Engineering Commons^™

Design Of Machine Tool Cross Beam Using Metal Big Area Additive Manufacturing, Tyler Poon

Masters Theses

The modern world would not be what it is now without machine tools. Advances in materials and processes, such as carbon fiber and additive manufacturing (AM), enable the design space for machine tool components to expand. However, machine tool components require accurate geometry, which is not available from parts produced by metal Big Area Additive Manufacturing (mBAAM). This project outlines the process in which a traditionally manufactured machine tool component, a welded box structure on an existing machine tool, was redesigned to be made using mBAAM. The goal was to design a structure that was printable using the MedUSA system …

Correlating Large-Format Additive Manufacturing Processing Parameters To Fiber Length And The Mechanical Performance Of Reinforced Polymer Composites, Andrew Phillip Rhodes

Masters Theses

The Big Area Additive Manufacturing (BAAM) system at Oak Ridge National Laboratory has been used to produce carbon fiber reinforced structures for several years, including vehicles, building constituents, composite tooling, etc. While the development of a large-format polymer additive manufacturing (AM) system has moved quickly, the impact of the BAAM’s extruder on the length of carbon fiber feedstock has not been systematically studied. Numerous studies in processing fiber reinforced thermoplastics in plasticizing and injection molding systems have shown that fibers are subjected to significant shear as they are processed, which can cause a drastic reduction in fiber length which negatively …

Optimized 3d-Printing Of Carbon Fiber-Reinforced Polyether-Ether-Ketone (Cfr-Peek) For Use In Overmolded Lattice Composite, Ryan C. Ogle

Masters Theses

Current orthopedic implants are overwhelmingly composed from metallic materials. These implants show superior mechanical properties, but this can additionally result in stress shielding due to a modulus mismatch between the bone tissue and implanted device. Polymeric implants reduce this stress shielding effect but have much lower mechanical properties, limiting their use. Polylactic acid (PLA) is a widely used biodegradable thermoplastic polymer, however, its use has been limited by the polymer’s mechanical properties and rapid loss of strength during degradation in vivo. Polyether-ether-ketone (PEEK) is another common biocompatible polymer , with chemical and mechanical properties which make it a popular alternative …

Structural Stability Of Thermosets During Material Extrusion Additive Manufacturing, Stian K. Romberg

Doctoral Dissertations

Over the past decade, the scale of polymer additive manufacturing has been revolutionized with machines that print massive thermoplastic parts with greater geometric complexity than can be achieved by traditional manufacturing methods. However, the heat required to print thermoplastics consumes energy and induces thermal gradients that can reduce manufacturing flexibility and final mechanical properties. With the ability to be extruded at room temperature and excellent compatibility with fibers and fillers, thermoset resins show promise to decrease the energy consumption, expand the manufacturing flexibility, and broaden the material palette offered by large-scale polymer additive manufacturing. However, structural instability in the uncured …

3d Printing Of Hybrid Architectures Via Core-Shell Material Extrusion Additive Manufacturing, Robert Cody Pack

Doctoral Dissertations

Biological materials often employ hybrid architectures, such as the core-shell motif present in porcupine quills and plant stems, to achieve unique properties and performance. Drawing inspiration from these natural materials, a new method to fabricate lightweight and stiff core-shell architected filaments is reported. Specifically, a core-shell printhead conducive to printing highly loaded fiber-filled inks, as well as a new low-density syntactic foam ink, are utilized to 3D-print core-shell architectures consisting of a syntactic epoxy foam core surrounded by a stiff carbon fiber-reinforced epoxy composite shell. Effective printing of test specimens and structures with controlled geometry, composition, and architecture is demonstrated …

Process-Structure-Property Relationships In 3d-Printed Epoxy Composites Produced Via Material Extrusion Additive Manufacturing, Nadim S. Hmeidat

Doctoral Dissertations

Extrusion-based additive manufacturing (AM) technologies, such as direct ink writing (DIW), offer unique opportunities to create composite materials and novel multi-material architectures that are not feasible using other AM technologies. DIW is a novel 3D-printing approach in which viscoelastic inks, with favorable rheological properties, are extruded through fine nozzles and patterned in a filament form at room temperature.

Recent developments in DIW of polymer composites have led to expanding the range of materials used for printing, as well as introducing novel deposition strategies to control filler orientation and create improved functional/structural composite materials. Despite these substantial advancements, the successful and …

Design And Fabrication Of Invar Layup Tool Molds Using Additive And Subtractive Manufacturing, Matthew Lamsey

Masters Theses

The development of novel additive manufacturing technologies, such as Wire Arc Additive Manufacturing (WAAM), has opened the door for the fabrication of complex part geometries that could not be achieved with traditional manufacturing methods. Best practices for designing parts for fabrication with WAAM are still in their infancy. This thesis presents a novel design and fabrication framework for parts created using WAAM, which was realized through the fabrication of two demonstration composite layup tool molds. The framework includes design principles for WAAM, finite element simulation of part performance, metrological analysis of printed preforms, and considerations for closely integrating the WAAM …

Development Of Data Science Tools For Part Qualification In Additive Manufacturing, Sujana Chandrasekar

Doctoral Dissertations

In recent years, metal additive manufacturing processes have become popular choices for part production especially for low volume, high complexity parts. To enable widespread adoption of these methods, it is essential to understand the link between process parameters and part properties. This is particularly because additive manufacturing processes cause inherently complex thermo-mechanical cycles and drastically different local process conditions within a part, compared to conventional manufacturing processes like casting and forging. Additionally, properties of feedstock material like metal powder impact final part properties. The focus of this dissertation is on development of data-driven methods using in situ monitoring, as a …

Measurement And Analysis Of Pressure Profile For Nozzle Based Single Screw Extrusion Systems, Jake Dvorak

Masters Theses

Most large-scale material-extrusion (MatEx) AM systems utilize a single screw extruder. Simulating flow rate and operating pressures of extrusion systems is notoriously difficult without resorting to full finite element analysis due to the phase change and non-Newtonian nature of relevant polymers. This study characterized two machines of interest: a Big Area Additive Manufacturing (BAAM) system and a Randcastle Microtruder. A custom nozzle adapter was fabricated to gather pressure data within the nozzle and mimic the die design of the BAAM on the Microtruder system. Several theories were tested for overall machine output and max pressure. Feed and compression zone theories …