Great interest exists in adding long fibers into polymeric fluids due to the increase in properties associated with the composite, as compared to the neat resin. These properties, however, are dependent on the fiber orientations generated during processing, such as injection molding. In an effort to optimize industrial processing, optimize mold design, and maximize desired properties of the final part, it is highly desirable to predict long fiber orientation as a function of processing conditions. The purpose of this research is to use rheology as a fundamental means of understanding the transient orientation behavior of concentrated long glass (> 1mm) fiber suspensions. Specifically, this research explores the method of using rheology as a means of obtaining stress tensor and orientation model parameters needed to accurately predict the transient fiber orientation of long glass fiber reinforced polypropylene, in a well-defined simple shear flow, with the hopes of extending the knowledge gained from these fundamental experiments for the use of simulating processing flows, such as injection molding. Two fiber orientation models were investigated to predict the transient orientation of the long glass fiber systems explored. One model, the Folgar-Tucker model, has been particularly useful for predicting fiber orientation in short glass fiber systems and was used in this paper to assess its performance with long glass fibers. A second orientation model, one that accounts for the semi-flexibility of fibers, was extended to describe non-dilute suspension and coupled with an augmented stress tensor that accounts for fiber bending. Stress tensor and orientation model parameters were determined (in all cases) by best fitting these coupled equations to measured stress data obtained using a sliding plate rheometer. Results showed the semi-flexible orientation model and stress tensor combination, overall, provided improved rheological results as compared to the Folgar-Tucker model when coupled with the stress tensor of Lipscomb (1988). Furthermore, it was found that both stress tensors required empirical modification to accurately fit the measured data. Both orientation models provided encouraging results when predicting the transient fiber orientation in a sliding plate rheometer, for all initial fiber orientations explored. Additionally, both orientation models provided encouraging results when the model parameters, determined from the rheological study, were used for the purpose of predicting fiber orientation in an injection molded center-gated disk. / Ph. D.

The boundary layer effect on viscosity and injection molding studies in radial and unidirectional flows were investigated for liquid crystalline (ethylene terephthalate) using Instron model 3211 capillary rheometer. Two copolyesters of PET modified with 60 and 80 mole percent parahydroxy benzoate were examined. Melt viscosities were measured as a function of temperature and wall shear rates. Mold filling characteristics were investigated by introducing different fluid pigments into the melt before injection. Molecular orientation of the molded parts was studied by measuring the shrinkage of the microtomed samples at various temperatures, injection speeds, and cavity thicknesses for these two molds. For PET/60 mole % PHB, the viscosity was found to be some function of the capillary diameter, showing a marked decrease with decreasing capillary diameter at 275 C; this possible phenomenon is not found in most polymer melts. During mold filling stage, fluid pigments indicated that these liquid crystalline melts flow and split in the core before they approach the flow front. Molecular orientation studies showed that high shrinkage across the flow direction than that measured along the flow direction. Studies also indicated that there existed a relative maximum molecular orientation away from the surface of the parts, corresponding to the shear zone. As the cavity thickness decreases or injection speed increases, this relative maximum peak moves to the surface of the molded parts. / Master of Science

The objective of this thesis investigation was to design an experiment to investigate superheat effect on gate velocities pressurized and unpressurized gating system each having two gates, and to analyze statistically any interrelationship between these variables in CO₂ molds. A discussion on metal flow through different parts of a gating system, with a minimum of turbulence and gas aspiration, and a discussion of hydrodynamic principles relating to gating systems were given. The realization of these conditions is desirable because it results in improved casting, fewer rejects, and greater economy in a casting production. This was followed by a discussion on metal flow variables. Principle and use of instrumentation used in the experiment was discussed. Split-split-plot type of statistical design was used. Statistical analysis of results were made. The author concluded that, the type of gating system (pressurized or unpressurized) and individual gate location have significant effect, whereas superheat (100-300°F.) has no significant effect on gate velocities of aluminum - 12 percent silicon in CO₂ molds. Also, all the there variables are independent of each other. / Master of Science

