Hierarchical Discrete Assembly of Mechanical Metamaterials with Application to Modular Unmanned Aerial Systems

Mechanical metamaterials (MMs) exhibit unique properties through rational design, thereby attracting significant research interest. However, most studies focus on their intrinsic mechanical characteristics, with limited exploration of multifunctional and system-level applications beyond mechanics. This limitation primarily arises from the fabrication of MMs heavily dependent on continuous additive manufacturing, which results in fixed mechanical properties, restricted scale, and degraded structural efficiency, hindering adaptation to multifunctional system demands. To address these aspects, a hierarchical discrete assembly strategy is developed to achieve a synergy of scalability, ultrahigh structural efficiency, and system-level functionality. Upon this strategy, a class of discretely assembled lattice metamaterials (DALMs) with different macroscopic dimensions (>1 m) is fabricated using L-shaped components. Then, compressive responses and failure mechanisms of the DALMs are investigated through experiments and finite element simulations. The DALMs demonstrate an ultralow density of 11 kg m⁻³, with specific stiffness and specific strength reaching 119 and 3 kPa m³ kg⁻¹, outperforming existing modular MMs by 32% and 98%, respectively. Finally, a modular unmanned aerial system (MUAS) is developed by integrating a DALM-based fuselage with functional modules. Compared with similars systems, the MUAS achieves a 85% increase in payload capacity to 1.5 kg, and a 42% increase in thrust-to-weight ratio to 1.76.