Definitive screening design for mechanical properties enhancement in extrusion-based additive manufacturing of carbon fiber-reinforced PLA composite

In the realm of material extrusion additive manufacturing, fused deposition modeling (FDM)/ fused filament fabrication (FFF) has gained widespread recognition for its cost-effective approach to producing engineering components with precise net-shapes. This study systematically investigates the influence of various FDM process parameters on the mechanical properties of printed parts of carbon fiber-reinforced poly-lactic acid (PLA-CF), specifically focusing on tensile strength (TS), flexural strength (FS), and impact strength (IS). Utilizing definitive screening design, nonlinear and quadratic regression models were developed to establish robust relationships between printing parameters and strength characteristics. Statistical evaluation confirmed the models’ efficacy in explaining observed variations and predicting responses. Contour plots further visually depicted the parameter impact on each strength aspect. For TS, FS and IS, crucial factors included layer height, followed by number of contours, infill density and fill angle. For multi-response optimization an integrated approach of grey relational analysis (GRA) and entropy were applied. Optimal parameter levels obtained were, a layer height of 0.1 mm, six contours, 50% infill density, 0° fill angle, 60 mm/s printing speed, 220 °C nozzle temperature, 90 °C bed temperature, and 0° part orientation. These parameters led to improved tensile strength (45.56 MPa), flexural strength (64.87 MPa), and impact strength (6.52 kJ/m²). This research provides important insights for enhancing FDM-printed part mechanical properties of PLA-CF and also offering a systematic methodology for process optimization and parameter selection in additive manufacturing.