Tunable Poisson’s ratio design in beetle-inspired honeycomb cores: in-plane compression mechanisms and dual-mode deformation

The beetle elytron has been identified as a natural sandwich structure whose core topology can be abstracted as a combination of honeycomb cells and trabeculae. Inspired by this biological architecture, the corresponding inspired structure is referred to as the beetle elytron plate (BEP). In this work, three types of cores—End-trabecular BEP (EBEP), Mid-trabecular BEP (MBEP), and the conventional honeycomb plate (HP)—were constructed based on the presence and location of trabeculae. Two cell geometries (regular and concave) and two global orientations (transverse and longitudinal) were also considered. A systematic study was conducted to investigate their load-bearing characteristics, deformation patterns, and Poisson’s-ratio evolution under in-plane compression. The results indicate that (1) MBEP exhibits the best overall performance for both cell geometries, outperforming EBEP and conventional HP in load-bearing capacity, deformation stability, and consistency of Poisson’s ratio; (2) regular configurations exhibit positive Poisson’s ratios, whereas concave configurations show negative Poisson’s ratios, and MBEP undergoes the most pronounced lateral deformation, highlighting the dominant role of trabecula placement in governing cell-wall compliance and transverse deformation modes; (3) a significant coupling exists between trabecula placement and loading direction, such that MBEP demonstrates higher stability under transverse compression, while EBEP shows stronger shape-recovery capability under longitudinal compression, indicating that the structural response is highly sensitive to global orientation. This study reveals the coupled regulatory mechanisms among trabecula placement, cell geometry, and layout direction, providing insights for the development of bio-inspired lightweight structures and mechanical metamaterials with tunable Poisson’s ratios, high stability, and enhanced load-bearing performance.