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The Araldite resin transfer moulding (RTS) system from Huntsman Advanced Materials has helped NRG Wheels to produce carbon/magnesium wheels for high-performance vehicles.

NRG’s recently invented carbon/magnesium car wheel is intended to create a better driving experience based on improved handling and better impact resistance as well as reduced fuel and engine emissions.

This has been achieved by focusing on the two main components of the wheel: the hub and the rim.

The forged, magnesium-alloy-based hub of the wheel has been designed to reduce the normal cast magnesium porosity and corrosion potential of the wheel to zero.

The other major feature influencing the wheel’s design and performance is the carbon composite wheel rim.

NRG developed and produced the wheel rim with the support of Huntsman Advanced Materials, which selected and provided an Araldite resin system especially adapted for RTM.

The resin was also designed to achieve a high level of targeted performance, defined by challenging criteria to deliver increased toughness and better impact resistance.

During the RTM process to produce the carbon rims, aerospace-type carbon fabrics are put into a mould and injected with epoxy resin.

Specially coated titanium fasteners working within specially bonded bushes fasten the hub to the epoxy carbon-fibre rim, so no additional auxiliary component bonding or finishing is required.

Thanks to the quality of both the resin and the processing conditions, the visible outer side of the rim has an aesthetically pleasing surface finish, showing the carbon-fibre pattern.

The surface is protected from ultraviolet light and other environmental elements with a tough, high-gloss lacquer paint finish.

Combining the properties of toughness and high-temperature resistance, the Araldite RTM system assists in creating a carbon wheel that offers better impact resistance than metal wheels and has high fatigue resistance.

The carbon/magnesium wheel is claimed to be 40 per cent lighter than the lightest aluminium or magnesium wheels.

Substituting conventional materials with composites creates a direct primary weight reduction, allowing the carbon rims on the wheel to have a noticeable effect on a car’s fuel economy, reducing fuel consumption and emissions while enhancing performance and handling.

When tested on a Porsche with a 380bhp engine, the carbon/magnesium wheels helped to achieve power savings of around 43bhp, equating to an approximate fuel saving of 10 per cent.

Coupled with reduced fuel consumption and engine emissions, the reduced energy requirement for composites manufacturing compared with aluminium alloy manufacturing results in significant energy savings during the life of the product, according to Huntsman.

These wheel types reduce gyroscopic effects and the moment of inertia.

This results in improved acceleration and braking with reduced stopping distances, better grip, lighter, sharper steering, improved wheel and tyre balancing, more stable tyre temperatures and pressures and reduced fuel consumption and engine emissions.

Bevis Musk, research and development director at NRG, said: ‘The special Araldite RTM resin was ideal for this application in meeting the high strength-to-weight ratios required for improved impact resistance, allowing the carbon/magnesium wheel to take more than two times the impact of metal wheels.

‘Thanks to the toughness offered by the Araldite resin system, the wheel demonstrates resistance up to an impressive 1,600 joules.

‘In contrast to metal wheels, cracks do not increase and the wheel reverts to its round shape while retaining great strength, rigidity and the flexibility required for both road and track.

‘This makes the wheel safer in road impacts as the tyre retains its air and the car can be driven safely, even following a major impact,’ he added.

The overall potential for carbon composite wheels is large but specific.

The wheels are suitable for higher-value and high-performance vehicles.

The instant performance advantage and simplicity of fitment makes the NRG carbon wheels a suitable choice for highly tuned vehicles, either OEM or aftermarket.

The reduced moment of inertia generated by using composites also makes the wheel suitable for use on delivery vehicles and buses, where stopping and starting is frequent.

For military applications, not only could carbon composite wheels prove useful in improving overall vehicle performance, they could also be beneficial in ballistic response settings.

When compared with metal wheels, in extreme blasts less shrapnel penetrates the vehicle equipped with carbon composite wheels.

RTM, with suitable epoxy resin systems, allows the production of reproducible high-quality parts within acceptable cure times.

The flexibility of this process also authorises new design ideas, such as the carbon wheel rim, which would not be possible with metal constructions.

Huntsman Advanced Materials

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