Particle-level simulation for the prediction of short fiber orientation in injection molding

Particle-level simulation is used to predict the motion of short glass fibers in a center-gated disk during injection molding to evaluate its applicability to the prediction of the fiber orientation distribution. The interaction of the flexible fibers is included in the simulation, and the experimentally obtained fiber length distribution and inlet orientation are used as initial conditions. In the sprue, the aligned orientation at the inlet is predicted to become random when the fibers reach the bottom because of the diverging flow. In the disk, the fibers are mainly oriented perpendicular to the flow, and the orientation profile along the thickness is found to change from asymmetric to symmetric about the channel center with increasing radial position. These predicted orientations closely match the experimental results obtained by X-ray micro-computed tomography. It is also demonstrated that the particle-level simulation successfully reproduces the dependence of the fiber orientation on the fiber length.