Effects of nozzle diameter and fiber volume fraction on tensile properties of FDM-printed CCF/PLA composites.

Abstract

This study investigates the effects of nozzle diameter and continuous carbon fiber (CCF) volume fraction on the tensile properties and failure mechanisms of fused deposition modeling (FDM) printed CCF/polylactic acid (PLA) composites. Two nozzle sizes (1.0 mm and 0.8 mm) and four CCF volume fractions (0%, 20%, 30%, 50%) were adopted to prepare six groups of specimens for uniaxial tensile tests and field emission scanning electron microscopy (FE-SEM) characterization. The results indicate that CCF-reinforced specimens exhibit nearly no plastic deformation and fail mainly by fiber fracture, while neat PLA shows obvious plastic deformation and tensile fracture. For the 1.0 mm nozzle, the tensile strengths reach 36.4 MPa, 34.8 MPa and 19.8 MPa at CCF volume fractions of 50%, 30% and 20%, respectively. The tensile strength is 16.9 MPa for specimens with 50% CCF printed using the 0.8 mm nozzle. Larger nozzle diameter effectively improves tensile strength, which increases approximately linearly with rising CCF content. Microscopic observations reveal that the 1.0 mm nozzle ensures uniform fiber distribution and strong fiber-matrix interfacial bonding. Considering mechanical performance and cost, 30% is determined as the optimal CCF volume fraction. With the merits of light weight, high strength and environmental friendliness, the composites are suitable for aerospace lightweight parts, automotive components, civil engineering load-bearing structures, customized tooling and medical devices.