Production of casting in sand molds is the basic original method employed by the foundry industry. Other methods are the results of the technological advances, but none has resulted in the extreme flexibility of the sand casting process. The control of the sand properties is important in order to produce casting of good quality. This paper presents a limited analysis of the properties of the green molding sand and the fluidity of Aluminum•Silicon alloys in the green sand molds. The fluidity is the casting property of an alloy or metal, in a qualitative measure to completely fill the mold before it solidifies and is normally expressed as inches of flow in a small channel. The properties of the green molding sand with change in the composition of sand viz., clay and moisture contents. The standard AFS procedure is suggested in testing the physical properties of the green molding sand. In fluidity test a standard method of molding, melting and pouring is suggested to control certain variables. The statistical analysis of results indicates that there is no appreciable difference in the fluidity values 1. For different metal composition (Aluminum 12% silicon and Aluminum 6% silicon) 2. In green sand molds of vary composition of clay and moisture (clay 5%, 7% and 10%, moisture 5% and 7%) / Master of Science

The random discontinuous fiber composite has uniform properties in all directions. The wetlay process is an efficient method to manufacture random discontinuous thermoplastic preform sheets that can be molded into random composite plaques in the hot-press. Investigations were done on the molding parameters that included the set-point mold pressure, set-point mold temperature and cooling methods. The fibers used in the study included glass and carbon fiber. Polypropylene (PP) and Polyethylene Terephthalate (PET) were used as the matrix. Glass/PP and Glass/PET plaques that had fiber volume fractions ranging from 0.05 to 0.50 at an increment of 0.05 were molded. Both tensile and flexural tests were conducted. The test results showed a common pattern, i.e., the modulus and strength of the composite increased with the fiber volume fraction to a maximum and then started to descend. The test results were analyzed to find out the optimal fiber volume fraction that yielded the maximum modulus or strength. Carbon/PET composites plaques were also molded to compare their properties with Glass/PET composite at similar fiber volume fractions. Micrographs were taken of selected specimens to examine the internal structure of the material. Existing micromechanics models that predict the tensile modulus or strength of random fiber composites were examined. Predictions from some of the models were compared with test data. / Master of Science

Within this research, factors affecting the orientation of injection molded long fiber composites in an end-gated plaque were investigated. Matrix viscosity was found to have a small effect on fiber orientation. The impact matrix viscosity had on orientation was dependent on fiber loading. At lower fiber loadings, the higher viscosity material had a more asymmetric orientation profile throughout the samples and less of a shell-core-shell orientation. At higher fiber loadings, there were few differences in orientation due to matrix viscosity. Fiber concentration was found to have a larger influence on fiber orientation than matrix viscosity. Increased fiber concentration led to a lower degree of flow alignment and a broader core region at all locations examined, following the trend previously reported for short fiber composites. The orientations of three different fiber length distributions of glass fiber (GF) were compared. The longer fibers in the fiber length distribution were shown to have a disproportionate effect on orientation, with weight average aspect ratio being better than number average aspect ratio at indicating if the GF and CF samples orientated comparably. To improve properties transverse to the main flow direction, the super critical carbon dioxide aided deagglomeration of multi-walled carbon nanotubes (CNTs) was used to create injection molded multiscale composites with CNT, CF, and polypropylene. The addition of CNTs greatly improved the tensile and electrical properties of the composites compared to those without CNTs. The degree of improvement from adding CNTs was found to be dependent on CF concentration, indicating that the CNTs were most likely interacting with the CF and not the polymer. A CNT concentration of 1 wt% with a tenfold degree of expansion at 40 wt% CF proved to be optimum. A large improvement in the tensile properties transverse to the flow direction was found implying that the CNTs were not highly flow aligned. Tensile and electrical properties began to fall off at higher CNT loadings and degrees of expansion indicating the importance of obtaining a good dispersion of CNTs in the part. / Ph. D.

