Mechanical performance of an assembled 3D auxetic hybrid structure under eccentric and axial compression

Recently, auxetic structures with complex and diverse configurations have emerged increasingly. However, due to the limitations of 3D metal printing technology, the integrated manufacturing of complex structures poses significant challenges. Here, we apply a bolt-welding modular assembly approach to 3D auxetic structures, successfully manufacturing both a novel dumbbell four-pointed-star hybrid structure (DFS) and a traditional re-entrant structure (TRS). This approach effectively avoids the challenges of overall printing, support residue, and uneven deformation during additive manufacturing. Through experiment and simulation, the mechanical performances of DFS were systematically analyzed under eccentric and axial compression, with a particular focus on eccentricity and aspect ratio effects, followed by a comparative analysis with typical re-entrant structures. The results demonstrate that DFS not only exhibits superior deformation and mechanical performance under eccentric loading but also shows greater sensitivity to large eccentricities. With increasing aspect ratios, DFS exhibits enhanced energy absorption under axial compression, while its auxetic effect follows a first-increases-then-decreases trend due to reduced structural stability. Meanwhile, DFS demonstrates superior mechanical characteristics and enhanced auxetic effects compared to several re-entrant structures. The significance of this work lies in providing a conceptual framework for future modular assembly of metamaterials and mechanical analysis under eccentric compression.