PREPREG PROCESSING SCIENCE AND ENGINEERING

Resin flow and fiber spreading during the prepregging process were inv estigated experimentally using a scale-down version of a commercial ho t-melt prepregger with bismaleimides and carbon fibers as model system s. Specifically, several dimensionless parameters such as the Prepreg Flow Number. fractional resin uptake, resin distribution function, fra ctional width change, and prepregging efficiency were defined to chara cterize the prepregging process as well as the quality of the prepreg. Fiber spreading during the prepregging process was observed to be a v iscoelastic phenomenon depending on the impregnation temperature. For resin impregnation into collimated fiber tows, all the experimental da ta points obtained at different operating conditions were superimposed onto a single line showing a temperature-pressure-velocity superposit ion for the prepregging process as predicted by the definition of the Prepreg Flow Number (PFN). Finally, three fundamental steps of the pre pregging process were identified and confirmed with cross-sectional mi crographs of unaged prepregs produced at different temperatures.