A MODEL FOR THE FLOW OF A CHOPPED FIBER REINFORCED POLYMER COMPOUND IN COMPRESSION MOLDING

The flow of a chopped fiber reinforced polymer compound in compression molding is modeled as a two-dimensional membrane-like sheet which extends uniformly through the cavity thickness with slip at the mold surface. The model is consistent with both the kinematic mechanisms observed in actual flow and the three-dimensional anisotropy caused by the arrangement of fibers in the sheet. The material resistance to extension is expressed in a constitutive equation for the two-dimensional stress resultant formed by integrating the planar stress components through the thickness of the cavity. This stress resultant is assumed to be a linear function of the corresponding planar rate of deformation in the molding compound. Through a mechanism of fiber-resin interaction, the material resistance to extension can be characterized by a single scalar function of the transverse temperature distribution.