Presented in

Polymer Composites

August 1994, Vol.15, No. 4

APPLICATIONS OF A FIBER ORIENTATION PREDICTION ALGORITHM FOR COMPRESSION MOLDED PARTS WITH MULTIPLE CHARGES

L. G. Reifschneider and H. U. Akay*

Technalysis
Indianapolis, Indiana 46268

An application of a finite element simulation of mold filling orientation in fiber filled compression molded parts is presented. Three- dimensional thin-walled geometries are considered. Following a simulation of the filling process, a set of transport equations are solved to predict the locally planar orientation of short fiber composites. The final orientation states throughout the part provide the necessary information to obtain a locally orthotropic mechanical model of the composite. A sheet molding compound part with a multiple charge pattern is used to illustrate the generality of the algorithms developed for compression flow, fiber orientation, and property predictions. Derivations of the orthotropic mechanical properties obtained from the fiber orientation results are outlined.

Introduction

Prediction of the fiber orientations in compression molded parts is a major concern in the automotive and aerospace industries because fiber orientations affect the elasto- and thermo-mechanical properties of the parts. Hence, an accurate prediction of the fiber orientation is needed to determine the warpage and structural integrity of molded parts. In this paper, the numerical simulation of the mold filling process is performed to determine the velocity history during the mold filling. Then, this velocity history is used to determine the change of fiber orientation during filling.

Finite element based algorithms have previously presented by the authors for numerical prediction of mold filling and fiber orientations of compression molded parts (1,2). Numerical results were also presented to illustrate the solution capabilities developed for simple geometries and single charge patterns. In this paper, the extension and applications of the previously developed algorithms are presented to more complicated charge patterns. In addition, methods of determining mechanical properties of final composite parts, from the calculated fiber orientations, are shown. The details of the numerical algorithms are described and the factors affecting the results are discussed.