Investigation of the influence of melt-impregnation parameters on the morphology of thermoplastic UD-tapes and a method for quantifying the same

Abstract

During the production of unidirectional fibre-reinforced thermoplastic semi-finished products (UD-tapes) in melt-impregnation processes, parameters such as melt viscosity, production speed and impregnation die setup have a significant influence on the quality of the produced UD-tapes. These influences are investigated in this article by producing UD-tapes in an extrusion-based melt-impregnation process with varying impregnation parameters. To quantify the homogeneity of the fibre distribution, a method is presented and applied, in which microscopic cross-sectional images of the UD-tapes are analysed and a homogeneity coefficient is calculated. The porosity is also determined by analysing microscopic cross-sectional images of the UD-tapes. The results show that a decreased melt viscosity and a high number of redirection elements in the die have a positive influence on the homogeneity of the fibre distribution. Furthermore, a significant influence of the melt viscosity, the production speed and the die setup on the porosity was proved.