Reinforced carbon-carbon
From Wikipedia, the free encyclopedia
Reinforced Carbon-Carbon (carbon-carbon or RCC) is a composite material consisting of carbon fiber reinforcement in a matrix of graphite, often with a silicon carbide coating to prevent oxidation. It was developed for the nose cones of intercontinental ballistic missiles, and is most widely known as the material for the nose cone and leading edges of the space shuttle. The Brabham team pioneered its use in the brakes of Formula One racing cars in 1976, and more recently it has also appeared in the brakes of some high end supercars, such as the Bugatti Veyron.
Carbon-carbon is well-suited to structural applications at high temperatures, or where thermal shock resistance and/or a low coefficient of thermal expansion is needed. While it is less brittle than many other ceramics, it lacks impact resistance; Space Shuttle Columbia was destroyed after one of its RCC panels was broken by the impact of a piece of foam insulation from the Space Shuttle External Tank. This was a catastrophic failure partly because original shuttle design requirements did not consider such a violent impact to be likely.
[edit] Production
The material is made in three stages:
First, material is laid up in its intended final shape, with carbon filament and/or cloth surrounded by an organic binder such as plastic or pitch. Often, coke or some other fine carbon aggregate is added to the binder mixture.
Second, the lay-up is heated, so that pyrolysis transforms the binder to relatively pure carbon. The binder loses volume in the process, so that voids form; the addition of aggregate reduces this problem, but does not eliminate it.
Third, the voids are gradually filled by forcing a carbon-forming gas such as acetylene through the material at a high temperature, over the course of several days. This long heat treatment process also allows the carbon to form into larger graphite crystals, and is the major reason for the material's high cost, exceeding $100,000 per panel.
