The fiber alignment shifts induced by the post-weld-shift (PWS) in laser-welded TO(Transistor outline)-Can type laser module packages is studied experimentally and numerically. The PWS induced fiber alignment shifts were quantitatively determined by four geometrical parameters: the lateral shift(r), the position angle(£\), the tilt angle(£Z), and the swing angle(£c). The measured coupling powers in laser module packages before welding, after welding, and after a compensation clearly confirmed with the measured fiber alignment shifts determined by the dominant parameters of the r and £\ that the fiber shifts due to the PWS could be realigned back closer to their original optimum position after applying a welding compensation, and hence the coupling powers loss due to the PWS could be regained. The measured coupling efficiency after laser welding was from 68% to 95%, and the overall coupling efficiency after the PWS compensation was from 77% to 97%. The increased coupling efficiency after this PWS compensation was from 2% to16%. A coupled thermal-elasto-plasticity model of finite-element method (FEM) analysis was performed to evaluate the effects of PWS on fiber alignment shifts in laser module packages. The measured fiber alignment shifts determined by the dominant parameters of the r and £\ were in good agreement with the numerical calculation of the FEM analysis. In this study, the combination of the experimental and numerical results have significantly provided a practical design guideline for fabricating reliable laser-welded TO-Can type laser module packages with a high yield and high performance for use in low-cost lightwave transmission systems. A novel measurement and compensation technique employing a high-magnification camera with image capturing system (HMCICS) to probe the post-weld-shift (PWS) induced fiber alignment shifts in high-performance butterfly-type laser module packages is investigated. The results show that the direction and magnitude of the fiber alignment shifts induced by the PWS in laser-welded butterfly-type laser module packaging can be quantitatively determined and then compensated. The measured coupling powers in laser module packages after welding and compensation clearly confirmed the measured fiber alignment shifts determined by the translational and rotational parameters that the fiber shifts due to the PWS could be realigned back closer to their original optimum position after applying a welding compensation, and hence the coupling powers loss due to the PWS could be regained. The measured coupling efficiency after laser welding was from 63% to 79%, and the overall coupling efficiency after the PWS compensation was from 69% to 89%. The increased coupling efficiency after this PWS compensation was from 3% to 10%. In comparison with previous studies of the PWS compensation by a qualitatively estimated technique in butterfly-type laser module packages, this novel HMCICS technique has significantly provided an important tool for quantitative measurement and compensation to the effect of the PWS on the fiber alignment shifts in laser module packages. Therefore, the reliable butterfly-type laser modules with a high yield and a high performance used in lightwave transmission systems can be developed and fabricated.

No description available.

Aligning and fixing the fiber and laser device is an important work in butterfly laser module packaging. Assembling these two component by laser welding is to achieve reliable and stable weld joint. However, during the welding process, rapid solidification of the welded region and the associated material shrinkage causes the fiber position moved. The relative movement between fiber and laser is called post-weld-shift(PWS). A few micrometers PWS makes coupled power lost. Therefore, minimizing the PWS between fiber and laser is a key research topic in butterfly laser module packaging. We can correct the PWS minimal by fiber shift inspect. But it has a difficult of space limit in butterfly laser module packaging. In this study, a video camera with image acquisition system was used to measure the PWS. We also used a mirror image to solve the problem of space limited. The PWS inspection result has matched our simulation. This method can successfully inspect the PWS in butterfly laser module.

Several active methods, which requires external control systems and moving parts, have been developed to control the fiber orientation during 3D printing. Active mechanisms like rotating nozzle, impeller, and magnetic field have been integrated to realize complex internal fiber structures. In this study, instead of using active methods, I investigate a passive method for controlling the fiber orientation without any moving parts or additional mechatronics added in the printing process. Composites of polydimethylsiloxane (PDMS) and glass fibers (GF) are 3D printed. Channels, such as helicoid, are designed and integrated to guide the ink flow and passively result in different pre-alignment of fibers before the ink flow into narrow nozzle space. While passing through the designed channels, the fibers orient due to the shear between channel walls and the ink. The effect of helicoids with different pitch sizes are investigated via mechanical experiments, microstructural analysis, and numerical simulations. The results show that both surface to volume ratio and helix angle of the channel affect pre-alignment of fiber orientation at the entry of nozzle. The internal fiber structures lead to enhanced and tunable mechanical properties of printed composites. Pitch size 7-9 mm (helix angle of 7.92- 10.15o) is found to be optimal for the 3D printed PDMS-GF composites. Stiffness and strength can be tuned up to 77.6% and 47.8%, respectively, compared with the case without helicoid channel. Channels of parallel holes, parallel holes with taper end and gradually changing pitch helicoids are experimentally tested, showing further enhancement in mechanical properties.

