A cyber manufacturing system (CMS) is a concept generated from the cyber-physical system (CPS), providing adequate data and computation resources to support efficient and optimal decision making. Examples of these decisions include production control, variation reduction, and cost optimization. A CMS integrates the physical manufacturing equipment and computation resources via Industrial Internet, which provides low-cost Internet connections and control capability in the manufacturing networks. Traditional quality engineering methodologies, however, typically focus on statistical process control or run-to-run quality control through modeling and optimization of an individual process, which makes it less effective in a CMS with many manufacturing systems connected. In addition, more personalization in manufacturing generates limited samples for the same kind of product designs, materials, and specifications, which prohibits the use of many effective data-driven modeling methods. Motivated by Additive Manufacturing (AM) with the potential to manufacture products with a one-of-a-kind design, material, and specification, this dissertation will address the following three research questions: (1) how can in situ data be used to model multiple similar AM processes connected in a CMS (Chapter 3)? (2) How to improve the accuracy of the low-fidelity first-principle simulation (e.g., finite element analysis, FEA) for personalized AM products to validate the product and process designs (Chapter 4) in time? (3) And how to predict the void defect (i.e., unmeasurable quality variables) based on the in situ quality variables. By answering the above three research questions, the proposed methodology will effectively generate in situ process and quality data for modeling multiple connected AM processes in a CMS. The research to quantify the uncertainty of the simulated in situ process data and their impact on the overall AM modeling is out of the scope of this research. The proposed methodologies will be validated based on fused deposition modeling (FDM) processes and selective laser melting processes (SLM). Moreover, by comparing with the corresponding benchmark methods, the merits of the proposed methods are demonstrated in this dissertation. In addition, the proposed methods are inherently developed with a general data-driven framework. Therefore, they can also potentially be extended to other applications and manufacturing processes. / Doctor of Philosophy / Additive manufacturing (AM) is a promising advanced manufacturing process that can realize the personalized products in complex shapes with unprecedented materials. However, there are many quality issues that can restrict the wide deployment of AM in practice, such as voids, porosity, cracking, etc. To effectively model and further mitigate these quality issues, the cyber manufacturing system (CMS) is adopted. The CMS can provide the data acquisition functionality to collect the real-time process data which directly or indirectly related to the product quality in AM. Moreover, the CMS can provide the computation capability to analyze the AM data and support the decision-making to optimize the AM process. However, due to the characteristics of AM process, there are several challenges effectively and efficiently model the AM data. First, there are many one-of-a-kind products in AM, and leads to limited observations for each product that can support to estimate an accurate model. Therefore, in Chapter 3, I would like to discuss how to jointly model personalized products by sharing the information among these similar-but-non-identical AM processes with limited observations. Second, for personalized product realization in AM, it is essential to validate the product and process designs before fabrication quickly. Usually, finite element analysis (FEA) is employed to simulate the manufacturing process based on the first-principal model. However, due to the complexity, the high-fidelity simulation is very time-consuming and will delay the product realization in AM. Therefore, in Chapter 4, I would like to study how to predict the high-fidelity simulation result based on the low-fidelity simulation with fast computation speed and limited capability. Thirdly, the defects of AM are usually inside the product, and can be identified by the X-ray computed tomography (CT) images after the build of the AM products. However, limited by the sensor technology, CT image is difficult to obtain for online (i.e., layer-wise) defect detection to mitigate the defects. Therefore, as an alternative, I would like to investigate how to predict the CT image based on the optical layer-wise image, which can be obtained during the AM process in Chapter 5. The proposed methodologies will be validated based on two types of AM processes: fused deposition modeling (FDM) processes and selective laser melting processes (SLM).

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.

