Investigation of flexural properties and failure mechanisms in FFF-fabricated PLA/CaCO ₃ biocomposites

This study investigates the flexural performance of polylactic acid (PLA) reinforced with eggshell-derived calcium carbonate (CaCO 3 ) at 5, 10, 15, and 20 wt.% for sustainable fused filament fabrication applications. Composite filaments were fabricated via extrusion, and test specimens were manufactured using fused filament fabrication (FFF). Standard three-point bending tests revealed that a 15 wt.% CaCO 3 composite achieved the highest flexural strength (76 MPa) and modulus (1404 MPa), indicating optimal filler–matrix interaction and efficient stress transfer. A 5 wt.% CaCO 3 addition significantly enhanced ductility, yielding a maximum strain to failure of 7.03%. Further increase to 20 wt.% resulted in mechanical degradation due to particle agglomeration and reduced matrix continuity. These findings demonstrate that eggshell-derived CaCO 3 is an effective sustainable reinforcement for tailoring stiffness and strength in PLA-based components intended for lightweight structural and eco-friendly engineering applications.