Comparison of the Poisson´s Ratio of Simulated Rigid and Elastic Auxetic Models Using Kinematic and Finite Element Analysis

Materials that possess a negative Poisson´s ratio are called Auxetics. They are characterized by the counterintuitive behavior of expanding in tension and contracting in compression. To justify this deformation behavior, there have been developed theoretical modelations like the reentrant and bowtie models. However, the most generalized models are based on geometries that possess rigid trusses and hinging nodes. This does not portrait the reality of the application of these models. In this study, there have been performed simulations, using kinematic analysis to characterize the auxetic behavior of the theoretical rigid/hinging models and finite element analysis to characterize elastic models that represent real bodies. There were determined and compared the Poisson´s ratios of the theoretical and elastic reentrant and bowtie. Additionally it was shown that there is a significant difference between the results. In conclusion the theoretical models predict lower values of Poisson´s ratio, while the elastic models that simulate a real body show less auxetic behavior.