Thermo-mechanical analysis of oxidation resistant carbon-carbon composites. Technical final report, February 1992-April 1995

The objective of this program was to develop a methodology for investigating the thermo-mechanical interactions between coatings and substrates in advanced oxidation resistant carbon-carbon composites. This methodology was to be utilized to suggest thermomechanically compatible material solutions for reducing the susceptibility of these materials to oxidation attack, or for controlling the rate of oxygen influx to the substrate by controlling the development of microcracks in the primary oxygen barrier - the external CVD coating. At any temperature, the oxidation rate of carbon-carbon composites is controlled by the oxidation rate of the base substrate and by the rate at which oxygen reaches the substrate via defects (cracks) in the external coating. Current, and proposed, advanced carbon-carbon oxygen protection systems seek to extend oxidation life by modifying both controlling mechanisms, i.e., by active and passive substrate oxidation inhibition concepts, and by active and passive crack management concepts. Substrate inhibition concepts which have been utilized, or proposed, include: particulate matrix inhibitors, matrix modifiers, matrix, crack fillers, and fiber coatings. Coating crack management concepts have included: crack sealers, multi-layer coatings, modified interface layers, and thermal cycling.