Date of Award

3-16-2018

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Anthony N. Palazotto, PhD.

Abstract

The research this paper focuses on is comparing the structural differences between the icosahedron and hexakis icosahedron frame and skin for use as a vacuum lighter than air vehicle (VLTAV), analyzing the stress concentrations in the hexakis icosahedron both with and without the skin, and finding the optimal location and size of the air evacuation method for creating the internal vacuum. Previous research to date has identified dynamic loading on the structure and optimization of the structure, but this will be the first research to analyze the manufacturing of the structure through the development of the air evacuation design. Findings demonstrated that the hexakis icosahedron was significantly stiffer when compared to the icosahedron, and the W=B ratio of the hexakis icosahedron was smaller for the same structural and material characterizations. The hexakis-icosahedron came the closest to the yield stress of the material in the frame by its self, consisting of the Carbon Nano-Tube (CNT)/Bismaleimide (BMI) composite at 3.38 GPa, with the yield stress being 3.8 GPa. The near zero stress in the frame considering individual beams was found to lie at approximately 20% and 66% of the beam length. Placing small holes for air evacuation resulted in minimal stress changes for the entrance to the evacuation system, but created failure points at the positions of the structure where the exit to the air evacuation system was located. Adding material to the exit system solved the failure point and kept the stress levels below yielding. Further research into the geometry of the vertex revealed interactions between the 10 beams conjoining on a single location and led to the development of a second air evacuation design and analysis. Analyzing the simplified model of the air evacuation resulted in a maximum stress of 3.484 GPa, which again is below the yield limit of the material and gave the structure an overall safety factor of 1.09.

AFIT Designator

AFIT-ENY-MS-18-M-246

DTIC Accession Number

AD1056554

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