Compound armour

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Compound armour was a type of armour used on warships in the 1880s . By the end of the decade it had been rendered obsolete by nickel-steel armour.

Prior to the 1880s, all naval armour plating was made from uniform homogenous iron or steel plates backed by several inches of teak to absorb the shock of projectile impact. 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 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 them together was solved independently by two Sheffield engineers, A. Wilson of John Brown & Company and J. D. Ellis of Cammell Laird. Wilson's technique, invented in 1877[1], 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 and 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 at Gavre in 1880 found compound armour superior to all-steel plates. An 1884 trial in Copenhagen 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 battleship Lepanto saw 20 inch thick compound armour plate demolished by two shots of the 100-ton guns 10-inch calibre guns which were to be fitted to the ship, whilst the same projectiles were shattered by 20 inches of French Cruesot steel plate.

[edit] References

• Brown, David K. (2003). Warrior to Dreadnought, warship development 1860-1905. Caxton Publishing Group. ISBN 1-84067-529-2.
• Gene Slover's US Navy Pages - Naval Ordnance and Gunnery
• Article on armour plates in 1911 edition of Encyclopedia Britannica

Succession of naval armour technologies:

Iron armour | Steel armour | Compound armour | Harvey armor | Krupp armour | Krupp cemented armour