Deployable structures are used for many different spacecraft applications like solar arrays, antennas, and booms. They allow spacecraft with large structural components to comply with the volume restrictions of launch platforms. This research optimizes the shape and size of these structural components with both the stowed and deployed configurations in mind. HEEDS, a commercial optimization software, and ABAQUS, a commercial finite element analysis software, are used to evaluate and alter the structure using a single simulation. This makes the design process more efficient than running many different simulations individually. The optimization objectives, design variables, and constraints are chosen to fit the mission requirements of the structure. The structure analyzed in this research is a composite tube with a compressible cross-section wrapped around a cylinder. The change in cross-section reduces the bending stiffness of the tube and allows it to be wrapped without damaging the material. The dimensions controlling cross-section shape and the thickness of the composite layers are the design variables for the optimization. The maximum strain energy stored in the wrapped tube, the minimum volume of the structure, and the minimum weight of the tube are the objectives for the optimization. The strain energy is maximized to get the stiffest possible structure and satisfy the minimum natural frequency constraint. The weight and volume of the tube are minimized because reducing weight and volume is important for any spacecraft structure. Constraints are placed on the design variables and objectives and the Hashin damage criteria are used to ensure wrapping does not cause material failure. Three optimization runs from different initial designs are completed using SHERPA and genetic algorithm optimization methods. The results are compared to determine which optimization method performs best and how the different starting points affect the final results. After the optimized design is found, the full wrapping and deployment simulation is completed to analyze the behavior of the optimized design. / Master of Science / Spacecraft are launched into space using launch vehicles. There is limited room inside the launch vehicle for the spacecraft, but the spacecraft often needs large components like solar panels, antennas, and booms to complete the mission. These components must be designed in a way that allows them to be stowed in a smaller space. This can be accomplished by designing a system that can change the configuration of the component once the spacecraft is in orbit. This is referred to as a deployable structure, and the objective of this research is to create an optimization method for designing this type of structure. This is challenging because both the stowed and deployed configurations must be considered during the optimization. HEEDS, a commercial optimization software, and ABAQUS, a commercial structural analysis software, are used to evaluate and optimize the structure in a single simulation. The optimization objectives, design variables, and constraints are chosen to fit the mission requirements of the structure. The structure examined in this research is a composite tube with a compressible cross-section wrapped around a cylinder. As the tube is wrapped, it flattens, reducing the bending stiffness so the tube can be wrapped without damaging the material. The variables controlling cross-section shape and the thickness of the composite material layers will be altered during the optimization. The maximum strain energy stored in the wrapped tube, the volume of the tube, and the minimum weight of the tube are the objectives for the optimization. The strain energy is maximized to get the stiffest possible tube when it is unwrapped to ensure there is enough stored energy to facilitate the full deployment and to satisfy the minimum natural frequency constraint. The weight and volume of the tube are minimized because reducing weight and volume is important for any spacecraft structure. Constraints are placed on the design variables and objectives and the Hashin damage criteria are used to ensure wrapping does not cause material failure. The Hashin damage criteria use the strength of the material and the stresses on the material to determine if it is likely to fail. Three optimization runs with different starting points are completed for both the SHERPA and genetic algorithm optimization methods. The results are compared to determine which optimization method performs best and how the different starting points affect the final results. After the optimized design is found, the full wrapping and deployment simulation is completed to analyze the behavior of the optimized design.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/104873 |
| Date | 30 August 2021 |
| Creators | Tulloss Jr., Robert Stuart |
| Contributors | Aerospace and Ocean Engineering, Kapania, Rakesh K., Artis, Harry Pat, Inoyama, Daisaku |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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