A model for a thermoplastic pultrusion process using commingled yarns

A pultrusion process using thermoplastic commingled yarns as raw material has been studied. In such a process, the degree of impregnation is one of the most important parameters affecting the mechanical properties of the final product. The degree of impregnation was estimated by dual-scale porous media flow models, including microscopic impregnating flow and macroscopic resin flow. Dimensionless parameters were adopted to describe the microscopic flow impregnating the fiber agglomeration. They were found to be useful in estimating the state of impregnation of thermoplastic composite with different types of raw materials. In order to verify the validity of the model, experiments were performed. A laboratory-scale pultrusion apparatus was designed and built and glass-fiber/polypropylene thermoplastic composites were fabricated with the apparatus. The degree of impregnation of the final product was measured by microscopic observations of the cross-section. The agreement between the experimental data and prediction by the model was found to be satisfactory.