Numerical and experimental eigenmode analysis of low porosity auxetic structures

This study presents an evaluation of the mechanical behaviour of low porosity, ductile auxetic structures. Using time-averaged speckle interferometry and a specific experimental set-up, the eigenmodes and displacement fields of three low-porosity metallic auxetic samples were assessed and compared with the numerical simulations obtained using the commercial software Abaqus/Standard (Simulia Providence, RI). Guided by the finite element predictions, the eigenmode analysis was carried out by vibrating the specimens—each characterized by a different pore geometry—from 100 Hz to about 10 kHz analysing the structural response. A good agreement between the numerical calculations and the experimental results was found. This study not only validates the numerical-experimental approach used to analyse materials, but also to open a way to test and validate the performances of negative Poisson’s ratio structures and meta-materials in general applications. Furthermore, the findings of this work provides a new convincing and reliable experimental data, enlarge the knowledge about the elastic instabilities in metallic auxetic structures, supporting their use in critical applications.