Friction in composites forming

A wide range of forming techniques have been developed for composites. There is a correspondingly large number of composite materials available, e.g. dry material or material pre-impregnated with resin, while the textile architecture can take many forms such as unidirectional or woven. A key motivation for introduction of these processes is increased automation, giving reduced cycle time and cost and increased repeatability and quality. However the development of the appropriate material and process for a given application has often proved problematic, with process development being a costly, empirical activity with a rather uncertain chance of success.

The goal of this project is to gain a fundamental scientific understanding of friction in composites forming, to develop standard tests which capture the appropriate mechanisms, and to demonstrate how these tests and models can be applied to manufacture of a case-study component. The value of the research will be demonstrated by application of the experiments and modelling to the case study component to quantify potential improvements in product quality.

Uni-directional and woven carbon will be used in dry form and as pre-prepreg. Friction between the tool or vacuum bag and the composite and between plies will be considered. Processing routes that will be explored will be a consolidation-type of deformation and a draping-type of deformation. In both cases idealised forms of geometry will first be used to gain the underlying scientific understanding. Observations of the contact conditions in laboratory-scale tests will be used to uncover the mechanisms leading to friction in composites forming. Tribological models of the contact between the various elements (tool to ply and ply to ply) will be developed and validated via tribological lab experiments. Standardised tests will developed to measure friction in a way that replicates the mechanisms found in the tribological tests. A case study geometry will be used to understand the implications for forming of components.

The work will be in close collaboration with the industrial partners who will assist with supply of materials, definition of appropriate tests methods and help with the case study formulation and implementation.

The potential benefits to society and hence impact beyond academia of this project is expected to be high, since the project will impinge on a wide range of composites manufacturing activities.

There has been considerable recent innovation and investment in composites forming by industry. By focussing on the scientific issues associated with friction in composites forming, the research will help the substantial commercial sector in the UK and worldwide working with composites, for example UK automotive and aerospace manufacturers (Jaguar Land Rover, Bentley Motors, Airbus, Rolls-Royce, Westland, Dowty, BAE Systems.), wind turbine companies such as GE Wind and Vestas and the transport and marine industries. Specific benefits to these companies of the research include reductions in weight due to better materials and manufacturing routes, improved confidence in design, reduced development times and costs, and a better understanding of the effect of manufacturing on product performance and quality assurance. The industrial partners will benefit specifically from a novel set of testing methodologies and from validated friction experiments across a range of configurations and materials.

Better knowledge of friction in composites forming can feed into academic research programmes developing new materials and process routes for composites. The National Composite Centre (NCC) has recently made a significant investment in large-scale tape lay-up and hot-drape forming equipment. Better modelling of friction will be needed to exploit these processes for the industrial collaborators in that venture.

The support of Granta Design, via their Granta MI materials information management system, will ensure that the custodianship of the data fully meets EPSRC's recently implemented policy framework on research data. The data will then be made available via a web interface in two forms, a commercial database for the industrial collaborators and a public interface for others to exploit. The fully documented way in which links are made between the test materials and methods will allow both Umeco and Jaguar Land Rover to include the data collected in the project in a certifiable way, enabling more effective exploitation of both test methods and specific findings. The public interface will provide an effective resource for other industries and academic beneficiaries to exploit.