Nozzle clogging during extrusion based additive manufacturing of polymer matrix composites—A numerical simulation insight into the process

Enhancing the performance of composite materials through controlled alignment of reinforcements during extrusion-based additive manufacturing (AM) remains a key challenge in engineering design. The extrusion process involves complex multiphase interactions that govern the orientation of dispersed reinforcements within a polymer matrix. In this work, a coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) framework is employed to analyze the behavior of graphite particles suspended in a polyvinyl alcohol (PVA) matrix during flow through a printing nozzle—an aspect difficult to capture experimentally.

The study identifies drag, pressure gradient, and virtual mass forces as dominant contributors influencing particle dynamics and alignment. A non-linear regression model is developed to quantify the relationship between these forces and reinforcement orientation. The orientation angle is treated as the response variable, while key process parameters—including nozzle outlet diameter, particle aspect ratio, volumetric flow rate, polymer viscosity, and filler concentration—are considered as inputs.

Furthermore, the issue of nozzle clogging is investigated using the developed computational model. Nozzle rotation is proposed as an effective strategy to reduce clogging and improve material flow consistency, thereby promoting better reinforcement alignment. Overall, this work provides deeper insights into the governing mechanisms of particle orientation in extrusion-based AM and presents a practical approach for optimizing process parameters to fabricate high-performance composites with tailored properties.