Coupled CFD-DEM analysis of SiC reinforcement flow and orientation in PVA composite extrusion

This study explores the extrusion-based additive manufacturing of silicon carbide (SiC)-reinforced polyvinyl alcohol (PVA) composites, focusing on the influence of reinforcement concentration (1 wt%, 3 wt%, and 5 wt%) and nozzle outlet diameter (0.6 mm, 0.8 mm, and 1 mm) on print quality, reinforcement distribution, and mechanical properties. The die swell effect, a critical factor in extrusion-based printing, was found to intensify with smaller nozzle diameters and higher reinforcement concentrations. Mechanical testing revealed a significant enhancement in tensile strength for samples containing 1 wt% SiC printed using 0.6 mm and 0.8 mm nozzles, whereas higher SiC concentrations negatively impacted strength. However, for the 1 mm nozzle, tensile strength improved progressively with increased SiC content. Scanning Electron Microscopy (SEM) of extruded wires demonstrated that reinforcement orientation varied with nozzle diameter. SiC particles aligned perpendicular to the flow in the 0.6 mm nozzle, while random orientation prevailed in larger nozzles. A coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model incorporating an adhesion force interaction effectively simulated the behavior of SiC particles within the nozzle. The model revealed that interactions between SiC particles and the nozzle wall dominated in the 0.6 mm nozzle, inducing perpendicular orientation. This comprehensive investigation provides insights into the interplay between process parameters, material distribution, and mechanical performance, offering guidance for optimizing extrusion-based printing of reinforced composites for advanced applications. The findings establish a foundation for tailored design of nozzle geometries and reinforcement concentrations in additive manufacturing of polymer composites.