Impregnation behaviour during the production of powder epoxy towpregs

This study focuses on the impregnation behaviour in a powder epoxy based towpregging line through a comprehensive approach integrating experimental and modelling studies. A heat transfer model, chemorheological model and impregnation model are used in tandem to analyse the production process in the line. A finite element analysis (FEA) model is used to predict the temperature distribution of the tow due to the infrared heating system. A chemorheological model is employed to estimate the viscosity values of the powder epoxy based on the temperature distribution. Using a one-dimensional Darcy's Law-based model in the Lagrangian frame, impregnation is predicted relative to the tow position in the line. Experimentally, produced towpreg samples are analysed through density-weight measurements and scanning electron microscopy (SEM) imaging to determine fibre volume fraction and void content. The experimental results highlight a towpreg void content below 10 %, which can be further reduced in the final part. The model reveals the significance of capillary pressure during the towpregging and suggests that the impregnation can be improved by adjusting key process parameters.