Injection molding simulation of short fiber reinforced thermosets with anisotropic and non-Newtonian flow behavior

Discontinuous fiber reinforced polymers (FRPs) are one of the most complex materials used in volume production, composing a transient chemo-thermomechanical matrix behavior and fiber-induced anisotropic physical properties. The fibers induce anisotropic behavior not only in structural properties, but also during material flow and hence during mold filling, which in turn influences the final physical properties. Therefore, the fibers influence the material flow and vice versa, the material flow causes fiber-reorientation. This interaction is typically decoupled in state of the art process simulations. To consider the fiber-flow interactions, the present work provides a new simulation method for reactive injection molding, describing the fiber-induced anisotropic flow behavior by a fourth order viscosity tensor. The matrix viscosity is modelled non-Newtonian and curing kinetics are taken into account. Numerical examples demonstrate anisotropic effects to verify the model implementations. Furthermore, cavity pressure and fiber orientations are validated with experimental data, showing good agreement.