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<p>The application aluminum sheet alloy for light vehicle development was limited by the high cost of alloy fabrication. The impurity iron, which is easily picked up during fabrication, deteriorates its formability. The sheet alloy produced by continuous casting techniques was showing lower in-service performance than the one produced with traditional high-cost direct-chill casting technique. Therefore, enhancing the general formability of the aluminum alloy became .the aim of many researchers and engineers in past decades.</p><p>This project was launched to detect a possible modification effect of rare-earth (RE) element on a Al-Mg-Fe alloy, which is a simplified AA5754 alloy. Cerium was chosen as the RE element to test with. The influence of this rare-earth element on the alloy grain microstructure, phase morphology, and corresponding mechanical behavior was investigated.</p><p>It was found that cerium had a modification effect on the phase morphology to some extent. Its addition provided a great grain refinement in as-cast alloys. However, after thermo-mechanical processing, this effect would be eliminated by the small broken particles and recrystallized fine grains. It was found that the mechanical performance of the cerium-containing AA5754 was neither enhanced nor deteriorated. The AA5754 alloy remained non-heat-treatable after the addition of cerium.</p> / Thesis / Master of Applied Science (MASc)

The overall goal of this work is to expand the materials library for the fused filament fabrication (FFF) material extrusion additive manufacturing (AM) process through innovations in the FFF process, post-process, and polymer composition. This research was conducted at two opposing ends of the FFF-processing temperature: low processing temperature (<100 °C) for pharmaceutical applications and high processing temperatures (>300 °C) for high-performance structural polymer applications. Both applications lie outside the typical range for FFF (190-260 °C). To achieve these goals, both the material and process were modified. Due to the low processing temperature requirements for pharmaceutical active ingredients, a water-soluble, low melting temperature material (sulfonated poly(ethylene glycol)) series was used to explore how different counterions affect FFF processing. The strong ionic interaction within poly(PEG8k-co-CaSIP) resulted in the best print quality due to the higher viscosity (105 Pa∙s) allowing the material to hold shape in the melt and the high-nucleation producing small spherulites mitigating the layer warping. Fillers were then explored to observe if an ionic filler would produce a similar effect. The ionic filler (calcium chloride) in poly(PEG8k-co-NaSIP) altered the crystallization kinetics, by increasing the nucleation density and viscosity, resulting in improved printability of the semi-crystalline polymer. A methodology for embedding liquids and powders into thin-walled capsules was developed for the incorporation of low-temperature active ingredients into water-soluble materials that uses a higher processing temperature than the actives are compatible with. By tuning the thickness of the printed walls, the time of internal liquid release was controlled during dissolution. This technique was used to enable the release of multiple liquids and powders at different times during dissolution. To enable the printing of high-temperature, high-performance polymers, an inverted desktop-scale heated chamber with the capability of reaching over 300 °C was developed for FFF. The design was integrated onto a FFF machine and was used to successfully print polyphenylsulfone which resulted in a 48% increase in tensile strength (at 200 °C) when compared to printing at room temperature. Finally, the effects of thermal processing conditions for printing ULTEM® 1010 were studied by independently varying the i) nozzle temperature, ii) environment temperature, and iii) post-processing conditions. The nozzle temperature primarily enables flow through the nozzle and needs to be set to at least 360 °C to prevent under extrusion. The environment temperature limits the part warping, as it approaches Tg (217 °C), and improves the layer bonding by decreasing the rate of cooling that allows more time for polymer chain entanglement. Post-processing for a longer time above Tg (18 hrs at 260 °C) promotes further entanglement, which increases the part strength (50% increase in yield strength); however, the part is susceptible to deformation. A post-processing technique was developed to preserve the parts' shape by packing solid parts into powdered salt. / Doctor of Philosophy / Fused filament fabrication (FFF) is the most widely used additive manufacturing (also referred to as 3D printing) process in industry, education, and for hobbyists. However, there is a limited number of materials available for FFF, which limits the potential of using FFF to solve engineering problems. This work focuses on material and machine modifications to enable FFF for use in both pharmaceutical and structural applications. Specifically, many pharmaceutical active ingredients require processing temperatures lower than what FFF typically uses. A low-temperature water-soluble material was altered by incorporating salt ions and ionic fillers separately. The differences in the printability were directly correlated to the measured variations in the viscosity and crystallization material properties. Alternatively, a technique is presented to embed liquids and powders into thin-walled, water-soluble printed parts that are processed using typical FFF temperatures, where the embedded material remains cool. The release time of the embedded material during dissolution is controlled by the thickness of the capsule structure. For structural applications, a machine was developed to allow for the processing of high-performance, high-temperature polymers on a desktop-scale system. This system uses an inverted heated chamber that uses natural convection to be able to heat the air around the part and not the electric components of the machine. The heated environment allows the part to remain at a higher temperature for a longer time, which enables a better bond between printed layers to achieve high-strength printed parts using high-performance materials. This machine was used to characterize the thermal processing effect for printing the high-performance polymer ULTEM® 1010. The nozzle temperature, environment temperature, and post-processing were tested where i) a higher nozzle temperature (360 °C) increases strength and prevents under extrusion, ii) a higher environment temperature (≥200 °C) increases the strength by slowing cooling and decreases warping by limiting the amount of shrinkage the occurs during printing, and iii) post-processing in powdered salt (18 hrs at 260 °C) increases part strength (50%) by allowing the printed roads to fuse.

