Co-authors​ :

 Karine LABASTIE (FRANCE), Puech LAURENT (FRANCE), Erb GREGORY (FRANCE) 

Facing the objective of the decarbonisation of the aeronautic sector for 2030, the industrials strive for identifying and developing different solutions. Among them, composites materials have been identified for a long time as performant solution for radically reducing the weight of aerostructures. Up to now, mainly applications with thermoset composites have been developed. Nevertheless, this class of materials are difficult to repair and they are not well adapted to automating and increasing production rates. Thermoplastic composites can be a solution to these constraints as by their chemistry they can be reprocessable, weldable and are suited for automated production processes. Nevertheless, they suffer from highest processing temperatures that affect their production costs versus the thermoset composites. For these reasons, out of autoclave consolidation processes have been pushed for this class of composites. Many studies highlighted that not all prepregs are well adapted for oven consolidation: due to the pressure reduction in comparison to autoclave process, residual porosity is present in the composite parts, affecting their final performances.
The goal of IRT Saint Exupéry’s study is to identify the influence of the morphological characteristics of a high performance thermoplastic carbon prepreg on the final quality and performance of the associated composite, in oven consolidation. To do this, an iterative methodology has been set up at the IRT SE, starting from the production of different prepreg morphologies thanks to the thermoplastic impregnation line installed at IRT SE, up to the evaluation of the mechanical properties of the composites going through the characterisation of the prepreg morphology. This study has been done with couples of carbon fibre/matrix well known from the aeronautic market. To be able to modify the morphology of the prepreg, IRT SE has developed an impregnation process coupling different technologies of impregnation. In parallel, methods of analysis and numerical tools have been developed to characterise the prepreg morphology, based on the analysis of pictures of the transversal section and the surface of the prepregs obtained respectively by optical and scanning microscopies. A similar approach combining experimental analyses and numerical tools has been carried out to evaluate and quantify the quality of the composites obtained using c-scan, optical analysis and mechanical properties. This work has confirmed that the prepreg morphology has a significant influence on the quality of the OOA consolidated composites. In addition, the coupled analysis of the prepreg morphology versus the quality of the final composites allowed defining an optimum prepreg morphology for OOA application for the studied carbon fibre/matrix couple.