Effect of Printing Velocity on the Microscopic Void Distribution of 3D-Printed Short-Fiber-Reinforced Composites

Fused deposition modeling (FDM) is gradually being widely used in the field of composite materials manufacturing, especially for short carbon fiber (SCF)-reinforced composites. In this paper, the effect of printing velocity on the microscopic void distribution of 3D-printed SCF/PA6 composites was explored. The high-resolution X-ray micro-computed tomography (μCT) was employed to quantitate the internal morphological characteristics. The internal voids of the samples including the independent voids and connected voids were quantitatively counted, respectively. Experimental results demonstrated that the proportion of internal voids increased with the increasing of the printing velocity. The number of independent voids increased firstly and then fell, and the connected voids gradually became the main existence form. By comparison, higher proportion of internal voids led to the lower compressive modulus. This is because the voids were more easily compacted, resulting in weak out-of-plane compressive resistance.