Chobham armour
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f3/XM-1_Abrams_during_a_demonstration_on_the_test_range_of_Fort_Knox%2C_1979.jpg/300px-XM-1_Abrams_during_a_demonstration_on_the_test_range_of_Fort_Knox%2C_1979.jpg)
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.
Within the
Although the construction details of the Chobham 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. Owing 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 British prototype vehicle, the FV4211, and first applied on the preseries of the American M1. Only the M1 Abrams, Challenger 1, Challenger 2, and K1 88-Tank[1] have been disclosed as being thus armoured. The framework holding the ceramics is usually produced in large blocks,[citation needed] giving these tanks, and especially their turrets, a distinctive angled appearance.
Protective qualities
Due to the extreme hardness of the ceramics used, the tiles offer superior resistance against a shaped charge jet and they shatter kinetic energy penetrators (KE-penetrators). The (pulverised) ceramic also strongly abrades 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 instead.[2]
Because the ceramic is so
This should not be confused with the effect used in
All versions of Chobham armour have incorporated a large volume of non-energetic reactive armour (NERA) plates, with added hard armour ahead of the NERA (intended to protect the NERA elements and disrupt the penetrator before it encounters the NERA) and/or behind the NERA (intended to catch the fragments of long rods or HEAT jets after they have been fractured or disrupted by the front plate and NERA. 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.[4]
To date, few Chobham 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 Chobham armour is difficult to ascertain as the extent to which such tanks are protected by ceramic modules is undisclosed.[citation needed]
During the second Iraq war in 2003, a Challenger 2 tank became stuck in a ditch while fighting in Basra against Iraqi forces. The crew remained safe inside for many hours, the Burlington LV2 composite armour protecting them from enemy fire, including multiple rocket propelled grenades.[5]
Structure
Ceramic tiles have a multiple hit capability problem in that they cannot sustain successive impacts without quickly losing much of their protective value.[6] 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 25 mm (approximately one inch), and the ratio of coverage provided by tiles would become unfavourable, placing a practical limit at a diameter of about ten centimetres (approximately four inches). The small hexagonal or square ceramic tiles are encased within the matrix either by isostatically pressing them into the heated matrix,[7] 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.[8]
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.[9] 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 modular, to be replaceable, and more adaptable to varied tactical situations. The thickness of a typical assemblage is today about five to six centimetres. Earlier assemblages, so-called depth of penetration (DOP) 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 Soviet tanks.
Ceramic tiles draw little or no advantage from
The backing plate reflects the impact energy back to the ceramic tile in a wider cone. This dissipates the energy, limiting the
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 gluing 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.[11] 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.[12]
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
A matrix using a
The backing plate can be made from
Heavy metal modules
The armour configuration of the first western tanks using Chobham armour was optimised to defeat
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.[16] They typically form an inner layer placed below the much more costly matrix,[17] 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 Challenger 2[18] or, in the case of the M1A1HA (Heavy Armor) and later American tank variants, a depleted uranium alloy.[19] Some companies offer titanium carbide modules.
