Numerical analysis of the flow and orientation of reinforcements in a polymer matrix during Direct Ink Writing process

Composites have many advantages over other materials such as high specific strength and stiffness, design flexibility, and durability. The orientation of the reinforcement with respect to the matrix is an important factor in determining the composite properties. This work presents a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) based numerical model to predict the orientation of the particle during printing of a graphite-reinforced polymer composite from a nozzle. The polymer flow is simulated by solving the mass, momentum and energy equations in three dimensions. The effect of polymer flow on the reinforcement graphite particles is calculated using one-way coupling of the fluid flow with particle mechanics. The particle position, distribution and orientation are computed using the DEM concepts. The computed particle orientation during the printing is compared with the orientation of the graphite particles during extrusion based Direct Ink Writing (DIW) process. The orientation of the particles has been optimized for the nozzle dimensions, melted polymer flow rate and reinforcement concentration. The results show that the coupled CFD-DEM method is effective in showing the reinforcement particle behaviour during printing of composite materials.