Date of Award

2015-01-01

Degree Name

Doctor of Philosophy

Department

Material Science and Engineering

Advisor(s)

David A. Roberson

Abstract

Additive Manufacturing technologies has been in continuous development for more than 35 years. Specifically, the later denominated Material Extrusion Additive Manufacturing (MEAM), was first developed by S. Scott Crump around 1988 and trademarked later as Fused Deposition Modeling (FDM). Although all of these technologies have been around for a while, it was not until recently that they have been more accessible to everyone. Today, the market of 3D printers covers all ranges of price, from very specialized, heavy and expensive machines, to desktop printers of only a few cubic inches in volume. Until recently, FDM technology had remained somewhat stagnant in terms of developments; however, with the new market boom, scholars and hobbyists have opened new doors for investigation in this area. The technology is now better understood from a software, mechanical, electrical and not less important, materials point of view.

The current availability of materials for MEAM is very broad: PLA (Polylactic Acid), ABS (Acrylonitrile Butadiene Styrene), PC (Polycarbonate), PEEK (Polyether Ether Ketone), nylon, polyurethanes, and many others. Even so, these are all materials that were used before for other technologies, adapted but not specifically developed for MEAM. The processes that take place during the production of a part are currently not very well understood, and the final properties exhibited are long ways away from reaching the potential of more traditional manufacturing techniques. Due to the nature of the process, all the material properties always display a certain level of anisotropy.

The research covered in these pages aims to shed some light on understanding the different mechanics taking place during the extrusion process of additive manufacturing. The development of new materials for MEAM has been explored. Several blends and composites have been developed, and their tensile properties and fracture mechanics evaluated. The blending of different combinations of ABS, UHMWPE (Ultra High Molecular Weight Polyethylene) and SEBS (Styrene Ethylene Butylene Styrene) were further examined due to the potential they demonstrated as low anisotropic materials in terms of strength. Also, the geometrical influence of different standard tensile specimens was studied.

The development of materials that lead to lowered anisotropy on the strength of 3D printed parts has been successfully demonstrated, and alternative methodologies for the evaluation of anisotropic characteristics has been proposed as well. The present work shows the beginning to a better understanding of the mechanics taking place during the fusion of deposited material in MEAM.

Language

en

Provenance

Received from ProQuest

File Size

154 pages

File Format

application/pdf

Rights Holder

Ángel Ramón Torrado Pérez

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