Thanks to all the members of the NDA Discussion for their help in this article.
Whenever you read about modern tanks then the term "Chobham armour" comes up time and again. The way the term is generally used makes it sound like all Chobham armour is equal. Its not. Its also very hard to prove or research, as most governments have spent a considerable time keeping the exact composition a secret, some with less success than others. So this little article may contain much that is speculation, or picked up from bits of information that is fragmentary.
And now for some speculation, there are a few files in an archive here in the UK which are still closed under the national security clause. They're part of Project Prodigal, and come from the atomic weapons research establishment and are talking about defeating projectiles. The interesting thing is the date on these files starts in 1950. It may well be this is the birth of modern composite armours. Anyway the first official work on what was to become the first of the Chobham family, then named "Burlington" started around 1960 or 1961, although the exact date is hard to pin point. Over the next fifteen years a lot of research was done. In 1971 the British started to share some, but not all, of their research with West Germany and the United States. The data given to Germany had an immediate effect on their new tank design, the Leopard 2.
T-72 Glacis plates, with their siliceous-core insets. The Polish army did look at removing the inserts and putting a more advanced armour type in, which would probably have been called Chobham by the press, even though it had no direct link.
Finally the British were about to start construction of phase 3 FV4030 Shir tanks for Iran. This was equipped with armour called Pageant, although that seems to have been identical to Burlington. The size of the construction order meant that more and more people would be exposed to the secrets. All these factors combined with the risk of losing the prestige of this development meant that the British decided to make an announcement on 15th June 1976 to NATO about the special armour. The day before they decided to give Iran, Germany and the United States a warning that they were going to make the announcement, to prevent them from stealing the British thunder. The following day there was to be a press release.
One of the earlier mentioned security breaches is rumoured to be a sample of the armour stolen from a West German lab in 1975. Its rumoured that elements of that sample influenced the T-80B's armour. However one big difference is the T-80 doesn't have the square sided look of modern western MBT's, so its unlikely it's the same armour.
Other changes include the US taking their version of the special armour and adding in layers of depleted uranium, there have been at least two upgrade packages in this. It also explains why US tanks have been heavier than their British counterparts. The British themselves continued to develop Burlington into Dorchester armour.
Of course all the above is likely to be in part wrong. As wrong as the experts who are quoted in this 1980's article on the M1 tank. Its well worth a read, just for some of the Chrysler responses.
media.moddb.com and www.panzerpower.de