Effect of thermal treatment on the mechanical behaviour of 3D-Printed carbon fiber-reinforced PLA bioplastic

This study investigates the combined influence of optimized fused deposition modeling (FDM) parameters and post-processing annealing on the mechanical, thermal, and dimensional performance of carbon fiber-reinforced polylactic acid (CF-PLA). Tensile, compressive, and flexural specimens were fabricated using FDM and subsequently annealed at 80°C, 100°C, and 120°C for holding times of 30, 60, and 90 min. Mechanical testing revealed that annealing significantly enhanced material performance when appropriate conditions were applied. The maximum tensile strength of 90.6 MPa was achieved at 80°C for 90 min, representing a 34 % improvement over untreated CF-PLA (67.43 MPa). The highest compressive strength of 90.9 MPa was obtained at 120°C for 60 min, corresponding to a 48 % improvement over untreated CF-PLA. Flexural strength reached a maximum value of 66.8 MPa, showing an improvement of about 25 % compared to untreated CF-PLA. Field Emission Scanning Electron Microscopy (FESEM) analysis confirmed enhanced interlayer adhesion, reduced porosity, and improved fiber–matrix bonding in optimally annealed samples. However, excessive annealing temperature or prolonged holding time led to polymer softening and reduced mechanical performance. The results demonstrate that controlled annealing is an effective post-processing strategy to significantly improve the mechanical reliability and structural integrity of FDM-printed CF-PLA components for load-bearing applications.