Mechanical metastructures

owing to their exceptional mechanical performance and structural adaptability

have shown broad application potential in fields such as aerospace and advanced engineering. However

most existing metastructures are fabricated using additive manufacturing (AM)

which often results in fixed mechanical properties and limited tunability. To overcome these limitations

this study proposes a programmable discrete assembly approach based on L-shaped modular elements. The proposed module exhibits geometric compatibility

allowing the construction and topological transformation of three representative lattice architectures—Octet

FCC

and Cuboctahedra—through variations in spatial configuration

thereby overcoming the structural singularity inherent in conventional assembly methods. A hybrid fabrication process combining 3D printing and mechanical fastening was adopted

achieving support-free printing while maintaining high fabrication efficiency and cost-effectiveness for metastructures. Finite element simulations were employed to systematically investigate the mechanical responses of the three discretely assembled lattices

elucidating the intrinsic relationships between lattice topology

stiffness

strength

and energy absorption characteristics. Furthermore

two performance modulation strategies—soft-hard layered hybridization and local lattice hardening—were proposed to enable programmable control of global and local mechanical properties. This study establishes a new design framework for tunable mechanical metastructures

providing an effective pathway for customized performance and lightweight design in large-scale aerospace and multifunctional structural applications.