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<p>Demand for lightweight, cost-effective, structural components is driving the development of continuous fiber thermoplastic tow preforms, also known as 3D-tow or tow reinforcements, to add material performance to hybrid-molded structures as an alternative to metal components. Tow reinforcements offer the performance advantages of continuous fiber composites within molded structures. The tow reinforcements also feature more tailorability of performance compared to fabric or organo-sheet reinforced hybrid-molded structures, improving their potential for design optimization. However, the added complexity of 3D-tow reinforcement structure requires the development of unique design principles and computer aided engineering (CAE) methodologies to effectively design components which meet manufacturing and performance requirements. </p> <p><br></p> <p>A systematic evaluation of design considerations was performed comparing parts manufactured with various design features, configurations, and materials. Choosing the structural profile and balance of material properties was shown to be an important component of achieving the desired performance especially where the tow reinforcement must work in conjunction with the overmolding material to provide structural performance. </p> <p><br></p> <p>By experimentally testing representative structures with features found on automobile components and molded sports equipment, performance was evaluated for a range of material combinations and reinforcement content. Tow reinforcements were made from continuous glass or carbon fiber reinforced PA6 prepreg tape and injection overmolded with unfilled or glass fiber filled PA6 adding a shear web and rib structures. Tow reinforcement significantly reduced warpage, and in tensile loading, demonstrated potential for 340\% strength increase over parts without tow. However, three-point bend performance was dominated by the overmolding material. High strain to break overmolding materials are recommended to avoid premature overmolding material cracking. </p> <p><br></p> <p>Tensile performance of tow reinforced structures is not accurately captured by conventional modeling processes. When wrapped around load introduction points, the fibers of a thick tow traverse a shorter distance at the inner radius than the outer radius leading to waviness on the inner region of each wrap. The Hsaio and Daniel model was used to predict local elastic properties of the wavy fiber composite and spatially varying material properties were applied to 3D finite element models of a suspension link. Neglecting fiber waviness overpredicted experimental tensile stiffness and strength by 36\% and 33\% respectively while modeling waviness overpredicted stiffness and strength by only 9\% and 14\% respectively. Tow wrap configuration, waviness propagation, and material parameters have significant effect on tensile performance while the tow has little effect on compressive performance.</p> <p><br></p> <p>In addition to fiber waviness, tow bundles also spread to reconcile path length differences. A method for accounting for tow spread orientations was developed and combined with fiber waviness modeling techniques. The effects of simulating the resulting fiber orientations and effective elastic properties was used to model representative beams in tension and bending load cases and compared to previous experimental results. Accounting for fiber waviness in tension demonstrated greatly improved part stiffness predictions. Spread tow bundles improved predicted strength and stiffness over simulations where tow was constrained to a uniform cross section. Increased tow reinforcement increased bending stiffness, but failure behavior was significantly influenced by the overmolding material.  </p> <p><br></p> <p>The studies in this work identified key performance attributes of 3D-tow reinforced hybrid composite structures. Design principles and modeling techniques were developed in this work, providing improved performance predictions which brings the technology closer to widespread adoption. </p>

Bacteria are known to adhere to surfaces, which allows for the formation of biofilms, possibly causing a surge in hospital-offset infections, perilous diseases, and in some cases, death. Although certain bacteria are present in the natural flora of the human skin, some present extreme clinical significance due to the ability to transmit and adhere, and can be resistant to antibiotics. They also evolve over time to survive in harsh environmental conditions. Current research reveals that design of plastic surfaces containing submicron structures, is becoming a popular approach to tackle issues concerning infection transmission, with inspiration being derived from biomimetics and self-cleaning surfaces, such as the surface of a gecko skin, and the hydrophobic wax layer of forest leaves. Main barriers to adoption include that these surfaces alone are difficult to manufacture on 3D products, expensive to fabricate on a large scale and do not last long when subjected to environmental wear. Replication of nano-scale ridges was carried out using micro-injection, and the various samples were characterised using a range of tools to determine physical and biomechanical parameters. The sample surfaces were then cultured with the pathogenic bacterium Staphylococcus aureus under several environmental conditions, and the results were statistically analysed to reveal that anti-fouling LIPSS (laser induced periodic surface structures) ridges perform better to reduce bacteria cell-substrate adhesion, when compared to flat surfaces, or surfaces containing dual structures (anti-fouling ridges combined with anti-wear walls). It was therefore demonstrated that nanotextured polymeric surfaces with hydrophobic characteristics have exceptional non-fouling properties, preventing S. aureus, a very significant bacterial strain, from initial adhesion, a critical primary mechanism in its ability to proliferate. Collectively, the findings of this study strongly support the literature, suggesting that the bacteria struggle to adhere onto polymeric topography with increased water contact angles and simple nanostructures. However, the addition of certain anti-wear micro-features increased bacterial adhesion, reducing the efficacy of the non-fouling nanostructures from preventing biofilm formation.

