PRESSURE CASTING FOR NEAR-NET SHAPE PRODUCTION OF LOW COST GRAPHITE MAGNESIUM SPACE STRUCTURES

THE FEASIBILITY IS BEING DETERMINED OF A LOW-COST, METAL MATRIX COMPOSITE (MMC) FABRICATION TECHNIQUE FOR NEAR-NET SHAPE FABRICATION OF SPACE STRUCTURAL JOINTS THAT WOULD INVOLVE FABRICATION OF A CUSTOM-TAILORED FIBER PREFORM AND A SPECIALIZED MOLD FOLLOWED BY INFILTRATION WITH MOLTEN MAGNESIUM ALLOY. INCORPORATION OF LOW-COST MATERIALS, TOOLING, AND PROCESSING WOULD MAKE THE PROCESS ECONOMICAL AS COMPARED TO CONTEMPORARY MMC FABRICATION METHODS. PRESSURIZATION DURING INFILTRATION WOULD ALLOW A HIGHER FIBER CONTENT AND THINNER WALLS THAN CONVENTIONAL VACUUM-ASSISTED LIQUID METAL INFILTRATION. A COMPLEX-SHAPE TRUSS JOINT COMPONENT IS BEING FABRICATED AND EVALUATED SUB-SCALE, WITH FIBER CONTENT ABOVE 55 PERCENT BY VOLUME AND WALL THICKNESS AROUND 0.010 IN. TO O.020 IN. WHEN SUCCESSFUL, LIGHTWEIGHT SPACE TRUSS JOINTS AND ULTRA HIGH SPECIFIC STIFFNESS AND STRENGTH, ZERO COEFFICIENT OF THERMAL EXPANSION, GOOD HARDNESS AGAINST DIRECTED ENERGY WEAPONS, NO OUTGASSING, AND EXCELLENT RESISTANCE TO SPACE ENVIRONMENT COULD BE PRODUCED ECONOMICALLY. LOWERING THE COST OF HIGHPERFORMANCE GRAPHITE-MAGNETISUM MMCS WOULD PROMOTE SEVERAL COMMERCIAL APPLICATIONS THAT REQUIRE HIGH STRENGTH AND STIFFNESS COMBINED WITH LIGHT WEIGHT AND HIGH TEMPERATURE CAPABILITY, INCLUDING AUTOMOTIVE ENGINE BLOCKS, CONNECTING RODS, FLYWHEELS, AND HELICOPTER JOINTS/FITTINGS.