Designing Composite Leaf Spring with a Validated Finite Element Method

Abstract

The leaf springs are one of suspension elements that play an important role in driving comfort and safety. These are commonly used in light and heavy commercial trucks, vans and some passenger cars. Generally, leaf springs are made of steels or composites. In this work, parabolic steel leaf springs and composite leaf springs are compared in terms of their stiffness and weight. For this purpose, a commercially available steel leaf spring was selected and a FEA model of this steel leaf spring was created. Steel leaf spring was modeled with a commercial FE software MSC Patran. Boundary and load conditions were implemented according to the test conditions. MSC Nastran software was used as solver. Static tests were performed to validate this model. During the test reaction, forces were measured with load cells on hydraulic piston, and stiffness value of steel leaf spring was obtained according to these results. In order to obtain similar stiffness characteristics of steel leaf spring, an alternative composite leaf spring 3D design is conducted and a second FEA model is generated. According to reaction force results taken from Nastran software, stiffness values of composite leaf spring were calculated. By iterating number of plies of composite leaf spring, a design that has the same stiffness value as steel leaf spring was obtained.