Metal meets plastic for Trelleborg brake pedal

  • 19-Jan-2011 09:26 EST

For Trelleborg's hybrid brake pedal, the metal insert is over-molded at the plastic injection stage via a process using water injection technology to fuse GFRP with metal to create a tubular body.

Every vehicle component is subject as never before to analysis of potential mass, with weight-saving solutions applied whenever feasible and cost-effective in areas that even a decade ago would not have been considered. To meet this need, Trelleborg Automotive has designed a lightweight hybrid brake pedal, which it states offers both savings in unit cost and contributes indirectly to CO2 emissions reduction.

The pedal blends glass fiber-reinforced plastic (GFRP) with metal. The result is a weight savings over a conventional metal pedal of at least 30% and up to 50%.

The pedal’s metal insert is over-molded at the plastic injection stage via a process using water injection technology to fuse GFRP with metal to create a tubular body. The process delivers the complete and final assembly in one step.

Explained Trelleborg Product Engineer Loic Lefebvre: “Car manufacturers are continually looking to introduce lighter plastic materials in preference to more costly, heavier metal parts, not least because a 10% decrease in a vehicle’s overall weight reduces CO2 emissions by 10%.”

He added that the new hybrid brake pedal gave OEMs aiming to cut parts costs a “win-win” situation. It meets performance specifications for all-metal components, including static and durability requirements.

Metal pedals typically need time-consuming and costly stamping and welding, he added, whereas the hybrid component comprises a single insert.

Lefebvre stated that the use of water injection technology to create a hollow part along the pedal arm enabled Trelleborg to “greatly improve” the mechanical behavior of the hybrid pedal. The technology also ensured that the pedal was more rigid than existing hybrid brake pedal designs, he said. Trelleborg has not issued specific figures for comparison.

Lefebvre also explained that while the shafts of previous hybrid pedals have been designed with a reinforced plastic rib material, in contrast, Trelleborg’s pedal has been developed with a hollowed-out section in the shaft.

The new hybrid pedal has undergone an extensive testing program. It was equivalent to the tests carried out on a traditional metal brake pedal to ensure that it offers the same performance and durability but with the benefit of significantly less weight.

Trelleborg carried out static testing on the pedal and demonstrated that it could support the limit resistance under force at 250 daN (562 lb). The durability of the pedal has also been successfully verified following tests of some 1.5 million cycles. This included both incidental and non-incidental cycles.

Lefebvre added: “The pedal has been in development for three years and we have utilized some really cutting-edge technology to ensure that the design is as rigid as a metal component, while offering the weight-saving benefits associated with a plastic part.”

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