No description available.

The conception of electrospinning can trace its roots back more than 400 years, when it was observed that rubbed amber can deform a droplet of water on a smooth surface, and is based upon simple concepts of charge separation and surface tension. Since that time, considerable effort has been directed at both the cause and utility of this phenomenon. The specific aim of this dissertation project was to develop an automated electrostatic processing apparatus that was capable of controlling the three-dimensional architecture of an electrospun scaffold to further improve its utility in tissue engineering. The efficacy of using this technique has been well documented and can be adapted to produce tissue engineering scaffolds for a variety of tissues and organs. This apparatus incorporates precise mandrel motion. The system is capable of 0 - 5000 revolution per minute rotation, 0 - 25 inch per second translation and ± 40° rotation about the electrospinning jet axis for repeatable scaffold production. Fiber alignment and scaffold density are precisely controlled by rotating a mandrel along one axis, translation along that same axis, and rotation around the second axis perpendicular to the electrospun fiber stream. The control is accomplished with a PC based "supervisory" control program written partially in the LabVIEW® programming language and partially in SI Programmer supplied by Applied Motion Products. Scaffold thickness and fiber diameters are determined by the syringe metering pump flow rate, material being electrospun and solution concentrations. Through extensive laboratory analysis (mechanical testing and both optical and electron microscopy), parameters such as fiber orientation, diameter and mechanics can be predictive from specific polymer setups. Our laboratory has demonstrated the ability to electrospin natural and synthetic polymers and this apparatus will be utilized to tailor scaffolds to meet specific tissue engineering needs by creating a truly biomimicking scaffold / extracellular matrix.

A eletrofiação é uma celebrada técnica de processamento de polímeros, capaz de produzir fibras de diâmetro nanométrico. A montagem comum do sistema de eletrofiação permite a captação de fibras aleatórias sob a forma de um não-tecido. Diversas modificações nessa montagem permitem a obtenção de diferentes morfologias de fibras. Tais modificações são revisadas e discutidas neste trabalho. Na produção de suportes de crescimento de células neurais, é interessante que seja incorporada alguma anisotropia no meio. Assim, um aparato de eletrofiação, capaz de produzir fibras alinhadas, foi construído e a variação dos parâmetros de seu processamento permitiu a obtenção de diferentes qualidades de alinhamento das fibras para dois polímeros biodegradáveis. Diversos parâmetros influenciaram a qualidade desse alinhamento, porém a velocidade de captação das fibras mostrou ser o mais impactante, em acordo com dados reportados na literatura. A morfologia das fibras foi avaliada quanto ao seu diâmetro, com o auxílio de micrografias de MEV e do software de edição de imagens ImageJ. Adicionalmente buscou-se avaliar a qualidade do alinhamento de tais fibras. Para tanto, foi desenvolvida uma metodologia de quantificação de qualidade de alinhamento de fibras, baseado nas micrografias e na ferramenta de FFT do ImageJ. A metodologia proposta foi capaz de ordenar de maneira objetiva e consistente a qualidade do alinhamento das fibras obtidas, mesmo quando a análise visual (usada como referência) se provava ineficiente. A metodologia proposta foi incorporada num plugin para ImageJ, via algoritmo computacional escrito em Java. Com o uso do plugin, foi possível processar diversas micrografias, obtidas em diferentes pontos das malhas eletrofiadas e com variadas magnificações, a fim de se criar uma estatística dos resultados obtidos para qualidade de alinhamento das fibras, algo inédito na literatura. Malhas eletrofiadas com diferentes qualidades de alinhamento de suas fibras foram utilizadas como substrato na cultura de células precursoras neurais, provenientes de neuroesferas. Foi feita a cultura de células progenitoras neurais, provenientes de neuroesferas, tendo como substrato malhas eletrofiadas com diferentes qualidades de alinhamento, a fim de se avaliar o impacto dos contatos físicos das fibras sobre a migração e diferenciação de tais células. / Electrospinning is a celebrated technique of polymer processing, able to produce fibers with nanometric diameter. Common assembly of electrospinning apparatus allows collection of random fibers in a non-woven matt. Several modifications on this assembly enable different fiber morphologies to be obtained. Such modifications are revised and discussed in this work. In the production of cell growth scaffolds, its interesting that some anisotropy is incorporated in the medium. Therefore, an electrospinning apparatus capable of producing aligned fibers was constructed. Variation of processing parameters of said apparatus enabled different alignment qualities of fibers to be attained for two biodegradable polymers. Many parameters influenced on the quality of said alignment; fiber collection speed, however, proved more impacting, in accordance with literature data. Fiber morphology was assessed in regard to its diameter with the aid of MEV micrographs and ImageJ software. Furthermore, assessment of fiber alignment quality was sought. For this matter, it has been developed a quantification methodology for fiber alignment quality, based on micrographs and ImageJ\'s FFT tool. The proposed methodology was able to objectively and consistently rank fiber alignment quality, even when visual analysis (used as reference) failed to do so. This methodology was incorporated in a plugin for ImageJ, via Java script algorithm. With the aid of this plugin it was feasible to process several micrographs, taken from electrospun mats at different spots and magnifications. This helped create statistics about obtained results of fiber alignment quality, on an unprecedented approach in written literature. Electrospun mats with varying quality in fiber alignment were used as substrate in the culture of neural precursor cells from neurospheres to assess the influence of contact guidance on migration and differentiation of such cells

