(180ah) The Effect of Glass Fiber Length On Experimental Orientation Distribution in the Entry Region of Injection Molded Composites

The Method of Ellipses (MoE) is an experimental technique originally developed to analyze the orientation state of rigid fibers within fiber-reinforced polymer composites.  For glass fiber systems, rigid fibers are classified as those possessing an average length, l, of less than 1 mm.  Glass fibers of this length are commonly referred to as “short.”  In this paper, the MoE has been extended for evaluation of composites reinforced with “long” glass fibers (i.e. l > 1 mm).  This study details the complexities of long glass fibers, including increased fiber flexibility, curvature, and clustering, as well as the resulting complications in evaluation of fiber orientation.  Furthermore, potential modifications to the MoE are discussed in order to improve the method for use specifically with long fiber composites.  Preliminary data is included to show the effect of increasing average fiber length on orientation, particularly within the entry and gate regions of injection molded parts.  Additionally, the effect of flow field complexity on fiber orientation distribution is discussed, by comparison of data from the 2-dimensional center-gated disc and the 3-dimensional end-gated plaque.