Histotripsy is a non-invasive, non-thermal, and non-ionizing therapy that utilizes converging high-pressure ultrasound waves at a focal point to produce cavitation and induce mechanical tissue destruction. Currently, rapid prototyped histotripsy transducers consist of multiple elements and are made using 3D printing methods. Multi-element transducers introduce size constraints and 3D printing has limitations in material choice, cost, and time for larger scale manufacturing. This thesis investigates the development of rapid prototyped single element histotripsy transducers and the use of injection molding for transducer fabrication, utilizing an in-house metal CNC mill for mold manufacturing and a desktop injection molding machine. Nylon 101 and 30% glass-filled nylon were chosen as the plastics to inject as these were found to have the most similar acoustic properties to WaterShed, an ABS-like plastic currently used. Six single-element transducers were constructed with a 2 MHz curved Pz26 piezoceramic disc: two with SLA 3D printed housing, two with SLS 3D printed housing, and two with injection molded housing. Electrical impedance, beam dimensions, focal pressure output, and cavitation were characterized for each element. The results show that rapid prototyped single element transducers can generate enough pressure to perform histotripsy. This marks the development of the first rapid prototyped single element histotripsy transducer and further confirms that injection molding can produce transducers comparable, if not identical or potentially superior, to 3D printed counterparts. Future work aims to further characterize these transducers, explore more material options, and apply injection molding to various transducer designs while optimizing both CNC and injection molding parameters. / Master of Science / Histotripsy is a form of cancer therapy that can non-invasively treat tumors using focused ultrasound waves. Focused ultrasound transducers are used to achieve this and are currently prototyped using 3D printing. However, these methods are limiting in material options and upscale manufacturing. Many of these devices currently used tend to be larger in size, comparable to the size of a mixing bowl, which limits its applications. This thesis investigates the development of single element histotripsy transducers and the use of injection molding for transducer fabrication, using an in-house metal CNC mill for mold manufacturing and desktop injection molding machine. Nylon 101 and 30% glass-filled nylon were chosen as the plastics to inject due to their ideal acoustic properties. Six single-element transducers were constructed: two with SLA 3D printing, two with SLS 3D printing, and two with injection molding. All transducers were tested and compared against each other. The results show that 3D printed single element transducers can perform histotripsy and that injection molding can produce comparable results. Future work should continue to test and characterize these transducers, explore more material options for injection molding, apply injection molding to other transducer designs, and optimize CNC and injection molding parameters.

Submitted by JOSIANE SANTOS DE OLIVEIRA (josianeso) on 2018-10-01T11:47:12Z No. of bitstreams: 1 Márcio Rafael Stracke_.pdf: 1667083 bytes, checksum: 7f8c37d9c5a822527980feaaec50278e (MD5) / Made available in DSpace on 2018-10-01T11:47:13Z (GMT). No. of bitstreams: 1 Márcio Rafael Stracke_.pdf: 1667083 bytes, checksum: 7f8c37d9c5a822527980feaaec50278e (MD5) Previous issue date: 2018-06-06 / HT Micron / Com o avanço da microeletrônica, cada vez mais surgem dispositivos eletrônicos portáteis. Isso traz diversos desafios à cadeia de semicondutores, desde o projeto, no desenvolvimento de circuitos integrados menores e mais eficientes até o encapsulamento, uma vez que os componentes tem ficado menores, mais finos e com um número maior de pinos de entrada e saída. Esses desafios estão presentes em todos os processos de fabricação de um chip e podemos citar a moldagem como um processo crítico em especial. A tecnologia de moldagem por transferência, que está consolidada e é a principal utilizada neste processo, necessita de cuidados especiais na otimização de seus parâmetros e materiais, tendo em vista os fatores citados e a consequente redução do diâmetro dos fios que realizam a interconexão do die com o substrato. Neste cenário, o wire sweep, que é o arraste destes fios de solda devido ao escoamento do encapsulante, acaba se tornando um problema, já que perdas no processo de moldagem implicam em sucatear o componente. A taxa de falhas devido a este tipo de falha podem chegar a 2,5%, segundo estudos de grandes fabricantes da cadeia de semicondutores divulgado em (SANDGREN; ROTH, 2004). Neste trabalho foi simulado o processo de moldagem de memórias DRAM com encapsulament do tipo BOC BGA, utilizando o módulo de FSI do software COMSOL. Os resultados da razão de wire sweep obtidos na simulação ficaram dentro do intervalo da média com um desvio padrão, na comparação com os valores reais medidos em peças fabricadas na condição simulada, tendo como erro máximo 15,26%. / The advancement of microelectronics makes more and more portable electronic devices emerge in our daily lives. This brings a number of challenges to the semiconductor chain, from design, to the development of smaller and more efficient integrated circuits to encapsulation, since the components have become smaller, thinner, and with a larger number of input and output pins. These challenges are present in all chip fabrication processes and we can define molding as a critical process in particular. The transfer molding technology, which is consolidated and the main one used in this process, requires special care in the optimization of its parameters and materials, since there are more and shorter wires realizing the connection between the die and the substrate. The wire sweep, which is the entrainment of the wires due to the flow of the mold compound, becomes a problem, since losses in the molding process imply scrapping the component. The failure rate due to this type of failure can reach 2.5%, according to studies by major semiconductor chain manufacturers disclosed in (SANDGREN; ROTH, 2004). In this project the DRAM memory molding process with BOC BGA encapsulation type was simulated using the FSI module in COMSOL software. Results of wire sweep ratio obtained are within the average adding or subtracting one standard deviation and the maximum error rate ranging was 15.26% considering manufactured boards using the simulation parameters.

