Date of Award

Fall 12-16-2016

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

William G. Davids

Second Committee Member

Andrew J. Goupee

Third Committee Member

Senthil S. Vel

Abstract

Inflatable structures have become a very important area of interest for many differing applications where lightweight packable structures are required. NASA is developing Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology that takes advantage of stacked, inflated fabric tori to form a decelerating spacecraft nose cone. The tori consist of a bladder, braided fabric shell, and reinforcing in the form of integral cords or externally bonded straps. The focus of this thesis is on the development of methods for the structural testing of inflated fabric tori and developing an enhanced understanding of their behavior. This is essential for providing insight into the mechanical behavior of the HIAD and improving simulation-based models of HIADs.

Experimentally testing braided inflated fabric tori is complex, and the University of Maine has improved on the setup originally developed by NASA for testing these articles. Further improvement of the test setup accomplished as part of this research included enhancing the control system used for torus testing to work in displacement control. This produced results that could be more easily used to validate simulation tools being independently developed by others. Testing of these torus articles was accomplished by applying discrete, multiple point loads in the radial direction, inducing compression and bending of a single torus. Torus testing was conducted using up to sixteen actuators attached to eight straps on the article allowing for many differing testing profiles and loading protocols to be performed. Testing was also performed at a variety of different pressures and for a large range of sizes of tori allowing for a better understanding of how these properties affect the response of the structure. Strict pressure regulation and test timing was used to ensure that the articles exhibited as little hysteretic effect as was feasible to avoid. Additionally, tori with different reinforcing schemes were tested to experimentally determine advantages and disadvantages of these reinforcing schemes.

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