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

回收碳纤维(RCF)复合材料是航空航天等行业迈向更闭环制造模式的有价值的解决方案。从制造废物或报废(EoL)部件中回收纤维提高了复合材料的材料效率，并减少了它们对后续层压板的环境影响，因为它们从摇篮到浇口的体现能量较低。再生品的制造成本也比原始产品低。RCF确实有它自己的缺点。根据所使用的回收工艺，纤维的模数、强度和表面能可能会降低。除此之外，大多数经济上可行的回收工艺将纤维砍成通常在3-25 mm之间的长度。其结果是，RCF材料通常被降级为不需要与原始碳纤维(VCF)组件相同承载能力的组件。这是因为大多数回收材料是随机取向的不连续纤维垫的形式，因此不具有更多结构应用所需的各向异性机械性能或高纤维体积分数。这不是对这种有价值的材料的最佳利用。这就是高性能不连续纤维(HiPerDiF)等纤维重新排列技术通过将长度在1 mm到12 mm之间的废旧纤维转化为重新排列的带子来缩小VCF和RCF复合织物之间的差异的地方。用这些胶带制成的层压板已经使用一系列方法来制造，如高压灭菌器、热压和3D打印，然而还没有使用液体复合模塑(LCM)技术来制造这些排列的不连续材料的能力的表征。本PHD旨在描述使用选定的用于结构航空航天部件的LCM技术来制造排列的不连续织物的能力。特别是，人们感兴趣的是，不连续的对准织物是否会被树脂前部取代，即所谓的纤维洗涤。将测量层板的纤维排列程度、纤维重叠和纤维体积分数，并将其与机械性能进行比较。所使用的力学表征方法将包括一系列准静态、高速率和热/湿试验，以全面了解这些层压板的简单静态响应和耐久性。在概念验证和试验台规模的样本都已创建之后，材料将被应用于示范案例研究。然后将对该部件进行机械测试，以比较当前的材料和制造方法。将建立有限元分析(FEA)模型，以验证与结构相比材料上的载荷分布。最后，可以进行生命周期评估(LCA)，以显示使用再生材料而不是原始材料的影响。这将有助于加强在更具挑战性的结构应用中使用回收材料的理由。该项目由GKN航空航天公司支持。

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.