Non-Planar Hierarchical Composition of Extending Metamaterials for Deployable Load-Bearing Structures

Structures and materials with geometric hierarchy commonly exhibit enhanced strength-to-weight ratio. Compositions of deployable mechanisms through planar hierarchy can offer surface area changes but have yielded little structural value for high-extension beam deployment. This work shows that non-planar hierarchical compositions can dramatically improve deployable beams' extension ratios and mechanical stiffness. This work describes the Pop-Up Extending Truss (PET), which uses the composition of scissor-like structures to enable multi-axis reorientation, enhancing the bending stiffness by over 100% compared to other scissor-like variants with equal mass and linear packing. Additionally, by combining PETs with Kresling mechanisms, we show our Hierarchical Extending and Reorienting Deployable Structures (HERDS) are capable of supporting 10x higher bending, compressive, torsional, and tensile stiffness at 25-200x extension ratios compared to non-hierarchical structures. A physical HERDS prototype achieved a 50x extension ratio and supported compressive and bending loading when deployed. Practical applications could include large space structures, deployable infrastructure, and medical devices.