Advancing the Commercial Applications of Graphene

The purpose of this project is to manufacture a graphene functionalised fibre-reinforced composite material in which the variability of nano-filler dispersion and distribution is eliminated by the targeted inkjet printing of a dispersion of plasma functionalised graphene onto composite intermediates (such as fibre preforms, interleaves, tissues or prepregs), on specific areas where the graphene is required. This approach will deliver property enhancements or multi-functionality such as structural health monitoring (SHM), electrical, thermal and barrier performance that are demanded by high-end applications such as in the space, aerospace, and high-tech marine sectors.

To achieve this, our approach will utilise the controlled introduction of graphene to the structured reinforcement phase of the composite. The graphene will be plasma-functionalised to ensure that it remains well dispersed in the carrier solvent and, as such, does not re-agglomerate which could either block the inkjet printheads or reduce the inherent properties of the graphene.

The proposed research will evaluate two novel processing methods (plasma functionalisation and inkjet printing) for graphene which will address specific problems and improve on relative shortcomings in the performance of graphene- based materials within composite structures at a reasonable cost. In addition the proposed application has the potential to support another UK priority area (High Value Manufacturing). To date, the current use of graphene within composites has focused on mixing or in-situ exfoliation of graphitic materials within bulk resin. This method is inefficient because large proportions of graphene are required to have a demonstrable effect and consequently, due to the cost per kg of the material, it is difficult to overcome the cost barriers.

This proposal takes a different approach: inkjet printing allows small, yet concentrated, quantities of graphene to be placed accurately and reproducibly into specific areas of a composite in order to achieve various different potential benefits. Plasma functionalisation of the graphene prior to inkjet printing is expected to solve the problem of graphene forming agglomerates which so far have limited efforts at inkjet printing it. The research will address specific applications of graphene within the aerospace sector to create multifunctional composite structures tailored to form structural circuits, structural sensors for structural health monitoring (SHM) or simply to gain targeted mechanical property increases.

Current on-board electronic systems require the use of PCB circuits, embedded copper and wiring all of which can add additional cost and weight, and reduce performance. Copper inserts for example would typically have to be laminated into the composite structure by hand and could then act as sites for interlaminar crack initiation. The use of graphene in the manner proposed above will not reduce performance as it is expected that interlaminar toughness will increase and the added weight is negligible. Due to the targeted, automated and scalable manufacturing method along with the small amounts of material required the costs are expected to be competitive even considering the current price of graphene. Multiple benefits of using graphene will be exploited within the project: 1) interlaminar toughness increases 2) high electrical conductivity of concentrated graphene regions, 3) the flexibility of the printed embedded paths allowing for strain within the structure and 4) the relative ease of manufacture using inkjet printing. As the process could be used to functionalise dry fibre preforms, prepreg, interleaves or cured structures a wide variety of down-stream composite processing methods can be applied and for this reason the consortium expect that there will be a plethora of additional potential applications in different sectors in addition to the targeted aerospace application.

The impact of employing inkjet printing to introduce conductive graphene features into carbon fibre composites will benefit sectors such as aerospace, motor-sports and space initially. In the longer term, sectors such as energy, construction, marine, automobiles and consumer goods also stand to gain. The principal benefit is involved with reducing the costs incurred by increased maintenance periods as the conductive features can act as a sensing component that will indicate internal damage or a propagating crack. The electrical performance of graphene can also be used to create 'structural circuits' that replace a separate PCB board, which would otherwise be additional weight. A further benefit is the increase in the range of applications for composite materials since the graphene features can be used for thermal as well as electronic conduction. Ultimately, the increased functionality offered by these types of carbon fibre composite will result in reductions in vehicle weight which contribute to fuel savings and continue to stimulate demand for using carbon fibre composites as a light-weight structural material. The research that forms the base of this application plays into this demand by providing carbon fibre composites with enhanced properties whilst maintaining weight.

The proposed research will evaluate two novel processing methods - plasma functionalisation and inkjet printing - for graphene which will address relative shortcomings in the performance of graphene-based materials within composite structures at a reasonable cost. Additionally, the this proposal provides support to another UK priority area: High Value Manufacturing.

To date, the current use of graphene within composites has focused on mixing or in-situ exfoliation of graphitic materials within bulk resin. These methods are inefficient because large amounts of graphene are required to have a demonstrable effect and consequently, due to the cost per kg of graphene significant cost barriers are established. By employing inkjet printing, small, concentrated quantities of graphene can be placed accurately and reproducibly at specific areas in a composite in order to achieve various different potential benefits. Plasma functionalisation of the graphene, prior to inkjet printing, will prevent graphene from forming agglomerates which would inhibit inkjet printing. The research will address specific applications of graphene within the aerospace sector to create multifunctional composite structures tailored to form structural circuits, structural sensors for structural health monitoring (SHM) or simply to gain targeted mechanical property increases.