Directional damping design of viscoelastic composites via topology optimization

Design of architected functional materials that possess desired damping performance is a topic of great interest in both academic research and industrial applications. This study investigates the concept of ‘directional damping’ for viscoelastic composites and develops a topology optimization framework to achieve directional damping design. Microstructures with both load-bearing capacity and dominant damping in the prescribed direction are obtained by maximizing the loss factor while imposing stiffness constraints. An optimized directional damping microstructure design exhibits a loss factor 1.8 times higher than the isotropic design in the prescribed direction. It is found that the optimized configurations with curved viscoelastic strips are similar as wavy ‘suture’ lines in the beaks of woodpeckers, which possess outstanding energy absorption performance. We have also verified the superiority of the directional damping design through numerical simulations and experiments of the microstructured composites. The experiment results show significant reduction of peak response for the directional damping design compared to the isotropic counterpart. To demonstrate the application potential of the optimized unit cell microstructures, a novel conceptual airless tire that exhibits improved stiffness and shock absorption performance is designed and validated through both numerical simulations and experiments.