Estimation of the cross-linking ratio and glass transition temperature during curing of amine-cross-linked epoxies

An estimation tool developed for the cure optimisation of carbon/epoxy prepreg has been improved to determine during a cure cycle the variation in component temperature, the cross-linking ratio, and the glass-transition temperature of the matrix. The cross-linking ratio, α, is fitted by solving by finite differences the relationship of Sourour and Kamal. The required parameters are identified with the experimental curve α=f (cure time) for partially cured samples. We have first established the exponential equations between Tg and α, then determine the change in Tg with the cure time by using these exponential equations and the estimation curve of α. To validate this estimation tool, a different cure temperature cycle was applied to the same prepreg and the experimental values of Tg and α of partially cured samples were satisfactorily compared to the calculated values.