Developing component-scale composites using nanocarbons

The phenomenal properties reported for nanocarbons such as carbon nanotubes and graphene have generated much interest for their use in composite materials. Theoretical predictions demonstrate the potential for significant improvements in strength, stiffness and multi-functionality of materials. Despite many promising results, the issues of repeatability and scale-up have yet to be adequately addressed, with manufacture limited to small lab-scale samples.

In the work described, researchers from Cardiff University and Haydale explore techniques for component-scale manufacture of hierarchical composites by liquid infusion, using both carbon nanotube and graphene materials. A unique plasma process, developed by Haydale, was adopted for controllable functionalisation of large batches of nanocarbons (100s of grams) prior to mixing with epoxy resin. A rheological study indicated that filler morphology, functionalisation and fill weight all have an effect on epoxy resin viscosity.

Using these developed nanocomposite resins, a Resin Infusion under Flexible Tooling (RIFT) technique was developed. Resin flow studies informed an optimum setup that facilitated full wet-out of large area UD carbon fibre laminates and the resulting materials showed significant improvements in mechanical properties, demonstrating up to an approximately 50% increase in Compression After Impact (CAI) properties. The RIFT process and tooling were further developed to enable the manufacture of I-section stiffeners and the production of component-scale (0.9x0.55m) stiffened panels was demonstrated.

The scalability of the Haydale graphene plasma functionalisation technique, resin mixing and resin infusion processes has been demonstrated by the manufacture of component-scale stiffened composite panels. The advances in composite material strength and stiffness will be of considerable interest to the aerospace and automotive industry in particular.