Enhanced specific stiffness and energy absorption in star-re-entrant hierarchical honeycombs featuring two plateau stages

This research introduces an innovative Star-Re-entrant Hierarchical (SRH) honeycomb structure, integrating the benefits of re-entrant and star-shaped configurations within a multi-level hierarchical design. To effectively evaluate the performance of the SRH structure, the 3D Equivalent Cauchy Model (3D-ECM) and 2D Equivalent Plate Model (2D-EPM) were constructed using the Variational Asymptotic Method (VAM). Validation of the 3D-ECM’s accuracy was conducted through uniaxial compression tests in two principal directions and detailed 3D FE simulations, revealing two plateau stages and an X-shaped deformation pattern in the re-entrant direction. Additionally, the 2D-EPM accurately predicted both in-plane auxetic and out-of-plane dome-shaped deformations with displacement errors of less than 5%. The SRH structure exhibited an elastic modulus 1.87 times higher than that of RH structures, along with a 1.5 times greater yield strength. Moreover, the EA and SEA values in the non-re-entrant direction for SRH significantly exceeded those of RH, primarily due to the integration of star-shaped hierarchies that help diminish local stress concentrations. Parametric studies indicated that the thickness ratio and re-entrant angle significantly affected both in-plane and out-of-plane shear modulus and Young’s modulus, whereas the Poisson’s ratio was notably influenced by the star and re-entrant angles. This research underscores the effectiveness of VAM-based models in evaluating SRH structures, offering valuable insights for optimizing their mechanical performance in advanced engineering applications. • Developed novel SRH structure with enhanced stiffness and energy absorption. • SRH with two plateau stages offers benefits in multi-stage energy dissipation. • SRH shows 1.87x specific modulus and 1.5x yield strength compared to RH. • The Poisson’s ratio of SRH are mainly affected by re-entrant and star angles. • Validated structural performance using advanced 3D-ECM and 2D-EPM.