3D-printed polylactide composites reinforced with short lyocell fibres – Enhanced mechanical properties based on bio-inspired fibre fibrillation and post-print annealing

In this study, 3D printable polylactide (PLA) composites reinforced with 10, 20 and 30 mass% of short lyocell fibres were produced by melt compounding PLA modified with maleic anhydride. Based on bio-inspired anchoring systems, fibrillated fibres were also employed in 30 mass% fibre composites. The resulting 3D printed samples displayed outstanding mechanical performance, particularly with high fibre content. Compared to neat PLA, unmodified formulations showed reduced tensile strength and strain at break with the addition of fibres, but they had a moderate improvement in Young's modulus. However, by combining fibre fibrillation, matrix modification, and post-printing annealing, we achieved an excellent balance of tensile strength (85 MPa), Young's modulus (7.2 GPa), and strain at break (3.2%) - the highest reported values for such composites. Incorporating fibres and increasing PLA crystallinity via heat treatment significantly enhanced the thermo-mechanical stability of the composites, raising the storage modulus up to 38 times at 60 °C and 200 times at 80 °C compared to neat PLA. This combined strategy paves the way for the 3D printing of high-performance structures using 100% bio-derived materials.