Obtaining repeatable initial fiber orientation for the transient rheology of fiber suspensions in simple shear flow

Abstract

Many researchers reporting the transient rheology of fiber suspensions have not experimentally verified the initial fiber orientation. An assumption for the initial orientation is then required to simulate the fiber orientation evolution and stress response. Measurements of fiber orientation obtained prior to testing in a rheometer can confirm the homogeneity of fiber orientation throughout a sample and repeatability between multiple samples. In this work, the transient rheology of glass fiber suspensions above 0.5 mm in length was measured in a sliding plate rheometer with the initial fiber orientation generated through compression molding, flow reversal, and injection molding. Measurements of shear stress and fiber orientation were obtained to evaluate each sample preparation method and to gain insight into the stress-microstructure relationship. Preshearing and applying flow reversal was used in an effort to control the initial fiber orientation for transient shear stress measurements, but fiber orient...