This case study discusses various factors related to the wishbone for an automotive application and also the Racetrak process. The finished part could be approximately around 40% lighter than the equivalent forged aluminum item and approximately up to 60% lighter than steel, making wishbone extremely cost competitive with a premium aluminum forging. This clearly puts wishbone in line with the automotive industry’s budget for weight saving technologies, estimated around €5 to €7 per kg as per some recent reports. Up to 80% of the material can be drawn from recycled sources, thus this will help solve the ever growing challenge presented by the end-of-life carbon composite co

This case study discusses various factors related to the wishbone for an automotive application and also the Racetrak process. The finished part could be approximately around 40% lighter than the equivalent forged aluminum item and approximately up to 60% lighter than steel, making wishbone extremely cost competitive with a premium aluminum forging. This clearly puts wishbone in line with the automotive industry’s budget for weight saving technologies, estimated around €5 to €7 per kg as per some recent reports. Up to 80% of the material can be drawn from recycled sources, thus this will help solve the ever growing challenge presented by the end-of-life carbon composite components.

Racetrak is a novel process which creates high strength structural members that link two or more points, such as link arms of aircraft landing gear, and automotive wishbones.

The technique draws on a proven design concept, where a continuous loop of unidirectional material - in this case carbon fibre - provides extremely high hoop strength. This localization of very high embedded strength allows substantial cost reduction which, when combined with high levels of automation, allows an affordable component that is dramatically lighter than traditional alternatives.

The Racetrak parts consist of three main components: a core of low cost, non-woven bulk material, a loop of unidirectional carbon fiber and on both sides of this, a protective shell made from die-cut woven fiber sheet. Manufacturing is fully automated, with the unidirectional loop robotically wound to create precise, repeatable tailored fiber placement. This reinforced material preform is then placed dry into a tool, which applies a light shaping pressure to create a removable cartridge.

This is placed into an industrial press, where a vacuum is applied and the resin is injected into the heated mould. Under these conditions, the resin takes approximately 90 seconds to cure. It is then ejected from the machine and a fresh cartridge loaded.

With a cycle time currently at just 120 seconds, a single press using this process can produce more than 500,000 units a year. The composition of the system also contributes to an attractive price / performance ratio as the most costly materials – notably the unidirectional carbon fiber – are used only where their unique mechanical properties are required to deliver high local strength, for example to link anchorage points. The woven shell increases load distribution across the component and enhances both sheer strength and damage tolerance.

The system allows a choice of resins, for example polyurethane instead of the more conventional epoxy resin, increasing the toughness of the system as well as reducing the cost, with the option to further increase energy absorption by adding ductile materials such as ground end-of-life CFRP. Polyurethane resin is also an effective adhesive, allowing in-mould integration of fixings and other components. For increased resistance to high temperatures, a phenolic resin could be specified.

The Racetrak process takes its name from the continuous loop of fiber around the load bearing area, said to resemble a race track when viewed from above. For maximum strength, carbon fibers are specified for this loop, but other fibers could be used. Fibers such as glass could be incorporated in the resin matrix to provide additional strength and toughness.

As with the new 223 process, automation ensures repeatability, removes the need for skilled labor, reduces cycle times and minimizes the quantity of premium material that is required for unidirectional lay-up. Each tool costs around one tenth the cost of a steel tool, making smaller production runs more affordable. The same tool can also make similar shaped components of different specifications, simply by changing the composition of the cartridge.

Williams Advanced Engineering proposes that with savings in process time, skilled labor, materials and capital investment, Racetrak will allow high strength, light weight composite components to be used in applications where CFRP was previously too costly.

Like 223, Racetrak also brings additional benefits, most notably the ability to embed components such as thin film sensors (which can be just 6 µm thick) and bearings, effectively removing another step from the current production process. Thin film sensor could, for example, be used to measure torque or to identify internal failures resulting from out of tolerance stress.

Racetrak is also environmentally attractive because it requires very little energy, and because the bulk material used in the core can be created from the multidirectional carbon created from the 223 and Racetrak manufacturing scrap (see above). It can also use a high proportion of ground material created from end-of-life recyclate, helping to solve the current challenge of how to recover and re-use carbon components from end-of-life vehicles as required by legislation, such as the European End-of-Life Directive.

Racetrak and 223 are both application-agnostic. Their inherent scalability and adaptability lend them to a wide variety of different functions and applications. However, Williams Advanced Engineering has identified three sectors where these techniques could bring particular benefits.

Discussion

Looking beyond product benefits, 223 and Racetrak also address two other areas of performance that are increasingly important to many industries: the growing need for end-of-life recovery and for low lifecycle emissions. The Williams approach addresses both issues: manufacturing can now use a very high proportion of end-of-life carbon recyclate and the CO2 whole life emissions of carbon is inherently substantially lower than either aluminium or steel, the manufacture and re-use of which require high-energy processes.

“Both 223 and Racetrak have the potential to be disruptive technologies, providing solutions to the obstacles that have so far prevented the volume adoption of carbon fibre,” concludes Williams Advanced Engineering Technical Director Paul McNamara. “These are the first internally-generated Intellectual Property discoveries that we are bringing to market ourselves, and both are outstanding examples of the inspired thinking that Williams Advanced Engineering is applying to deliver advanced engineering for a sustainable future.”