Mechanical behaviour of auxetic cellular structures built from inverted tetrapods at high strain rates

Auxetic cellular structures build from inverted tetrapods were experimentally tested at high strain rate compression loading for the first time. The strain rates up to 10,000 s(-1) were achieved with gas powder gun, where the shock deformation mode is predominant. The deformation localizes in the deformation front between the impacting specimen and the fixed plate due to the inertia effects. This deformation mode results in stiffness increases in comparison to the quasi-static response. The results from experimental testing were used for validation of developed computational models in finite element explicit code LS-DYNA. Furthermore, the validated computational models were used for critical strain rate analysis, determination of critical loading velocities and analysis of deformation modes together with analytical constitutive crushing models of cellular structures.