The Dynamic Behavior of a Concentrated Polymeric Suspension Containing Non-Brownian Glass Fibers in Simple Shear Flow

In this paper we study the dynamic behavior of a concentrated short glass fiber suspension subject to simple shear flow. In particular we are interested in determining the relationship between the stress growth functions (shear and first normal stress) and the evolution of the fibers’ orientation distribution within the sample. Stress growth experiments, in start-up of flow, are performed on a Rheometrics Mechanical Spectrometer (RMS-800). Samples at rest are deformed at a constant strain rate for a specified time (i.e. strain) that correlates various points of interest on a stress growth vs. strain plot. The sample temperature is then lowered below the suspension melt temperature “freezing” the fiber orientation. The fiber orientation within the sample is characterized using confocal laser microscopy. The experimental results are then compared to predictions based on the generalized Jeffery equation. It is found that the theory predicts the fiber orientation to evolve faster than is seen experimentally.