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

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.

There are seven principal groups of beneficiaries for our new EPSRC Centre for Doctoral Training in Composites Science, Engineering, and Manufacturing.

1. Collaborating companies and organisations, who will gain privileged access to the unique concentration of research training and skills available within the CDT, through active participation in doctoral research projects. In the Centre we will explore innovative ideas, in conjunction with industrial partners, international partners, and other associated groups (CLF, Catapults). Showcase events, such as our annual conference, will offer opportunities to a much broader spectrum of potentially collaborating companies and other organisations. The supporting companies will benefit from cross-sector learning opportunities and

- specific innovations within their sponsored project that make a significant impact on the company;
- increased collaboration with academia;
- the development of blue-skies and long-term research at a lowered risk.

2. Early-stage investors, who will gain access to commercial opportunities that have been validated through proof-of-concept, through our NCC-led technology pull-through programme.

3. Academics within Bristol, across a diverse range of disciplines, and at other universities associated with Bristol through the Manufacturing Hub, will benefit from collaborative research and exploitation opportunities in our CDT. International visits made possible by the Centre will undoubtedly lead to a wider spectrum of research training and exploitation collaborations.

4. Research students will establish their reputations as part of the CDT. Training and experiences within the Centre will increase their awareness of wider and contextually important issues, such as IP identification, commercialisation opportunities, and engagement with the public.

5. Students at the partner universities (SFI - Limerick) and other institutions, who will benefit from the collaborative training environment through the technologically relevant feedback from commercial stakeholder organisations.

6. The University of Bristol will enhance their international profile in composites. In addition to the immediate gains such as high quality academic publications and conference presentations during the course of the Centre, the University gains from the collaboration with industry that will continue long after the participants graduate. This is shown by the

a) Follow-on research activities in related areas.
b) Willingness of past graduates to:

i) Act as advocates for the CDT through our alumni association;
ii) Participate in the Advisory Board of our proposed CDT;
iii) Act as mentors to current doctoral students.

7. Citizens of the UK. We have identified key fields in composites science, engineering and manufacturing technology which are of current strategic importance to the country and will demonstrate the route by which these fields will impact our lives. Our current CDTs have shown considerable impact on industry (e.g. Rolls Royce). Our proposed centre will continue to give this benefit. We have built activities into the CDT programme to develop wider competences of the students in:

a) Communication - presentations, videos, journal paper, workshops;
b) Exploitation - business plans and exploitation routes for research;
c) Public Understanding - science ambassador, schools events, website.