Orthotropic 3D Circular‐Curve Structures Endowed With a Mechanism for On‐Demand Mechanical Property Modulation

ABSTRACT Anisotropic metastructures, a key type of advanced functional materials in mechanical engineering, achieve controllable deformation by adjusting orientational stiffness, meeting aerospace demand for dynamic shape adjustment of variant aircraft. This study proposes the 3D circular‐curve auxetic structure (3D‐CAS), meticulously engineered via the ordered assembly of complementary circular‐curve rods under strict fourfold rotational symmetry constraints—this configuration ensures structural integrity during deformation and enables stable auxetic behavior under external loads. The energy method is used to derive equations for 3D‐CAS's Young's modulus and Poisson's ratio along X ‐ and Y ‐directions. Under periodic boundary conditions, the parametric study based on numerical simulations reveals the quantitative regulation laws and underlying deformation mechanisms of geometric parameters (the circular‐curve angle θ , the rod width b , and the rod thickness t ) on Young's modulus and Poisson's ratio of 3D‐CAS. To validate the accuracy of the theoretical model and numerical results, uniaxial compressive testing is performed on fabricated 3D‐CAS specimens. The test results demonstrate excellent consistency between the theoretical predictions and numerical simulation outcomes, thus confirming the reliability of both the theoretical model and numerical simulation methods. 3D‐CAS shows distinct orthotropic anisotropy, meaning its mechanical properties (e.g., stiffness, Poisson's ratio) differ significantly along the X ‐ and Y ‐directions. The study defines the factor C 22 / C 11 ( C 22 / C 11 = X / Y ‐stiffness) to evaluate it. θ most affects anisotropy, and maximum C 22 / C 11 reaches 19.26, highlighting potential for tailored anisotropic responses.