Effect of Atmospheric Plasma Treatment on Mechanical Properties of 3D-Printed Continuous Aramid Fiber/PLA Composites

In this study, an aluminum heating block with two inlets (for the Polylactic acid (PLA) filament and the continuous aramid fiber) was produced and placed onto an extruder, and continuous-aramid-fiber-reinforced PLA composites were fabricated by using the nozzle impregnation method. Layer height values of 0.4 mm, 0.6 mm, and 0.8 mm and hatch spacing values of 0.6 mm, 0.8 mm, and 1.0 mm were used for the investigation of the processing parameters on the properties of composites by differentiating the reinforcement volume fraction. Additionally, atmospheric plasma treatment was used for the surface modification of the reinforcement fiber. The properties of composites reinforced by using surface-modified fibers were also investigated in order to reveal the efficacy of the atmospheric plasma treatment on the properties of composites. The effect of the atmospheric plasma treatment on the fiber properties was investigated by using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Continuous-aramid-fiber-reinforced PLA composites were characterized mechanically by fiber pull-out, tensile, and flexural testing. The fracture surfaces of composites were analyzed by using SEM. The combination of a reduced layer height and a narrower hatch spacing yielded the best mechanical performance, with a tensile strength of 410.25 MPa achieved at a 0.6 mm layer height and a 0.4 mm hatch spacing. This combination minimizes void formation, enhances fiber alignment, and strengthens interlayer adhesion, leading to superior mechanical properties. The FTIR and XPS results showed that atmospheric plasma modification can enhance the interfacial bonding strength by improving the surface morphology and increasing the content of polar groups on the fiber surface. By combining optimized manufacturing conditions with the atmospheric plasma treatment, the mechanical performance of continuous-aramid-fiber-reinforced PLA composites was enhanced.