Modelling Fiber Orientation during Additive Manufacturing-Compression Molding Processes

The production of high-performance thermoplastic composites reinforced with short carbon fibers can be achieved by a novel “additive manufacturing-compression molding” technique. An advantage of such a combination is two-fold: controlled fiber orientation in additive manufacturing and less void content by compression molding. In this study, a computational fluid dynamics model has been developed to predict the behavior of printed layers during fiber-reinforced thermoplastic extrusion and subsequent compression molding. The fiber orientation was modelled with the simple quadratic closure model. The interaction between the fibers was included using a rotary diffusion coefficient that becomes significant in concentrated regimes. Finally, the second rank orientation tensor was coupled with the momentum equation as an anisotropic part of the stress term. The effect of different fiber orientation within printed layers was investigated to determine the favorable printing scenarios in the strands that undergo compression molding afterwards. The developed numerical model enables design of high-performance composites with tunable mechanical properties.