Novel, bioinspired, aligned-discontinuous reclaimed fibre composites for enhanced compressive performance

尽管经过60多年的积极研究，拉伸强度和抗冲击性等性能得到了相当大的改善，但复合材料的压缩强度水平仍比测量的纵向拉伸强度低约40%。这种相对的弱点，以及系统地模拟所产生的各向异性失效机制的困难，是这些材料在工业上更广泛采用的一个重大障碍。该研究项目是EPSRC支持的下一代纤维增强复合材料（NextCOMP）计划的一部分，专注于开发新型复合材料以应对这一挑战。一个主要的重点是研究层次结构的材料，灵感来自天然复合材料，如骨骼和木材。这些生物材料的特点是不同的，但互补的增强系统在整个长度尺度上，并表现出更高的压缩承载能力比传统制造的复合材料。预计能够模仿这种结构的新一代制造复合材料将在航空航天、能源和汽车领域找到许多创新的工业应用。不连续纤维材料由于较低的总体机械性能而在历史上被用作制造的复合结构中的本体增强。其性能的一个关键决定因素是纤维排列的程度。布里斯托大学开发的高性能不连续纤维（HiPerDif）工艺是一种经过验证的方法，可利用水作为转移介质，生产长度在1至12 mm之间的高度对齐的不连续纤维的复合带。该工艺提供了生产具有与连续纤维复合材料的机械性能相当的材料的潜力，给定足够高的纤维纵横比以允许负载转移和纤维拔出。此外，高度对齐的纤维复合材料在克服连续纤维材料当前的局限性方面表现出了强大的前景，例如：缺乏延展性，以及由此产生的可用成形方法的限制;复杂几何形状的大批量无缺陷自动化生产的困难;以及循环经济中所需的真正可持续生产方法的整合。该项目将研究一系列制造的高度对齐的纤维材料在压缩中的行为，并评估它们在NextCOMP计划中正在研究的分层结构复合材料中的应用潜力。研究一系列高度排列的不连续碳纤维复合材料在压缩中的行为。- 评估在更大的复合材料结构中利用这些材料的潜力，灵感来自天然复合材料，并具有层次结构。- 研究这种复合材料的潜在加工方法，以改善有益的材料性能和生产率特性。包括自动铺带、预浸料缠绕和人机协作等机械化工艺。- 进行不连续纤维复合材料的试验，以确定压缩性能和制造效率。- 制造、测试和评估示范结构，将不连续纤维复合材料作为更复杂的分层结构中的一个元素。结构几何形状和材料成分应与工业相关。识别和评估不连续碳纤维复合材料的加工方法和来源。- 确定合适的几何形状和制造方法，用于有用的样品和演示器测试和数据采集。- 获得使用自动化复合材料加工方法的适当经验。- 确定合适的机械测试制度，产生有用的和可重复的比较数据。- 在NextCOMP计划的背景下持续评估结果。

Despite over 60 years of active research and considerable improvements in properties relating to tensile strength and impact resistance, compressive strength levels in composites are still some 40% lower than measured longitudinal tensile strengths. This relative weakness, and the difficulty in systematically modelling the resultant anisotropic failure mechanisms, represents a significant barrier to the wider industrial adoption of these materials. This research project forms part of the EPSRC supported Next Generation Fibre-Reinforced Composites (NextCOMP) programme, concentrated on developing novel composite materials to meet this challenge. A principal focus is investigating hierarchically structured materials, inspired by natural composites such as bone and wood. These biomaterials feature dissimilar but complementary reinforcement systems across length scales and exhibit higher compressive load carrying capacities than traditional manufactured composites. It is anticipated that a new generation of manufactured composite materials able to mimic such architectures will find numerous innovative industrial applications including in the aerospace, energy, and automotive sectors. Discontinuous fibrous materials have historically been used as bulk reinforcement in manufactured composite structures due to lower overall mechanical properties. A key determinant of their performance being the degree of fibre alignment. The High-Performance Discontinuous Fibre (HiPerDif) process developed at the University of Bristol is a proven method for producing composite tapes of highly aligned discontinuous fibres of between 1 and 12mm in length, utilising water as a transfer medium. The process offers the potential to produce materials with mechanical properties comparable to those of continuous fibre composites, given a fibre aspect ratio high enough to allow load transfer and fibre pull out. Furthermore, highly aligned fibre composites have shown strong promise in overcoming current limitations of continuous fibre materials such as: lack of ductility, and the resultant restrictions in available forming methods; difficulties in high volume, defect-free automated production of complex geometries; and integration of the truly sustainable production methods required in a circular economy. This project will investigate the behaviour of a range of manufactured highly aligned fibrous materials in compression and assess their potential for use in the hierarchically structured composite materials being researched within the NextCOMP programme. AIMS - Investigate the behaviour of a range of highly-aligned discontinuous carbon-fibre composites in compression. - Assess the potential for utilising these materials within larger composite structures, inspired by natural composites, and featuring hierarchical architectures. - Investigate potential processing methods for such composites that improve beneficial material property and production rate characteristics. To include mechanised processes such as automated tape laying, prepreg filament winding and human-robot collaboration. - Undertake trials of discontinuous fibre composites to determine compressive performance and manufacturing efficiency. - Manufacture, test and assess demonstration structures, featuring discontinuous fibre composites as one element within a more complex hierarchical architecture. Structural geometries and material composition to be industrially relevant. OBJECTIVES - Identify and assess processing methodologies and sources of discontinuous carbon-fibre composite materials. - Determine appropriate geometries and manufacturing methods for useful sample and demonstrator testing and data acquisition. - Acquire suitable experience in using automated composite processing methods. - Identify suitable mechanical testing regimes that generate useful and repeatable comparative data. - Continually assess results in the context of the NextCOMP program.