Additive Manufacturing (AM) provides a unique opportunity for fabrication of personalized medicine, where each oral dosage could be tailored to satisfy specific needs of each individual patient. Binder jetting, an easily scalable AM technique that is capable of processing the powdered raw material used by tablet manufacturers, is an attractive means for producing individualized pharmaceutical tablets. However, due to the low density of the printed specimens and incompatible binder-powder combination, tablets fabricated by this AM technology suffer from poor strength. The research is introducing an additional composition in the binder jetting powder bed (e.g., powdered sugar) could significantly enhance the compressive strength of the as-fabricated tablets, as compared with those tablets fabricated without the additional powder binding agent. However, no previous research demonstrated comprehensive approaches to enhance the poor performance of the 3D printed tablets. Therefore, the goal of this work is to identify processing techniques for improving the strength of binder jetted tablets, including the use of (i) novel jettable polymeric binders (e.g., 4-arm star polyvinylpyrrolidone (PVP), DI water, and different i) weight percentage of sorbitol binder) and (ii) introducing an additional powder binding agent into the powder bed (e.g.., different wt% of powdered sugar). / M.S. / Three-dimensional printing is well-known as 3D printing. 3D printing pills are printed from the 3D printer. As of today, we now stand on the brink of a fourth industrial revolution. By the remarkable technological advancements of the twenty-first century, manufacturing is now becoming digitized. Instead of using a large batch process as traditional, customized printlets with a tailored dose, shape, size, and release characteristics could be produced on- demand. The goal of developing pharmaceutical printing is to reduce the cost of labor, shorten the time of manufacturing, and tailor the pills for patients. And have the potential to cause a paradigm shift in medicine design, manufacture, and use. This paper aims to discuss the current and future potential applications of 3D printing in healthcare and, ultimately, the power of 3D printing in pharmaceuticals.

Hybridizing additive manufacturing (AM) structures and direct write (DW) deposition of conductive traces enables the design and physical creation of integrated, complex, and conformal electronics such as embedded electronics and complex routing on a fully AM structure. Although this hybridization has a promising outlook, there are several key AM substrate-related limitations that limit the final performance of these hybridized AM-DW electronic parts. These limitations include low-temperature processability (leading to high trace resistivity) and poor surface finish (leading to electronic shorts and disconnections). Recently discovered ultraviolet-assisted direct ink write (UV-DIW) all-aromatic polyimide (PI) provides an opportunity to address these previous shortcomings previously due to its high-temperature stability (450C) and superior surface finish (relative to other AM processes). The primary goal of this thesis is to characterize the integration of this UV-DIW PI with DW-printed conductive inks as a means for obtaining high-performance hybrid AM-DW electronics. This goal has been achieved through an investigation into the increased temperature stability of AM PI on the conductivity and adhesion of DW extrusion and aerosol jet (AJ) silver inks, determining the dielectric constant and dissipation factor of processed UV-DIW PI, and determining the achievable microwave application performance of UV-DIW PI. These performance measurements are compared to commercially-available PI film and relative to existing AM substrates, such as ULTEM 1010. The temperature stability of UV-DIW PI enabled higher-temperature post-processing for the printed silver traces, which decreased DIW trace resistivity from 14.94±0.55 times the value of bulk silver at 160 °C to 2.16±0.028 times the resistivity of bulk silver at 375 °C, and AJ silver trace resistivity from 5.27±0.013 times the resistivity of bulk silver at 200 °C to 1.95±0.15 times the resistivity of bulk silver at 350 °C. The adhesion of these traces was not negatively affected by higher processing temperatures, and the traces performed similarly on UV-DIW PI and commercial PI. Furthermore, at similar thicknesses, UV-DIW PI was found to have a similar dielectric constant and dissipation factor to commercial Dupont Kapton PI film from 1 kHz to 1 MHz, indicating its ability to perform highly as a dielectric electronics substrate. Finally, the decrease in resistivity was able to decrease the gap in microwave stripline transmission line performance when compared with ULTEM 1010 processed at 200°C, with peak 10 GHz S21 loss differences decreasing from 2.46 dB to 1.32 dB after increasing the UV-DIW processing temperature from 200 °C to 400°C. / Master of Science / Due to the extensive potential benefits and applications, researchers are looking to hybridize additive manufacturing (AM) processes with direct write (DW) techniques to directly print a 3D part with integrated electronics. Unfortunately, there are several key substrate-related limitations that hinder the overall performance of a part fabricated by hybrid AM-DW processes. Specifically, typical AM materials are not capable of providing an electronics substrate with combined sufficient surface resolution, surface finish, and high-temperature processing stability. However, the recent discovery of a novel AM-processable all-aromatic polyimide (PI) presents an opportunity for addressing these limitations as its printed form offers a high surface resolution, superior surface finish, and mechanical stability up to 400 °C. The primary goal of this thesis is to evaluate the benefits and drawbacks of this PI, processed via ultraviolet-assisted direct ink write (UV-DIW) AM, as an AM-DW electronics substrate. Specifically, the author characterized the effect of the increased temperature stability of the printed PI on the resultant conductivity and adhesion of silver inks printed via direct ink write (DIW) and aerosol jetting (AJ) DW processes. These results were also compared to the performance of the inks on commercial PI. Furthermore, the dielectric performance of printed PI was evaluated and compared to commercial PI. To demonstrate and evaluate the hybridized approach in a potential end-use application, the author also characterized the achievable microwave application performance of UV-DIW polyimide relative to the existing highest performance commercially available printed substrate material. The experiments in this thesis found an 83% and 66% decrease in resistivity from extrusion and AJ printed inks due to the ability of the printed PI to be processed at higher temperatures. Furthermore, UV-DIW PI was found to have similar dielectric properties to commercial PI film, which indicates that it can serve as a high-performance dielectric substrate. Finally, the high-temperature processing stability was able to decrease the performance gap in microwave application performance between the higher performing dielectric substrate, ULTEM 1010. These results show that UV-DIW could serve as a dielectric substrate for hybridized AM-DW electronic parts with higher performance and the ability to be deployed in harsher environments than previous AM-DW electronic parts explored in literature.

