A fiber-reinforced composite leaf spring based on the polyurethane matrix resin Loctite MAX 2 from Henkel is being used in the chassis of the new Volvo XC90, a premium crossover SUV of which the innovative rear axle concept is to serve as a platform for other model series. BENTELER-SGL, a leading manufacturer of composite components for automotive applications, is aiming to produce several hundred thousand of these leaf springs per year.
Composite materials based on glass or carbon fibers combine savings in weight with strength, thereby offering enhanced safety and good crash behavior. In its alliance with BENTELER-SGL aligned to the development and large-scale production of a composite leaf spring for Volvo Cars, Henkel has contributed its process know-how in relation to RTM (resin transfer molding) so as to further optimize the cycle times that occur in the manufacture of fiber-reinforced components.
Because of its low viscosity, the polyurethane matrix resin Loctite MAX 2 from Henkel rapidly fills the mold and quickly yet gently impregnates the fiber material, resulting in short injection times. With the curing rate also substantially faster than that of epoxy resins, cycle times are shorter overall. Loctite MAX 2 has been successfully used in the mass production of leaf springs since 2013.
In addition, the current project uses selected additives that make the curing process faster and more flexible.
The suspension of the new Volvo XC90 offers the innovative feature of a transverse fiber-reinforced composite leaf spring instead of the usual array of coil springs. This gives rise to a highly compact design as well as producing a weight saving of some 4.5 kilograms (10 lbs) compared to a conventional coils spring concept.
Further functional benefits arise from a smoother ride and improved NVH (noise, vibration, harshness) behavior. The trunk volume is also increased because there are no suspension turrets.