Non-contact quality monitoring of laid fabric carbon/epoxy resin prepreg using near infrared spectroscopy

Near infrared (NIR) spectroscopy has been applied for non-contact monitoring of the quality of laid fabric carbon/epoxy resin prepreg. Partial least square regression was used to develop the models with 94 samples in the calibration set and 30 samples in the prediction set, respectively. The NIR spectroscopy method was able to predict the resin content and the volatile content with root mean square error of prediction of 0.85% and 0.22%, respectively. The developed models of resin content and volatile content were put into process control software so that during manufacture the laid fabric carbon/epoxy resin prepreg could be monitored and the processing parameters could be adjusted according to the results given by the NIR analysis. The prepreg could be analysed once within 30s without sample destruction. The change of the concentration of epoxy resin solution and the distance of nip rollers could be used to control the resin content and an increase or decrease in the concentration of the solvent and the production speed could control the volatile content. This study indicates that NIR analysis is sufficiently accurate and effective for quality control in laid fabric carbon/epoxy resin prepreg.