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Ce travail porte sur les processus de conception et de mise en forme des préformes textiles pour procédés de moulage en phase liquide (LCM), appliqués à la fabrication de pièces non structurales complexes. Les moules pour la fabrication de ces pièces composites ont une géométrie complexe et leur drapage est problématique. Fondamentalement, ce travail vise à prédire et à optimiser le processus de conception et de drapage des préformes. En outre, le travail vise à documenter et à améliorer 1) la sélection du tissu et de son orientation la plus appropriée pour le drapage d’une géométrie donnée et 2) la prédiction des temps de drapage. Les propriétés des renforts associées au drapage telles que le cisaillement, la flexion, la friction et la stabilité des tissus secs dépendent de la construction des tissus et de la géométrie complexe à draper. Le développement de patrons de découpe inclut la sélection de l’orientation des tissus et le positionnement des coupes et des joints. Malgré toute l’expérience industrielle liée au drapage des préformes, les processus existants pour le développement des patrons de découpe comportent une faible reproductibilité et deumeurent basés sur l’expérience de techniciens expérimentés. Avec la compétition en aérospatiale, le partenaire industriel Hutchinson doit développer des méthodes pour formaliser et quantifier la conception de patrons de découpe. Afin de décrire, formaliser et évaluer le drapage de différents tissus sur des géométries complexes, ce travail propose un premier outil prédictif du drapage permettant d’évaluer le temps de drapage, de permettre la sélection du tissus le plus approprié pour le drapage d’une géométrie, de déterminer l’orientation des fibres préférable ainsi que la position des coupes et des joints dans le patron de découpe. Ce travail inclut une caractérisation de 4 tissus secs utilisés en production chez Hutchinson. Des outils de caractérisation portatifs ont été développés afin de permettre l’évaluation rapide du cisaillement dans le plan, du retour élastique en cisaillement, du retour élastique en flexion dans un coin et sur les bords, de la friction entre les plis et avec le moule, de l’effilochement, ainsi que de la résistance des goupilles de localisation. Les essais de caractérisation ont été effectués sur ces équipements portatifs et certains ont été validés par comparaison avec des essais. À partir de ces caractéristiques de drapage, une méthode d’évaluation du comportement en drapage a été développée permettant de déterminer la façon dont un tissu donné se comporte lorsqu’il est drapé sur des géométries spécifiques. Plusieurs géométries de base ont été repérées sur les moules réels de Hutchinson, permettant la reconstruction d’autres moules par une combinaison de ces géométries de base. Le comportement en drapage pour chaque géométrie de base a été analysé et validé avec des essais expérimentaux directement sur les moules. Le travail de caractérisation et la méthode d’évaluation des géométries de base ont été combinés dans un algorithme empirique permettant d’évaluer la difficulté de drapage d’une géométrie complexe selon le tissu utilisé et son orientation. Des exemples montrent que l’algorithme réussit à atteindre les objectifs liés à l’évaluation des temps de drapage, de la sélection du tissu et de son orientation les plus appropriés en plus de guider le positionnement des coupes et des joints pour le développement des patrons de découpe. Les objectifs d’abaissement, de prédiction des temps de drapage et de détermination de l’emplacement des coupes et des joints dans les patrons ont été atteints.

The thermal diffusivity and conductivity of several ceramic composites were determined experimentally to observe the effect of temperature, heat treatment and orientation on these properties. The thermal conductivity and diffusivity of SiC whisker reinforced Ba-osumilite glass-ceramic exceeded that of SiC fiber reinforced osumilite due to higher thermal conductivity and diffusivity of the whiskers. An anisotropy was observed in thermal conductivity of the whisker composite due to whisker orientation normal to hot-pressing direction. Thermal conductivity of carbon fiber reinforced borosilicate glass parallel to the fiber plane was about twice that of the normal orientation and of the matrix. Heating the composite to above 600°C resulted in permanent decrease in thermal conductivity due to void formation by relaxation of the elastically bent fibers by viscous flow of the matrix. Thermal conductivity of iniaxial carbon fiber reinforced lithia-aluminosilicate glass-ceramic was over ten times higher parallel to the fibers than perpendicular. Permanent decrease of thermal conductivity normal to the fibers was due to matrix cracking caused by relief of internal stresses due to matrix crystallization and thermal gradients during fabrication. Modification of the original theories of Maxwell and Rayleigh permitted derivation of expressions for thermal conductivity of composites of a continuous matrix with dilute concentrations of spherical and cylindrical geometries and of parallel flat plates with thermal resistance at the interfaces. / M.S.

