Fiber breakage modeling based on hydrodynamic Forces in macroscopic process simulations

Injection molding is one of the most important processes for manufacturing parts from discontinuous fiber reinforced polymers. Fiber length and orientation do not only influence the final structural behavior in an anisotropic way, but also the flow field and hence the mold filling process. Therefore, fiber length distribution and fiber breakage modeling are important aspects of an adequate process simulation. For fiber breakage modeling, hydrodynamic forces from matrix on fibers are considered within this work. Knowing the flow field and fiber orientation distributions of the homogenized material, flow-induced hydrodynamic forces on the fibers can be calculated. The fiber orientation tensor is used to determine reference fibers in every element. Based on this information an advanced approach for fiber breakage modelling is proposed. The fiber length distribution in the final part is compared to experimental data of a reactive injection molding process, showing good agreement.