A eletrofiação é uma celebrada técnica de processamento de polímeros, capaz de produzir fibras de diâmetro nanométrico. A montagem comum do sistema de eletrofiação permite a captação de fibras aleatórias sob a forma de um não-tecido. Diversas modificações nessa montagem permitem a obtenção de diferentes morfologias de fibras. Tais modificações são revisadas e discutidas neste trabalho. Na produção de suportes de crescimento de células neurais, é interessante que seja incorporada alguma anisotropia no meio. Assim, um aparato de eletrofiação, capaz de produzir fibras alinhadas, foi construído e a variação dos parâmetros de seu processamento permitiu a obtenção de diferentes qualidades de alinhamento das fibras para dois polímeros biodegradáveis. Diversos parâmetros influenciaram a qualidade desse alinhamento, porém a velocidade de captação das fibras mostrou ser o mais impactante, em acordo com dados reportados na literatura. A morfologia das fibras foi avaliada quanto ao seu diâmetro, com o auxílio de micrografias de MEV e do software de edição de imagens ImageJ. Adicionalmente buscou-se avaliar a qualidade do alinhamento de tais fibras. Para tanto, foi desenvolvida uma metodologia de quantificação de qualidade de alinhamento de fibras, baseado nas micrografias e na ferramenta de FFT do ImageJ. A metodologia proposta foi capaz de ordenar de maneira objetiva e consistente a qualidade do alinhamento das fibras obtidas, mesmo quando a análise visual (usada como referência) se provava ineficiente. A metodologia proposta foi incorporada num plugin para ImageJ, via algoritmo computacional escrito em Java. Com o uso do plugin, foi possível processar diversas micrografias, obtidas em diferentes pontos das malhas eletrofiadas e com variadas magnificações, a fim de se criar uma estatística dos resultados obtidos para qualidade de alinhamento das fibras, algo inédito na literatura. Malhas eletrofiadas com diferentes qualidades de alinhamento de suas fibras foram utilizadas como substrato na cultura de células precursoras neurais, provenientes de neuroesferas. Foi feita a cultura de células progenitoras neurais, provenientes de neuroesferas, tendo como substrato malhas eletrofiadas com diferentes qualidades de alinhamento, a fim de se avaliar o impacto dos contatos físicos das fibras sobre a migração e diferenciação de tais células. / Electrospinning is a celebrated technique of polymer processing, able to produce fibers with nanometric diameter. Common assembly of electrospinning apparatus allows collection of random fibers in a non-woven matt. Several modifications on this assembly enable different fiber morphologies to be obtained. Such modifications are revised and discussed in this work. In the production of cell growth scaffolds, its interesting that some anisotropy is incorporated in the medium. Therefore, an electrospinning apparatus capable of producing aligned fibers was constructed. Variation of processing parameters of said apparatus enabled different alignment qualities of fibers to be attained for two biodegradable polymers. Many parameters influenced on the quality of said alignment; fiber collection speed, however, proved more impacting, in accordance with literature data. Fiber morphology was assessed in regard to its diameter with the aid of MEV micrographs and ImageJ software. Furthermore, assessment of fiber alignment quality was sought. For this matter, it has been developed a quantification methodology for fiber alignment quality, based on micrographs and ImageJ\'s FFT tool. The proposed methodology was able to objectively and consistently rank fiber alignment quality, even when visual analysis (used as reference) failed to do so. This methodology was incorporated in a plugin for ImageJ, via Java script algorithm. With the aid of this plugin it was feasible to process several micrographs, taken from electrospun mats at different spots and magnifications. This helped create statistics about obtained results of fiber alignment quality, on an unprecedented approach in written literature. Electrospun mats with varying quality in fiber alignment were used as substrate in the culture of neural precursor cells from neurospheres to assess the influence of contact guidance on migration and differentiation of such cells

