Auxetic (negative Poisson’s ratio) structures comprising rotating square unit cells have attracted considerable attention due to their tunable shape control, strength, and strain energy absorption capacity. This study explores the multiscale mechanical behavior of rotating-square auxetics under various strain rates, emphasizing their response under impact loadings, and establishing a relationship between mesoscale kinematics and macroscopic mechanical characteristics. Specifically, the interrelations between cell rotation, strain rate, and Poisson’s behavior in lightweight auxetics additively manufactured from rubber-like materials are explored. The structures are subjected to compressive loads at quasi-static, intermediate strain rates, and high-velocity impact conditions. The mechanical behavior of the structures in each case is characterized by digital image correlation (DIC), allowing for the in-situ identification of the primary deformation mechanisms across various length and time scales. The rate sensitivity of the structures is correlated with that of the base polymer, revealing the activation of apparent inertia-induced effects at strain rates greater than 1000 (1/s). These inertia effects are also identified as the main contributor to the rate-sensitive Poisson’s behavior of the structures, leading to various degrees of rate-dependent auxeticity. The competing roles of cell rotation and hinge bending are also discussed.
2025-04-09 09:00:00