In an effort to save weight, transportation and aerospace industries have increasing investigated magnesium alloys because of their high strength-to-weight ratio. Further efforts to save on material use and machining time have focused on the use of additive manufacturing. However, anisotropic properties can be caused by both the HCP structure of magnesium alloys as well as by layered effects left by typical additive manufacturing processes. Additive Friction Stir (AFS) is a relatively new additive manufacturing technology that yields wrought microstructure with isotropic properties. In this study, Additive Friction Stir (AFS) fabrication was used to fabricate WE43 magnesium alloy, with both atomized powder and rolled plate as filler material, into multilayered structures. It was found that the WE43 alloy made by AFS exhibited nearly isotropic tensile properties. With aging these properties exceeded the base material in the T5 condition. The toughness measured by Charpy impact testing also showed an increase over the base material. The relationships among tensile properties, Vickers microhardness, impact toughness, microstructure and thermal history are developed and discussed. / Master of Science

<p dir="ltr">Printed Circuit Boards have become a vital component in the connected world in which we live in today. They can be found in all electronic devices, but their shape and function has been limited by the manufacturing capabilities of PCBs. The methods for manufacturing PCBs are well researched and optimized but have pitfalls as they are only capable of producing two dimensional, planar devices. As the demand for more integrated circuitry and electronics in devices like wearable technologies increases so will the need for a more flexible method for producing PCBs.</p><p dir="ltr">The purpose of this study was to create and analyze a method of creating PCBs using multi-material 3D printing and an electroplating process. The analysis includes an experimental procedure that will conclude whether the specimens created can conduct electricity at the same level of traditionally manufactured PCBs. This research proposed a procedure for manufacturing the PCBs and a testing apparatus designed to inject current at a specified level into the specimens so that the voltage could be measured. This allowed for the resistance of the specimens to be calculated and compared to known values for common materials used in PCB manufacturing.</p><p><br></p>

Globally distributed additive manufacturing is a relatively new frontier in the field of product lifecycle management. Designers are independent of additive manufacturing services, often thousands of miles apart. Manufacturing data must be transmitted electronically from designer to manufacturer to realize the benefits of such a system. Unalterable blockchain legers can record transactions between customers, designers, and manufacturers allowing each to trust the other two without needing to be familiar with each other. Although trust can be established, malicious printers or customers still have the incentive to produce unauthorized or pirated parts. To prevent this, machine instructions are encrypted and electronically transmitted to the printing service, where an authorized printer decrypts the data and prints an approved number of parts or products. The encrypted data may include G-Code machine instructions which contain every motion of every motor on a 3D printer. Once these instructions are decrypted, motor drivers send control signals along wires to the printer's stepper motors. The transmission along these wires is no longer encrypted. If the signals along the wires are read, the motion of the motor can be analyzed, and G-Code can be reverse engineered. This thesis demonstrates such a threat through a simulated attack on a G-Code controlled device. A computer running a numeric controller and G-Code interpreter is connected to standard stepper motors. As G-Code commands are delivered, the magnetic field generated by the transmitted signals is read by a Hall Effect sensor. The rapid oscillation of the magnetic field corresponds to the stepper motor control signals which rhythmically move the motor. The oscillating signals are recorded by a high speed analog to digital converter attached to a second computer. The two systems are completely electronically isolated. The recorded signals are saved as a string of voltage data with a matching time stamp. The voltage data is processed through a Matlab script which analyzes the direction the motor spins and the number of steps the motor takes. With these two pieces of data, the G-Code instructions which produced the motion can be recreated. The demonstration shows the exposure of previously encrypted data, allowing for the unauthorized production of parts, revealing a security flaw in a distributed additive manufacturing environment. / Master of Science / Developed at the end of the 20th century, additive manufacturing, sometimes known as 3D printing, is a relatively new method for the production of physical products. Typically, these have been limited to plastics and a small number of metals. Recently, advances in additive manufacturing technology have allowed an increasing number of industrial and consumer products to be produced on demand. A worldwide industry of additive manufacturing has opened up where product designers and 3D printer operators can work together to deliver products to customers faster and more efficiently. Designers and printers may be on opposite sides of the world, but a customer can go to a local printer and order a part designed by an engineer thousands of miles away. The customer receives a part in as little time as it takes to physically produce the object. To achieve