Self-sensing composites: cure monitoring

The ability to monitor the cure kinetics at the fibre-matrix interface and the effects induced by the presence of silane coupling agents was the main focus of this study. E-glass reinforcing fibres were used as chemical sensors to eliminate the potential problems associated with implanting a foreign body into a composite structure in the form of an optical fibre. This study demonstrated conclusively that E-glass reinforcing fibres can be used to monitor the cure of an epoxy/amine resin system in-situ; the data generated via evanescent wave spectroscopy (EWS) using the reinforcing E-glass fibres showed excellent correlation with conventional transmission Fourier transform infrared spectroscopy over a range of temperatures. EWS via E-glass fibres was used to study the effects of the following coupling agents on the cure behaviour: (i) 3-glycidyloxypropyltrimethoxysilane (GPS); and (ii) 3-aminopropyltriethoxysilane (APS). The epoxy and amine functional groups in the resin system were affected by the presence of the silane coupling agents during cure. Increased GPS concentration induced faster rates of epoxy conversion, but reduced the final degree of epoxy conversion. The amine functional groups of the curing resin were converted at faster rates with APS treatment, but the final degree of amine conversion was reduced