Modifying the Mechanical Property of PLA-Carbon Fiber Composite Fabricated by FDM Via Adjusting Process Parameters and Heat Treatment

Abstract

Fused deposition modeling (FDM) has become one of the most widely used additive manufacturing technologies, while polylactic acid reinforced by short carbon fibers (PLA-CF) is increasingly applied in structural components. However, the mechanical properties of FDM-printed parts are strongly affected by printing parameters and show obvious anisotropy owing to weak interlayer bonding. In this work, PLA-CF composites with fiber mass fractions of 4 wt.%, 7 wt.%, and 15 wt.% were prepared by FDM. The effects of filling angle (0°, 45°, 90°), printing hatch (0.35 mm, 0.45 mm), and annealing treatment on tensile properties and mechanical anisotropy were systematically studied. The results show that filling angle dominates the tensile strength, which reaches the maximum at 0° filling angle due to favorable fiber alignment and load transfer. Reducing printing hatch can improve interlayer bonding and significantly enhance the strength of 45° and 90° specimens. The fiber mass fraction presents an angle-dependent influence on tensile performance. Moreover, heat treatment effectively reduces anisotropy. Vacuum annealing at 180°C for 3 h increases the tensile strength of 90° specimens by 105.6% and minimizes the strength gap between 0° and 90° specimens to only 2.5 MPa. This work provides a feasible strategy for preparing high-performance, low-anisotropy PLA-CF components.