Multi-nozzle impregnation and parameter optimization of continuous carbon fiber/PLA prepreg filaments

For fused deposition modeling (FDM) applications, high-quality continuous carbon fiber prepregs are essential to achieve enhanced mechanical performance in printed composites. Here, we present a novel cascaded multi-nozzle impregnation system that employs progressively decreasing orifice diameters (1.00 to 0.75 to 0.50 mm) to drive staged geometric constriction. This architecture significantly improves polylactic acid (PLA) penetration into the fiber tows while strictly mitigating shear-induced fiber damage. Nine processing conditions were systematically evaluated to decouple the effects of localized impregnation temperature (225–235 °C) and effective linear drawing speed (15.7–22.0 mm/s). Monofilament tensile testing and scanning electron microscopy (SEM) were coupled with quantitative physical metrics, specifically Unimpregnated Area Fraction (UAF) and nominal Fiber Volume Fraction ( FV F nom ), to comprehensively assess microstructural consolidation. Two-way ANOVA indicates that temperature is the dominant factor governing tensile performance, achieving a peak mean tensile load of 129.99 N at 235 °C and 15.7 mm/s. Microstructural analysis reveals that higher temperatures and extended residence times successfully eliminate internal macroscopic voids. Furthermore, the influence of drawing speed exhibits a temperature-dependent reversal, revealing a competing mechanism between preventing thermal/shear fiber damage and ensuring sufficient impregnation kinetics. With their optimized consolidation state and superior mechanical integrity, the prepared CCF/PLA filaments demonstrate strong potential for subsequent FDM-based additive manufacturing.