A novel re-entrant circular star-shaped auxetic honeycomb with enhanced energy absorption and anisotropic Poisson’s ratio

Traditional auxetic honeycomb structures often exhibit limited energy absorption capacity, particularly under large deformation conditions. This study proposes an anisotropic auxetic configuration—the re-entrant circular star-shaped honeycomb (RECSH)—to enhance energy absorption and reduce initial peak force. A comprehensive investigation involving experimental testing, theoretical modelling, and finite element (FE) simulations was carried out to evaluate the in-plane quasi-static compressive behaviour of RECSH. The results revealed a two-plateau deformation response, each of which exhibited a distinct stress plateau attributed to the structural support provided by the embedded circular geometry. A theoretical framework based on plastic dissipation was developed to predict plateau stresses, and the influence of key geometric parameters on deformation modes and energy absorption was systematically examined. A multi-objective optimisation strategy was used by a Kriging surrogate model and NSGA-II algorithm to identify an optimal configuration with improved crashworthiness. Compared with conventional designs, the optimised RECSH demonstrates enhanced specific energy absorption (SEA) and reduces initial peak stress (IPS) in both x- and y-directions. This novel auxetic structure offers promising potential for applications in impact mitigation and crash protection systems.