Elastic Shape Morphing of Ultra-Light Structures by Programmable Assembly

The technology uses a base set of the substructure, interface, and skin building blocks to design an aerostructure that maximize the aerodynamic loading of the aero structure while maintaining the appropriate safety factor. The main substructure building blocks used are octahedral unit cells, which, when connected at their nodes, produce a cuboctahedral lattice structure. The interface building block set connects the vertices of the substructure building blocks to the skin components and the root and tip plates. The skin is a collection of flat and curved plates that are designed to overlap one-another and to transfer aerodynamic pressure loads directly to the substructure through the interface parts. Panels are not interconnected and thus do not behave as a structural stressed skin. Neighboring panels overlap by 10.2mm to ensure a continuous surface for airflow while still allowing panels to slide past one another during aeroelastic shape change. The structure was developed with adherence to the following guidelines: (i) All second voxel type groupings are limited to linear string shapes; (ii) No second voxel type grouping string can be longer than three blocks long; (iii) Second voxel type grouping strings can not be placed within two unit spaces of each other; (iv) Second voxel type grouping strings placed spanwise will reduce bending and torsional stiffness; (v) Second voxel type grouping strings placed chordwise decreases airfoil shape stability; (vii) Second voxel type grouping strings reduce the total length of building block extrusion. Aerostructure parts made from ultra-light materials, such as a lattice covered by a skin, present an opportunity to dramatically increase the efficiency of load bearing aerostructures. NASA Ames Research Center has been developing lighter-than-air vehicle and structure concepts using octahedral unit cells called voxels that are the building blocks for creating larger aerostructures. This novel addition to the family of technologies introduces interface parts to connect a skin to a voxel substructure. The skin is designed to transfer aerodynamic pressure loads directly to the substructure through the interface parts. The parts can be tuned to achieve aerodynamic efficiency gains through substructure programmability. The substructure can be morphed by aeroelastic tuning to increase aerodynamic efficiency. Tuning the substructure’s torsional stiffness response can also program the anisotropic substructure stiffness to promote tip twist under aerodynamic loads.