<p>Wireless communications and interconnected devices have become ubiquitous in our everyday life. As the rollout of the 5th generation (5G), wireless communication technology is well underway, the number of interconnected devices is increasing exponentially. Estimations for 2021 predicted that 1.5 billion smart devices would sell globally, representing a $53.45 billion market size by 2022. With the increase of communication channels and transmitted data within these networks, the challenge of coexistence without interference will become prominent. Simultaneously, 5G networks are introducing more frequency bands while densifying the network of communication towers. Forecasts predict a 100X increase of the network at the edge by introducing small cell towers, with projections estimating 45 million installed by 2031. As a result, rapid exponential growth in hardware costs is expected. Also, these dense networks will require a higher degree of self-configuration to prevent adjacent band interference.</p> <p>Tunable filters and large-scale manufacturing technologies are two solutions to address these challenges. Reconfigurable high-quality evanescent-mode (EVA) filters have been extensively presented in the literature. Different mechanisms have been employed for tuning, such as piezoelectric actuators and motors, and magnetostatic and electrostatic actuators. Furthermore, these implementations have been realized with printed circuit board (PCB) technology, computer numerical control (CNC) machining, 3D printing, and silicon (Si) micro-machining. Specifically, PCB manufacturing of three-dimensional front-end tunable filters has been promising and can deliver excellent performance. In addition, they can be integrated into the existing manufacturing lines and circuitry for the RF front-end.</p> <p>Nonetheless, there are limitations in fabrication tolerances that PCB manufacturing could reach. Consequently, there are restrictions on the frequency bands that these devices can be manufactured as dimensions become smaller in higher bands. Moreover, EVA cavities have been proven to yield higher performance filters when compared to unloaded quality factors and power handling of currently used substrate integrated waveguide (SIW) based technologies. Specifically, EVA filters produced with silicon micro-manufacturing combined with MEMS actuators have been demonstrated with remarkable performance up to 100s of GHz. Also, cost limitations per unit built are significant compared to other technologies like injection molding.</p> <p>The research goal of this work is to investigate scalable, low-cost manufacturing processes and techniques while maintaining a high-performance device. Combining knowledge from silicon RF MEMS tuned EVA filters and the cost-effective mass manufacturing injection molding technology to deliver a high-Q, high power handling, low-cost tunable filter. Demonstrating these characteristics within the same manufactured prototype would be a unique solution within the existing literature on tunable filters.</p> <p>This thesis is organized into three parts. The first part is focused on design for manufacturing (DFM). Si micromachining has been used to produce tunable resonators and filters at lower bands, but higher bands have yet to be demonstrated. The low-cost batch fabrication of already established Si micromachining lines makes this an attractive technology to realize these devices. This section presents network densification’s challenges and the economics of scale-up manufacturing. Furthermore, using Si micromachining, the first high Q tunable W band RF resonator is demonstrated tuned with MEMS technology.</p> <p>In the second part, the focus is on design for performance (DFP). Si micromachining is optimized to demonstrate high-performance RF MEMS tunable filters up to 100s GHz. High Q, wide tuning range, and low actuation voltages for the MEMS tuners have been realized.</p> <p>In the third part, the focus is on design for cost (DFC), where injection molding manufacturing technology is proven to have significant advantages in low cost with respect to other large-scale manufacturing technologies. A high-performance tunable resonator and filter in the sub-6 GHz frequency band are manufactured. They prove that simultaneously high Q, widely tunable, high power capable filters can be produced with low-cost scalable manufacturing technology.</p>

In this project, a stackable and foldable basket would be developed. The basket will be used for grocery shopping, where it can replace single use bags. Private individuals would own and use the basket for grocery shopping and grocery stores would use it for home deliveries. The project was divided into two phases. In the first phase, the research phase, relevant facts were gathered. A literature study focusing on sustainability was conducted as well as user studies. All information resulted in a number of insights that formed the basis for the coming phase. Some ofthe major insights were that people appreciate the feeling of ‘close to nature’ in relation to food and that shopping for food must not take up unnecessary time or be complicated. Also, it was realized that a basket intended for home delivery and a basket intended for private use would differ. Therefore, it was decided to focus on making a basket intended for private use. In the second phase, the design phase, a large number of ideas were generated. CAD, sketching and rapid prototyping were used as tools. Iterations resulted in four concepts of baskets. The baskets were folded in different ways and had different value-added