Advantages of Structural Composites in Class 8 Truck Suspensions

The Liteflex^™ composite spring has been manufactured by Delphi Chassis Systems, a division of Delphi Automotive Systems, since 1981 when it was introduced on the Chevrolet Corvette. In its early history, applications concentrated on passenger cars and vans. Over the past decade, however, composite engineering development has also focused on heavy duty suspension applications for tractors and trailers. The results include a Liteflex^™ trailer suspension spring, a Liteflex^™ tractor steer axle spring a Liteflex^™ tractor drive axle spring, and a Litecast^™ suspension link. A typical tandem axle trailer suspension incorporates four 3-leaf steel springs. Replacing each with a 13 kg lighter Liteflex^™ spring offers a weight savings of 52 kg (115 lb.). This includes the assembly and mounting hardware. For the tractor, replacing two 2-leaf steel steer axle springs with Liteflex^™ springs offers a combined weight savings of 55 kg (120 lb.). Furthermore, substituting the tractor's four 3-leaf steel drive axle springs with Liteflex^™ springs decreases the weight by a total of 64 kg (140 lb.). This results in a total mass savings of 171 kg (337 lb.) for a vehicle totally equipped with composite springs. For those vehicles which use additional steel leafs on the steer or drive axles, the weight savings are substantially greater. Another potential for weight savings is in the Litecast^™ suspension link, which is currently in its final stage of development. Weight savings up to 2.3 kg (5 lb.) per link are anticipated depending on suspension design.

Weight savings is not the only advantage the composite components offer compared to their steel counterparts. Each Liteflex^™ spring inherently displays visible, energy absorbing (or ‘soft’) damage modes, which allow for planned maintenance of the vehicle.

In addition, Liteflex^™ springs last much longer than steel springs. The physical capabilities of advanced composites were exploited by researching and developing the material selection, process design, and mechanics of unidirectional composites in flexure. An in-depth study [1] was performed in 1995 on the Liteflex^™ trailer suspension spring to characterize the fatigue behavior and compare it to OEM and after market steel springs. At an applied load of 2.5 times the GVW, the number of cycles the Liteflex^™ spring could endure was greater by at least an order of magnitude more than either variety of steel spring.