There are presently many solutions to dealing with aging or deteriorated structures. Depending on the state of the structure, it may need to be completely over-hauled, demolished and replaced, or only specific components may need rehabilitation. In the case of bridges, rehabilitation and maintenance of the decks are critical needs for infrastructure management. Viable rehabilitation options include replacement of decks with aluminum extrusions, hybrid composite and sandwich systems, precast reinforced concrete systems, or the use of pultruded fiber-reinforced polymer (FRP) shapes. Previous research using pultruded glass fiber-reinforced polymer (GFRP) decks, focused on behaviour under various strength and serviceability loading conditions. Failure modes observed were specific to delamination of the flexural cross sections, local crushing under loading pads, web buckling and lip separation. However certain failure mechanisms observed from in-situ installations differ from these laboratory results, including behaviour of the connectors or system of connection, as well as the effect of cyclic and torsional loads on the connection. This thesis investigates the role of mechanical and non-mechanical connectors in the composite action and failure mechanisms in a pultruded GFRP deck system. There are many interfaces including top panel to I-beam, deck panel to girder, and panel to panel, but this work focuses on investigating the top panel connection. This is achieved through comparative component level shear, uplift, and flexure testing to characterize failure and determine connector capacity. Additionally, a connection of this GFRP deck system to a concrete girder is investigated during the system-level test. Results show that an epoxy non-mechanical connection may be better than mechanical options in ensuring composite behaviour of the system.

Innerhalb dieser Arbeit wird ein Fertigungsverfahren entwickelt und erprobt, das den additiven Aufbau von großvolumigen faserverstärkten Kunststoffbauteilen in Skelettbauweise erlaubt. Dafür wird ein modifizierter Extruder zusammen mit einer speziellen Kinematik genutzt. Der Fokus liegt auf der Analyse des Einflusses der Steuergrößen auf geometrische und mechanische Eigenschaften, sowie Haftung im Bauteil. Hinsichtlich der geometrischen Eigenschaften wird ein Prozessmodell entwickelt, das die Abhängigkeit der Strangbreite und -höhe von den Steuergrößen darstellt. Durch experimentelle Untersuchungen werden die Prozessgrenzen und an diesen auftretende Effekte ermittelt. Das Verfahren weist hier große Freiräume auf. So können z.B. mit einer 1 mm Düse Strangbreiten von 1,2 bis 3,2mm erzielt werden. Die mechanischen Eigenschaften in Strangrichtung erreichen im 3D-Druck annähernd die Steifigkeit und Festigkeit der Spritzgießreferenz. Prozessbedingt ist eine Porosität im Material nicht ganz vermeidbar, allerdings sind die Fasern stark ausgerichtet und die Faserlänge im Granulat bleibt im Prozess weitestgehend erhalten. Mittels direktem 3D-Drucken auf endlosfaserverstärktes Tape kann mit Vorheizen des Tapes ein guter Haftverbund generiert werden. Ergänzend wurden zwei Komponenten entwickelt, die für eine Industrialisierung des Prozesses entscheidend sind: Zum einen wurde ein neues Düsenkonzept vorgestellt, das eine schnelle Anpassung des Massestroms während des 3D-Druckens ermöglicht. Zum anderen wurde eine Temperierdüse vorgestellt, mit der mittels Konvektion der abgelegte Strang gekühlt bzw. erhitzt werden kann.:1 Einleitung 2 Zielstellung 3 Literaturübersicht 4 Konzeption eines neuartigen 3D-Druck-Verfahrens 5 Analyse der kinematischen Eigenschaften 6 Betrachtung der Haftungsmechanismen 7 Untersuchung der mechanischen Eigenschaften 8 Weiterentwicklung von Anlagenkomponenten 9 Zusammenfassung und Ausblick / In this thesis, a manufacturing process is presented which enables the additive manufacturing of largevolume fibre-reinforced plastic components in skeleton construction by using an extruder together with special kinematics. The focus is on the analysis of the influence of the control variables on geometric and mechanical properties, as well as adhesion in the component. With regard to the geometric properties, a process model is being developed that shows the dependence of the strand width and height on the control variables. Experimental investigations are used to determine the process limits and the effects occurring at these limits. The procedure knows here large free spaces, so e.g. with a 1 mm nozzle strand widths of 1,2 bis 3,2mm can be obtained. The mechanical properties in the strand direction in 3D printing approximate the stiffness and strength of the injection molding reference. Due to the process, porosity in the material cannot be completely avoided, however, the fibers are strongly oriented and the fiber length in the granulate is largely retained in the process. Direct 3D printing on continuous fiber-reinforced tape can be used to generate a good adhesive bond by preheating the tape. In addition, two components were developed that are decisive for industrializing the process: On the one hand, a new nozzle concept was introduced that enables rapid adjustment of the mass flow during 3D printing. On the other hand, a nozzle was presented with which the deposited strand can be cooled or heated by convection.:1 Einleitung 2 Zielstellung 3 Literaturübersicht 4 Konzeption eines neuartigen 3D-Druck-Verfahrens 5 Analyse der kinematischen Eigenschaften 6 Betrachtung der Haftungsmechanismen 7 Untersuchung der mechanischen Eigenschaften 8 Weiterentwicklung von Anlagenkomponenten 9 Zusammenfassung und Ausblick

