Reinforced carbon-carbon

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 catastrophic failure was due in part to original shuttle design requirements which did not consider the likelihood of such violent impacts.

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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.

RCC is a generally hard material that can be made highly resistant to thermal expansion, temperature gradients, and thermal cycling, depending on how the fiber scaffold is laid up and the quality/density of the matrix filler.

Mechanical Properties

The strength of carbon-carbon with unidirectional reinforcement fibres is up to 700MPa. Carbon-carbon materials retain their properties above 2000C. ^[1]

References

See also

• Atmospheric reentry