Injectin molding of short fiber reinforced thermoplastics in a center‐gated mold

We have studied injection molding of a rectangular box using short fiber reinforced polypropylene. The fiber orientation distribution and the local stiffness properties in radial and transverse directions have been measured in the bottom plane. The deduced orientation tensors are compared with predictions of a commercial computer code. Discrepancies are related to approximations made in the calculations and effects not accounted for by the present modeling approach. In the calculations the fiber interaction coefficient was varied seeking to fit experiments. We comment on the out‐of‐plane components of the orientation tensor, the relative thickness of skin and core layers, and the radial dependence of the fiber orientation in each layer. Values of the components of the 4^th‐order orientation tensor calculated from the measured orientation distribution are used to compare different closure approximations referred in the literature. Anisotropy in the stiffness properties, calculated form the measured fiber orientation, agree well with measurements.