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

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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.