Processing and treatment of natural fibers as reinforcement in polylactic acid composites

Three-dimensional (3D) printing is an emerging technique in composite manufacturing that allows the design and production of more intricate structures than those possible with traditional manufacturing processes. Polylactic acid (PLA) is the most commonly used filament in 3D printing, as it is safe, affordable, easy to print, and biodegradable. This article highlights the extraction of natural plant fibers, the chemical treatment of these fibers, and the preparation of filaments incorporating natural fiber fillers. Additionally, various methods for fabricating composites using natural fibers, including the 3D printing technique, are discussed. This review comprehensively emphasizes the incorporation of chemically treated natural plant fibers into PLA-based 3D printing filaments. It explicitly highlights the effect of fiber treatment processes on the printability and mechanical properties of natural fiber-reinforced composites. In addition, the review also identifies a significant knowledge gap in standard processing methods and optimization techniques for achieving even fiber dispersion and uniform filament quality, which are essential for further developing this sustainable manufacturing method. The research has revealed that natural fibers treated with alkali could enhance tensile strength by as much as 25% and interlayer adhesion by 18% relative to untreated fibers. Additionally, filament diameter variability of greater than ± 0.05 mm is a significant factor in print quality. This work will provide a comprehensive and detailed overview that facilitates the design of high-performance, biodegradable 3D-printed composites, leading future studies in the direction of improved fiber treatment protocols, filament production methods, and quality control protocols for natural fiber-reinforced PLA systems.