Numerical modeling of fiber orientation in multi-layer, isothermal material-extrusion big area additive manufacturing

Fiber orientation is a critical factor in determining the mechanical, electrical, and thermal properties of 3D-printed short-fiber polymer composites. However, the current numerical studies on predicting fiber orientation are limited to straight single-strand configurations, while the actual printed parts are often composed of complex multi-layer structures. To address this issue, we conducted numerical simulations of material extrusion in multi-layer big-area additive manufacturing without any post-deposition strand morphology modification mechanism. By examining the effects of material properties and printing conditions when extruding and depositing strands on a fixed substrate as well as previously deposited layers, it was possible to observe the complex interplay between multiple layers and its impact on fiber orientation. The work and methodology presented in this paper can be used to identify optimal extrusion-to-nozzle speed ratios, material rheology, fiber content, and fiber aspect ratio to achieve the desired performance and thermo/mechanical properties of additively manufactured parts. This work is an important contribution towards the manufacture of high-performance, short-fiber polymer composites as the presented methodology can enable engineers to precisely predict and tailor the fiber orientation in 3D printed parts.