The Volvo XC90 Polyurethane Composite Leaf Spring Utilizes a Unique Curing Process

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The rear axle of Volvo XC90, using Loctite Matrix resin from Henkel

Benteler-SGL is producing a glass fiber reinforced polyurethane leaf spring for the new Volvo XC90 SUV and plans to manufacture several hundred thousand of the leaf springs annually.

Henkel used the polyurethane matrix resin called Loctite MAX 2 and worked with Benteler-SGL to develop the resin transfer moulding (RTM) process for the leaf spring. The polyurethane resin rapidly fills the mould and quickly impregnates the fibre reinforcement, resulting in short injection times, thanks to the polyurethane resin’s low viscosity.

The curing rate is much faster than that of epoxy resins, resulting in shorter overall cycle times. Selected additives also make the curing process faster and more flexible.

“Within the development network comprising ourselves, Benteler-SGL and Volvo Cars, the component manufactured with our polyurethane resin was subjected to extensive automotive-specific testing and validation,” reports Frank Kerstan, Global Program Manager Automotive Composites, Henkel Adhesive Technologies.

“Applying our expertise in process optimisation, we were able to demonstrate that this polyurethane technology could satisfy all the criteria of long service under environmental influences such as temperature and humidity.”

“The example of our leaf spring for Volvo Cars demonstrates that fibre composite mass production is today already a reality,” says Frank Fetscher, Head of Business Development at Benteler-SGL Automotive Composites.

“What’s more, with this flexible component design, we are able to cover an entire platform with a relatively small number of spring variants. Having the right partner in Henkel, we have been able to build on our expertise, enabling us to further optimise the level of automation applied in our composite manufacturing operation.”