Visual Analysis of Fiber Orientation Process by Glass-Inserted Mold

Abstract

For the analysis of the fiber orientation mechanism, it is very important to observe the dynamic behavior of fibers inside an injection mold. We have proposed a visual observation method utilizing a new Glass-Inserted Mold, in which two parallel glass blocks are fitted in the opposite faces of the injection cavity, across from each other. Using this method, we have attempted to directly observe the fiber orientation behavior during the cavity filling process of polystyrene with low fiber concentration of 0.1-0.2wt%. The results obtained through the visual analysis are summarized below.(1) The back-lighting method utilizing Glass-Inserted Mold and Ni-coated tracer fibers is effective for the dynamic observation of the fiber orientation process.(2) Based on the comparison between the analysis of molded products and VTR images, it has been confirmed that seven different orientation layers are obviously formed along the cavity thickness during the filling process under several molding conditions.(3) The fibers in the frozen region are subjected to large extensional flow during the fountain flow process. In terms of the orthogonal layers, this frozen region can be classified into two fiber orientation layers: Skin layers-I and -II. As cavity thickness increases, the fibers in Skin layer-I tend to be strongly oriented towards the flow direction.(4) In the flowing region, the fiber orientation angle is subjected to the influence of velocity profile along the cavity thickness. Core layer, in which most of the fibers are oriented perpendicular towards the flow direction, corresponds to a flat velocity region around the cavity thickness center. Intermediate layer, in which a considerable number of fibers are oriented towards the flow direction, corresponds to the steep velocity region appearing on both sides of the core layer.