The pursuit of reducing waste and carbon emissions in the building industry is a challenge which is collective, prescient, and an opportunity for explorations of new material practices and fabrication methods. This thesis seeks to show how digital fabrication can serve as a tool in material reclamation and reuse in architecture. Utilizing the design of a pharmaceutical headquarters in Boston, Massachusetts as a vessel for investigation, both the challenges and potentials of such a process are evaluated. This proposal includes a process by which material reclamation drives design decisions in order to show that when architects consider material lifecycles and design for a process, rather than just a product, new possibilities can be realized for a building and its implications. By reusing existing metal cladding in the pharmaceutical building's solar veil, not only is waste reduced, but a narrative is conveyed about possible futures. Through creative material practices and digital tools, architects have the opportunity to create a future that is locally grounded, resource efficient, and less wasteful while meeting the needs of an expanding global population. This thesis raises a number of questions around material use in buildings, fabrication methods, facade design, and the balance between performance and embodied traits. The journey of designing for material systems is documented here in order to show the possibilities for change in the industry towards more sustainable material practices. / Master of Architecture / Around the world, buildings are one of the top producers of carbon emissions and waste. Responsible and creative methods for material use in buildings is imperative to address the current global climate and environmental crises. This thesis seeks to show how digital fabrication can serve as a tool in material reclamation and reuse in architecture. Utilizing the design of a pharmaceutical headquarters in Boston, Massachusetts as a vessel for investigation, both the challenges and potentials of such a process are evaluated. In this proposal, material reclamation drives design decisions in order to show that when architects consider material lifecycles and design for a process, rather than just a product, new possibilities can be realized for a building and its larger impacts. By reusing existing metal cladding in the pharmaceutical building's solar veil, not only is waste reduced, but a narrative is conveyed about possible futures. Through creative material practices and digital tools, architects have the opportunity to create a future that is locally grounded, resource efficient, and less wasteful while meeting the needs of an expanding global population. This thesis raises a number of questions around material use in buildings, fabrication methods, facade design, and the balance between performance and embodied traits. The journey of designing for material systems is documented here in order to show the possibilities for change in the industry towards more sustainable material practices.

Even though computer simulation of environmental factors and manufacturing technologies have experienced a fast development, architectural workflows that can take advantage of the possibilities created by these developments have been left behind and architectural design processes have not evolved at the same rate. This research presents design to fabrication workflows that explore data driven design to improve performance of facades, implementing for this purpose computational tools to handle environmental data complexity and proposes robotic fabrication technologies to facilitate façade components fabrication. During this research three design experiments were conducted that tested variations on the design to fabrication workflow, approaching the flow of information in top-down and bottom-up processes. Independent variables such as material, environmental conditions and structural behavior, are the framework in which workflow instances are generated based on dependent variables such as geometry, orientation and assembly logic. This research demonstrates the feasibility of a robotic based fabrication method informed by a multi-variable computational framework plus a simulation evaluator integrated into a design to fabrication workflow and put forward the discussion of a fully automated scenario. / Master of Science