functions. Prototypes were made and used during user tests, which resulted in no longer continuing to develop any type of value-added function. It was also decided to continue developing the concept of The straight collapsible basket. This basket was similar to a box in shape and would therefore, for practical reasons, also be well suited for home delivery. Likewise, with eliminated value-added functions, the basket would not risk becoming too complex. Therefore, home delivery was again included within the use of the basket. A detailed CAD model was made where the design was adapted tothe requirements of injection moulding. Likewise, the design and material were adapted to the mood board that had been developed. The material was also selected based on a smaller LCA, made in the GRANTA EduPack program. In parallel, solid mechanics calculations were made to ensure that the basket would meet the load capacity requirements. The result is a product proposition that meets the requirements of stackability and foldability. It is adapted for both private use and home delivery. / I detta projekt skulle en vikbar och stapelbar korg utvecklas. Korgens ska användas till mathandling, där den kan ersätta engångspåsar. Privatpersoner kan äga och använda korgen till mathandling och livsmedelsbutiker kan nyttja den vid hemleverans. Projektet var uppdelat i två faser. I den första fasen, researchfasen, samlades relevant fakta inom området. En litteraturstudie med fokus på hållbarhet gjordes och användarstudier utfördes. Informationen resulterade i ett antal insikter som låg till grund för den kommande fasen. Några av de större insikterna var att människor uppskattar känslan av naturnära i relation till mat och att mathandling inte får ta upp onödig tid eller vara krångligt. Framförallt insågs att skillnaderna mellan en korg ämnad för hemleverans och en korg ämnad för privat bruk skulle riskeras vara för stora. Därför beslutades det att fokusera på att göra en korg anpassad för privat bruk. I den andra fasen, designfasen, genererades ett stort antal idéer. CAD, skiss och rapid prototyping var verktyg som användes. Iterationer resulterade i fyra koncept, bestående av korgar. Korgarna fälldes ihop på olika sätt och hade olika mervärdesfunktioner. Prototyper av kartong gjordes som sedan användes vid användartester. Användartesterna resulterade i att inte längre fortsätta utveckla någon typ av mervärdesfunktion samt att fortsätta utveckla konceptet av The straight collapsible basket. Denna korg var lik en låda till formen och skulle därför av praktiska skäl lämpa sig bra även inom hemleverans. Likaså, med eliminerade mervärdesfunktioner skulle korgen inte riskera att bli komplex att hantera. Därför blev det aktuellt att åter inkludera hemleverans inom användandet av korgen. En detaljerad CAD-modell gjordes där designen anpassades efter de kravsom tillverkningstekniken formsprutning ställer. Likaså anpassades designen och materialet efter den mood board som tidigare tagits fram. Materialet valdes också baserat på en mindre LCA, gjord i programmet GRANTA EduPack. Parallellt gjordes hållfasthetsberäkningar för att säkerställa att korgen skulle möta de krav som hade satts gällande last. Resultatet är ett produktförslag som uppfyller kraven på stapel- och vikbarhet. Den är anpassad för både privat bruk och hemleverans.

Injection molded short fiber reinforced composites have generated commercial interest in the manufacturing of lightweight parts used in semi-structural applications. Predicting these materials’ fiber orientation with quantitative accuracy is crucial for technological advancement, but the task is difficult because of the effect of inter-particle interactions at high concentrations of fiber found in parts of commercial interest. A complete sample preparation procedure was developed to obtain optical micrographs with optimal definition of elliptical and non-elliptical footprint borders. Two novel aspects in this procedure were the use of tridimensional markers to identify specific locations for analysis and the use of controlled-etching to produce small shadows where fibers recede into the matrix. These images were used to measure fiber orientation with a customized image analysis tool. This tool contains several modifications that we introduced in the method of ellipses which allow us to determine tridimensional fiber orientation and to obtain measurements in regions with fast changes in orientation. The tool uses the location of the shadow to eliminate the ambiguity problem in orientation and characterizes non-elliptical footprints to obtain the orientation in small sampling areas. Cavitywise measurements in two thin center-gated disks showed the existence of an asymmetric profile of orientation at the gate and an orientation profile that washed out gradually at the entry region until disappearing at about 32 gap widths. This data was used to assess the prediction of cavitywise orientation using a delay model for fiber orientation with model parameters obtained from rheometrical experiments. Model predictions combining slip correction and experimentally determined orientation at the gate are in agreement with experimental data for the core layers near the end-of-fill region. Radialwise measurements of orientation at the shell, transition and core layer, and microtextural description of the advancing front are included in this dissertation. The analysis and assessment of the radial evolution of fiber orientation and advancing front based on comparing the experimental data with simulation results are under ongoing investigation. / Ph. D.

