Investigating microstructural features and tensile properties of 3D-printed co-polyester reinforced with carbon fibres

This study investigates the 3D printing of carbon fibre-reinforced copolyester (COP-CF) composites using fused filament fabrication (FFF) technology, with a focus on the influence of printing parameters on mechanical performance and microstructure. We explore the effects of different printing angles (0° to 90°) on the tensile behaviour, pore connectivity, and microstructural characteristics of 3D-printed COP-CF specimens. Synchrotron X-ray microtomography is employed to analyse the internal structure of printed parts, revealing insights into porosity distribution and fibre alignment. Our results indicate that a 45° printing angle yields the highest mechanical performance, with a tensile strength improvement approaching 70 MPa and a Young’s modulus nearing 1 GPa, attributed to filament alignment in the loading direction and optimal load transfer. Additionally, the elongation at break reaches approximately 10 %, indicating a balance between strength and ductility. The study also highlights the role of process-induced porosity and its impact on mechanical properties. Additionally, the design and testing of a 3D-printed curved hook demonstrate the material's potential for functional applications under mixed-mode loading conditions effectively at a 45° printing angle—outperforming other angles by a factor of 1.71. The findings underscore the importance of printing angle and microstructure control in optimizing the mechanical performance of 3D-printed COP-CF composites for technical applications.