Star hourglass shaped honeycomb structures: Structural optimization in equivalent stiffness and energy absorption

This research investigates the material characteristics of a hybrid star hourglass shaped auxetic honeycomb, which can be manufactured using 3D printing techniques. New analytical formulations are developed using an energy-based approach, focusing on a single unit cell, to predict the equivalent in-plane mechanical properties. The plateau stress of the proposed honeycomb structure is assessed at the densification stage of the unit cell by employing energy conservation principles, balancing external work with plastic energy dissipation. The accuracy of the derived equations for equivalent stiffness is verified against experimental data, demonstrating a favorable agreement between analytical predictions and experimental findings. Finite element analyses are performed to validate the obtained relationships for plateau stress. Leveraging the established analytical models, multi-objective optimization using Genetic Algorithm is applied to identify optimal values for both stiffness and plateau stress. According to the obtained results, to select the best value for strut angle results in the optimum stiffness and plateau stress, ranges between 9.5°-60° and 85°-88° proposed for θ1 and θ2 respectively.