Towards sustainable additive manufacturing of continuous natural yarn-reinforced thermoplastic biocomposites: a review

The application of 3D printing with natural materials emerges as a promising strategy for achieving more sustainable production practices. Natural fibers offer an eco-friendly alternative for reinforcing composite materials due to their biodegradability, reusability, and low environmental impact. This review presents an in-depth analysis of continuous natural fiber-reinforced thermoplastic composites (CNFRTPCs) produced through fused filament fabrication (FFF), focusing on incorporating Continuous Natural Yarn Reinforcement in a polymer matrix. Key parameters influencing the FFF process, such as insertion methods, nozzle design, printing speed, and curvature, are evaluated for their effects on critical printing properties, including fiber-matrix adhesion and porosity. Furthermore, the influence of natural yarn incorporation on material performance - specifically mechanical strength and printability - is thoroughly examined. The findings highlight the potential of natural yarns for large-scale applications, providing a sustainable alternative to synthetic fibers and enhancing the eco-friendliness of 3D-printed composites.