The team says replacing a metal wheel well with a composite one could enable Volvo to reduce the number of batteries needed to power the electric motor. They believe this could lead to a 15% reduction in the car’s overall weight, which should significantly improve the range of future hybrid cars.

The potential for such a multifunctional composite material which can simultaneously carry mechanical loads whilst storing (and delivering) electrical energy, writes Dr. Emile Greenhalgh, project coordinator, Department of Aeronautics at Imperial College London, has been demonstrated by researchers at the US Army Research Lab.

In a paper presented at the Materials Research Society Symposium in 2005, South et al. provided three examples of multifunctional power-generating and energy-storing materials: structural lithium-ion batteries, structural proton exchange membrane (PEM) fuel cells, and structural capacitors. These systems were deliberately designed, the researchers wrote, so that material elements participating in power or energy processes are also carrying significant structural loads, a necessary condition for achieving mass savings through multifunctional design.

Polymer composites have now reached a level of maturity at which such adventurous and novel material configurations can be developed. The laminated architecture of fibre composites mirrors the configuration of many current electrical storage devices. In fact, carbon fibre (CF) composites are attractive as they are commonly used as both electrodes and high performance structural reinforcements; usually, the forms of carbon are different, but there is an opportunity to unify these roles with appropriate tailoring of both the matrix and the reinforcement.

—Dr. Emile Greenhalgh

Researchers at the Polymers and Composites Engineering group at Imperial had earlier been investigating development of a carbon fiber reinforced polymer composite which can act as a supercapacitor and show good mechanical properties (Young’s Modulus, Shear stiffness, compression strength, and peel and shear toughness) as a proof-of-concept.

The new material under development by the Imperial-led team could be charged by plugging a hybrid car into household power supply, the researchers say. The researchers are also exploring other alternatives for charging it such as recycling energy created when a car brakes.

For the first stage of the project, the scientists are planning to further develop their composite material so that it can store more energy. The team will improve the material’s mechanical properties by growing carbon nanotubes on the surface of the carbon fibres, which should also increase the surface area of the material, which would improve its capacity to store more energy. They are also planning to investigate the most effective method for manufacturing the composite material at an industrial level.

In addition, the researchers believe the material, which has been patented by Imperial, could potentially be used for the casings of many everyday objects such as mobile phones and computers, so that they would not need a separate battery. This would make such devices smaller, more lightweight and more portable.

We are really excited about the potential of this new technology. We think the car of the future could be drawing power from its roof, its bonnet or even the door, thanks to our new composite material. Even the Sat Nav could be powered by its own casing. The future applications for this material don’t stop there – you might have a mobile phone that is as thin as a credit card because it no longer needs a bulky battery, or a laptop that can draw energy from its casing so it can run for a longer time without recharging. We’re at the first stage of this project and there is a long way to go, but we think our composite material shows real promise.

—Dr. Emile Greenhalgh

The 3-year European Union funded project includes researchers from the Departments of Chemistry, Aeronautics and Chemical Engineering and Chemical Technology at Imperial College London. European academic and industrial partners include Swerea SICOMP, INASCO Hella, Chalmers, Advanced Composites Group, Nanocyl, Volvo Car Corporation, Bundesanstalt Fur Material forschung undprufung, ETC Battery and Fuel Cells Sweden.

Resources

• Joseph T. South, Robert H. Carter, James F. Snyder, Corydon D. Hilton, Daniel J. O’Brien, and Eric D. Wetzel (2005) Multifunctional Power-Generating and Energy-Storing Structural Composites for US Army Applications (Mater. Res. Soc. Symp. Proc. Vol. 851)

• Shirshova, N., Shaffer, M., Steinke, J.H.G., Greenhalgh, E., Curtis, P. and Bismarck, A. (2007) Structural Polymer Composites for Energy Storage Devices (International Conference on Advanced Capacitors (ICAC2007))

• J.F. Snyder, D.M. Baechle, E.D. Wetzel, K. Xu (2008) Multifunctional Structural Composite Batteries for US Army Applications (ASC 2008)