This research project is partnership project involving industrial, university and government collaborators. The overall objective is to develop and enhance tools for use in Resin Transfer Moulding (RTM) design technology in order to re-design existing metallic parts using composite materials. / The specific objective of this work is to present preliminary research findings of the development of an optimized design of a leading edge slat (horizontal stabilizer component) from the Bell Model 407 Helicopter. The results presented here focus on the static stress analysis and the structure design aspects. The findings will serve as a basis for future design optimization as well as further developments in the use of RTM technology in re-designing metallic aeronautic components and can be considered to be "semi-optimized". / This research is based on extensive finite element analysis (FEA) of several composite material configurations, with a comparison made with the original metallic design. Different key criteria of the part design such as ply lay-up, bracket geometry, angle and configuration are tested using FEA technology with the objective of selecting the design which is minimizing stress concentrations. The influence of the modification of model-related parameters was also studied. / Preliminary comparative studies show that the slat configuration with half brackets opened towards the inside with an angle of 70 degrees (angle between the top of the airfoil and the side of the bracket) is the best option according to minimum stress concentration and structural flexibility. This choice is confirmed by other factors such as material savings and ease of processing.

Cette thèse s’intéresse à la fabrication de pièces composites par le procédé Resin Transfert Molding (ou RTM), appliquée à des tubes de protection thermiques. Plus particulièrement, cette thèse vise à démontrer la faisabilité d’utiliser ce procédé pour la fabrication cette pièce complexe. La phase d’imprégnation de préformes sèches est plus particulièrement étudiée. Après mise en oeuvre, cette pièce peut présenter des défauts tels que de la porosité ou des déplacements de plis constituant la préforme. L’objectif de cette thèse est donc de comprendre l’origine de ces défauts et de minimiser voire de d’empêcher leur apparition. Pour cela, une démarche expérimentale a été mise en place. Celle ci comprend la réalisation d’un pilote de laboratoire permettant d’appliquer différentes conditions d’imprégnation aux préformes considérées. La perméabilité des renforts considérés a aussi été évaluée à différentes échelles grâce à l’utilisation de moyen dédiés à l’échelle macroscopique (banc de perméabilité planaire et transverse), et grâce à l’utilisation d’un code de calcul se basant sur des images de tomographie synchrotron à l’échelle microscopique. Enfin, une analyse de la qualité des prototypes réalisés a été menée en suivant des procédures mises en place lors de ce projet et les résultats analysés et mis en relation avec les conditions de mise en oeuvre. Cette approche expérimentale est couplée aux simulations numériques de la phase d’imprégnation que nous avons aussi mise en oeuvre au cours de cette thèse. Par l’utilisation combinée de la simulation numérique et des essais expérimentaux, nous avons défini des critères estimant le risque d’apparition des défauts. Ces critères ont montré leur efficacité sur les solutions innovantes que nous avons proposées puisque répondant aux exigences du cahier des charges industriel. / This work concerns the manufacturing of composite parts using the Resin Transfer Molding (RTM) process. A major goal of this study is to test the feasibility of using this process to manufacture a thick tubular part with a complex shape. This study concerns the different stages of the process with an important focus on the injection step of dry preforms. The goal of this thesis is to understand the generation of manufacturing defect (mainly porosity and preform deformation) that possibly takes place during the injection step to avoid them. An experimental procedure is proposed. An experimental setup was developed to study the influence of the different process parameters on the quality of the composite parts. The determination of the longitudinal and through the thickness permeabilities was conducted experimentally on sheared and un-sheared samples. An alternative technique to estimate the permeability is presented based on simulation software using X-ray tomography images at the microscale. At last, a quality control procedure was developed and applied to the tubes manufactured within this project. This experimental work was compared to numerical simulations of the injection stage. Using both numerical simulations and experiments, criteria on process and material parameters to predict the quality of the tailored parts are presented. Those criteria are successfully compared to experimental data and were applied to design innovative injection solutions that meet industrial specifications.