Study of the mechanical behavior under compression of a tetrachiral auxetic tubular structure

Abstract

Additive manufacturing enables the fabrication of architected materials with geometries unattainable through conventional processes. Among these, auxetic metastructures, characterized by a negative Poisson's ratio, have attracted considerable interest owing to their unusual deformation mechanisms and superior energy absorption and dissipation. This study investigates the mechanical behavior of a tetrachiral tubular structure made of AA7075-T651 aluminum alloy under axial compression, focusing on the influence of boundary conditions at the part–machine interfaces. Finite element simulations accounted for frictional contact, geometric nonlinearity, and the rotational kinematics of tetrachiral cells. The results reveal that friction governs the onset and magnitude of the auxetic response. Under highly constrained contact (μ = 0.8), ligament rotation is suppressed, and the structure deforms conventionally, exhibiting a positive effective Poisson's ratio (ν ≈ +0.28), limited twisting (two turns), and a maximum compressive load of 3.877 kN. Reducing friction to μ = 0.2 with a fixed base promotes in-plane node rotation, activating the tetrachiral mechanism and yielding ν ≈ −0.25, four turns, and a higher load of 3.883 kN. The most pronounced auxetic response arises when both ends are free to slide under low friction, producing ν ≈ −0.32, five turns, and an 8.2% contraction of the outer diameter. Across the investigated configurations, the effective Poisson's ratio varies by 0.60. These findings demonstrate that the auxetic behavior of tetrachiral tubes is highly sensitive to frictional and kinematic constraints, which must be carefully controlled to ensure reproducible mechanical performance.