REAL TIME IN-SITU DIELECTRIC MONITORING OF ADVANCED COMPOSITE CURING PROCESSES

A NOVEL TECHNIQUE FOR MONITORING PHYSICAL AND CHEMICAL CHANGES OCCURRING DURING THE CURE PROCESS IN ADVANCED COMPOSITE, ORGANIC MATRIX, LAY-UPS IS UNDER DEVELOPMENT AT PCI. CHANGES IN DIELECTRIC PROPERTIES THROUGH THE THICKNESS OF THE LAMINATE ARE DIRECTLY MEASURED, DISPLAYED, AND RECORDED IN REAL TIME. THESE CHANGES ARE CORRELATED WITH CRITICAL STEPS IN THE PROCESS WHICH MUST BE PROPERLY CONTROLLED TO PRODUCE CONSISTENT, HIGH QUALITY COMPOSITES. THIS DIELECTRIC MONITORING TECHNIQUE, CALLED RES-CAP (TM), HAS PROVED PARTICULARLY PRACTICAL AND USEFUL IN PROCESS CONTROL FOR POLYIMIDE COMPOSITES AND WORKS WITH ALL TYPES OF REINFORCEMENTS. IN THIS PROGRAM, RES-CAP TECHNIQUE WILL BE EXTENDED TO DETECTING CRITICAL EVENTS IN PROCESSING (1) CARBON-CARBON PRECURSOR STRUCTURES, AND (2) HIGH TEMPERATURE RESISTANT THERMOPLASTIC AND THERMOSETTING COMPOSITES. IMPROVEMENTS IN DETECTOR SENSITIVITY, OPERATION AT HIGHER FREQUENCIES AND MODIFICATIONS OF ELECTRODES TO WITHSTAND TEMPERATURES OF 800 DEG F MAY BE REQUIRED. DIELECTRIC RESPONSE VS TIME WILL BE CORRELATED WITH THE EVOLUTION OF INTRINSIC FEATURES RELATED TO QUALITY, UNIFORMITY AND REPRODUCIBILITY.