Composite Armour

Composite armour is a type of vehicle armour consisting of layers of different material such as metals, plastics, ceramics or air. Most composite armours are lighter than their all-metal equivalent, but instead occupy a larger volume for the same resistance to penetration. It is possible to design composite armour stronger, lighter and less voluminous than traditional armour, but the cost is often prohibitively high, restricting its use to especially vulnerable parts of a vehicle. Its primary purpose is to help defeat high explosive anti-tank (HEAT) rounds.

HEAT had posed a serious threat to armoured vehicles since its introduction in World War II. Lightweight and small, HEAT rounds could nevertheless penetrate hundreds of millimetres of the hardest steel armours. The capability of most materials for defeating HEAT follows the "density law", which states that the penetration of shaped charge jets is proportional to the square root of the shaped charge liner density (typically copper) divided by the square root of the target density. On a weight basis, lighter targets are more advantageous than heavier targets, but using large quantities of lightweight materials has obvious disadvantages in terms of mechanical layout. Certain materials have a sweet spot in terms of density that makes them particularly useful in this role.