Elastic Shape Morphing of Ultra-Light Structures by Programmable Assembly

Aerospace
Elastic Shape Morphing of Ultra-Light Structures by Programmable Assembly (TOP2-329)
Mission Adaptive Digital Composite Aerostructure Technologies
Overview
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.

The Technology
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.
Madcat tunnel A large-scale, ultralight adaptive structural system. A) Modular building block unit, B) 4x4x4 unit cube during mechanical testing, C) Single half-span wing structure composed of 2088 building block units, D) Blended wing body aerostructure with skin, mounted to central load balance in the 14x22 subsonic wind tunnel at NASA Langley Research Center
Benefits
  • Seeks to incorporate manufacturing at scale and offers extensibility across designs and applications, enabling cost-effective production and broad adaptability
  • The basic building blocks are 3-dimensional parts such as octahedral unit cells. The interface parts are molded parts that connect the unit cells together to form a cubooctahedral lattice
  • The addition of an actuation system creates an active structural mechanism, enhancing roll control during flight in addition to passive shape change
  • Utilizes a building-block based design and ultra-light structure, offering improved efficiency and reduced weight for enhanced performance
  • Design flexibility extends the application space for a single building block set, allowing for versatile use across various scenarios
  • Adaptive structures are finding an increasing number of applications due to their ability to respond to changing environments and use-cases

Applications
  • Aerospace industry
  • Manufacturing industry
  • Architectural applications - building construction, and infrastructure maintenance
  • Autonomous robotic assembly industries
  • Design, manufacture, and assembly of modular lattice structures composed of cuboctahedron unit cells
  • Morphing aerostructures at various scales
  • Reconfigurable large-scale infrastructure
  • High-performance on-orbit assembled infrastructure
  • Commercial air vehicle application, including UAVs
  • Automotive industry (including autonomous vehicles)
Technology Details