The first part of this research constituted the study of oligomeric incorporation into an inorganic network leading to the fonnation of a hybrid material by the sol-gel process. The oligomeric species chosen was silanol terminated poly(dimethylsiloxane) (PDMS) and the inorganic oxide precursor chosen was titanium tetra-isopropoxide (TIP). The rationale for choosing these materials stemmed from the desire to make materials for optical filters since a gradient of optical properties can be derived based on the composition and the initial reaction conditions. 29Si NMR studies were conducted to investigate the incorporation process which led to the conclusion that the PDMS chains were being degraded by the TIP. This problem led to the synthesis of TIP endcapped PDMS which was then used as the oligomeric component in the hybrid materials. The endcapping changed the functionality of the oligomer to six, and more importantly, its reactivity which was now closer to that of the TIP. Also, having the same functionality at the ends as the precursor affects the compatibility of the two components. Hybrid materials in the form of free standing films were fabricated from varying TIP/pDMS compositions and different initial reaction conditions. The hybrid materials synthesized were then subjected to a systematic structure-property relationship study. The degree of phase mixing or the encapsulation of the siloxane phase by the inorganic oxide increases with higher TIP content. This behaviour was seen by both the dielectric and dynamic mechanical studies. The modulus and the stress to break increased with higher TIP content while the strain to break decreased. At the 50/50 TIP/PDMS composition there was an abrupt change in the mechanical properties which signified a morphological change in these materials. The refractive indices of the materials also showed a trend similar to that of the mechanical properties. Three different cure procedures, viz., room temperature, thermal cure at 70 °C and microwave cure at 70 °C were utilized to fabricate the films. More phase separation occurred in the microwave cured over the thermally cured materials as evident from dielectric and dynamic mechanical studies. However, the effect diminished with higher TIP content in the materials. Changing the initial reaction conditions by varying the initial water and acid content changed the properties observed in the final products. Dielectric and dynamic mechanical studies showed that the phase separation was higher with increased water content. Also, the modulus of the materials made with increased water content was higher. Decreased acid content led to better dispersion of the two components as shown by the dielectric and dynamic mechanical experiments. The effect of using a less reactive inorganic component tetra-ethyl orthosilicate (TEOS), instead of TIP was also studied. The TEOS/pDMS materials showed more phase mixing than the TIPIPDMS materials, although, the dielectric tan δ peak maxima appeared at a lower temperature. The TEOS/PDMS materials were also less stiff than the TIP/PDMS materials. Structural studies were conducted by means of solid-state NMR, electron microscopy and small angle x-ray scattering (SAXS). With few exceptions, these studies correlated very well with the properties observed in these materials. The spin-lattice relaxation times obtained from the solid-state NMR correlated with the better phase mixing observed in the TEOSIPDMS materials relative to the TIPIPDMS materials. Electron microscopy in the backscattered mode showed the presence of microphase separation in these materials. At the 50/50 TIPIPDMS composition connectivity of the inorganic oxide phase was complete, perhaps encapsulating the siloxane phase totally. Microstructural differences were observed due to the variation in the cure modes. The domain sizes of the oxide phase were finer in the thermally cured as compared to the room temperature cured materials. Higher water content led to a very different microstructure when compared to materials made with lower water content. Smaller spherical particulate type structures were observed in the material made with higher water content. The domain sizes of the oxide phase in the TEOS/PDMS material were bigger than those in the TIP/PDMS material of equivalent composition. These differences may be intimately related to the reactivity difference between TIP and TEOS. The SAXS data supported the microstructure seen by electron microscopy and the properties observed by dynamic mechanical, dielectric and mechanical studies. / Ph. D.