These metal modules function on the principle of perforated armour (typically employing perpendicular rods), with many expansion spaces reducing the weight by up to one third while keeping the protective qualities fairly constant. The depleted uranium alloy of the M1 has been described as "arranged in a type of armour matrix"[20] and a single module as a "stainless-steel shell surrounding a layer (probably an inch or two thick) of depleted uranium, woven into a wire-mesh blanket".[21]
Such modules are also used by tanks not equipped with Chobham armour. The combination of a composite matrix and heavy metal modules is sometimes informally referred to as "second generation Chobham".[22]
Development and application
The concept of ceramic armour goes back to 1918, when Major Neville Monroe Hopkins discovered that a plate of ballistic steel was much more resistant to penetration if covered with a thin (1–2 millimetres) layer of enamel.[23][24] Further, the Germans experimented with ceramic armour in World War I.[25]
Since the early 1960s there were, in the US, extensive research programmes ongoing aimed at investigating the prospects of employing composite ceramic materials as vehicle armour.[26] This research mainly focused on the use of an aluminium metal matrix composite reinforced by silicon carbide whiskers, to be produced in the form of large sheets.[27] The reinforced light metal sheets were to be sandwiched between steel layers.[28] This arrangement had the advantage of having a good multiple-hit capability and of being able to be curved, allowing the main armour to benefit from a sloped armour effect. However, this composite with a high metal content was primarily intended to increase the protection against KE-penetrators for a given armour weight; its performance against shaped charge attack was mediocre and would have to be improved by means of a laminate spaced armour effect, as researched by the Germans within the joint MBT-70 project.[29]
An alternative technology developed in the US was based on the use of glass modules to be inserted into the main armour;[28] although this arrangement offered a better shaped charge protection, its multiple hit capability was poor. A similar system using glass inserts in the main steel armour was from the late fifties researched for the Soviet Obiekt 430 prototype of the T-64;[30] this was later developed into the "Combination K" type, having a ceramic compound mixed with the silicon oxide inserts, which offered about 50% better protection against both shaped charge and KE-penetrator threats, relative to steel armour of the same weight.[31] It was, later in several improved forms, incorporated into the glacis of many subsequent Soviet main battle tank designs. After an initial period of speculation in the West as to its true nature, the characteristics of this type were disclosed when the dissolution of the Soviet Union in 1991 and the introduction of a market system forced the Russian industries to find new customers by highlighting its good qualities;[32] it is today rarely referred to as Chobham armour. Special armour much more similar to Chobham appeared in 1983 under the name of BDD on the T-62M upgrade to the T-62, was first integrated to an armour array in 1986 on the T-72B, and has been a feature of every Soviet/Russian MBT since. In its original iteration, it is built directly into the cast steel turret of the T-72 and required lifting it to perform repairs.[33]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/9f/MBT-80_ATR2_drawing.png/300px-MBT-80_ATR2_drawing.png)
In the United Kingdom another line of ceramic armour development had been started in the early 1960s, meant to improve the existing cast turret configuration of the
However, on 11 December 1974 a Memorandum of Understanding was signed between the Federal Republic of Germany and the US about the common future production of a main battle tank; this made any application of Chobham armour dependent on the eventual choice for a tank type. Earlier in 1974 the Americans had asked the Germans to redesign the existing Leopard 2 prototypes, considered by them too lightly armoured, and had suggested adoption of Burlington for this purpose, of which type the Germans had already been informed in March 1970; the Germans however in response in 1974 initiated a new armour development programme of their own.[39] Having already designed a system that in their opinion offered satisfactory protection against shaped charges, consisting of multiple-laminate spaced armour with the spaces filled with ceramic polystyrene foam[40] as fitted to the Leopard 1A3, they put a clear emphasis on improving KE-penetrator protection, reworking the system into a perforated metal module armour.[citation needed] A version with added Burlington was considered, including ceramic inserts in the various spaces, but rejected as it would push vehicle weight well over sixty metric tonnes, a weight then seen as prohibitive by both armies.[41] The US Army in the summer of 1974 faced the choice between the German system and their own Burlington, a decision made more difficult because Burlington offered, relative to steel armour, no weight advantage against KE-penetrators:[42] the total armour system would have a RHA equivalence against them of about 350 mm (compared to about 700 mm against shaped charges).[43] No consensus developing, General Creighton Abrams himself decided the issue in favour of Burlington.[44] Eventually each army procured its own national tank design, the project of a common tank failing in 1976. In February 1978 the first tanks protected by Burlington left the factory when the first of eleven pilot M1 tanks were delivered by Chrysler Corporation to the US Army.
Beside these state projects, private enterprise in the US during the 1970s also developed ceramic armour types, like the Noroc armour made by the Protective Products Division of the
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/61/M1-A1_Abrams_1.jpg/300px-M1-A1_Abrams_1.jpg)
In the United Kingdom application of Chobham armour was delayed by the failure of several advanced tank projects: first that of a joint German-British main battle tank; then the purely British
In France from 1966
The latest version of Chobham armour is used on the Challenger 2 (called Dorchester armour), and (though the composition most probably differs) the M1 Abrams series of tanks, which according to official sources is currently protected by
Though it is often claimed to be otherwise, the original production model of the Leopard 2 did not use Chobham armour,
Future and replacements
In the future, Chobham armour is to be replaced by Epsom armour, while Dorchester is to be replaced with Farnham armour. The first tank to abandon Chobham and Dorchester in favour of Epsom and Farnham armour will be the Challenger 3.[52] Whether the MoD will permit Epsom and Farnham for export and licensed production is yet to be determined.
