Dynamic behaviour of auxetic metamaterials

Auxetic metamaterials have enhanced indentation and penetration resistance due to their high shear strength and modulus. Its auxetic performance under dynamic loading cases is an important property for shields and armour applications. In the present study, compressive tests at different impact velocities on auxetic metamaterials were conducted for two different initial geometries. A photographic technique was applied to measure the Poisson's ratio. When the dynamic data are compared with those of quasi-static experiments, it is found that the NPR for the buckling induced metamaterial is sensitive to the rate of loading, while the NPR for the metamaterial with initial auxetic behaviour is insensitive to the loading rate. It is also found that impact force measured by the test machine was dominated by the inertia force of the metamaterials.