Date of Award

3-26-2020

Document Type

Thesis

Degree Name

Master of Science in Astronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Carl R. Hartsfield, PhD

Abstract

Additive manufacturing is revolutionizing industries ranging from medicine to space. However, the structural characteristics of plastic parts created by these methods are not as well understood as their more established counterparts. This research explored two relevant areas: how the structural characteristics of ULTEM 9085 plastic behaved after exposure to orbital conditions and the design of the cross-sectional area of a beam to be 3-D printed in microgravity based on the expected loads from the printer. To study orbital effects, ULTEM 9085 was printed into 1/4th scale ASTM D638- 14 dogbones using a Stratasys 450mc printer. These dogbones were placed in a vacuum chamber and exposed to ultraviolet (UV) radiation and high temperatures. The dogbones were removed regularly from the testing environments after up to 980 hours in the chamber and subjected to axial loading tests using an MTS Microtester. Using the initial shape of the dogbones and the collected force values, the stressstrain curve for each sample in each exposure duration was found, and the Young's modulus, Ultimate Tensile Strength (UTS), Yield Tensile Strength (YTS), Poisson's ratio, and Fracture Strain calculated. The ULTEM 9085 became stronger as a result of the vacuum and more brittle as a result of the UV radiation. Simultaneously, data from previous studies into ULTEM 9085's structural characteristics was imported into Hyperworks' Optistruct software module. The data was used to optimize a beam's internal structure based on several possible loading configurations expected during printing on orbit. A general design was selected and its maximum allowable end moment was found. The above information will be helpful in designing ULTEM 9085 structures for use on orbit.

AFIT Designator

AFIT-ENY-MS-20-M-262

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