Aerospace applications
The first ceramic plates found application in the aerospace sector: in 1965, the helicopter
See also
Notes
- ^ Lett, Philip (January 1988). International Defense Review 1/1988: Korea's Type 88 comes of age. Janes.
{{cite book}}
: CS1 maint: date and year (link) - ^ Chang, Albert L. and Bodt Barry E., "JTCG/AS Interlaboratory Ballistic Test Program – Final Report", Army Research Laboratory – TR-1577 – December 1977 p. 12
- ^ Chan, H. M., "Layered ceramics: processing and mechanical behavior", Annu Rev Mater Sci 1997; 27: p. 249–82
- ^ United Kingdom Ministry of Defence, "Feasibility study of Burlington (Chobham armour) fitted to Chieftain tank – WO 194/1323 – 1969
- ^ "Dragoon guards survive ambush". 2 April 2003. Archived from the original on 24 July 2017. Retrieved 7 February 2015.
- ^ W. S. de Rosset and J. K. Wald, "Analysis of Multiple-Hit Criterion for Ceramic Armor", US Army Research Laboratory TR-2861, September 2002
- ^ Bruchey, W., Horwath, E., Templeton, D. and Bishnoi, K.,"System Design Methodology for the Development of High Efficiency Ceramic Armors", Proceedings of the 17th International Symposium on Ballistics, Volume 3, Midrand, South Africa, March 23–27, 1998, p.167-174
- ^ Hauver, G. E., Netherwood, P. H., Benck, R. F. and Kecskes, L. J., 1994, "Enhanced Ballistic Performance of Ceramics", 19th Army Science Conference, Orlando, Florida, June 20–24, 1994, p. 1633-1640
- ^ V. Hohler, K. Weber, R. Tham, B. James, A. Barker and I. Pickup, "Comparative Analysis of Oblique Impact on Ceramic Composite Systems", International Journal of Impact Engineering 26 (2001) p. 342
- ^ D. Yaziv1, S. Chocron, C. E. Anderson, Jr. and D. J. Grosch, "Oblique Penetration in Ceramic Targets", 19th International Symposium of Ballistics, 7–11 May 2001, Interlaken, Switzerland TB27 p. 1264
- ^ Yiwang Bao, Shengbiao Su, Jianjun Yang, Qisheng Fan, "Prestressed ceramics and improvement of impact resistance", Materials Letters 57 (2002) p. 523
- ^ Chu, Henry S.; McHugh, Kevin M. and Lillo, Thomas M., "Manufacturing Encapsulated Ceramic Armor System Using Spray Forming Technology" Publications Idaho National Engineering and Environmental Laboratory, Idaho Falls, 2001
- ^ a b c S.G. Savio, K. Ramanjaneyulu, V. Madhu & T. Balakrishna Bhat, 2011, "An experimental study on ballistic performance of boron carbide tiles", International Journal of Impact Engineering 38: 535-541
- ^ S. Yadav and G. Ravichandran, "Penetration resistance of laminated ceramic/polymer structures", International Journal of Impact Engineering, 28 (2003) p. 557
- ^ Chen Mingwei, McCauley James W & Hemker Kevin J. 2003. "Shock induced localized amorphization in boron carbide". Science 299: 1563-1566
- ^ Lakowski, Paul, Armor Basics, p. 1
- ^ Clancy 1994, p. 65.
- ^ Claessen, Luitenant-kolonel A.H.J., Tanks & Pantserwagens – De Technische Ontwikkeling, Blaricum, 2003, p. 96
- ^ Zaloga & Sarson 1993, p. 13.
- ^ Gelbart, Marsh, Tanks – Main Battle Tanks and Light Tanks, London 1996, p. 126
- ^ Clancy 1994, p. 61.
- ^ Gelbart, Marsh, Tanks – Main Battle Tanks and Light Tanks, London 1996, p. 114
- ^ Hazell, P.J. (2010), "Sviluppi nel settore delle corazzature ceramiche", Rivista Italiana Difesa, 5: 36-44
- ^ "Archived copy" (PDF). Archived (PDF) from the original on 16 August 2016. Retrieved 29 June 2012.
