Correlating Microstructure and Mechanical Performance in Compatibilized Cork‐ PLA Sustainable Composites for Fused Granular Fabrication

Large‐format additive manufacturing (LFAM) of polymer composites is vital for the circular economy, yet the link between processing, microstructure, and performance remains unclear. This study provides an in‐depth 3D microstructural characterization of polylactic acid (PLA) composites filled with 10% w/w cork residues and fabricated by fused granulate fabrication (FGF). Using X‐ray computed tomography (XCT), we reveal that high‐shear processing compromises the cork's cellular integrity, reducing occluded air to less than 1%. Consequently, composite properties are dictated by process‐induced porosity within the matrix rather than cork's intrinsic cellular nature. We compared two compatibilization strategies: a conventional maleic anhydride‐based system caused catastrophic mechanical degradation due to reduced melt strength and large void formation. In contrast, a novel bio‐inspired compatibilizer based on suberic acid acted as an effective compatibilization route under the FGF conditions studied here, significantly improving structural integrity and consolidation without inducing degradation. This work underscores the importance of quantitative 3D characterization to understand structure–property relationships in these composites and identifies a promising bio‐inspired formulation route for improving FGF processing of PLA/cork materials.