Performance and Thermal Properties of 3D Printed CF-Reinforced PLA Monofilaments

This study reports the fabrication of carbon fiber-reinforced poly(lactic acid) (CF-PLA) monofilaments using 3D printing technology. The effects of print head movement speed and retraction rate on the diameter of the CF-PLA monofilaments were investigated. The surface morphology and properties were analyzed using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The CF-PLA monofilaments were also printed into boards with varying CF content, and the mechanical properties of these boards were assessed. The results showed that the optimal printing parameters were a nozzle diameter of ϕ0.4 mm, fiber feed rate (Vf) of 3 mm/s, print head movement speed (Vm) of 40 mm/s, and retraction speed (Vr) of 5 mm/s. At a CF-PLA monofilament diameter of ϕ135 µm, the tensile strength and Young’s modulus reached maximum values of 48.3 MPa and 2481.8 MPa, respectively. Numerous CF monofilaments (approximately 135 µm in diameter) were observed on the surface and within the CF-PLA boards, significantly enhancing their strength. When the CF content was 4 vol%, the thermal decomposition temperature of the CF-PLA monofilament was 312.53 °C. At 8 vol% CF content, the thermal decomposition temperature increased to 342.62 °C—approximately 30 °C higher than that of the monofilament with 4 vol% CF. The CF-PLA monofilaments fabricated at 8 vol% demonstrated high thermal stability.