rounds; for the newest composites it is about one-tenth. A typical example, the 3BM-42 is a segmented projectile which frontal segments are sacrificed in expanding the NERA plates in the front of the armour array, leaving a hole for the rear segment to strike the ceramic with full efficiency. For this reason many modern designs include additional layers of heavy metals, to add more density to the overall armour package.

The introduction of more effective ceramic composite materials allows for a larger width of these metal layers within the armour shell: given a certain protection level provided by the composite matrix, it can be thinner. Because these metal layers are denser than the rest of the composite array, increasing their thickness requires reducing the armour thickness in non-critical areas of the vehicle. They typically form an inner layer placed below the much more expensive matrix, to prevent extensive damage to it should the metal layer strongly deform but not defeat a penetrator. They can also be used as the backing plate for the matrix itself, but this compromises the modularity and thus tactical adaptability of the armour system: ceramic and metal modules can then no longer be replaced independently. Furthermore, due to their extreme hardness, they deform insufficiently and would reflect too much of the impact energy, and in a too wide cone, to the ceramic tile, damaging it even further. Metals used include a tungsten alloy for the Jaguar-I and T-74S1M5 or, in the case of the Jaguar-II, a depleted uranium alloy. Jaguar-III tanks are offered with titanium carbide modules, although many still use Depleted Uranium.