Methodology for automated designing of composite structures in suspension systems

Kurzfassung

Composite materials in automotive structures have the potential to reduce CO2 emissions by simultaneously saving weight and improving fatigue performance. Further weight reduction potential can be obtained by integrating additional functions into composite structures. Regarding a suspension system, the control arms and coil springs in a McPherson front axle can be substituted by a transverse composite leaf spring. Designing this composite leaf spring structure with wheel controlling functionality is extremely challenging due to the high number of design parameters influencing the geometry and the laminate layer setup. In particular, large deformations due to bending of the control arm during wheel travel while preserving longitudinal and lateral stiffness and strength complicates the finding of solutions. Meta-model-based optimization methods can be used to identify solutions in the complex design space. Therefore, automation in the modelling process is essential. In the Next Generation Car project (NGC) of the German Aerospace Center (DLR), new development methods are investigated for automated designing and dimensioning by using optimization algorithms. The programmed process chain is connecting CAD, finite element and multi body simulation software is controlled by optimization software. All obtained displacements are cross-checked with the reference trajectory. The parametric CAD model and layer setup is controlled by meta-model-based optimization software. The resulting geometry is meshed and an implicit finite element model is created to directly identify the structural response. The design space of the optimizer includes different geometric designs of the composite structure and each layer of the laminate which are sized according to the load cases. To ensure elastic deformation, the Tsai-Wu criterion is applied as an optimization constraint. The first results show that the selected optimization approach has a high potential for finding structures which can achieve the desired wheel travel. The investigated process chain creates transverse leaf spring geometries with reasonable layer sequences.