Glass fiber based polymer composites based injection molded parts provide a light-weight high-strength alternative for use in automobile applications. These composites have enhanced mechanical properties compared to those of pure polymers, if the fibers are oriented in the right direction. One of the major challenges in processing of these composites is to control the fiber orientation in the final product. The evolution of short glass fiber orientation in a center-gated disk was experimentally determined along the radial direction at three different heights representative of the shell, transition and core layers, respectively. Orientation data along the shell and transition layers in the lubrication region show shear flow effects, which tends to align the fibers along the flow direction. In the core layer, where the extension in the "-direction dominates, fibers tend to get aligned along the "-direction. In the frontal flow region orientation in the flow direction drops in all three layers due to fountain flow effects. Fiber orientation predictions in coupled and decoupled transient simulations using the Folgar-Tucker model, and the two slow versions of the Folgar-Tucker model, namely the slip Folgar-Tucker model and the reduced strain closure (RSC) model were compared with the experimental data. Measured inlet orientation was used in all simulations and model parameters were determined by fitting model predictions to rheological data under startup of shear. Pseudo-concentration method was implemented for the modeling of the advancing front and fountain flow effects in the region near the front. Discontinuous Galerkin finite element method and a third order Runge-Kutta total variance diminishing time integration scheme were implemented for the solution of the orientation and transport equations. In the lubrication region of the shell layer, all three orientation models provided a good match with the experimental data. In the frontal region, fountain flow simulations showed characteristic features seen in r- and z-profiles of orientation, although the experimental data showed these features at a relatively larger distance behind the front while the simulations predicted these effects only up to a small distance behind the front. On the other hand, orientation predictions with the Hele-Shaw flow approximation showed significant over-predictions in the frontal region. With model parameters determined from fitting to rheological data, coupling did not show any significant improvements. However, with the use of a smaller value of the fiber interaction parameter, coupling showed significant improvement in orientation predictions in all three layers in the frontal region. The simulation scheme was extended to long fiber systems by comparing available long fiber orientation data in a center-gated disk with model predictions using the Bead-Rod model which considers fiber bending, a property exhibited by long semi-flexible fibers. The Bead-Rod model showed improvements over rigid fiber models in the lubrication region of the shell layer. However, close to the front, both models showed similar predictions. In fountain flow simulations, the flow features seen in the r- and z-profiles were much better predicted with both the models while Hele-Shaw flow approximation showed over-prediction of orientation in the flow direction, especially in the shell layer. / Ph. D.

The diploma thesis focuses on the optimization of technological parameters of plastic injection molding and the study of the influence of technological parameters on the quality of molded test specimens’ type 1A. The quality of molded parts for 3 types of polypropylene (PP) with different melt flow rate (Mosten GB 002, Mosten GB 218, Mosten MA 230) and 1 type of polystyrene (PS) (Krasten PS GP 154) was evaluated in terms of dimensional stability and weight. The contribution of software for modeling the plastic injection molding process was evaluated in this work. SOLIDWORKS Plastics software was used to optimize technological parameters. The construction of the bodies, mold and cooling system was constructed, and test bodies were produced on the basis of parameters obtained from the simulation of the injection molding process. Their quality parameters were compared with a 3D model and for each of the studied materials the optimal technological parameters were selected in terms of quality and the degree of influence of individual injection parameters on the quality of moldings was evaluated. The accordance of the results of the theoretical simulation with the real experiment was proved and a computational module independent of the optimized quality parameters, generally suitable for optimizing the quality parameters of the injected parts, was developed.

Thesis (M. Tech. (Engineering: Mechanical)) -- Central University of Technology, Free State, 2013 / This research examines the suitability of Additive Manufacturing (AM) for manufacturing dies used in aluminium high pressure die casting. The study was guided by the following objectives: • The reviews of applicable literature sources that outline technical and application aspects of AM in plastic injection moulds and the possibilities of applying it to high pressure casting die. • To introduce AM grown die components in die manufacture. Further, to develop a methodology that will allow industry to apply AM technology to die manufacture. • Revolutionise the way die manufacture is done. The potential for AM technologies is to deliver faster die manufacture turnaround time by requiring a drastically reduced amount of high level machining accuracy. It also reduces the number of complex mechanical material removal operations. Fewer critical steps required by suitable AM technology platforms able to grow fully dense metal components on die casting tools able to produce production runs. • Furthermore, promising competitive advantages are anticipated on savings to be attained on the casting processing side. AM technology allows incorporation of features in a die cavity not possible to machine with current machining approaches and technology. One such example is conformal cooling or heating of die cavities. This approach was successfully used in plastic injection mould cavities resulting in savings on both the part quality as well as the reduction on cycle time required to produce it (LaserCUSING®, 2007). AM technology has evolved to a point where as a medium for fast creation of an object, it has surpassed traditional manufacturing processes allowing for rapidly bridging the gap between ideas to part in hand. The suitability of the AM approach in accelerating the die manufacturing process sometime in the near future cannot be dismissed or ignored. The research showed that there is promise for application of the technology in the not too distant future. In the South African context, the current number and affordability of suitable AM platforms is one of the main stumbling blocks in effecting more widespread applied research aimed at introduction of the technology to die manufacture.

