Repeated compression behavior and customizable energy absorption capacity of a bio-inspired graded metamaterial

Abstract Conventional mechanical metamaterials designed for energy absorption are predominantly single-use, as their energy dissipation relies on irreversible deformation mechanisms. This inherent limitation restricts their applicability in scenarios that demand repeated energy absorption. Inspired by the variable cross-section and double curved rod features of human skull cancellous bone, this study proposes a tangent arc curved metamaterial (TACM) and investigates the repeatable compression behavior and customizable energy absorption capacities. First, two-dimensional TACM with different variable thickness coefficients α t are designed, and the compressive response is analyzed to screen the optimal unit cell for 3D structural construction. Subsequently, three types of three-dimensional TACM (3D-TACM) (tensile, tensile-rotational, orthogonal) are developed, followed by quasi-static repeated compression tests, graded stiffness design, and dynamic compression simulations. Experimental and finite element results demonstrate that all three 3D-TACMs exhibit stable and repeatable energy absorption, achieving a highest specific energy absorption of 1.445 J g −1 in the first cycle and a compressive resilience ratio of approximately 89%. Furthermore, graded TACMs produce stepwise enhanced stress-strain responses, enabling customizable mechanical properties through the adjustment of graded coefficients. Under medium-to-low velocity impacts (⩽50 m s −1 ), TACMs maintain their structural integrity and retain repeatable energy absorption capacity. In summary, this work provides a bio-inspired design strategy for repeatable energy-absorbing metamaterials. This strategy broadens potential applications in areas such as cushioning, seismic isolation, and other engineering fields that require resistance to cyclic loading.