this, the printer needs manufacturing information such as object dimensions, material parameters, and machine settings from the designer. The designer risks unauthorized use and the loss of intellectual property if the manufacturing information is exposed. Legal protections on intellectual property only go so far, especially across borders. Technical solutions can help protect valuable IP. In such an industry, essential data may be digitally encrypted for secure transmission around the world. This information may only be read by authorized printers and printing services and is never saved or read by an outside person or computer. The control computers which read the data also control the physical operation of the printer. Most commonly, electric motors are used to move the machine to produce the physical object. These are most often stepper motors which are connected by wires to the controlling computers and move in a predictable rhythmic fashion. The signals transmitted through the wires generate a magnetic field, which can be detected and recorded. The pattern of the magnetic field matches the steps of the motors. Each step can be counted, and the path of the motors can be precisely traced. The path reveals the shape of the object and the encrypted manufacturing instructions used by the printer. This thesis demonstrates the tracking of motors and creation of encrypted machine code in a simulated 3D printing environment, revealing a potential security flaw in a distributed manufacturing system.

Powder bed fusion (PBF) is one of seven technology modalities categorized under the term additive manufacturing (AM). Beyond the advantages of fabricating complex geometries and the "tool-less manufacturing" paradigm common to all types of AM, polymer PBF shows potential for significant industrial relevance through exploiting the technique's characteristic powder-filled bed (a.k.a. build piston) to utilize the full printer volume for batch-style production. Although PBF should be a suitable processing technique for all semi-crystalline polymers, the polyamide family currently occupies around 90% of the commercial market for polymer PBF. This commercial dominance of polyamides is mirrored in the focus of research publications. The lack of chemical variety in published research questions the universality of reported Structure-Property-Process and Process-Structure-Property relationships for PBF. This dissertation presents the findings from identifying Structure-Property-Process relationships critical to fabricate multi-layer parts for poly(phenylene sulfide) (PPS) by PBF towards expanding PBF material selection and evaluating universality of relationship guidelines. PPS is an engineering thermoplastic used for its high strength, rigidity, dielectric properties, and chemical resistance at elevated temperatures. These properties are attributed to PPS' highly crystalline morphology. Its current use in the automotive and aerospace industries, which are early adopters of AM technologies, makes PPS a prime candidate for AM applications. Therefore, the goal of this work is to demonstrate PPS printing by PBF, study its behavior throughout the PBF lifecycle, and abstract general trends in polymer PBF relationships. First, theoretical ranges for print parameter values are determined from properties of an experimental grade PPS powder feedstock. Successful printing of PPS by PBF is demonstrated in a way contrary to published empirical polymer-PBF relationships. Low temperature printing (i.e., bed temperature more than 15 °C lower than polymer peak melting temperature) of PPS successfully fabricated dimensionally accurate parts with reasonable mechanical properties compared against injection molding values. This distinct PPS behavior does not follow empirical guidelines developed for either polyamides or poly(aryl ether ketones). The unique success of low-temperature PBF prompted further investigation into potential benefits of low-temperature printing. Structure-Property-Process relationships were characterized over the course of simulated powder reuse to show that low-temperature printing prolonged the time when PPS powder properties remained in the "printable" range. Significantly re-used PPS powder was shown to be printable when print parameters were adjusted to accommodate structure and property changes. Successful prints from reused powder is uncommon among published reports of PBF printing of high-performance engineering thermoplastics. Observations of a change in molecular architecture through branching and crosslinking during simulated powder reuse motivated investigating if similar reactions occur in printed parts. PPS is commonly used at elevated temperatures in the presence of oxygen, which is the ideal environment for branching and crosslinking. Structural changes manifested in increased glass transition temperature and high temperature storage modulus. The relative change in structure when printed parts were thermo-oxidatively exposed was observed to be significant for parts printed from new powder, but minimal for parts printed from reused powder. This is a result of the structural changes occurring as powder feedstock during reuse over multiple builds. The changing architecture of reused PPS exposed shortcomings with print parameter value selection based solely on polymer thermal properties. Branching and crosslinking reduced crystallinity, resulting in calculated less energy required to melt; however, it also increased melt viscosity. This negative impact on coalescence behavior was not reflected in the methodology for process parameter value determination because current guidelines neglect rheological properties. These observations motivated proposing a method for selecting print settings