The effect of fabric tension and the number of impregnation rollers on woven fabric prepreg quality and cured laminates

The effects of fabric tension and number of impregnation rollers used during hot-melt prepreg processing were investigated as they relate to woven fabric prepreg and final composite part quality. Specifically, the processing parameters varied in a design of experiments (DOE) were applied fabric tension and the number of impregnation rollers, while maintaining the same impregnation force. Six experimental prepregs were characterized in terms of prepreg thickness, resin content, tack, and morphology. The results show that fabric tension had a large influence on the prepreg characteristics due to more cylindrical tow shapes and a ridged fiber bed. The number of impregnation rollers was found to affect only the characteristics of the prepregs manufactured with no tension. To investigate the effects of tension on cured composites, six ply laminates were made with each experimental prepreg. Two cure cycles, differing only in consolidation pressures, were used to examine the void content and morphology in the cured laminates. The laminates made with prepregs manufactured with high tension and cured only under vacuum had a greater void content than laminates made with prepregs manufactured with no tension. In both cure cycles, the tow shape in the laminates made from the prepreg manufactured with high tension remained in almost the same shape as in the uncured prepreg. The void content, however, was negligible for all laminates cured at higher consolidation pressure.