Energy Absorption Performance of Cylindrical Star‐Diamond Honeycombs With Gradient Design

Cylindrical star‐diamond honeycombs (CSDH), composed of star and diamond unit cells, exhibit both negative Poisson’s ratio effect and multiplateau energy absorption characteristics. These structures exhibit superior load‐bearing stability and energy absorption capacity, enabling them to be further rolled into cylindrical shells for broader engineering applications. Traditional 2D honeycombs are prone to out‐of‐plane instability and insufficient energy dissipation under complex loads and in curved surface applications, thus failing to meet practical engineering requirements. Therefore, this paper introduces star‐diamond unit cells into cylindrical honeycombs. By adopting angle and thickness gradient designs, the energy absorption capacity and engineering application value of the honeycomb can be effectively improved. This paper systematically investigates the influence of different gradient types, design methods and orientations on the mechanical response and the specific energy absorption (SEA) of CSDH. The compressive stress, Poisson’s ratio and energy absorption of the structure are investigated through experiments and numerical simulations. The results show that unidirectional and bidirectional angle gradients can effectively extend the plateau stage and improve energy absorption capacity. The optimal angular‐unidirectional (AU) increases SEA by 29%. Unidirectional, bidirectional, and layered thickness gradients exhibit multiplateau collapse in the middle and late deformation stages, effectively delaying densification. The corresponding optimal thickness‐unidirectional (TU) improves SEA by 43%. Further parameter regulation analysis of the gradient models reveals the nonmonotonic variation of the thickness gradient model and the unimodal characteristics of the angle gradient model. Finally, five optimal models are determined, and these optimal models are combined on this basis. The combined C–AU–TU model exhibits the highest SEA with an increase rate of 58.9%, demonstrating excellent energy absorption performance and structural stability. The research results provide a theoretical basis and engineering reference for the optimal design of gradient cylindrical honeycombs.