This project is a proposal on the versatile use of glass, its properties and technologies as well as its aesthetic qualities. A photovoltaic charging station for electric scooters is proposed for the Virginia Tech campus, combined with a bus shelter to allow mobility and integration of transportation. / Master of Science

No / Glass-ionomer cements (GICs) have been widely used for over forty years, because of their desirable properties in dentistry. The most important advantages of the GICs are associated with their ability to release long-term antimicrobial agents. However, GICs used as restorative materials have still lots of challenges due to their secondary caries and low mechanical properties. Recent studies showed that the fluoride-releasing activity of conventional GICs is inadequate for effectual antibacterial conservation in many cases. Therefore, many efforts have been proposed to modify the antibacterial features of GICs in order to prevent the secondary caries. Particularly, for achieving this goal GICs were incorporated into various biomaterials possessing antibacterial activities. The scope of this review is to assess systematically the extant researches addressing the antibacterial modifications in GICs in order to provide with an authoritative, at the same time in-depth understanding of controlled antibacterial release in this class of biomaterials. It also gives a whole perspective on the future developments of GICs and challenges related to antibacterial GICs.

Envisioning novel fully monolithic fiber-optical devices, this dissertation investigates four fiber optical devices both, active and passive, that contribute to the goal of further integrating and miniaturizing fiber optics. An all phosphate glass fiber laser was designed in an effort to reduce laser intensity noise by reducing cavity losses and low mechanical strength that arise from intra-cavity fusion splices between silica fiber Bragg gratings (FBG) and phosphate active fiber in state of the art phosphate single frequency fiber lasers. Novel phosphate glass based FBGs have been fabricated utilizing high intensity laser pulses at 193 nm and a phase-mask. Net reflectivities of up to 70 % and a bandwidth of 50 pm have been achieved in the FBGs. The laser design comprised two of the novel FBGs and a short section of Er³⁺Yb³⁺ phosphate fiber to form a distributed Bragg reflector (DBR) laser. The performance of the new laser has been compared to a conventional phosphate fiber laser. Particular focus was put on the laser intensity noise due to its dependence on intra-cavity losses. Relative intensity noise (RIN) amplitudes of -80 dB/Hz have been measured for both lasers when operating at comparable output powers. For similar levels of absorbed pump power the relaxation oscillation frequencies (ROF) were shifted towards lower frequencies in the new laser. ExcessFBG scattering losses and mode-field miss-match between the active and passive fiber limited the output power of the new laser to 16 mW compared to 140 mW in the conventional laser. A monolithic all-phosphate glass fiber laser with up to 550 mW output power that is operating at a single longitudinal mode and exhibiting narrow linewidth is presented. The laser cavity has been formed by inscribing FBGs directly into heavily Er³⁺Yb³⁺ doped phosphate glass fiber using femtosecond laser pulses and a phase mask, completely eliminating the need for intra-cavity fusion splices. A linewidth of less than 60 kHz and relaxation oscillation peak amplitudes below -100 dB/Hz without active suppression of RIN have been measured. The compact form factor and higher output power combined with the low noise and narrow linewidth characteristic make this laser an ideal candidate for ranging, interferometry and sensing applications. Strong and robust Bragg gratings in optical fiber fabricated from highly photosensitive photo-thermo-refractive (PTR) glass are demonstrated. The fibers were drawn at 900 °C from a machined PTR-glass preform. A low power two beam interference pattern from a continuous wave (cw) He-Cd laser with a wavelength of 325 nm was used to write gratings into the fibers, achieving peak grating strengths of 20 dB and a spectral width of 45 pm. The gratings showed no sign of degradation when exposed to a high temperature environment of 425 °C for several hours. This is significantly higher when compared to standard Telecom FBGs which are rated for operation temperatures below 200 °C. A detailed study of novel mode-field adapters (MFA) based on multi-mode interference in graded index multi-mode fibers (GIMF) is presented. MFAs are often used in cases when low coupling losses between single mode fibers with very different mode-field diameters are needed. Here a new type of MFAs has been fabricated and characterized from a selection of commercially available single mode and graded index fibers. Compared to existing techniques the presented MFAs can be fabricated very quickly and are not limited to certain fiber types. Insertion losses of 0:5 dB over a spectral range of several hundred nm have been obtained with an ultra compact MFA with a length of 275 μm.

