On-line cure monitoring and viscosity measurement of carbon fiber epoxy composite materials

Abstract

Cure monitoring is important for the quality control and improvement of the mechanical properties of thermosetting resin-matrix composite materials. Dielectrometry is the most promising technique among the techniques developed so far to monitor the cure of thermosetting resin-matrix composite materials. In this study, a new simple dielectric cure monitoring device which consists of a simple electric circuit, two comparators and a digital oscilloscope was developed to monitor the dielectric constants during the cure of the thermosetting resin-matrix composite materials. Using the device developed, the size- and shape-effects of the electrodes, and also the sensitivity in measuring the dielectric constants of parallel and series type electrodes, were investigated experimentally. Also, an insitu viscosity measuring device was developed to match the measured dielectric constants to the viscosity of the thermosetting resin of the composite material. The combined devices could monitor the temperature, cure rate and resin viscosity simultaneously during the cure of carbon fiber epoxy composite materials, from which the relationship between the cure rate and viscosity could be derived. It was revealed that the data obtained by this method could be used in the smart autoclave cure of the thermosetting resin-matrix composite materials.