SENSORS FOR CURE MONITORING OF COMPOSITE MATERIALS Yoseph Bar-Cohen*, Arniya Chatterjee and Mark West Mission Research Corporation Costa Mesa, CA 92626 INTRODUCTION Monitoring and control of the integrity and properties of materials at all stages of structural life, from cradle to retirement, is a growing NDE field. A typical system consists of a sensor, data acquisition, processing and control setup with a host personal computer. For composites, the stage of cure is the only time when an adequate actuation can easily affect the cause of unacceptable characteristics or possibly eliminate the formation of defects. Real-time monitoring of the cure process of plastic-reinforced composites can prevent overbleeding, minimize trapped volatiles, alert of vacuum leak, indicate cure rate and optimize the material properties. For many years, the process of curing composites has been an empirical science and has evolved through a trial-and-error approach. In recent years, significant progress has been made towards understanding the process as a result of data accumulation and progress in mathematical modelling of the composite cure process. Computer science is increasingly applied to support the process analysis using artificial intelligence and knowledge base systems. Controlling cure with adequate feedback requires capable sensors that provide real-time information about the conditions of the material being processed. In recent years, several effective cure monitoring techniques were reported including dielectrics [1], fluorescence [2], fiber optics [3], acoustic emission, thermography and ultrasonics [4]. The most widely and longest in use is the dielectrometrics. Such sensors measure changes in the dielectric properties of the curing resin which are related to the resin viscosity and the degree of cure. Recent developments in microdielectrics have made available tool-mount type sensors which can be used repeatedly. The main limitation of this sensor is the strong dependence of the results on the composition (i.e. batch) of the composite materials. * Consultant. Affiliation - JPL, Caltech, Pasadena, CA. Review of Progress in Quantitative Nontkstructive Evaluation, Vol. 12 Edited by D.o. Thompson and D.E. Chimenti, Plenum Press, New York, 1993 1039