COMPARISON AND EVALUATION OF GAS ANALYZERS AS IN-PROCESS SENSORS FOR THE INTELLIGENT PROCESSING OF CARBON/CARBON COMPOSITES

CARBON/CARBON COMPOSITES ARE HIGH STRENGTH MATERIALS WHICH WILL BE INCREASINGLY USED IN ADVANCED AEROSPACE AND DEFENSE SYSTEMS. AS MATERIAL PERFORMANCE REQUIREMENTS BECOME MORE STRINGENT, THE CURRENT PROCESS CONTROL METHODS WILL BECOME INADEQUATE AND MANUFACTURING VARIABILITIES WILL IMPACT ON SYSTEM PERFORMANCE, COST AND RELIABILITY.CURRENT MANUFACTURING SYSTEMS RELY HEAVILY ON TEMPERATURE AND PRESSURE SENSORS AS PRIMARY MEANS OF CONTROLLING THE FINAL MATERIAL PROPERTIES. MORE ATTENTION SHOULD BE PAID TO THE CHEMICAL AND PHYSICAL CHANGES WHICH ARE OCCURRING IN-PROCESS. ADVANCED CONTROL SYSTEMS MUST MONITOR THESE CHANGES WITH APPROPRIATE SENSORS AND PROVIDE A MEANS VIA AN INTELLIGENT PROCESSOR OF ADJUSTING THE PROCESS TO OBTAIN LESS PRODUCT VARIABILITY AND DESIRED PROPERTIES. CARBONIZATION IS A KEY PROCESS STEP USED IN C/C MANUFACTURING. AN INHERENT FEATURE OF PITCH MATRIX PRECURSORS IS MESOPHASE FORMATION, WHICH IS A DISPERSED PHASED FORMED BY THE CHEMICAL REACTION OF SELECT COMPONENTS IN THE PITCH. MESOPHASE FORMATION AND COALESCENCE ARE ESSENTIAL TO THE FORMATION OF GRAPHITIC MATRIX MICROSTRUCTURE. THUS, IMPROVED CONTROL OF THIS STEP MAY LEAD TO INCREASED COMPOSITE PERFORMANCE AND DECREASED VARIABILITY. GAS EVOLUTION, DUE TO CHEMICAL REACTION, ALSO OCCURS DURING THE CARBONIZATION PROCESS. THUS, IN SITU GAS ANALYZERS COULD BE USED AS CARBONIZATION PROCESS SENSORS.