Flexural properties of 3D printed continuous flax fiber reinforced polyethylene composites

Natural fibers are classified as green energy materials and have embodied the principles of sustainable development. This paper impregnated natural continuous flax fibers (CFF) with polyethylene (PE) on a self-developed melt impregnation device, obtained CFF/PE prepreg filaments. A fused deposition machine was used to 3D print CFF/PE composites. The effect of impregnation temperature on tensile properties of CFF/PE filaments was explored. The influence of various 3D printing parameters on bending performance and dimensional accuracy of CFF/PE composites was investigated. The results indicated that the tensile strength of the prepreg filament reached to the maximum value (12.41 MPa) at impregnation temperatures of 150 °C–155 °C. At a layer width of 1.5 mm, a layering thickness of 0.8 mm, a printing speed of 10 mm/min, and a printing temperature of 200 °C, the flexural strength of CFF/PE composites was improved to 24.74 MPa from 13.14 MPa. When the layer width was 2.0 mm and the layer thickness was 0.6 mm, the porosity was reduced to 3.88%. At a layer width of 1.5 mm, severe polymer accumulation occurred between adjacent printing lines, resulting in a significant impact on the dimensional accuracy of the composites. The maximum deviation was approximately 1.45 × 0.57 × 2.32 (mm). As the number of bendings increased, the bending rebound angle decreased, and the bending performance deteriorated, until it kept level.