Thesis (PhD (Industrial Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Injection moulding of polymer components is subject to ever increasing demands for improved part quality and production rate. It is widely recognised that the mould cooling strategy employed is crucial to achieving these goals. A brief overview of injection moulding units and different types of injection moulds is given. The modern Additive Manufacturing (AM) technology for processing metal powders such as Direct Metal Laser Sintering (DMLS) and Selective Laser Melting (SLM) offers almost full freedom to the mould designer. Some of these modern manufacturing methods based on metal powders, which are able to produce complex cooling channels are analysed. A drastic change has entered the mould design domain - shifting the paradigm from design for manufacture to manufacture for design. In combination with suitable AM methods the concept of surface cooling moulds can now be efficiently implemented. This study presents a new approach of predicting the minimum cooling time required for the produced part. Different cooling layouts are analysed taking the heat transfer into consideration. The lumped heat capacity method is implemented in this research in order to determine the minimum cooling cycle time required. A new approach was developed to determine the most suitable cooling layout configuration, such as conventional cooling, conformal cooling or surface cooling, required for a moulded part based on its characteristics such as shape complexity, space available for the cooling layout, part quality requirements, production volume, and product life cycle. A mould cooling design process including simulation, reverse engineering and manufacturing of the mould insert was implemented in this study. In order to validate the generic model developed during the course of this research comparative experiments were carried out to determine the difference in performance of injection moulding using conventional or surface cooling methods. The experimental results showed a significant improvement in part quality produced with reduced cycle times using the surface cooling method. / AFRIKAANSE OPSOMMING: ‘Injection Moulding’ van polimeer komponente word al meer gedruk vir verbeterde kwaliteit en vinniger produksie tyd. Dit is orals bekend dat die gietvorm afkoeling strategie ‘n groot rol speel om hierdie twee doelwitte te bereik. Eers word ‘n kort oorslag gegee van ‘Injection Moulding’ eenhede en van verskillende ‘Injection Moulding’ vorms. Die moderne Aditatiewe Vervaardigingstegnologie vir die prosessering van metaal poeiers soos bv. Direkte Metaal Laser Sintering (DMLS) en Selektiewe Laser Smelting (SLM) bied basies volle vryheid ten opsigte van gietvorm ontwerp. Party van die moderne vervaadigings metodes, wat op metaal poeiers gebaseer is, wat komplekse koelings kanale kan produseer word geanaliseer. Die ontwerpers arena het ‘n groot verandering ondergaan deurdat die fokus van ontwerp vir vervaardiging verskuif het na vervaardiging vir ontwerp. In kombinasie met toepaslike aditatiewe vervaardigings metodes kan oppervlak verkoeling nou effektief geïmplementeer word. Hierdie studie bied a nuwe manier om die minimum verkoelings tyd benodig vir ‘n part te voorspel. Verskeie verkoelings uitlegte word geanaliseer waar hitte oordrag in ag geneem word. Die “lumped heat capacity” metode word gebruik om die minimum siklus tyd te bepaal. ‘n Nuwe benadering is ontwikkel om die mees geskikste verkoelings uitleg soos bv. konvensionele verkoeling, konvorme verkoeling of oppervlak verkoeling te bepaal vir ‘n spesifieke part gebaseer op die part se vorm kompleksiteit, spasie beskikbaar vir verkoelings kanale, kwaliteit vereistes en produk lewensiklus. Die volgende is in die studie geïmplementeer: ‘n vorm verkoelings ontwerp proses met simulasie, ‘reverse engineering’ en vervaardiging van die vorm insetsel. Om die generiese model te verifieer gedurende die studie is vergelykende eksperimente uitgevoer om die verskil in prestasie te bepaal tussen die gebruik van konvensionele en oppervlak verkoelings metodes. Die eksperimentele resultate het ‘n beduidende verbetering in part kwaliteit getoon met ‘n verkorte siklus tyd tydens die gebruik van die oppervlag verkoelings metode.