Carbon Oxidation in Extreme Environments

The oxidation of carbon fi ers commonly proceeds through a characteristic surface consumption mode referred to as pitting(1-6) (see Fig. 1): rather than consuming the surface uniformly, oxidation proceeds preferentially through the growth in depth of multiple cavities scattered on the originally smooth surface of the fi er. This phenomenon, which has also been observed in the corrosion behavior of other materials such as aluminum(7-10), results in a net in- crease of the exposed surface, which, in addition, is formed of highly reactive sites. Both effects accelerate the rate of oxidation, making it potentially dangerous because the fi er's strength is seriously compromised. Furthermore, we hypothesize that this may lead to the early break-up of the fi ers, reducing dramatically the protecting properties. It is therefore crucial to understand and model this phenome- non in order to be capable of predicting both the protective and mechanical behavior of these materials.