(708b) Recent Advancements for Simulating Long Glass Fiber Composites in Injection Molding Applications

 Recent Advancements for Simulating Long Glass
Fiber Suspensions in Injection Molding Applications

Kevin
J. Meyer, John T. Hofmann, and Donald G. Baird

            The
properties of fiber-filled composites are strongly influenced by the
orientation of the fibers within the composite structure. A popular way to
reinforce composite materials cheaply is through the introduction of both short
glass fibers (SGF) and long glass fibers (LGF) into the polymer matrix. This
allows current industrial molding techniques to be utilized with little or no
modification while significantly increasing the molded part's properties. Traditionally
the Folgar-Tucker model, with the addition of a delay
parameter, has been employed to predict fiber orientation in injection molded
parts and has attained wide success when the fibers are short
. In suspensions where the glass fibers can be
considered long
 bending of fibers
has been seen as a consequence of complex flow fields which arise in injection
molding. The modified Folgar-Tucker model becomes
less accurate as the flexibility of fibers increases. Hence, the ?Bead-Rod?
model, where the semi-flexible fiber is represented as two rods connected by a
hinge, is proposed as an alternative to the modified Folgar-Tucker
model. The Folgar-Tucker and Bead-Rod models are used
to predict fiber orientation in center-gated and end-gated test geometries for
LGF systems. Predictions for both models are compared to experimentally
obtained data of long fiber orientation. The Bead-Rod model is observed to
agree more closely with experimentally observed LGF orientation than the modified
Folgar-Tucker model at a number of sampling points
through the mold cavity.