Geometrical and Mechanical Characterization of Interlayer Bonding Quality in Fused Filament Fabrication*

To obtain a fundamental understanding of the large variation of mechanical properties and geometry of printed parts prepared by fused filament fabrication (FFF), we focused on the interlayer bonding region of polycarbonate samples prepared by FFF and performed 3D geometrical characterizations using micro-CT followed by uniaxial tensile tests. The results showed significant property variations depending on printing conditions. Specifically, the layer height impacted bonding area. In addition, there was an almost linear relation between bonding zone area and fracture strength. However, when nozzle temperature increased, the strength showed a rising trend first then reached plateau. Interestingly, we also found a trend of Young’s modulus reduction with higher layer height, which could be explained by finite element simulations based on scanned sample geometries, indicating the bonding zone geometry change is the main reason of modulus variation. We envision that our findings can guide the selection of printing parameter as well as provide benchmark data for future simulation models.