Mechanical behaviors of star honeycombs with symmetry-broken lattices

This study investigates the in-plane compression and flexural performance of star-shaped honeycomb metamaterials, focusing on conventional symmetric and novel symmetry-broken designs. The mechanical behavior of these metamaterials under compressive and bending loads was examined through a combination of experimental tests and finite element simulations. Stress-strain curves, deformation mechanisms, and energy absorption properties were analyzed to compare the benchmark honeycomb structure with the proposed single (SSS) and double (DSS) symmetry-broken models. Results show that both SSS and DSS models outperform the conventional star design in specific energy absorption (SEA) and effective Young's modulus (E_e) during compression, with DSS exhibiting 68.8 % higher E_e and SSS achieving 35.6 % higher SEA at 0.5 strain. Under flexural loading, the SSS design surpassed the conventional structure by approximately 26.8 % in SEA at 40 mm deflection. Additionally, the study explores the impact of different assembly mechanisms, including interspaced array and chiral vertex configurations, on compressive performance. It was found that assembly patterns significantly affect the load distribution and energy absorption of the metamaterials. Under out-of-plane compression, DSS and SSS honeycombs showed 19.73 % and 19.16 % higher SEA at 0.3 strain, respectively. Furthermore, the DSS design demonstrated 21.43 % greater SEA under out-of-plane bending compared to the benchmark. The SSS design, particularly when using interspaced array or chiral vertex assemblies, demonstrated superior SEA and structural stability compared to the benchmark and DSS models. This research highlights the potential of symmetry-broken honeycomb structures for applications requiring enhanced mechanical performance and energy absorption.