Cure Monitoring of CFRP Using Electric Capacitance Change with Applied AC Frequency
Takaomi INADA and Akira TODOROKI
Abstract:Authors have developed an electric resistance change method for monitoring delaminations of CFRP laminates. The method employs reinforcement fibers as sensors, and the electrodes are co-cured. In the present study, the co-cured electrodes are adopted as sensors for monitoring of degree of cure. The present study proposes a new method for monitoring of the degree of cure without embedding or attaching sensors on the basis of the electrical capacitance change. Charging alternating current during curing process between the electrodes provides dielectric properties of CFRP composites. As same as the conventional dielectric sensors for cure monitoring, the degree of cure of composites is monitored by means of measuring the dielectric constant of the composites here. The dielectric constant of the epoxy resin changes as the change of the frequency of the applied alternating current. Using the dependency of the applied alternating current of the dielectric constants, the degree of cure is directly measured without curve fitting and without cumbersome measurements with DSC. The proposed method is applied to a single ply CFRP and a multi-ply CFRP laminate here. As a result, the method shows excellent estimations of the degree of cure without additional sensors. Key Words:CFRP, Degree of cure, Cure monitoring, Permittivity, Co-cured electrode, Alternating current frequency