High thermal conductivity continuous pitch carbon fiber 3D printed using a 6-axis robot arm

Previous research showed that continuous pitch carbon fibers (PCF) could be 3D printed and resulted in composites with moderately high effective thermal conductivities despite a relatively large degree of fiber breakage. This study presents an alternative method to 3D print continuous PCF composites using a modified fused filament fabrication extruder and a 6-axis robotic arm to understand factors affecting fiber breakage and explore the thermal performance of different printed individual raster geometries. Continuous pitch carbon fibers were coated with polylactic acid (PLA) to create PCF filaments, which were then fed into a single nozzle extruder mounted to a 6-axis robot arm for motion control. The nozzle was angled with respect to the printing surface to reduce fiber breakage during extrusion. Rasters were printed at a range of extrusion angles, and shallower angles resulted in higher effective fiber conductivity (up to 82% of the specified fiber conductivity). The ability to articulate the angled nozzle during printing was leveraged to print continuous curved raster paths and corners with different radii of curvature. These geometries were investigated to simulate potential printing practices and understand limitations of these geometries on the resultant thermal conductivity of the samples. Generally, samples printed with a radius of less than 30 mm showed a decrease in thermal conductivity and that sharp angles caused significant fiber breakage.