Manufacturing for structural applications of multifunctional composites

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Manufacturing for structural applications of multifunctional composites

Host Institution: Imperial College London, The University of Bristol

Lead Investigator: Ivana Partridge

Co-Investigator: Arjun Radhakrishnan, Caroline O’Keeffe, Carwyn Ward, Dmitry Ivanov, Emile Greenhalgh, Ian Gent, Kaan Bilge, Maria Valkova, Milo Shaffer

Aims

The over-arching aim of the project is to investigate and address the design and manufacturing issues associated with multifunctional composites, addressing specifically the transport phenomena of heat and electrical conduction.

Aim 1: To explore novel manufacturing methods for creating multi-matrix and multi-fibre graded composites and local integration of functionalised patches. The locality within matrix is achieved through liquid resin printing enabling integration of additive-rich resins in predefined patterns through the thickness and in-plane of composite laminates. The specific focus of the matrix study is on the relation between processing parameters (injection, consolidation, curing), chemorheology of injected resins, and the morphology of printed patches. The specific focus of the fibre modification is the insertion of novel multi-material threads and fibres into dry fibre preforms, both in-plane and out-of plane of the structure.

Aim 2: To explore the manufacturing issues associated with the creation of structural power materials (structural supercapacitors), which simultaneously store, and deliver, electrical energy whilst carrying mechanical loads. Such multifunctional materials offer a completely different approach to using composites in transport and mobile electronics, and have the potential to provide a step change in weight and volume driven designs.

The research to date has focussed on demonstration of the concept and addressing the scientific challenges associated with this novel class of materials, but within this Composite Manufacturing Hub project, the general design and manufacturing issues associated with structural power materials are being addressed. Such research is vital to facilitate adoption of these materials by industry, and is of general relevance to a wide range of potential multifunctional composite systems which must harmonise conflicting requirements.

Progress

At Bristol, the new Hertzog microbraider has been commissioned (see image) and preliminary work carried out using standard reinforcing thread types. Early trials using metallic wires and threads to cobraid with fine carbon fibre rovings are producing flexible but stable braids of under 1 mm in diameter. The limits of achievable braiding patterns are being explored for different material combinations.

Promising stable multi-material braids have resulted from early braiding trials at Bristol, potentially addressing a current industrial problem by protecting fragile commercial carbon fibre threads from frequent breakage in the tufting operation. A collaboration between Bristol and the NCC ensures that such early braided products can be tested for suitability of use in the industrial tufting head, thus providing pointers for future modification of the braiding patterns.

Regarding Carbon Aerogel (CAG) development in the context of structural supercapacitors, trials on precursor infusion and pyrolysis have been undertaken at Imperial College on a number of different dry fabrics, such as spread tow weaves and NCF materials. Good infusion of the CAG into the interior of the tows and bonding of the CAG to the fibres has been achieved, however, interaction with the binder for the spread-tow has caused some difficulties. Further development work is currently underway to introduce active elements onto the CAG to further enhance the electrical performance. In parallel, studies are underway to rank and identify the best separator materials.

Figure 1: Carbon Aerogel (CAG) is infused into the interior of the tows in multimaterial structural supercapacitors

Figure 1: Carbon Aerogel (CAG) is infused into the interior of the tows in multimaterial structural supercapacitors

Work has started to address structural supercapacitor device design and modelling of mechanical performance. Finite element models (Abaqus) are being developed to predict the compaction of the devices during consolidation (see image), to understand how processing will influence the microstructure and hence the performance of the devices.

Figure 2: University of Bristol’s microbraider

Figure 2: University of Bristol’s microbraider

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