Mechanical Failure and Fractographic Analysis of Toughened <scp>PLA</scp> / <scp>PBS</scp> Biopolymer Blends for Additive Manufacturing

ABSTRACT Polylactic acid (PLA) is one of the most widely used polymers in fused deposition modeling (FDM) due to its ease of processing and bio‐based origin; however, its inherent brittleness and poor impact resistance often result in premature failure in load‐bearing and functional printed components. This study investigates the mechanical failure and fracture mechanisms of conventional and FDM printed PLA/polybutylene succinate (PBS) biopolymer blends. PLA/PBS blends containing 0–40 wt% PBS were prepared via melt mixing and processed into filaments suitable for FDM, with compression‐molded samples used as baseline references to decouple material effects from AM‐induced anisotropy. FDM specimens were printed at a constant speed of 60 mm/s with infill densities of 15% and 80% to evaluate the influence of internal architecture on mechanical behavior. Among the printed compositions, the PLA80/PBS20 blend exhibited the highest tensile performance, particularly at 80% infill density, attributed to improved interlayer bonding and enhanced phase compatibility between PLA and PBS. Fractographic analysis revealed a transition from brittle interlayer fracture to ductile deformation with increasing PBS content, characterized by fibrillation and effective energy dissipation mechanisms. The results demonstrate that low PBS loadings significantly enhance interlayer adhesion and mechanical reliability in FDM‐printed PLA without compromising printability. This work establishes PLA/PBS blends as promising sustainable feedstocks for additive manufacturing, offering a viable pathway toward tougher, biodegradable materials for structural FDM applications.