Quasi-static multiaxial and dynamic mechanical behavior of disordered auxetic foam

Auxetic metamaterials have attracted significant attention for protective applications due to their counterintuitive deformation behavior and superior energy absorption capabilities. However, comprehensive characterization of their multiaxial yield behavior and dynamic response remains limited. This study investigates the quasi-static multiaxial and dynamic mechanical behavior of disordered auxetic foam (DAF) fabricated via additive manufacturing based on Voronoi tessellation and triaxial pre-compression. The complete multiaxial yield surface of DAF is constructed through combined experimental tests and finite element simulations. The yield surface demonstrates significant pressure sensitivity and tension-compression asymmetry, with non-convex characteristics arising from pronounced shear strengthening behavior. Additionally, dynamic compression tests across a wide range of strain rates reveal significant strain rate sensitivity, with a deformation mode transition observed from progressive collapse at low-to-intermediate rates to localized fragmentation-dominated failure at high rates. The quantified multiaxial yield surface and strain rate-dependent mechanical response provide a framework for designing auxetic foam protective structures under complex impact scenarios.