based on polymer coalescence behavior. Because it is based on coalescence, this method can predict the transition in governing physics from viscous coalescence to bubble diffusion, which is accompanied by a change in the dependence of mechanical properties on laser energy density. Most work in polymer PBF has focused on "printed part triad'" Process-Property relationships. Work presented in this dissertation contributes to the "printability triad'" of Structure-Property-Process relationships and does so using the novel-to-PBF polymer, PPS. Additional polymers must be explored to continue to discern which polymer-manufacturing relationships are universal among all polymers and which are specific to one subset. The observations and connected interpretation to principles of polymer physics add to the body of knowledge for the polymer PBF field. These contributions will help pave the way for investigations into other polymer families and will re-shape the field's normative logic use when answering the question "what makes a polymer printable by PBF?" Understanding the connection between polymer properties and physical stimuli characteristic of PBF manufacturing will result in parts tailored for specific applications and more sustainable manufacturing, thus realizing additive manufacturing's full potential. / Doctor of Philosophy / Powder bed fusion (PBF) is one of seven distinct additive manufacturing (AM, also known as ``3D printing'') technologies. The manufacturing process creates solid, three-dimensional shapes through selectively heating, melting, and fusing together polymer powder particles in a layer-by-layer manner. Currently, organizations are interested in complementing existing manufacturing technology with PBF for one of three general reasons: (1) "complexity is free" PBF has the ability to make shapes that are difficult or expensive to fabricate using other manufacturing technologies. (2) "tool-less manufacturing" PBF only requires a digital design file to fabricate objects. This enables small changes to be easily made via computer-aided design (CAD) programs without the need to invest time and money into tooling (e.g., molds, jigs, fixtures, or other product-specific tools). This enables "mass customized" products (e.g., custom-fit medical devices and implants) to be economically feasible. (3) "material efficiency" AM is attractive as it often generates less waste than subtractive manufacturing techniques like milling. This is particularly a concern for organizations that manufacture parts from expensive, high-performance polymers, such as in the aerospace and medical industries. Despite these benefits, the state of the art for polymer PBF has room for improvement. Specifically, there are many details regarding material behavior during PBF manufacturing that are unknown; any unknown behaviors present challenges to building confidence in production quality. Additionally, approximately 90% of current PBF use is nylon-12 or else another material in the polyamide family of semi-crystalline thermoplastics. This limited selection of commercially available materials compared against other forms of manufacturing contributes to PBF's circular quandary: the manufacturing process physics are not robustly understood because most experimentation and research has been carried out on one family of polymers; however, a wider variety of polymers has not been developed because there is a limited understanding of the process physics. This dissertation presents research toward answering both PBF challenge areas. The first three chapters present investigations into relationships between the properties of a novel, experimental grade poly(phenylene sulfide) (PPS) semi-crystalline thermoplastic polymer powder, the stimuli imposed on this polymer during PBF processing, and the resultant properties of printed parts (i.e., "property-process-property relationships"). The target polymer, poly(phenylene sulfide), is a high-temperature, high-performance polymer that is traditionally melt processed, but has not yet been commercialized for PBF. Prior literature has established mathematical representation for the interaction between manufacturing energy input and the thermal response of the polymer resulting in melting. This framework has been created through studying the polyamide family. Work presented in this dissertation evaluates existing guidelines for PBF process parameter selection using measured thermal behavior of PPS (i.e., a polysulfide, not a polyamide) to predict the range of manufacturing energies affecting geometrically accurate printed parts of high density and strength. In addition, the impact of thermal exposure from repeated PPS powder reuse over the course of multiple PBF prints was evaluated on powder, thermal, and rheological properties identified as critical for PBF printing. Changes to the molecular structure and properties of reused PPS powder were observed to follow different trends than those reported for other materials traditionally used. The effect of thermal exposure on printed parts was also investigated to determine if the observed changes in molecular structure occurring during thermal exposure of the powder would result in changes to mechanical performance properties of printed parts. The importance of rheological flow properties in dictating printed part performance was observed to be a common theme throughout working with PPS. The final chapter presents a novel method for quantitatively predicting particle fusion during PBF and connecting the extent of particle fusion to mechanical properties of printed parts. The presented method is "polymer agnostic" and advances the state of the art in understanding the physics guiding polymer response to stimuli imposed during PBF AM.

