THIN-WALLED METAL MATRIX COMPOSITES FOR SPACECRAFT APPLICATIONS

GRAPHITE-MAGNESIUM AND GRAPHITE-ALUMINUM MMCS ARE IDEAL MATERIALS FOR SPACECRAFT APPLICATIONS OWING TO THEIR HIGH STRENGTH AND STIFFNESS, LIGHT WEIGHT, NO OUT-GASSING, GOOD THERMAL AND ELECTRICAL CONDUCTIVITY, AND RESISTANCE TO THE SPACE ENVIRONMENT. CONTINUOUSLY REINFORCED, THIN-WALLEDMETAL MATRIX PARTS WILL BE PARTICULARLY USEFUL IN SPACECRAFT AS STIFF, DIMENSIONALLY STABLE STRUCTURAL MEMBERS. THINNER PARTS WILL PERMIT MORE EFFICIENT DESIGNS, RESULTING IN REDUCED WEIGHT, INCREASED PAYLOAD, AND HIGHER STRUCTURAL RESONANCES. CONTINUOUS REINFORCEMENT WILL ALLOW DESIGN OF ZERO CTE STRUCTURES FOR INCREASED DIMENSIONAL STABILITY OVER WIDER TEMPERATURE RANGES AND MORE ACCURATE POINTING ANGLES FOR REFLECTORS AND ANTENNAE. TO TAKE FULL ADVANTAGE OF MMCS, THIN-WALLED CONTINUOUSLY REINFORCED PARTS OF COMPLEX SHAPE ARE REQUIRED.A PARTICULARLY URGENT NEED IS FOR STIFF DIMENSIONALLY STABLE JOINTS FOR TUBULAR TRUSS MEMBERS IN LARGE SPACE STRUCTURES. WE PROPOSE A TECHNIQUE FOR PRODUCING SUCH MMC PARTS USING VERY THIN PREFORMS, FOLLOWED BY PRESSURE CASTING. PHASE I WILL EVALUATE THE FEASIBILITY OF PRODUCING THIN-WALLED TUBULAR PREFORMS (0.005 IN.) USING SPREAD TOWS OF GRAPHITE, THEN INFILTRATING THE PREFORM WITH AN ALUMINUM ALLOY USING A SPECIALLY ADAPTED PRESSURIZED SHELL MOLD CASTING TECHNIQUE. THIS WORK WILL FORM THE FOUNDATION FOR MORE COMPLEX JOINT STRUCTURES, LARGE COMPONENTS, AND OTHER ALLOYS OF ALUMINUM AND MAGNESIUM.