Effect of build-up orientations and process parameters on the tensile strength of 3D printed short carbon fiber/PA-6 composites

3D printers using fused filament fabrication (FFF) with thermoplastic filaments have been employed for rapid prototyping applications. The present research focuses on 3D-printed short carbon fiber/PA-6 composites. Specimens with four types of build-up orientations (0 degrees, 90 degrees, +/- 45 degrees, and layup) were fabricated using two types of 3D printer: Mark Two, produced by Markforged, and X-Plus produced by Qidi Tech. Tensile tests were performed on these specimens. X-ray CT and SEM observations were conducted to investigate the defects and gaps between the print paths. The effect of the bed temperature and extrusion rate were experimentally investigated. For the +/- 45 degrees specimens fabricated using Mark Two, a large gap between the print paths was confirmed. An increase in the extrusion rate of 5% (1.05) and a minor increase in the nozzle temperature of 3.6% (from 275 degrees C to 285 degrees C) yielded a smaller gap between the print paths, 20 % higher tensile strength of the +/- 45 degrees specimen, 10 % higher tensile strength of the 0 degrees specimen, and 4% higher strength of the lay-up direction specimen with X-Plus. The bed temperature had a minor effect on tensile strength.