Multifunctional composites have gained significant interest as they enable the integration of sensing and communication capabilities into structural, lightweight composites. Researchers have explored additive manufacturing processes for creating these structures through selective patterning of electrically conductive materials onto composites. Thus far, multifunctional composite performance has been limited by the conductivity of functional materials used, and the methods of integration have resulted in compromises to both structural and functional performance. Integration methods have also imposed limitations on part geometry due to an inability to adequately deposit conductive material over concave surfaces. Proposed methods of integrating functional devices within composites have been shown to negatively affect their mechanical performance. This work presents a novel method for integrating printed electronics onto the interior surfaces of closed, complex continuous fiber composite structures via the transfer of selectively printed conductive inks from additively manufactured sacrificial tooling to the composite surface. The process is demonstrated by creating multifunctional composites via embossing printed electronics onto structural composites without negatively affecting the mechanical performance of the structure. Additionally, this process expands the ability to pattern devices onto complex surfaces and demonstrates that the transferred functionality is well integrated (adhered) with the composite surface. The process is further validated through the successful completion of two separate case studies. The first is the integration of a functioning strain gauge onto an S-glass/epoxy composite, while a second process demonstration shows a composite surface featuring a band stop filter at the X-band, otherwise known as a frequency selective surface (FSS), to show the process' suitability for high performance, aerospace grade multifunctional composites. / Master of Science / Significant interest has been given in the past few decades to strong, lightweight materials for structural purposes. Among these materials, specific interest has been paid to fiber-reinforced composites, which are made of strong fibers and advanced resins. Recently, researchers have tried to use electrically conductive inks and 3D printing techniques to put antennas and other devices onto composites. These composites could possess additional functions beyond their structural purpose and are therefore called multifunctional composites. So far, the performance of multifunctional composites has been limited by the methods used to add additional functions. These methods often result in a weaker composite material and poor performance of the added devices. In this work, a new method for integrating devices onto complex-shaped composite structures is demonstrated. This is done by printing a mold for a composite, then putting a conductive ink onto the mold and transferring the ink to the composite surface. This process is demonstrated without weakening the composite. Additionally, this process allows researchers to put devices onto complex surfaces and demonstrates that the devices are secured to the composite surface. The process is used to make two separate devices and combine them with a composites surface. The first demonstration is the integration of a functioning strain gauge (used to measure a change in material dimension) onto a structural composite, while a second process demonstration shows a composite surface featuring an electromagnetic filter, otherwise known as a frequency selective surface (FSS), to show the process' suitability for high performance, aerospace grade multifunctional composites.

Background: Manufacturing sectors are focusing on developing new manufacturing strategies and improving technologies since there has been a decrease in productivity in recent times. This has led to a massive growth in AM but also due to the benefits of implementing AM technologies. However, there are some challenges to overcome with AM implementation.  Purpose: The purpose of this study is to explore the AM implementation to achieve sustainability in manufacturing companies.   Research questions:  ·      What are the challenges in achieving sustainability with AM implementation for manufacturing companies? ·      How can manufacturing companies achieve environmental and economic sustainability with AM implementation through an industrial technology center?  Method: This study is based on a qualitative method with an abductive approach. The theoretical framework has been gathered through a literature review and the empirical data is based on interviews at the case company. The analysis is based on a thematic analysis method.  Conclusion: This thesis concluded that challenges in achieving sustainability with AM implementation are related to inaccuracies of produced parts and components and geometric complications. This was based on design complexities and printer capabilities. The other conclusion made was that there are aspects that contribute to environmental and economic sustainability through AM implementation such as enhancing process efficiency and low setup costs.