Aerospace
TOP2-329
ARC-18393-1
12,103,676
https://pubmed.ncbi.nlm.nih.gov/33479558/ https://www.researchgate.net/publication/331664560_Elastic_shape_morphing_of_ultralight_structures_by_programmable_assembly https://bej.pages.cba.mit.edu/home/Gregg_et_al-2018-Advanced_Engineering_Materials__1_.pdf
Similar Results
NASA US Patent No. 12,011,857
Method for discrete assembly of Cuboctahedron Lattice Materials
The novel technology is a method for the design, manufacture, and assembly of modular lattice structure based mechanical metamaterials composed of cuboctahedron unit cells. The main parameters for determining the behavior of an architected lattice material are 1. Lattice geometry: base unit cell topology defines joint connectivity and informs general lattice behavior (e.g. bending or stretch dominated), which can then be used for performance prediction relative to constituent material and density. Cell size (edge length) and edge thickness (cross section) can be used to calculate relative density; 2. Base constituent material: solid properties (mechanical, thermal, electrical, etc.) are used to calculate effective properties of resulting lattice, as well as to inform manufacturing processes. The invention relates particularly to a cuboctahedral lattice geometry, which can be decomposed into face connected cuboctahedrons. The material used is determined by the manufacturing process, such as injection molding. This offers a range of high-performance options such as glass fiber and carbon fiber reinforced polymer (GFRP, CFRP) composites. The size of the lattice can vary based on the application. Molded individual faces (bottom left figure) are then assembled into the cuboctahedron voxel building block (bottom right figure). This assembly can be achieved with a number of methods, including permanent methods such as welding or gluing, or reversible methods such as bolting or riveting.
Cross-Linked Areogels
Polymer Cross-Linked Aerogels (X-Aerogels)
Researchers at NASA's Glenn Research Center have developed an approach to significantly improve the mechanical properties and durability of aerogels without adversely affecting their desirable properties. This approach involves coating conformally and cross-linking the individual skeletal aerogel nanoparticles with engineering polymers such as isocyanates, epoxies, polyimides, and polystyrene. The mechanism of cross-linking has been carefully investigated and is made possible by two reactions: a reaction between the cross-linker and the surface of the aerogel framework and a reaction propagated by the cross-linker with itself. By tailoring the aerogel surface chemistry, Glenn's approach accommodates a variety of different polymer cross-linkers, including isocyanates, acrylates, epoxies, polyimides, and polystyreneenabling customization for specific mission requirements. For example, polystyrene cross-linked aerogels are extremely hydrophobic, while polyimide versions can be used at higher temperatures. Recent work has led to the development of strong aerogels with better elastic properties, maintaining their shape even after repeated compression cycling. By tailoring the internal structure of the silica gels in combination with a polymer conformal coating, the aerogels may be dried at the ambient condition without supercritical fluid extraction.
A small sample of Layered Composite Insulation (LCX)
Layered Composite Insulation for Extreme Conditions (LCX)
The approach in developing the LCX system was to provide a combination of advantages in thermal performance, structural capability, and operations. The system is particularly suited for the complex piping, tanks, and apparatus subjected to the ambient environment common in the aerospace industry. The low-cost approach also lends the same technology to industrial applications such as building construction and chilled-water piping. The system can increase reliability and reduce life cycle costs by mitigating moisture intrusion and preventing the resulting corrosion that plagues subambient-temperature insulation systems operating in the ambient (humidity and rain) environment. Accumulated internal water is allowed to drain and release naturally over the systems normal thermal cycles. The thermal insulation system has a long life expectancy because all layer materials are hydrophobic or otherwise waterproof. LCX systems do not need to be perfectly sealed to handle rain, moisture accumulation, or condensation. Mechanically, the LCX system not only withstands impact, vibration, and the stresses of thermal expansion and contraction, but can help support pipes and other structures, all while maintaining its thermal insulation effectiveness. Conventional insulation systems are notoriously difficult to manage around pipe supports because of the cracking and damage that can occur. Used alone or inside another structure or panel, the LCX layering approach can be tailored to provide additional acoustic or vibration damping as a dual function with the thermal insulating benefits. Because LCX systems do not require complete sealing from the weather, it costs less to install. The materials are generally removable, reusable, and recyclable, a feature not possible with other insulation systems. This feature allows removable insulation covers for valves, flanges, and other components (invaluable benefits for servicing or inspection) to be part of original designs. Thermal performance of the LCX system has been shown to equal or exceed that of the best polyurethane foam systems, which can degrade significantly during the first two years of operation. With its inherent springiness, the system allows for simpler installation and, more importantly, better thermal insulation because of its consistency and full contact with the cold surface. Improved contact with the cold surface and better closure of gaps and seams are the keys to superior thermal performance in real systems. Eliminating the requirement for glues, sealants, mastics, expansion joints, and vapor barriers provides dramatic savings in material and labor costs of the installed system.
Aerofoam
The Aerofoam composites have superior thermal and acoustic insulation properties when compared to conventional polyimide foams. In addition, they provide greater structural integrity than the fragile aerogel materials can provide independently. In general, polymer foams can provide excellent thermal insulation, and polyimide foams have the additional advantage of excellent high-temperature behavior and flame resistance compared to other polymer systems (they do not burn or release noxious chemicals). Incorporating aerogel material into the polyimide foam as described by this technology creates a composite that has been demonstrated to provide additional performance gains, including 25% lower thermal conductivity with no compromise of the structural integrity and high-temperature behavior of the base polyimide foam. The structural properties of Aerofoam are variable based on its formulation, and it can be used in numerous rigid and flexible foams of varying densities. Aerofoam has a number of potential commercial applications, including construction, consumer appliances, transportation, electronics, healthcare, and industrial equipment. In addition, these high-performance materials may prove useful in applications that require insulation that can withstand harsh environments, including process piping, tanks for transporting and storing hot or cold fluids, ship and boat building, and aerospace applications.
Passenger Airplane
Real-Time Drag Opti-mization Control Framework
According to the International Air Transport Association statistics, the annual fuel cost for the global airline industry is estimated to be about $140 billion in 2017. Therefore, fuel cost is a major cost driver for the airline industry. Advanced future transport aircraft will likely employ adaptive wing technologies that enable the wings of those aircraft to adaptively reconfigure themselves in optimal shapes for improved aerodynamic efficiency throughout the flight envelope. The need for adaptive wing technologies is driven by the cost of fuel consumption in commercial aviation. NASA Ames has developed a novel way to address aerodynamic inefficiencies experienced during aircraft operation. The real-time drag optimization control method uses an on-board, real-time sensor data gathered from the aircraft conditions and performance during flight (such as engine thrust or wing deflection). The sensor data are inputted into an on-board model estimation and drag optimization system which estimates the aerodynamic model and calculates the optimal settings of the flight control surfaces. As the wings deflect during flight, this technology uses an iterative approach whereby the system continuously updates the optimal solution for the flight control surfaces and iteratively optimizes the wing shape to reduce drag continuously during flight. The new control system for the flight control surfaces can be integrated into an existing flight control system. This new technology can be used on passenger aircraft, cargo aircraft, or high performance supersonic jets to optimize drag, improve aerodynamic efficiency, and increase fuel efficiency during flight. In addition, it does not require a specific aircraft math model which means it does not require customization for different aircraft designs. The system promises both economic and environmental benefits to the aviation industry as less fuel is burned.
Stay up to date, follow NASA's Technology Transfer Program on:
facebook twitter linkedin youtube
Facebook Logo X Logo Linkedin Logo Youtube Logo