PREPREG PROCESSING SCIENCE AND ENGINEERING

Resin flow and fiber spreading during the prepregging process were investigated experimentally using a scale-down version of a commercial hot-melt prepregger with bismaleimides and carbon fibers as model systems. Specifically, several dimensionless parameters such as the Prepreg Flow Number. fractional resin uptake, resin distribution function, fractional width change, and prepregging efficiency were defined to characterize the prepregging process as well as the quality of the prepreg. Fiber spreading during the prepregging process was observed to be a viscoelastic phenomenon depending on the impregnation temperature. For resin impregnation into collimated fiber tows, all the experimental data points obtained at different operating conditions were superimposed onto a single line showing a temperature-pressure-velocity superposition for the prepregging process as predicted by the definition of the Prepreg Flow Number (PFN). Finally, three fundamental steps of the prepregging process were identified and confirmed with cross-sectional micrographs of unaged prepregs produced at different temperatures.