Compression molding of semi-concentrated fiber suspensions: Flow and fiber orientation

Abstract

The focus of this paper is compression molding of semi-concentrated fiber suspensions. During compression molding a premeasured amount of raw material (charge) is placed between two halves of a die. The die is then closed so that the charge is compressed, thus taking the shape of the die. In this paper we used the theory developed by Dinh and Armstrong for semi-concentrated fiber suspensions, although the theoretical background and numerical procedures developed in this paper can be extended to other theories as well. The constitutive equations are expressed in terms of the flow kinematics through the use of Finger and Cauchy finite deformation tensors which are approximated numerically using a semi-implicit finite difference scheme. The full unsteady form of the governing equations are formulated using a mixed Eulerian-Lagrangian description and solved using a classical Galerkin Finite Element Method. Results are shown for the filling of a two-dimensional cavity under various process conditions such as constant compression rate, constant compression force and at different fiber concentrations and fiber aspect ratios.