Flow Induced Fiber Orientation in the Moldings of Potassium Titanate Fiber/Polystyrene Composites II. Multi-layered Structure of Injection Molding Plaques

The effects of molding conditions on fiber orientation patterns were studied using X-ray diffraction. From an analysis of the diffraction patterns in the depth direction, it was determined that the plaque consists of three or four layers with different orientation patterns and thicknesses. Preferential directions of fibers the outer two layers, namely, skin and intermediate, are independent of molding conditions. The skin layer is preferentially oriented transverse to the flow direction, while intermediate layer is highly parallel. The patterns in the core layer can be classified into two different types. Type I, with transverse orientation, appears in a plaque under fast mold filling conditions. When the plaque thickness is over 1 mm, a sub-layer appears near the intermediate layer, the thickness of this sub-layer decreases with increasing flow length. Type II shows the parallel orientation as opposed to that of type I and appears at a slower flow rate.