A Practical Approach for Validation of Aptitude of Sized Carbon Fibers for the In-Mould -Impregnation Process

Abstract

As a new and innovative processing method for carbon fiber reinforced thermoplastic composites, the In-Mould-Impregnation process (IMI) adopts carbon fibers as a heating element by electrical conduction. During heating of the dry carbon fibers in the production process, temperatures up to over 500°C can occur. However, the surface properties of carbon fibers and sizing may change under such conditions and thus affect the resulting composite. The present study is a practical approach to validate the suitability of sized carbon fibers for the IMI. The influence of a thermal treatment according to the parameters of the IMI-Process on carbon fiber-thermoplastic matrix interfacial adhesion was investigated by means of micromechanical and optical test methods. The experimental results demonstrate that the thermal treatment of carbon fibers causes a reduction of tensile strength of single fibers. It does not show an influence on the micromechanical breaking behavior in a PA 6 composite but the surface tension of carbon fibers changes. The change in surface tension can affect the wettability of the carbon fiber with a thermoplastic matrix.