Kanchan armor is a composite armor also called sandwich armor. During the initial days, India had approached the British to co-develop a composite armor. British armor research was based in British tank research centre on Chobham Common, the reason the generic name Chobham armor for all such type of composite armor. The British were not favorable to the Indian proposal.
Development of a composite armor was earnestly taken up at Armour Design & Development Division at the Defence Metallurgical Research Laboratory (DMRL), Kanchan Bagh, Hyderabad. Like the British name Chobham, Kanchan Armor got its name from Kanchan Bagh.
Kanchan Armor uses the same principle as the Chobham armor, but the composition is different. It has Rolled Homogenous Armor (RHA) and composites. RHA is a type of steel sheet used as protection for the armored vehicles since World War II. Kanchan Armor has a composite panel sandwiched between RHA. The number of layers is decided based on the user requirement.
When a projectile is fired, the armor stops it via compression and de-compression method. As the projectile hits the armor, it faces compression because of the RHA, and then it faces decompression because of the composite. When the projectile passes through several such sandwiched layers, it breaks up the APFDS or HEAT shot. A HESH shot is ineffective against a spaced armor. It definitely will not go through a layered armor.
In 1980’s the Kanchan composite had a composition of ceramic, alumina, fiber glass and some other such materials mixed. The RHA tried out had two thicknesses, i.e. a 350 mm plate and a 315 m plate. However these two plates had the same weight as a 120mm RHA. Hence it is said that Kanchan armor is more volume at same weight. The anti-tank munitions have problems in penetrating denser mass.
This is the time when the Russian Tank T-72 imported by Indian Army could not penetrate the Kanchan Armor protected Arjun Tank , with APFDS at point blank range. Subsequently, the debate took place if the Russians had supplied us with training rounds rather than the actual ammunition. As a side note, in January 2000 at Proof & Experimental Establishment (PXE), Balasore, Arjun tank armor defeated all available HESH and FSAPDS rounds including Israeli FSAPDS rounds.
Back to 1980’s, after the T-72 incident, a 106 mm RCL gun was tried on the Arjun Tank. 106 RCL’s were effective anti-tank weapons those days. It played havoc on enemy tanks in 1971 war. The Kanchan armor defeated that too.
Kanchan armor composition has undergone massive changes since 1980’s. The volume of the RHA has been reduced to lesser mass because of better metallurgy. The composite has evolved too and it does not use the 1980’s technology anymore.