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

尽管经过60多年的积极研究，在抗拉强度和抗冲击性能方面取得了相当大的进步，但复合材料的抗压强度水平仍然比测量的纵向抗拉强度低40%左右。这种相对的弱点，以及在系统地模拟由此产生的各向异性破坏机制方面的困难，代表了这些材料更广泛的工业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）项目的一部分，该项目专注于开发新型复合材料来应对这一挑战。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，如骨和木材。这些生物材料在长度尺度上具有不同但互补的增强系统，并表现出比传统制造复合材料更高的压缩承载能力。可以预见的是，能够模拟这种结构的新一代人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。由于整体力学性能较低，不连续纤维材料历来被用作人造复合材料结构的大块增强材料。其性能的一个关键决定因素是纤维的排列程度。布里斯托尔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，可以生产长度在1至12毫米之间的高度排列的不连续纤维复合带，利用水作为传输介质。该工艺为生产具有与连续纤维复合材料相当的机械性能的材料提供了潜力，只要纤维长径比足够高，可以允许负载转移和纤维拔出。此外，高度排列的纤维复合材料在克服当前连续纤维材料的局限性方面显示出强大的前景，例如：缺乏延展性，以及由此产生的可用成型方法的限制；复杂几何形状的大批量、无缺陷自动化生产困难；并整合循环经济所需的真正可持续的生产方法。该项目将调查一系列制造的高度排列纤维材料在压缩中的行为，并评估它们在NextCOMP计划中研究的分层结构复合材料中的应用潜力。目的-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。-评估在大型复合材料结构中使用这些材料的潜力，灵感来自天然复合材料，并具有分层结构。-研究此类复合材料的潜在加工方法，以提高有益材料的性能和生产率特征。包括机械化过程，如自动铺带，预浸丝缠绕和人机协作。-进行不连续纤维复合材料的试验，以确定压缩性能和生产效率。-制造，测试和评估演示结构，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组成与工业相关。目标-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测试和数据采集。-具备使用自动化复合加工方法的相关经验。-确定合适的机械测试制度，产生有用和可重复的比较数据。-在NextCOMP项目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.