Fused Filament Fabrication and Recycling of Bio-based Polyamide 11 Reinforced with Recycled Short Carbon Fibers

This research investigates the fused filament fabrication (FFF) and recycling of bio-based polyamide 11 (PA11) reinforced with recycled short carbon fibers (rCFs), aiming at enhancing the sustainability of polymer additive manufacturing. The study evaluates the rheological, thermal and mechanical properties of PA11 reinforced with 10% and 20% rCFs, analyzing both hot-pressed (HP) and 3D-printed samples across multiple recycling cycles. The results reveal that while the addition of rCFs improves tensile stiffness and strength, it reduces ductility and impact strength. Mechanical properties degrade progressively after each recycling step, more noticeably in 3D-printed specimens due to fiber breakage and matrix degradation. Despite this, PA11/rCF composites retain up to 95% of their elastic modulus and 80% of their ultimate tensile strength; thus, highlighting a strong potential for circular manufacturing. These findings highlight the potential of bio-based PA11 composites for a more sustainable additive manufacturing, while also emphasizing the need for further optimization to mitigate the adverse effects of recycling on mechanical performances.