Use of Slotted Waveguide Antenna Stiffened Structures (SWASS) in future commercial and military aircraft calls for the development of an airworthiness certification procedure. The first step of this procedure is to provide a computationally low-cost method for modeling waveguide antenna arrays on the scale of an aircraft skin panel using a multi-fidelity model. Weather detection radar for the Northrop Grumman X-47 unmanned air system is considered as a case study. COMSOL Multiphysics is used for creating high-fidelity waveguide models that are imported into the MATLAB Phased Array Toolbox for large-scale array calculations using a superposition method. Verification test cases show that this method is viable for relatively accurate modeling of large SWASS arrays with low computational effort. Additionally, realistic material properties for carbon fiber reinforced plastic (CFRP) are used to create a more accurate model. Optimization is performed on a 12-slot CFRP waveguide to determine the waveguide dimensions for the maximum far-field gain and separately for the maximum critical buckling load. Using the two separate optima as utopia points, a multi-objective optimization for the peak far-field gain and critical buckling load is performed, to obtain a balance between EM performance and structural strength. This optimized waveguide is then used to create a SWASS array of approximately the same size as an aircraft wing panel using the multi-fidelity modeling method that is proposed. This model is compared to a typical conventional weather radar system, and found to be well above the minimum mission requirements. / Master of Science / Antennas used in military and commercial aircraft have traditionally been designed independently from the aircraft structure. Increasingly, e↵ort has been made to integrate these processes, in order to create more efficient, dual-purpose structures. Slotted waveguide antennas, hollow rectangular tubes with slots cut in one face, are commonly used to create arrays for aircraft on-board weather radar. A type of structurally embedded antenna, slotted waveguide antenna stiffened structures (SWASS), consists of slotted waveguides that are sandwiched between two layers of a composite material. This sandwich structure can be used in place of the conventional structure used for aircraft skin, allowing the slotted waveguides to function not only as antennas, but also as part of the aircraft’s load-bearing structure. Because of the geometric complexity of the slotted waveguides, generating accurate models of the antenna performance can be difficult and requires a great deal of computational power. This thesis presents and validates a method for reducing the complexity of modeling the antenna performance of SWASS arrays. Additionally, optimizations are performed to improve both the waveguide’s performance as an antenna and as a load-bearing part of the aircraft structure. Finally, the optimized SWASS array is compared to the actual mission requirements of the Northrop Grumman X-47 unmanned aircraft, and is found to perform above the required levels.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/81959 |
| Date | 29 January 2018 |
| Creators | Albertson, Nicholas James |
| Contributors | Aerospace and Ocean Engineering, Canfield, Robert A., Manteghi, Majid, Patil, Mayuresh J. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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