Process parameter effects on the mechanical behavior of FDM-printed PLA/CF

Abstract In this study, the effects of printing temperature and travel speed on the mechanical properties of carbon fiber–reinforced polylactic acid (PLA/CF) filaments, fabricated by the fused deposition modeling (FDM) process, are investigated. Surface morphology, crystallinity, and functional groups were characterized, and mechanical properties were evaluated. The experimental results from tensile tests were compared with numerical analyses performed using by the software KSP V6.2 based on the so-called Projected Fiber Approach. The results indicate that the PLA/CF structure remained stable after printing, particularly at higher printing temperatures. Both experimental and numerical analyses confirmed that the carbon fibers became preferentially oriented along the printing direction, in contrast to the more random distribution in the as-received PLA/CF filament. Morphological analysis of the printed samples exhibit irregular porosity, overlapping fibers, weak fiber–matrix adhesion, and fiber pull-out. The elastic modulus decreased by a factor of approximately 2.4 after printing. The numerical results further validate that the printed PLA/CF filaments have a lower modulus than the unprinted PLA/CF filament. The inferior mechanical properties of the printed PLA/CF filaments are likely attributed to poor fiber–matrix bonding during carbon fiber alignment in the printing process, as well as porosity formation.