Investigation of mechanical and microstructure properties of pa6 composite filament material by melt deposition modeling

In this study, the effects of processing parameters and post-annealing on the mechanical properties of carbon-fiber-reinforced polyamide-6 (ePA-CF) fabricated by fused deposition modeling were evaluated. Three parameters—printing speed, infill density, and nozzle temperature—were chosen as control factors. Experiments followed a Taguchi L9 orthogonal design, and specimens were produced according to ASTM D638 (tension) and ASTM D790 (flexure). One specimen set was left as-printed, whereas the other was annealed at 120 °C for 4 h. Data were analyzed using Analysis of Variance (ANOVA) together with main-effect and interaction plots, and fracture surfaces were examined via scanning electron microscopy (SEM). Results show that all investigated parameters and heat treatment significantly influenced the mechanical response. Annealing raised strength: the maximum tensile strength increased from 40.71 to 49.33 MPa, and flexural strength from 46.09 to 60.83 MPa. However, it reduced ductility, resulting in a more brittle material. SEM observations indicated that low strength was associated with raster voids, whereas high strength stemmed from a compact interior and a strong fiber–matrix interface. After annealing, fracture behavior shifted away from ductile features and proceeded in a more brittle mode.