DEVELOPMENT OF ELECTROMAGNETIC INDUCTION HEATING FOR FUSION OF ADVANCED THERMOPLASTIC GRAPHITE FIBER COMPOSITES

MANUFACTURING PROBLEMS INVOLVED WITH THE FUSION AND COMPACTION OF ADVANCED THERMOPLASTIC-GRAPHITE PRECURSOR TAPE IN CONSTRUCTION OF COMPOSITE STRUCTURES HAVING CONTOURED SHAPES HAS SERIOUSLY RETARDED THE ACCEPTANCE OF THESE HIGH PERFORMANCE MATERIALS BY INDUSTRY. THE 700 TO 800 DEG F FUSION TEMPERATURE HAVE PRECLUDED THE USE OF RESILIENT POLYMERIC PRESSURE APPLICATORS CAPABLE OF CONTOUR CHANGES WHILE APPLYING UNIFORM COMPACTING PRESSURE. EXPLORATORY EXPERIMENTS HAVE SHOWN THAT HEAT PRODUCED BY INDUCTION CURRENTS WITHIN THE GRAPHITE FIBER ARRAY CAN BE DIRECTED AND CONFINED PRIMARILY AT THE INTERFACE BOND LINE BETWEEN THE FEED TAPE AND THE SUBSTRATE. CONSEQUENTLY, THE COMPACTION HEAD IN CONTACT WITH THE (HOT) PRECURSOR TAPE CAN BE CONSTRUCTED OF RESILIENT POLYMERIC MATERIALS SUCH AS TEFLON (TFE) THAT WILL READILY CONFORM TO MOLD CONTOURS. THE PROPOSED EFFORT WILL STUDY THE EXPERIMENTAL PARAMETERS INVOLVED WITH ELECTROMAGNETIC INDUCTION HEATING TECHNIQUES, FERRITE MAGNETS, COIL DESIGNS, EDDY CURRENT BRAKES, ARC SUPPRESSORS AND OTHER FEATURES, IN ORDER TO ASSESS THE FEASIBILITY OF USING THIS APPROACH FOR FABRICATING ADVANCED THERMOPLASTIC COMPOSITES. THE QUALITY OF THE INDUCTION FUSED COMPOSITE WILL BE EVALUATED USING ESTABLISHED PROCEDURES.