SOL-GEL TRANSFER MOLDING OF CERAMIC MATRIX COMPOSITES

THE INNOVATION WE PROPOSE, "SOL-GEL TRANSFER MOLDING" (SGTM), USES A NEW SOL-GEL TECHNIQUE AND A FIBER PREFORM TO PRODUCE NEAR NET-SHAPE, LOW COST, HIGH PERFORMANCE, CERAMIC MATRIX COMPOSITES (CMCS) COST EFFECTIVELY. THIS NEW SOL-GEL PROCESS USES A PROCESSING AID AND AS A RESULT YIELDS CRACK-FREE CERAMIC OXIDES WITH GREATER THAN 90 PERCENT THEORETICAL DENSITY (COMPARED TO ONLY 50 PERCENT FOR CONVENTIONAL SOL-GEL PROCESS). THIS ADDRESSES ALL THE KEY PROBLEMS SUCHAS SHRINKAGE, MICROPOROSITY, AND CRACKING, WHICH HAVE LONG HINDERED THE MORE WIDE-SPREAD USE OF SOL-GEL PROCESS FOR COMPOSITES. OUR APPROACH IS BASED ON "RESIN TRANSFER MOLDING," WIDELY USED IN THE PLASTICS INDUSTRY FOR FIBER REINFORCED COMPOSITES, AND WILL INVOLVE INTRODUCING A LOW VISCOSITY SOL-GEL SOLUTION INTO A SPECIALLY DESIGNED MOLD CONTAINING A FIBER PREFORM. COMPLEX SHAPES WITH MINIMUM POST-PROCESS MACHINING CAN BE MADE BY THIS TECHNIQUE. THE PHASE I WILL DEMONSTRATE THE FEASIBILITY OF THIS TECHNOLOGY BY (A) DESIGNING AND TESTING OF A SOL-GELTRANSFER MOLDING APPARATUS: (B) FABRICATING CYLINDRICAL PARTS OF ONE OXIDE COMPOSITION, (C) CHARACTERIZING THE TOUGHNESS, MICROSTRUCTURE, AND MECHANICAL PROPERTIES OF THE RESULTING COMPOSITES, AND (D) SUGGESTING DESIGN IMPROVEMENTS FOR THE PHASE II PROGRAM. THE PHASE II PROGRAM WILL OPTIMIZE THE PROCESS FOR MAXIMUM STRENGTH, TOUGHNESS AND HIGH TEMPERATURE PERFORMANCE. WE WILL FABRICATE MORE STRENGTH, TOUGHNESS AND HIGH TEMPERATURE PERFORMANCE. WE WILL FABRICATE MORE COMPLEX GEOMETRIES (SUCH AS ROTOR BLADES) USING REINFORCING FIBERS AND TWO CERAMIC MATRICES OF INTEREST TO THE DARPA. THE SUCCESS OF THE PROPOSED APPROACH WILL PROVIDE THE DOD WITH A RAPID, COST-EFFECTIVE MEANS OF PRODUCING HIGH PERFORMANCE COMPLEX GEOMETRY CMCS. ANTICIPATED BENEFITS/POTENTIAL COMMERCIAL APPLICATIONS - THE TECHNOLOGY DEVELOPED UNDER THIS PROPOSED PHASE I PROGRAM WILL LEAD TO HIGH PERFORMANCE, HIGH TEMPERATURE, AND SUBSTANTIALLY IMPROVED