Impregnation of stitched continuous carbon fibre textiles by Sheet Moulding Compounds

This thesis deals with the fibre impregnation of a carbon fibre reinforcement by a Sheet Moulding Compound (SMC). In the beginning, the carbon fibre reinforcement has no impregnation. Instead, the impregnation of the carbon fibre is performed by the resin within the SMC material during compression moulding. The combination leads to a Hybrid SMC composite, which is characterized by a high design freedom, good mechanical properties, and high production rates at the same time. The main objective of this study is the development of an analytical impregnation model for Hybrid SMC composites. The impregnation model predicts the final void content with regard to the properties of the semi-finished products and the process implementation. The fibre impregnation is influenced by the viscosity of the SMC material, the processing compression, the permeability, and the thickness of the carbon fibre reinforcement. Among all these parameters, the viscosity is an essential factor for the fibre impregnation, because it is dependent on the temperature and the time. The final impregnation model is developed by an approach of fluid dynamics to track the flow front particles within the SMC material during compression moulding. At the same time, experiments are realized and the void content is determined by using microscopic analysis of the Hybrid SMC composites. The evaluated void contents of the experiments are used to compare the results with the impregnation model. All in all, the investigations have led to an analytical impregnation model with a high accuracy. A deviation of 5% for more than 82% of the specimens was achieved.