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Compound armour was a type of
armour Armour (Commonwealth English) or armor (American English; see American and British English spelling differences#-our, -or, spelling differences) is a covering used to protect an object, individual, or vehicle from physical injury or damage, e ...
used on
warship A warship or combatant ship is a naval ship that is used for naval warfare. Usually they belong to the navy branch of the armed forces of a nation, though they have also been operated by individuals, cooperatives and corporations. As well as b ...
s in the 1880s, developed in response to the emergence of
armor-piercing shell Armour-piercing ammunition (AP) is a type of projectile designed to penetrate armour protection, most often including naval armour, body armour, and vehicle armour. The first, major application of armour-piercing projectiles was to defeat th ...
s and the continual need for reliable protection with the increasing size in naval ordnance. Compound armour was a non-alloyed attempt to combine the benefits of two different metals—the hardness of steel with the toughness of iron—that would stand up to intense and repeated punishment in battle. By the end of the decade it had been rendered obsolete by
nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...
-steel armour. However, the general principle of compound iron was used for case-hardened armour, which replaced nickel-steel in the mid-1890s and is still used today.


Prior armours

Prior to the 1880s, all naval armour plating was made from uniform homogeneous
wrought iron Wrought iron is an iron alloy with a very low carbon content (less than 0.05%) in contrast to that of cast iron (2.1% to 4.5%), or 0.25 for low carbon "mild" steel. Wrought iron is manufactured by heating and melting high carbon cast iron in an ...
plates on top of several inches of
teak Teak (''Tectona grandis'') is a tropical hardwood tree species in the family Lamiaceae. It is a large, deciduous tree that occurs in mixed hardwood forests. ''Tectona grandis'' has small, fragrant white flowers arranged in dense clusters (panic ...
to absorb the shock of projectile impact. A typical installation consisted of several inches of equal measures of iron and wood (typically teak), with a combined thickness of up to 4ft in the most extreme cases. Various experiments were carried out in order to improve the armour, which included breaking up the armour into a laminate of several thinner layers of iron with wood between them, as well as various experiments with cast vs. wrought iron. In all of these experiments, simple blocks of wrought iron consistently proved to provide the best protection. There had been several attempts to improve on iron with the addition of harder steels on the face, but these all failed for the same reason as the earlier laminate experiments; the ability for the armour to spread sideways into its softer backing allowed it to be penetrated more easily. In the case of steel facing, the problem was that the steel would not adhere well to the underlying iron, allowing it to shift or separate entirely. The first compound armour were designed by the Austrian engineer Friedrich Thiele. The monitor ships SMS Leitha and the SMS Maros were equipped with these armours. In 1876 a competition was held by the
Italian Navy The Italian Navy (; abbreviated as MM) is one of the four branches of Italian Armed Forces and was formed in 1946 from what remained of the ''Regia Marina'' (Royal Navy) after World War II. , the Italian Navy had a strength of 30,923 active per ...
at Spezia to trial new armours. By that point conventional iron armours had to be thick to stop contemporary naval artillery. The decisive winner was a new soft steel from the French firm of Schneider et Cie, but this proved to be prone to breakage when stressed, making it less useful in naval applications.


Compound armour

Compound armour was made from two different types of steel; a very hard but brittle high-carbon steel front plate backed by a more
elastic Elastic is a word often used to describe or identify certain types of elastomer, Elastic (notion), elastic used in garments or stretch fabric, stretchable fabrics. Elastic may also refer to: Alternative name * Rubber band, ring-shaped band of rub ...
low-carbon wrought iron plate. The front plate was intended to break up an incoming shell, whilst the rear plate would catch any splinters and hold the armour together if the brittle front plate shattered. Steel plates positioned in front of iron plates had been tried unsuccessfully, for example in a trial by the Italian Navy at Spezia in 1876. The problem of
welding Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, primarily by using high temperature to melting, melt the parts together and allow them to cool, causing Fusion welding, fusion. Co ...
them together was solved independently by two
Sheffield Sheffield is a city in South Yorkshire, England, situated south of Leeds and east of Manchester. The city is the administrative centre of the City of Sheffield. It is historically part of the West Riding of Yorkshire and some of its so ...
engineers, A. Wilson of
John Brown & Company John Brown and Company of Clydebank was a Scottish Naval architecture, marine engineering and shipbuilding firm. It built many notable and world-famous ships including , , , , , and ''Queen Elizabeth 2 (ship), Queen Elizabeth 2''. At its heig ...
and J. D. Ellis of
Cammell Laird Cammell Laird is a British shipbuilding company. It was formed from the merger of Laird Brothers of Birkenhead and Johnson Cammell & Co of Sheffield at the turn of the twentieth century. The company also built railway rolling stock until 1929, ...
. Wilson's technique, invented in 1877, was to pour molten steel onto a wrought iron plate, whilst Ellis' was to position the two plates close together and pour molten steel into the gap. In both cases, the plate formed was rolled down to about half of the original thickness. The steel front surface formed about one-third of the thickness of the plate. Compound armour was initially much better than either iron or steel plates, about a 25% improvement. Throughout the decade continuous improvements were made in techniques for manufacturing both compound armour and steel armour. Nevertheless by the end of the decade all-steel plates had decisively edged ahead of compound armour, and the latter had become obsolete. Two major reasons for this were the introduction of forged chrome-steel shot in 1886 and the discovery of nickel-steel alloys in 1889 which proved particularly effective as armour plate. For instance, a trial by the
French Navy The French Navy (, , ), informally (, ), is the Navy, maritime arm of the French Armed Forces and one of the four military service branches of History of France, France. It is among the largest and most powerful List of navies, naval forces i ...
at Gâvres in 1880 found compound armour superior to all-steel plates. An 1884 trial in
Copenhagen Copenhagen ( ) is the capital and most populous city of Denmark, with a population of 1.4 million in the Urban area of Copenhagen, urban area. The city is situated on the islands of Zealand and Amager, separated from Malmö, Sweden, by the ...
found that there was little difference between the two types, although compound armour was subsequently ordered by the Danish Navy, probably because it was cheaper. At the same time a similar trial to select the armour of the Italian
ironclad An ironclad was a steam engine, steam-propelled warship protected by iron armour, steel or iron armor constructed from 1859 to the early 1890s. The ironclad was developed as a result of the vulnerability of wooden warships to explosive or ince ...
saw compound armour plate demolished by two shots of the 10-inch calibre guns which were to be fitted to the ship, whilst the same projectiles were shattered by 20 inches of French Creusot steel plate.


References


Sources


''Armor and Ships: Journal of the United States Artillery'' (Fort Monroe, Virginia: Coast Artillery School Press, 1910), Issue 80, July-August 1906. At Google Books. Accessed 13 April 2012.
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Chapter XII, Armor {{Naval armour Naval armour