In this study, the mechanical properties of a fiber-reinforced cementitious composite (FRCC) were derived for specimens fabricated using two different methods of casting: conventional cast construction and pump-driven extrusion. Through the extrusion process, fibers are more likely to be oriented along the length of the member being cast and will therefore be more efficient since they are aligned parallel to the tensile stresses produced in flexure testing. The FRCC employed 0.5% and 1% polyvinyl alcohol (PVA) fiber reinforcement by volume. The flexural properties of FRCC were determined using four-point bend tests according to a modified ASTM C1609. Calculations included the modulus of rupture (MOR) and flexural toughness based on load-deflection curves. The fracture properties of FRCC were determined by using three-point bend tests on the same design but having notched beams using the two-parameter fracture model (TPFM). Calculations included the Mode I critical stress intensity factor (KIC), the critical crack tip opening displacement (CTODc), the strain energy release rate (GIC), and the total fracture energy (GF). The results show that enhanced ductility and post-peak behavior are achieved in concrete to which fibers have been added, as has been demonstrated in other studies, although this study further demonstrated how preferential fiber alignment produced via an extrusion can enhance fracture and flexural properties of cementitious composites. / Master of Science / Fiber-reinforced cementitious composite (FRCC) is a type of cementitious composite that contains fibers that are added to the mixture to improve its strength, durability, and ductility. One of the key factors of FRCC that affects its mechanical properties is the fiber alignment. Extrusion can be used as a method to preferentially align the fibers in order to maximize the benefit of fibers. Extruded FRCC can be pumped through a nozzle, making fiber alignment a convenient option for construction projects where traditional concrete placement methods would be difficult. One of the main benefits of aligning fibers in pump-extruded FRCC is that it can improve cementitious composites' fracture and flexural toughness. Fracture toughness refers to the ability of a material to resist crack propagation, while flexural toughness refers to its ability to withstand bending. By adding fibers to the mixture, the fibers act as reinforcement and help to distribute stress more evenly throughout the material, leading to increased strength and ductility. Furthermore, the alignment of fibers within the mixture also plays a critical role in the fracture and flexural strength of the material. Research has shown that when fibers are aligned in a specific direction, they can improve the tensile strength of the concrete and decrease the likelihood of crack propagation. This can be especially useful in structures that are exposed to seismic activity or long-lasting heavy loads. Overall, the use of pump extrusion-based method as a fiber alignment for FRCC can significantly improve the fracture and flexural strength of concrete. This makes it an attractive option for construction projects that require strong and durable members.

Ausgangspunkt für dieses Anschlussprojekt am Institut für Tragwerksplanung der TU Braunschweig war der Wunsch, die Effektivität des Faseranteils derjenigen Betonbauteile zu erhöhen, die zuvor im SPP-Projekt Entwicklung neuartiger Verbindungen für komplexe Stab-, Flächen- und Raumtragelemente aus UHPFRC (S. 50 ff . in diesem Buch) hergestellt und untersucht wurden. Voruntersuchungen und Versuche zum Thema der magnetische Faserausrichtung in UHPFRC werden am ITE seit 2014 kontinuierlich durchgeführt [1]–[4]. Diese Voruntersuchungen berührten bereits zentrale Aspekte dieses Forschungsvorhabens und lieferten konkrete Hinweise auf die zu erwartenden Ergebnisse zur robotergestützten, magnetischen Ausrichtung und Verteilung der Mikrostahlfasern (MSF). Im Fokus der Forschung standen zum einen die Möglichkeiten der digitalen und robotergestützten Bauteilfertigung und zum anderen das Potenzial der Faserausrichtung zur Steigerung der Materialeffizienz von UHPFRC. In der Entwicklung des Verfahrens der magnetischen Faserausrichtung (MFA) wurden diese beiden Ansätze zusammengeführt. / The starting point for this follow-up project, which was carried out at the Institute of Structural Design at the Technical University of Braunschweig, was the desire to increase the effectiveness of the fibre content of the type of concrete components that were previously manufactured and investigated in the SPP project Development of novel jointing systems for complex beam surface and spatial elements made of UHPFRC (p. 50 et seq. in this book). Preliminary investigations and tests on the topic of magnetic fiber alignment in UHPFRC have been carried out continuously at ITE since 2014 [1]–[4]. These preliminary investigations already touched upon central aspects of this research project and provided concrete indications of the expected fi ndings on robot-assisted magnetic alignment and distribution of the micro steel fi bres (MSF). The research focused on the possibilities of digital and robot based component production on the one hand and the potential of fibre orientation to increase the material efficiency of UHPFRC on the other. In the development of the magnetic fibre alignment (MFA) process, these two approaches were brought together.