Cure Monitoring for Heat-Resistant Tough Epoxy Resin Matrix CFRP

Autoclave curing processes of CFRP (carbon fiber reinforced plastics) laminates composed of carbon fiber/heat-resistant tough epoxy resin prepreg used as aircraft structure material were monitored by dielectric sensors. Then, monitored dielectric properties were compared with the degree of cure predicted by Springer's model and resin viscosity, Reciprocal dielectric loss factor (1/(ε"ε0ω) or ion viscosity), which is considered to correspond to degree of cure, becomes constant at 30-40% degree of cure. And the ion viscosity before gelation does not correspond to resin viscosity. Besides, the exothermic reaction rate peak point shown as temperature overshoot does not correspond with the peak point of differential coefficient of ion viscosity. In the case of this particular resin we selected, motion of free charges or dipoles in the resin is presumed to become insensitive after the degree of cure reaches 30-40%.