MATRIX ALLOY DEVELOPMENT FOR GRAPHITE/ALUMINUM SPACE STRUCTURES

THE USE OF GRAPHITE/MAGNESIUM COMPOSITES FOR SPACE STRUCTURES WITH ZERO THERMAL EXPANSION CHARACTERISTICS HAS BEEN HAMPERED BY THE HYSTERESIS CAUSED BY MATRIX YIELDING. THIS HYSTERESIS HAS BEEN ELIMINATED IN LABORATORY SAMPLES BY HEAT TREATING THE COMPOSITE TO OBTAIN A MATRIX YIELD STRENGTH IN EXCESS OF 40 KSI FOR ALUMINUM MATRIX COMPOSITES. THE REQUIRED HEAT TREATMENT WILL BE IMPRACTICAL WHEN LARGE (15 METER LONG TUBES) STRUCTURES ARE MANUFACTURED. THIS PROJECT WILL DEVELOP A NON HEAT-TREATABLE MATRIX ALLOY FOR GRAPHITE/ MAGNESIUM COMPOSITES THAT WILL HAVE A HIGH ENOUGH YIELD STRENGTH TO ELIMINATE HYSTERESIS AFTER MODIFIED HEAT TREAT CYCLES. THE COMPOSITES WILL BE MADE WITH THE DWG PROCESS THAT RESULTS IN IMPROVED INFILTRATION AND MINISTRUCTURE COMPARED WITH PRESENT TECHNIQUES. THIS TECHNIQUE CAN EASILY USE MATRIX ALLOYS WITH MODIFICATIONS THAT IMPROVE FIBER WETTING. THE PHASE I EFFORT WILL DEFINE USEFUL MATRIX ALLOYS COMBINATIONS AS WELL AS PRODUCE 8-INCH BY 8-INCH BY 8-PLY COMPOSITE PLATES WHICH EXHIBIT LOW THERMAL EXPANSION WITH ZERO HYSTERESIS. THE IMPROVEMENT IN FIBER DISTRIBUTION AND MATRIX WETTING WILL BE DEMONSTRATED. THE PHASE II EFFORT WILL TRANSLATE THE MATRIX ALLOY TECHNOLOGY INTO 4-FOOT TUBE STRUCTURES WITH A FIBER ORIENTATION TO PRODUCE ZERO (OR NEGATIVE) THERMAL EXPANSION WITH ZERO HYSTERESIS.