A novel isotropic auxetic structure with stable deformation and excellent energy absorption

Abstract To address the issues of susceptibility to local buckling instability and unstable deformation modes in star-shaped honeycomb (SSH) structures under quasi-static compression, this study proposes a novel star-triangle honeycomb (STH) structure with a negative Poisson’s ratio (NPR). The core innovation of this work lies in the geometric coupling of a triangular stabilizing frame (right-angled triangle) with the SSH unit, which actively suppresses the inherent asymmetric torsional deformation mode of the SSH that leads to performance degradation. Through a combination of experimental and finite element methods, the in-plane compressive mechanical properties, deformation mechanisms, and energy absorption capacity of the STH structure were systematically investigated. Under identical geometric dimensions, the STH structure demonstrates significantly superior deformation stability, initial stiffness, and plateau stress compared to the SSH structure. Benefiting from this strategy of ‘actively locking’ the unstable deformation mode, the STH structure achieves a synchronized enhancement in its NPR effect (reaching −0.64, an improvement of approximately 82.9%) and a near doubling of its energy absorption efficiency (with specific energy absorption increased by 99%). Parametric analysis further reveals the influence of the star-shaped angle ( θ ₁), triangular angle ( θ ₂), and their respective wall thicknesses ( t ₁, t ₂) on the mechanical response. By employing an active geometric design strategy, this study simultaneously enhances multiple key properties of the auxetic structure, providing a novel approach for designing metamaterials with both high energy absorption efficiency and stable deformation modes.