C/C composite oxidation model I. Morphological experimental investigations

A model of the oxidation behaviour of C/C composites was developed. The purpose of the model is to predict the carbon loss that occurs at the outer surface and within the porosity of the composite. It rakes into account the transport of species in the material, chemical gas-gas and gas-solid reactions, the interaction of both transport phenomena and chemistry, the morphological parameters of the unoxidized composite and their evolution due to the consumption of carbon inside the composite. In order to obtain the intrinsic morphological parameters required to document the oxidation model, specific experimental facilities were designed. Two apparatuses for measuring porous solid permeability were designed. For simple oxidation problems where Darcy's law is relevant, a small pressure gradient facility was developed. For mixed oxidation/injection where Darcy's law becomes irrelevant, another facility was designed. A more accurate and complex momentum conservation law including a supplementary intrinsic morphological parameter (Ward number) was studied. A morphological analysis of several C/C composites (from 2D to 3D), before and after oxidation, was realized with the use of standard facilities such as mercury porosimetry, helium pycnometry, image analysis and of permeability devices. The coherence between the morphological parameters determined by all these facilities was checked for uncoated and coated composites. (C) 1999 Elsevier Science Ltd. All rights reserved.