{{cite web}}
: CS1 maint: archived copy as title (link) - ^ "DSpace Angular Universal".
- ^ Hanby, K.R., Fiber-Reinforced Metal-Matrix Composites-1967, Defense Metals Information Center DMIC-S-21, MCIC-005839 PL-011311 MMC-700204
- ^ Kolkowitz, W. and Stanislaw, T.S., "Extrusion and Hot Rolling – Two Advanced Fabrication Techniques for the Preparation of Whisker-Metal Composites", Proceedings of the 14th National Symposium and Exhibit, Vol. 14 – 'Advanced Techniques for Material Investigation and Fabrication', 5-7 Nov 68, Cocoa Beach, Florida, Paper No. 11-4A-3
- ^ a b c Zaloga & Sarson 1993, p. 5.
- ^ Trinks, Walter, "Hohlladungen und Panzerschutz – Ihre wechselweise weiterentwicklung", Jahrbuch der Wehrtechnik 8, 1974, p. 156
- ^ Soviet/Russian Armor and Artillery Design Practices, p. 88
- ^ Soviet/Russian Armor and Artillery Design Practices, p. 92
- ^ Soviet/Russian Armor and Artillery Design Practices, p. 164-169
- ^ Journal of Military Ordnance – "T-72B MBT – The First Look at Soviet Special Armor", 2002, pp. 4-8
- ^ Thomas H. Flaherty (1991), The Armored Fist – New Face of War, Time Life Education, p. 82
- ^ Kelly 1989, p. 111.
- ^ Long, D., Modern Ballistic Armor – Clothing, Bomb Blankets, Shields, Vehicle Protection, Boulder 1986, pp. 82-84
- ^ House of Commons, Debates of 11 November 1976, vol. 919 cc272-3W
- ^ Zaloga & Sarson 1993, p. 6.
- ^ Spielberger Walter J., Von der Zugmachine zum Leopard 2, München 1980, p.230
- ^ Van Zelm, G. and Fonck B.A., "Leopard-1 Gevechtstank", De Tank, Juni 1991 p. 53
- ^ Claessen, Luitenant-kolonel A.H.J., Tanks & Pantserwagens – De Technische Ontwikkeling, Blaricum, 2003, p. 95
- ^ Clancy 1994, p. 5.
- ^ Zaloga & Sarson 1993, p. 9–10.
- ^ Kelly 1989, p. 13–43.
- ^ Duncan Crow and Robert J. Icks, Encyclopedia of Tanks, p. 75, Barrie & Jenkins, London 1975
- ^ Griffin 2001, p. 155.
- ^ Griffin 2001, p. 156.
- ^ Griffin 2001, p. 157.
- ^ Richard Strickland, Jane's Armour & Artillery Upgrade, 2004-2005, p 143, London 2005
- ^ Clancy 1994, p. 298.
- ^ a b Marc Chassillan, (2005); Char Leclerc: De la guerre froide aux conflits de demain, Editions ETAI
- ^ "@ChurchillsOwn". Twitter. Retrieved 13 March 2023.
- ^ P. J. Hazell, RID, May 2010, Sviluppi nel settore delle corazzature ceramiche
References
- Clancy, Tom (1994). Armored Cav – a guided Tour of an Armored Cavalry Regiment. Berkley Books, New York. ISBN 9780425158364.
- Griffin, Rob (2001). Chieftain. The Crowood Press, Ramsbury.
- Hull, Andrew W; Markov, David R.; Zaloga, Steven J. (2000). Soviet/Russian Armor and Artillery Design Practices: 1945 to Present. Darlington Productions, Darlington. ISBN 9781855322837.
- Kelly, Orr (1989). King of the Killing Zone. New York, New York: W. W. Norton & Company. ISBN 0-425-12304-9.
- ISBN 1-85532-283-8.
Further reading
Jeffrey J. Swab (Editor), Dongming Zhu (General Editor), Waltraud M. Kriven (General Editor); Advances in Ceramic Armor: A Collection of Papers Presented at the 29th International Conference on Advanced Ceramics and Composites, January 23–28, 2005, Cocoa Beach, Florida, Ceramic Engineering and Science Proceedings, Volume 26, Number 7;