IMPROVED OXIDATION RESISTANCE OF 3-D CARBON/CARBON COMPOSITES

THE COATING OF CARBON FIBERS WITH SILICON CARBIDE OFFERS ENHANCED OXIDATION RESISTANCE FOR CARBON/CARBON COMPOSITES. RESEARCH TO FORM A THIN, UNIFORM, COHERENT LAYER ON FIBERS IN A TOW, TAPE, OR 3-D PREFORM IS DESCRIBED. THE RESEARCH INVOLVES THE USE OF AN ADVANCED POLYCARBOSILANE POLYMER WHICH CAN BE CONVERTED TO SILICON CARBIDE. SUPERCRITICAL FLUIDS WILL BE USED TO DISSOLVE THE PRECURSOR POLYMER. A SUPERCRITICAL SOLUTION, BECASUE OF ITS ADVANTAGEOUS TRANSPORT AND SURFACE TENSION PROPERTIES, CAN BE PENETRATE MICROCHANNELS SUCH AS THOSE IN A TIGHTLY PACKED TOW, TAPE, OR 3-D PREFORM. DEPOSITION CONDITIONS TO PRODUCE THE THIN COATING WILL BE DEVELOPED. AFTER COATING, THE POLYMER WILL BE CROSS-LINKED AND PYROLYZED TO SILICON CARBIDE, AND OXIDATION RESISTANCE OF COATED CARBON FIBERS OR PREFORMS WILL BE MEASURED AND COMPARED TO UNCOATED CARBON FIBERS OR PREFORMS. AS A MEANS OF ASSESSING THE VALUE OF THE PHASE II EFFORT, AND ECONOMIC VIABILITY EVALUATION OF THE PROCESS FOR IMPROVED COATED CARBON FIBERS WILL BE MADE ON THE PHASE I PROGRAM.