A MODEL OF THE RESIN IMPREGNATION IN THERMOPLASTIC COMPOSITES

Impregnation of thermoplastic resin into continuous unidirectional fiber tows was investigated. A power-law was employed to describe the effect of the shear rate on the viscosity of the molten resin. The effect of the impregnation pressure on the permeability of the fiber tow was also taken into consideration. The degree of impregnation was defined as the ratio between the number of impregnated fibers and the total number of fibers of a tow. A model was developed to describe the degree of impregnation as a function of time, pressure, temperature and tow size. The radial inward flow of resin through the fiber tow was assumed to be a flow through porous media and thus governed by Darcy's law. Experiments were performed to evaluate the validity of the model for different impregnation conditions such as impregnation time, pressure, temperature and tow size. From microphotographs of the cross-sections of the samples obtained from the experiments, the degree of impregnation was measured. Good agreement was found between the model and the experimental data.