Effect of surface-treated wild almond fibre particles on the mechanical and thermal properties of FDM-printed PLA composites

This study examines the mechanical, impact and thermal behaviour of fused deposition modelling printed polylactic acid composites reinforced with maleic anhydride and polyethylene glycol-treated wild almond fibre particles at fibre contents of 3, 6 and 9 wt.%. Fourier transform infrared spectroscopy confirmed that the treatment reduced non-cellulosic surface components while preserving the cellulose structure of the fibre. The analysis also suggested possible interfacial interaction between the treated wild almond fibre particles and the polylactic acid matrix through hydrogen bonding. At a printing layer thickness of 0.1 mm, the flexural strength increased from 51.4 MPa for neat polylactic acid to 109.0 MPa for the 9 wt.% wild almond fibre composites, while the tensile strength reached 77 MPa at the same reinforcement level. The impact strength increased from 27.0 to 29.0 kJ/m² with the addition of 9 wt.% wild almond fibre. Thermogravimetric analysis showed that the reinforced composites retained higher residual mass at 500 °C compared with neat polylactic acid due to char formation from the lignocellulosic fibre component. These results indicate that surface-treated wild almond fibre particles have potential as a bio-based reinforcement for fused deposition modelling printed polylactic acid composites with improved mechanical performance and enhanced thermal stability characteristics.