A novel approach to study thermoplastic matrix materials’ impregnation behavior of woven fibres

With increasing demand of thermoplastic composites for the automotive and aviation industry, thermoplastic matrix materials’ impregnation behavior of woven fibres is of rising interest. Due to the temperature dependent flow behavior and the wide range of physical properties of thermoplastic melts, predictions of the wetting of the weft fibres by the melt are hard to make. This work focusses on a new attempt to study the impregnation behavior by investigating the wetting of fabrics by polymeric melts. The experiments were conducted in a Krüss drop shape analyzer (DSA30), equipped with a high-temperature chamber. Due to the fact that fabrics usually do not exhibit a flat surface which is additionally altered with increasing temperature depending on the thermal expansion of the material, a special sample holder had to be constructed to overcome those obstacles. The study includes different polymeric melts and a variety of woven fabrics. Polymeric pellets are placed on the preheated fabrics in the nitrogen-flooded high-temperature chamber and the time-dependent contact angle and the basic geometries as height and drop radius of the melt droplets are measured. The contact angle gives information about the wetting behavior, while the geometries can deliver data about the impregnation of the melt drops. The results show, that the impregnation behavior is strongly dependent on the area weight of the fabric and the kind of weave that is used. Furthermore, the temperature plays an important role in the wetting properties. An additional influence is derived from the interaction of the polymer with the fibres.