Sustainable development of additively manufactured PLA composites reinforced with agro-waste derived bio-filler: Structural and flame-retardant performances.

The increasing reliance on conventional composite materials has raised concerns regarding cost and environmental sustainability, particularly due to poor waste management. This study explores the potential of underutilized pineapple leaf fibre (PALF) agro-waste from North-Eastern India as a low-content natural reinforcement for PLA-based material-extrusion (MEX) 3D printing. Chemically treated PALF was incorporated at low concentrations (1-5 wt%) to develop lightweight bio-composites, with their surface, structural, chemical, mechanical, and flame-retardant characteristics systematically investigated. XRD analysis revealed an increase in crystallinity, while FTIR confirmed the absence of new chemical bonds, indicating predominantly physical interactions between PLA and PALF. The incorporation of PALF improved Shore D hardness, tensile strength, and compressive strength by 2.5%, 65.81%, and 7.61%, respectively, with the 95PLA/5PALF composite exhibiting the optimum overall performance. In contrast, flexural strength decreased relative to neat PLA. Flammability testing further demonstrated enhanced flame resistance, attributed to char formation and the resulting barrier effect, which reduced the burning rate. The developed PLA/PALF bio-composites provide a sustainable pathway for converting region-specific agricultural residues into functional 3D-printable materials with enhanced mechanical performance and flame resistance. The results also demonstrate their potential as lightweight, sustainable materials for structural and semi-structural applications while contributing to the development of a circular material economy.