Mechanical characteristics of a novel rotating star-rhombic auxetic structure with multi-plateau stages

Auxetic structures have attracted further attention owing to their outstanding designability and mechanical properties. Designing innovative cellular structures with improved mechanical behavior is critical to achieving structural crashworthiness. In this paper, a novel rotating star-rhombic auxetic structure (RSAS) inspired by the rigid square rotating units is proposed, which has significant negative Poisson's ratio characteristics and enhanced energy absorption capacity. The mechanical responses of the RSAS are investigated by quasi-static experiments and finite element (FE) simulations, and a multi-stage deformation mode that facilitates the tuning of mechanical properties is found. The theoretical model based on the theory of plastic dissipation is validated, and it can accurately predict the plateau stresses and critical strains of the RSAS in multiple deformation stages. In addition, parametric analysis shows that the second plateau stress is close to the average plateau stress, it decreases with increasing the re-entrant angle α and pre-rotation angle β, and increases with increasing t or decreasing b. Increasing t/b can significantly enhance the plateau stresses, and the thickness gradient strategy further improves energy absorption. These studies can provide insights into the optimum design of auxetic cellular structures and the improvement of energy absorption.