FLOW AND FIBER ORIENTATION CALCULATIONS IN REINFORCED THERMOPLASTIC EXTRUDED TUBES

A calculation of fiber orientation of reinforced thermoplastics in two tube die geometries is presented. The flow field and fiber motion are calculated using coupled anisotropic constitutive equation and equati on of change for fiber orientation. A finite element method is used fo r the flow field computation, and a simplified characteristic method f or the fiber orientation. Results show that fibers orient parallel to the tube axis in a classical die of constant radius in the final land whereas fibers have a more isotropic orientation in a die with a final divergent land. Experimental observations and quantification of fiber orientation in reinforced thermoplastic tubes extruded with the two d ies are presented. Results of the calculation agree well with the expe rimental data for the classical die. For the diverging die, the agreem ent is good at the tube surface, but the calculation underestimates th e degree of orientation perpendicular to the tube axis in the core of the tube.