Dielectric monitoring of cure in a commercial carbon-fibre composite

• Published in: Composites science and technology 1995, Vol.53 (4), p.355-359
• Main Authors: Maistros, George M., Partridge, Ivana K.
• Format: Article
• Language: English
• Subjects: Applied sciences; composite cure; Composites; cure monitoring; epoxy; Exact sciences and technology; Forms of application and semi-finished materials; gelation; Polymer industry, paints, wood; Technology of polymers; vitrification
• ISSN: 0266-3538; 1879-1050
• DOI: 10.1016/0266-3538(95)00007-0

Cure of Fibredux 924, based on carbon fibre and a formulated epoxy resin matrix, has been studied by means of dynamic dielectric analysis with embedded sensors. Rheological measurements and independent characterisation of the kinetics of cure were first carried out on the unreinforced matrix resin. These data enabled the main physical transformations in the resin, namely gelation and vitrification, to be assigned to particular features observed in the dielectric response of the resin during cure at 140, 150, 160 and 180 °C. With this information, it was then possible to use in situ dielectric measurements in a composite curing at 150 °C to identify both the time at which maximum resin flow is expected and the time at which the resin matrix undergoes gelation, and to predict the vitrification time whilst the cure was proceeding. A theoretical model has been used to extract the dipolar relaxation data from the overall signal which, in this kind of a complex commercial system, is dominated by ionic conduction.