Consolidation of hybrid textiles for aerospace applications

Side-by-side hybrid textiles consist of layers of woven reinforcing fibres and thermoplastic fibres fabrics alternatively stacked on each other, as represented in Figure 1. Press moulding of side-by-side hybrid textiles is a manufacturing method where a near-net shape final part is produced in a single step, unlike pre-impregnated materials which require a separate impregnation step. This intermediate material offers a great drapeability and vast design freedom as the hybrid system can be easily and locally modified by changing the textile architecture of a single layer or locally adding a polymer layer for instance. These advantages could be used to locally tailor the composite properties, such as using the full potential of composites to create high-performance parts. However, the prerequisite for such an optimization approach is a consolidation model that can be implemented into a finite element analysis, which is not available yet. We demonstrate the concept's relevance for the aerospace industry by producing and consolidating such a hybrid textile with carbon fibres and polyetherimide into semi-complex shapes. A quasi unidirectional fibre architecture is used for the carbon fibres to keep the properties close to a unidirectional layer, as proved by mechanical characterization. As a first step towards a consolidation model, we develop an impregnation model that considers entrapped air, including dissolution into the polymer melt. The model is validated by consolidating flat plates, which confirm that air entrapment can play a major role in impregnation and needs to be accounted for the prediction of porosity.