Unambiguous orientation in short fiber composites over small sampling area in a center-gated disk

A modified version of the method of ellipses was successfully developed, validated, and implemented to characterize short fiber orientation. Unambiguous orientation and a small sampling area were obtained by distinguishing between in-plane angles of ϕ and ϕ + π for every fiber and characterizing non-elliptical footprints, respectively. Measurements in two thin center-gated disks showed the existence of an asymmetric profile of orientation at the gate, which differs from the 3D random orientation commonly assumed in simulations. This profile washed out gradually at the entry region until disappearing at about 40% of flow length. A detailed set of orientation data for comparing fiber orientation to calculated values was obtained.