Beyond the Ideal Lattice: Investigation of Defects on Topologically Tunable Kagome Kirigami Metamaterial

Abstract

Mechanical metamaterials are engineered materials that process unconventional properties derived from its geometry, topology, and structural makeup rather than material composition. Recently, art forms like origami and kirigami have emerged as prominent fabrication methods for creating mechanical metamaterials with programmable tunable properties. Researchers have found ways to create metamaterials that contain the ability to switch stiffnesses and wave propagation by combining this paper folding technique with foundational topology theory. The Kagome Maxwell pattern is a lattice class that demonstrates asymmetrical mechanical responses when topology configuration changes. The folded kirigami technique is used to transform a single sheet of cut paper into a 3-dimensional metamaterial with close to ideal hinge conditions, allowing the lattice to closely match predicted theoretical behaviors. However, existing research is primarily on defect free lattices, leaving a critical gap in understanding how real-world imperfections impact material performance. This study addresses the gap by investigating how two categories of defects, vacancies and weak joint zones, affect the mechanical properties and polarization in Kagome lattices using the folded kirigami construction method. Results from this study reveal that vacancies disrupt polarity in the polar topological configuration of the Kagome lattice, meaning that lattices with vacancies no longer exhibit extremely polarizing stiffness behavior. The shape and position of the vacancy also have their respective impacts on the mechanical behavior, suggesting meaningful interaction between vacancy geometry and loading direction. Additionally, weak joint zones surprisingly did not consistently reduce stiffness across all configurations but rather changes as deformation displacement increases. These findings demonstrate that real world defects introduced partially predictable changes to topologically tunable metamaterials, implying that defects are crucial design considerations controlling deformation, stress distribution and other mechanical behaviors.