GRAPHITE REINFORCED TITANIUM ALUMINIDES FOR THE AEROSPACE PLANE STRUCTURES

WE PROPOSE TO DEVELOP A HIGH PERFORMANCE GRAPHITE FIBER-REINFORCED TITANIUM ALUMINIDE COMPOSITE MATERIAL, WELL-SUITED FOR AEROSPACE PLANE STRUCTURAL APPLICATIONS. ADVANTAGES OF GRAPHITE FIBERS OVER SIC AS REINFORCEMENT FOR INTERMETALLIC COMPOUNDS INCLUDE: HIGHER STRENGTH, STIFFNESS (USING SPECIALTY GRAPHITE FIBERS); SMALLER FILAMENT DIAMETER - ALLOWING THINNER WALLS AND MORE COMPLEX SHAPES; LOWER COST. THESE ADVANTAGES OF GR FIBERS CAN BE EXPLOITED IN THE NATIONAL AEROSPACE PLANE (NASP) PROGRAM AFTER DEMONSTRATION OF SUCCESSFUL FABRICATION OF GR REINFORCED INTERMETALLICS. DURING PHASE I, THE PRINCIPAL PROCESSING RELATED PROBLEMS FOR GR/TIAL SYSTEMS WILL BE ALLEVIATED THROUGH THE FOLLOWING TECHNIQUES: FIBER SURFACE REACTION WITH INTERMETALLIC MATRIX - THROUGH PROPRIETARY COATINGS. CTE MISMATCH BETWEEN FIBER AND MATRIX PHASES - USING "COMPLIANT" FIBER COATINGS. POOR FLOW CHARACTERISTICS OF INTERMETALLIC MATRIX (AT REASONABLE TEMPERATURE) - THROUGH INCLUSION OF A PHASE WITH A LOW MELTING POINT. DURING PHASE II, A THOROUGH PARAMETRIC STUDY WILL BE CONDUCTED INVESTIGATING THE EFFECT OF PROCESSING CONDITIONS ON IMC QUALITY AND MECHANICAL PROPERTIES. ALSO, SPECIMENS WITH ULTRATHIN WALL SECTIONS (T=0.005 IN.) WILL BE FABRICATED AND EVALUATED AGAINST CURRENT HIGH TEMPERATURE MATERIALS. DEMONSTRATING THE SUPERIORITY OF THIS MATERIAL OVER CURRENT TECHNOLOGY WILL ESTABLISH A FIRM BASIS FOR A COMMERCIALLY SUPPORTED PHASE III PROGRAM.