Mechanical and Thermal Properties of 3D-Printed Continuous Bamboo Fiber-Reinforced PE Composites

Continuous fibers with outstanding mechanical performance due to the continuous enhancement effect, show wide application in aerospace, automobile, and construction. There has been great success in developing continuous synthetic fiber-reinforced composites, such as carbon fibers or glass fibers; however, most of which are nonrenewable, have a high processing cost, and energy consumption. Bio-sourced materials with high reinforced effects are attractive alternatives to achieve a low-carbon footprint. In this study, continuous bamboo fiber-reinforced polyethylene (CBF/PE) composites were prepared via a facile two-step method featuring alkali treatment followed by 3D printing. Alkali treatment as a key processing step increases surface area and surface wetting, which promote the formation of mechanical riveting among bamboo fibers and matrix. The obtained treated CBF (T-CBF) also shows improved mechanical properties, which enables a superior reinforcement effect. 3D printing, as a fast and local heating method, could melt the outer layer PE tube and impregnate molten plastics into fibers under pressure and heating. The resulting T-CBF/PE composite fibers can achieve a tensile strength of up to 15.6 MPa, while the matrix PE itself has a tensile strength of around 7.7 MPa. Additionally, the fracture morphology of printed bulks from composite fibers shows the alkali-treated fibers-PE interface is denser and could transfer more load. The printed bulks using T-CBF/PE shows increased tensile strength and Young's modulus, with 77%- and 1.76-times improvement compared to pure PE. Finally, the effect of printing paraments on mechanical properties were analyzed. Therefore, this research presents a potential avenue for fabricating continuous natural fiber-reinforced composites.