Prepreg process-structure-property analysis and scale-up for manufacturing and performance

A model epoxy based resin was used to hot-melt impregnate unidirectional carbon fibers under different processing conditions. The processing parameters were investigated using a full factorial design of experiments (DOE) in which impregnation temperature and pressure, as well as manufacturing line speed were varied. There were 27 possible combinations of parameter settings with each parameter setting having three levels. The prepreg manufactured in this study was characterized in terms of impregnation, resin content, morphology, and tack providing both a qualitative and quantitative assessment of inter-relations between prepreg processing, structure and properties. Impregnation temperature was observed to have the greatest effect on the degree of impregnation followed by impregnation pressure. Line speed, on the other hand was found to have little effect on the degree of impregnation. However, both qualitative and quantitative tack as well as the nature of impregnation was affected by the line speed. Specifically tack quality was examined through the Manufacturing Human Perceptive Rating (MHPR) while guantitative tack was viewed as a process descriptor and measured through a compression-tension experiment. Collectively, these results examined the importance of understanding the influence of prepreg processing and manufacturing conditions on the final properties and resulting structure of the prepreg, which in turn can strongly affect the utilization of these materials for the manufacturing of high performance composite parts.