Topology-Enriched Toughness Enhancement in Quasi-Periodic Metastructures Featuring Tailorable Strong-Weak Network

Thin-walled cellular structures deliver ultralow density and high specific strength for damage-tolerant components. Yet periodic lattices may hard-wire repeating weak features that promote tensile-catastrophic fracture, whereas aperiodic networks erase this threat by relinquishing geometric modulation. In this work, a quasi-periodic Dart-Kite metastructure (QDK) is built, inspired by the order-disorder synergy of skeletal muscle. Its golden-ratio-constrained geometry forms an intrinsic network of strong and weak bonds, enabling simultaneous improvements in strength, toughness and damage tolerance. QDK substantially surpasses the periodic structure, increasing initial fracture resistance and fracture energy by 211% and 133%, and achieving 1.7× higher cyclic energy absorption. These gains arise from a dispersed stress field generated by the diverse unit orientations and connectivity, which enlarge the plastic zone and promote crack deflection, branching, and arrest. Mechanical performance and crack trajectories remain robust across orientations (<2.5% variation). Introducing architected weak bonds, serving a role similar to the muscle Z-line, provides controllable fracture pathways while preserving structural performance; notably, toughness rises further, with QDK-D2 achieving a 24% increase. These features establish quasi-periodicity as a design principle that unlocks the simultaneous realization of mechanical programmability and high fracture resistance, enabling tunable high-toughness performance across both general and failure-specific scenarios.