3D printing continuous natural fiber reinforced polymer composites: A review

With the growing prominence of environmental conservation awareness, there has been a notable surge in the exploration of renewable materials, particularly in the realm of natural fiber reinforced polymer composites. This heightened focus is underscored by the recent advancements in additive manufacturing techniques dedicated to continuous natural fiber reinforced composites (CNFRCs), which have inherently opened unprecedented avenues for the holistic customization of CNFRCs with meticulously tailored properties. This work reviewed the advanced techniques for 3D printing CNFRCs and addressed their challenges and perspectives in the future. First, the 3D printing processes of CNFRCs were reviewed, and the use of reinforcement and matrix phases was classified in detail. Then, CNFRCs were discussed in terms of their mechanical performances and novel function of shape-changing. Further, performance optimization and prediction methods of 3D printed CNFRCs were discussed. In conclusion, a perspective on future study opportunities of 3D printed CNFRCs was provided from design, manufacturing, prediction to application.