"Repair of Thermoplastic Composites: Processing, Modelling and Characterization"

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To successfully achieve cost and weight reduction in the next generations of business and commercial airplanes, new advanced structural materials must be investigated. Thermoplastic composite materials have the potential to lead to such cost and weight reductions with some advantages over thermosetting composites like their better damage tolerance. This advantage makes them ideal candidates for applications in which impact damage is likely, e.g., wing leading edges. Repair methods were developed for thermosetting composites. In the case of bonded repairs, the damaged composite plies are removed from the component's surface and new pre-impregnated plies are applied on the surface. Curing of the material is then achieved by applying heat and pressure. When it comes to thermoplastic composites, the damaged components are currently being replaced instead of being repaired, with associated negative cost and environmental impacts. The lack of research done on repair of thermoplastic composites also limits their use to small components as it would become very expensive to replace a large and complex aerospace structure component. In light of the above, this research program aims to develop methodologies for repairing high performance thermoplastic composite structures by means of modelling, processing and characterization. The long-term environmental degradation and ageing of thermoplastic composite welded joints will be investigated and innovative manufacturing techniques will be developed to repair thermoplastic composites, taking into account their unique ability to be re-processed or re-welded. This will include repair of delamination created in a weld line by impact or repair of more severe damage, e.g., replacement of several plies of a composite components, always with the goal of restoring the initial mechanical properties of the component. The manufacturing techniques will be linked to process models that predict the consolidation, crystallinity and degradation of the polymer as it is re-processed or re-welded. This work will provide Canadian aerospace industry with repairing methods for high performance thermoplastic composite structures, thus achieving cost reduction and positive environmental impact.