Numerical Simulation and Experimental Study on the Melt Flow Behavior of 3D-Printing Polylactic Acid Composites Filaments Reinforced with Iron Fillers

The melt flow behavior of polylactic acid (PLA) composites reinforced with iron fillers at different extrusion temperatures was significantly explored to improve their hot melt extrudability and printability in FFF 3D printing technology. PLA/Fe composites have been developed to produce 3D polymer composite (PMCs) filaments for high-strength and magnetic filament applications. The melt flow properties, including melt flow rate (MFR) and flow behavior index (n), of PLA/Fe composite filaments were measured at 200 °C, 220 °C, and 240 °C. Furthermore, the velocity measurement on the composite filament melt was conducted during the melt flow test. A simulation model of the capillary tube in melt flow indexer was developed to predict the melt flow behavior and properties of the polymer composite using Computational Fluid Dynamics (CFD) simulation. The extrusion velocity of the model was compared with the experimental results. The cell Reynolds numbers of the PMCs melt were determined at the testing temperatures. The extrusion velocity and cell Reynolds numbers of the PMCs tended to increase with increasing testing temperatures, while the average velocity decreased four times with doubling the extruder diameter.