Cure kinetics and viscosity modeling for the optimization of cure cycles in a vacuum-bag-only prepreg process

This study focuses on the development of a process-based simulation model coupled with differential scanning calorimetry (DSC) and dynamic mechanical analyzer (DMA) experiments. The cure kinetics and rheology of an epoxy-amine resin were characterized in order to predict the degree of cure and viscosity behavior in an out-of-autoclave (OOA) process condition. Both phenomenological reactions and chemo-rheological models were applied to effectively predict the degree of cure and resin viscosity. Using these results, it is possible to predict the minimum viscosity, gelation, and vitrification, which are the main process factors of the multi-stepped cure cycles, and reduce the number of process trials. It was found that there was a good correlation between the experimental results and model predictions under isothermal and non-isothermal temperature profiles. Furthermore, this study demonstrates that there is an additional scope for optimization in the conventional cure cycles recommended by prepreg manufacturers, especially when a low viscous state is required. The optimized cure cycle led to a substantially high fiber fraction (58.96 vol%) and a low void content (0.15 vol%), as compared to the conventional cure cycles.