My engagement with making is a metaphor that contains the interior landscapes of my mind. I continue to explore it by comparing and contrasting exterior and interior, investigating surface and depth, covering and exposing, and taking apart and putting together. I work to translate my individual experiences and emotions into a tangible form. The visual dialogues that I engage in with my work explore a range of aspects that are inherent and specific to my Japanese cultural heritage. It often springs from my daily encounters with the subtle nuances and observable oddities of living in the “West”. These experiences have added to my self-awareness, and my sense of identity. I’ve always been fascinated by the visual phenomenon that occurs when light is transmitted, reflected, and/or refracted on/in/and through glass materials. I integrate these observable optical phenomena into personal narratives; by using “the-perceptional-shifts” that only the quality of glass it-self can generate, I transform my emotions into concrete materiality. The body of work that has developed over the past two years focuses on integrating my experiences, emotions and feelings, distance and time, and memories of and longing for my twin sister. I marry new technology with old, and attempting to bring the sensitivity of craft to new methods of making. Embedded in this work is my passion for life, materials, and making.

O objetivo deste estudo foi comparar, in vitro, a resistência à compressão de 30 raízes bovinas, tratadas endodonticamente, divididas em 3 grupos com 10 raízes cada e restauradas com pino metálico fundido (Grupo 1), pino pré-fabricado de fibra de vidro (Grupo 2) e pino anatômico (Grupo 3). Todas as raízes, com comprimentos de 15mm, foram preparadas internamente para que a espessura dentinária cervical ficasse com 1,5mm, com o objetivo de aumentar a largura do canal radicular. O espaço para o pino foi preparado com 10mm de comprimento. O diâmetro do pino de fibra de vidro escolhido foi o número 2, do sistema utilizado, para que houvesse um espaço entre ele e a estrutura radicular. O Grupo 1 recebeu pino e núcleo metálico fundido cimentado com cimento de fosfato de zinco. O Grupo 2 recebeu pino préfabricado de fibra de vidro cimentado com cimento resinoso Panavia F e núcleo de resina composta Z100. O Grupo 3 recebeu um pino de fibra de vidro modelado no interior do canal com resina composta Z100, cimentado com cimento resinoso Panavia F e núcleo de resina composta Z100. Em todas as raízes dos grupos, um coping metálico foi cimentado com cimento de fosfato de zinco. As raízes foram incluídas em resina acrílica quimicamente ativada, previamente inserida no interior de tubos de PVC e submetidas a testes de compressão em máquina de ensaio Kratos, modelo k2000MP. A carga de compressão foi aplicada a um ângulo de 135 graus ao longo eixo do dente, na face palatina, até que ocorresse uma trinca ou and analysed. The results revealed a statistical difference among groups. Group 1 presented a stronger resistance to fracture than the other groups, which did not present statistical difference. The roots restored with post and cast metallic core were the only ones that presented radicular fracture in the apical root third. The roots that were restored with fibre glass posts presented similar fractures, from the cervical root third to the middle root third. / The aim of this study was to compare, in vitro, the resistance to compression strength of 30bovine roots among canines and incisors endodontically treated, divided into 3 groups with 10 roots each and restored with cast metallic post (Group 1), prefabricated fibre glass post (Group 2), and anatomical post (Group 3). All the roots, with a length of 15mm, were internally prepared so as to their cervical dentin wall thickness would be of 1,5mm, in order to enhance the width of the radicular canal. The space for the post was prepared with 10mm. The diameter of the glass fibre post chosen was the number 2, of the adopted system, so as to create a space between the glass fibre post and the radicular structure. Group 1 received post and cast metallic core cemented with zinc phosphate cement. Group 2 received prefabricated fibre glass post cemented with resin cement Panavia F and composite resin core Z100. Group 3 received a fibre glass post modeled inside the canal with composite resin Z100, cemented with resin cement Panavia F and composite resin core Z100. In all groups, all the roots were cemented with a metallic coping with zinc phosphate cement. The roots were mounted inside pvc pipes with chemically activated acrylic resin, and submitted to compression tests in a universal testing machine Kratos, model k2000MP. The compressive load was done in an angle of 135o in relation to the long axes of the roots, until the occurrence of failure or fracture. The amount of load correspondent to the occurrence of failure or fracture was statistically registered and analysed. The results revealed a statistical difference among groups. Group 1 presented a stronger resistance to fracture than the other groups, which did not present statistical difference. The roots restored with post and cast metallic core were the only ones that presented radicular fracture in the apical root third. The roots that were restored with fibre glass posts presented similar fractures, from the cervical root third to the middle root third.