Fiber orientation morphological layers in injection molded long fiber reinforced thermoplastics

Flow-induced fiber orientation can vary significantly across the thickness of injection molded parts and is usually present in the form of through-thickness layers. In this work, fiber orientation was examined both on the flow plane and through the thickness. The thickness of a shell layer with fiber orientation in the flow direction and a core layer with a fiber orientation mainly transverse to the flow were measured via microscopy. The effect of filling speed and mold thickness on the molded plaque morphology was iden-tified. Mold-filling simulations were undertaken in order to provide the characteristic shell and core layer fiber orientations as well as the frozen layer thickness at the end of filling and the gap-wise shear rate gradients. The combined frozen and high shear rate regions were correlated with the experimental shell layer thicknesses.