NET FABRICATION OF GRAPHITE/MAGNESIUM MMC SPACE STRUCTURAL JOINT COMPONENTS WITH BUILT-IN METALLIC INSERTS NET SHAPE FABRICATION OF GRAPHITE/MAGNESIUM MMC SPACE STRUCTURAL JOINT COMPONENTS WITH BUILT-IN METALLIC INSERTS

A LOW-COST MMC FABRICATION METHOD IS PROPOSED FOR NET SHAPE FABRICATION OF SPACE STRUCTURAL JOINTS WITH BUILT-IN METALLIC INSERTS. TWO INNOVATIONS WILL BE DEMONSTRATED DURING PHASE I: (A) LOW COST, REUSABLE TOOLING TO PRESSURE CAST GR/MG COMPONENTS TO NET SHAPE; (B) "BUILT-IN" METALLIC INSERTS IN THE COMPONENT TO PRODUCE STRONG AND RELIABLE MMC JOINTS USING CONVENTIONAL METAL JOINING TECHNIQUES. FOSTER-MILLER HAS PRESSURE CAST GR/AL AND GR/MG COMPONENTS EXHIBITING A COMPLETE PREFORM INFILTRATION AND A CONTROLLED FIBER/MATRIX INTERFACE CHEMISTRY. THE MMC SPECIMENS HAVE SHOWN RULE-OF-MIXTURES MODULUS AND A HIGH STRENGTH (>100 KSI). THE MAJOR ISSUES THAT NEED TO BE RESOLVED TO ENCOURAGE WIDESPREAD UTILIZATION OF MMCS IN SPACE SYSTEMS ARE REDUCING THE COST OF TOOLING AND PROCESSING, AND THE DEVELOPMENT OF JOINING TECHNIQUES FOR MMC COMPONENTS. THE PROPOSED TOOLING WILL SIGNIFICANTLY REDUCE THE COST OF MMC PARTS BY VIRTUE OF ITS REUSABILITY. INCORPORATION OF METALLIC INSERTS WILL ENABLE ASSEMBLY OF THE MMC COMPONENTS USING EXISTING TECHNIQUES SUCH AS WELDING, BOLTING, BRAZING,ETC. A COMPLEX SHAPES GR/MG JOINT COMPONENT WITH METALLIC FITTINGS WILL BE SELECTED, FABRICATED AND EVALUATED DURING PHASE I. THE PROCESS WILL BE OPTIMIZED TO DEMONSTRATE REPEATABILITY IN COMPONENT PROPERTIES DURING THE FOLLOW ON PHASE II EFFORT.