Short fiber reinforced thermoplastics. II. Interrelation between fiber orientation and rheological properties of glass fiber-reinforced Noryl

Mechanical properties of short fiber reinforced thermoplastics depend on the fiber orientation distribution produced during the melt flow processing step. An experimental investigation of fiber orientation during shear flow through a circular die is presented. A quantitative determination of the glass fiber orientation distribution was done by analyzing photomicrographs of polished extrudate sections. Planar and axial fiber orientation distributions as affected by shear rate and total shear are discussed. The reliability of a classical metallographic technique for fiber orientation determination was evaluated. Orientation effects are expressed by a single orientation parameter which is used to account for the average fiber orientation contribution to the relative viscosity. The influence of shear rate, total shear, fiber concentration, and temperature on fiber orientation has been investigated. It is concluded that an orientation parameter should be used to account for fiber concentration effects on the relative viscosity. Calculated values, considering the orientation parameter, show good agreement with the experimental relative viscosity results.