INCREASING DEPOSITION RATES AND QUALITY OF ADDITIVELY MANUFACTURED HIGH FIBER FRACTION CONTINUOUS FIBER COMPOSITES

A previous published study performed by the authors had already shown the application of commingled yarn in a direct digital manufacturing approach to additively manufacture composites averaging 50 % fiber volume fraction, but quality of parts diminished when deposition speed was increased. In order to employ this processing approach in a commercial setting, it is necessary to maintain composite quality while at the same time increasing deposition rates. In this current effort, two process modifications are used to address this challenge: increasing length of heated zone and increasing number of tows. Here, samples were manufactured at 3 different levels of print speeds, 3 different heated zone lengths and 2 levels of tow count. Matrix pyrolysis was performed to evaluate composite quality by determination of fiber and void fractions. Experimental results show a significant improvement in quality when at a set baseline deposition rate, void fraction was reduced by about 70 % with increased heated zone length. Further, doubling of the deposition rate still yielded a 23 % drop in void fraction compared to baseline when heated zone length was increased.