Multi-Fidelity Design of Flexible Aircraft Structures in High-Speed, High-Temperature Flow
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Date
2023-05
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The Ohio State University
Abstract
The Air Force Research Laboratory (AFRL) is leading current hypersonic research efforts, which is at the forefront of the aerospace industry. An important consideration in hypersonic problems is the strong multi-physics coupling between aerodynamics, thermodynamics, and structures, which is called aerothermoelasticity. A high-fidelity aerothermoelastic model is often computationally intractable, therefore leveraging multi-fidelity solutions has become a viable option for modeling hypersonic problems. Currently, many hypersonic vehicles have skin made of very thin material supported by a substructure typically designed to maximize strength and minimize weight. The research in this thesis is part of a larger research effort with the ultimate goal of designing the substructure of a hypersonic vehicle so that the skin has a variable thickness distribution aiming to minimize weight without sacrificing strength. The variable thickness panel will ultimately be manufactured then tested in the Mach 6 High Reynolds Number Facility (M6HRF) at the Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base in Dayton, Ohio. The research detailed in this thesis focuses on the first step to achieving a variable thickness panel design, which is creating a baseline constant thickness panel. This was done by performing multi-fidelity aerothermoelastic simulations in ABAQUS Finite Element Analysis (FEA) software for a range of constant thickness panels. This analysis was split into two steps of different fidelities. The first step is an aerothermodynamic high-fidelity transient heat transfer analysis on a three-dimensional model. The second step is a low-fidelity nonlinear aerothermoelastic static stress analysis on a simpler shell model. The baseline panel was designed to be the minimum constant thickness panel that met the required factors of safety of the intended test facility, M6HRF, which is 3 for the yield strength of the panel's material and 4 for the ultimate strength. The baseline constant thickness panel was found to be 0.075 inches, which will be recommended to Dr. Kevin McHugh at AFRL, who is working on the next piece in the design process for the variable thickness panel. The baseline panel provides insight as to the thickness the panel should have while the modal design optimization (MDO) code, which Dr. McHugh is working on, provides insight as to the shape of the thickness distribution. The analysis done to obtain the baseline panel showed how the multi-physics interactions will drive the final design since panel thickness affects heat transfer and stress in a very nonlinear fashion. Ultimately, the weight of the baseline constant thickness panel will be compared to the variable thickness panel, which will determine the effectiveness of the variable thickness design. This research aims to build computational capability to be able to evaluate these types of designs. The experiment will also aim to validate the modeling shown in this thesis as well as provide hypersonic experimental data in the field.
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Keywords
aerospace engineering, hypersonics, aerothermoelasticity