Controlled directionality in 3D printing of graphite-reinforced polymer composite with enhanced mechanical properties

In extrusion-based 3D printed polymer composites, the mechanical performance is strongly influenced by factors such as reinforcement orientation, spatial distribution, and inherent porosity. In this study, we demonstrate precise control over reinforcement alignment by systematically tuning key printing parameters, including nozzle diameter and volumetric flow rate. Experimental results indicate a clear relationship between printing conditions and the resulting reinforcement directionality, porosity, and overall mechanical response.

Compared to conventionally film-cast samples, the printed composites exhibit significant improvements, with approximately 108% increase in tensile strength, 520% enhancement in toughness, and 188% rise in fracture strain. To gain deeper insights into the underlying mechanisms, a coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) framework is employed to simulate and visualize the evolution of reinforcement orientation within the nozzle during extrusion.

The numerical predictions are further used to establish process–structure–property relationships, linking controllable parameters to reinforcement alignment and resulting mechanical behavior. The combined experimental and computational approach provides a comprehensive understanding of how processing conditions influence composite performance. These results highlight the potential of extrusion-based additive manufacturing as a powerful tool for engineering polymer composites with tailored and enhanced properties.