Investigating the Effects of the Post-Impregnation Temperature on the Properties of Carbon Fiber Towpreg for the Production of High-Performance Components in the Automotive Industry

In recent years, the automotive industry has witnessed a growing trend towards the utilization of carbon fiber reinforced plastics (CFRP) for their exceptional mechanical properties and lightweight characteristics. This shift has driven the need for advanced manufacturing processes to meet the demands of high-performance automotive components. This thesis delves into a crucial aspect of CFRP production—carbon fiber towpreg manufacturing, with a specific focus on the influence of post-impregnation zone (PIZ) temperature. The research conducted at the Chair of Carbon Composites (LCC), Technical University of Munich, investigates the impact of varying PIZ temperatures on towpreg characteristics. Mechanical properties, including inter-laminar shear stress (ILSS) and curved beam bending tests, indicate a subtle improvement with increasing PIZ temperature, attributed to enhanced impregnation facilitated by reduced resin viscosity. However, size effects in ILSS tests necessitate further analysis, while curved beam bending tests prove valuable for comparing process parameters and evaluating flexural behavior in cylindrical components. Microscopy analysis reveals higher porosity percentages in cured plates compared to literature values for carbon fiber prepregs. The distribution of porosities in interlaminar and intralaminar regions, along with their relationship to fiber volume fraction (FVC), is explored. Thermal characterization, employing dynamic and isothermal Differential Scanning Calorimetry (DSC) scans, indicates that rapid production speeds result in low residence time and high cooling rates, preventing significant crosslinking reactions during towpreg production. Two kinetic curing models are developed, enhancing the understanding of curing kinetics for different resin systems. Furthermore, probe tack tests highlight the low tackiness of the Huntsman resin system, necessitating a future investigation with a tackier resin to explore the effect of PIZ-temperature on tackiness.