Predicting the performance of sustainable composite materials in a range of manufacturing techniques

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Recycled carbon fibre (rCF) composites are a valuable solution for industries such as aerospace to move towards a more closed-loop manufacturing model. Reclaiming fibres from manufacturing waste or end-of-life (EoL) components increases the material efficiency of composite materials and decreases their environmental impact of subsequent laminates due to their lower embodied energies from cradle to gate. Recyclates are also cheaper to manufacture than their virgin counterparts. RCF does have its own drawbacks. Depending on the recycling process used, the fibre's modulus, strength and surface energy can be diminished. In addition to this, the majority of economically viable recycling processes chop the fibre into lengths typically between 3-25mm. The result of this is that rCF materials are often downcycled into components that do not require the same load-bearing capabilities as virgin carbon fibre (vCF) components. This is because most recycled materials are in the form of randomly oriented discontinuous fibre mats and therefore do not possess the anisotropic mechanical properties or high fibre volume fractions required for more structural applications. This is not the best use of this valuable material. This is where fibre realignment techniques, such as High-Performance Discontinuous Fibre (HiPerDiF), are closing the discrepancy between vCF and rCF composite fabrics by transforming waste fibres between the lengths of 1 and 12mm into realigned tapes. Laminates made from these tapes have been manufactured using a range of methods such as autoclave, hot press and 3D printing, yet there has not yet been a characterisation of the ability to manufacture these aligned discontinuous materials using liquid composite moulding (LcM) techniques.This PhD will aim to characterise the ability to manufacture aligned discontinuous fabrics using a selected range of LcM techniques for structural aerospace components. In particular, there is interest in whether the discontinuous aligned fabrics will be displaced by the resin front, known as fibre washout. The degree of alignment of the laminates' fibres, fibre overlap, and fibre volume fraction will be measured and compared to the mechanical properties. The mechanical characterisation methods used will include a range of quasi-static, high-rate and hot/wet tests to understand the full scope of both the simple static response and durability of these laminates. After both proof of concept and bench scale specimens have been created, the materials will then be applied to a demonstrator case study. Mechanical testing of this component will then take place as a way of comparing the current materials and manufacturing methods. A finite element analysis (FEA) modelled will be created to validate the load distribution on the materials compared with the structure. Finally, a life cycle assessment (LCA) can be made to show the impact of using reclaimed materials instead of virgin. This will help to strengthen the case for using recyclates in more challenging structural applications.This project is supported by GKN Aerospace.