Rheology of thermoplastic matrix short glass fiber composites

An experimental investigation of the processing of glass-fiber reinforced polypropylene is presented. Final fiber length distribution, chopped strand disgregation, matrix and composite rheological properties, die swelling, and surface morphology are analyzed. Strand disgregation is observed to increase with shear rate and fiber concentration and to decrease with the length of the die. Final fiber length distribution appears to be independent of die length but decreases with fiber concentration and shear rate. The viscosity and first normal coefficient functions show a linear dependence with shear rate and increases with fiber concentration. The extruded filament surface shows a minor roughness when the shear rate increases. The results of this experimental characterization give useful information for determining the influence of processing variables on the final properties of short fiber reinforced polypropylene and constitutes the first part of a more ambitious project that also includes the development of a modeling strategy of the processing behavior of short fiber composites.