Vacuum bags in conjunction with autoclaves are currently employed to generate the consolidation pressures and temperatures required to manufacture aerospace level composites. As the scale of continuous fiber composite structures increases autoclaving becomes prohibitively expensive or impossible. The objective of this work is to develop flexible magnetic clamping structures to increase the consolidation pressure in conventional vacuum bagging of composite laminates, thereby obviating the need for an autoclave. A ferromagnetic rubber, which consists of rubber filled with iron, is being developed as a conformable and reusable vacuum bag that provides increased consolidation through attractive forces produced by electromagnets. Experiments and finite element modeling indicate that consolidation pressure in the range of 100 kPa can be generated by such a device with realistic power requirements. The effects of the magnetic clamping device process parameters on the consolidation pressure magnitude are modeled and characterized. In addition, a method for the efficient design of the magnetic clamping device is developed.

This thesis presents a technique used to stochastically estimate the location of hidden discontinuities in carbon fiber composite materials. Composites pose a challenge to signal processing because speckle noise, as a result of reflections from impregnated laminas, masks useful information and impedes detection of hidden discontinuities. Although digital signal processing techniques have been exploited to lessen speckle noise and help to localize discontinuities, uncertainty in ultrasonic wave propagation and broadband frequency based inspections of composites still make it a difficult task. The technique proposed in this thesis estimates the location of hidden discontinuities stochastically in one- and two-dimensions based on statistical data of A-Scans and C-Scans. Multiple experiments have been performed on carbon fiber reinforced plastics including artificial delaminations and porosity at different depths in the thickness of material. A probabilistic approach, which precisely localizes discontinuities in high and low amplitude signals, has been used to present this method. Compared to conventional techniques the proposed technique offers a more reliable package, with the ability to detect discontinuities in signals with lower intensities by utilizing the repetitive amplitudes in multiple sensor observations obtained from one-dimensional A-Scans or two-dimensional C-Scan data sets. The thesis presents the methodology encompassing the proposed technique and the implementation of a system to process real ultrasonic signals and images for effective discontinuity detection and localization.

Les composites à matrice polymère sont de plus en plus utilisés dans le secteur automobile. Afin de remplir les conditions exigeantes du cahier des charges vis-à-vis des conditions de mise en service, les pièces en composite doivent maintenir leur forme géométrique sous des conditions thermo-mécaniques parfois extrêmes. Par exemple, un assemblage de hayon composite est soumis à des contraintes mécaniques élevées associées à des variations de température importantes lors des essais de validation du cahier des charges. Les enjeux de la thèse sont axés sur l’aide à la conception dans le domaine quasi-statique de pièces industrielles injectées en thermoplastique renforcé de fibres discontinues. L’amélioration des outils numériques doit permettre un dimensionnement virtuel optimal de ces pièces en anticipant les variations rencontrées en service et les distorsions résiduelles résultantes de chargements thermo-mécaniques. Cette démarche s’appuie sur la connaissance du comportement thermo-mécanique du matériau de l’étude, celui du renfort de hayon, un polypropylène renforcé à 40% en masse de fibres de verre discontinues, et sur la modélisation du comportement de ce type de matériau. / Discontinuous fibers reinforced thermoplastic materials have been widely used for several years in the automotive industry. These parts must resist demanding service life conditions and must meet thermo- mechanical specifications. Indeed, structural automotive spare parts have to endure high temperatures, like a few tens of degrees Celsius, for a long duration, at least a few hours. As an example, a structural part of tailgate is subject to high mechanical loading, associated to strong temperature variations, during the validation test, regarding specifications. The purpose of this work is to improve the design of complex industrial parts, like the tailgate in quasi-static domain, by relying on numerical simulation. One of the challenges related to the use of such material, is to have a reliable virtual design of industrial parts by predicting the geometrical variations during service life conditions, and residual strain. Therefore, it is necessary to characterize and to model the thermo-mechanical behavior of the tailgate material, a polypropylene matrix reinforced with discontinuous glass fibers, with a given mass fraction of 40%

L’utilisation des fibres végétales dans les polymères composites suscite de nombreuses investigations. Avant de mélanger les fibres végétales dans le polymère, un traitement chimique peut être effectué permettant de réduire l’hydrophilicité des fibres et d’améliorer l'adhérence à l’interface fibre/matrice. Dans cette thèse, l'eau et l'alcali sont utilisés d'abord pour traiter les fibres de chanvre, puis trois agents silane : 3-(triméthoxysilyl)propyl méthacrylate (MPS), N-[3- (triméthoxysilyl)propyl] aniline (PAPS) et (3-Aminopropyl)-triéthoxysilane (APS), sont utilisés pour modifier plus ou moins la surface des fibres de chanvre. Ces fibres traitées ou modifiées sont ensuite mélangées avec le polypropylène (PP) pour la fabrication des composites. Les effets de ces différents traitements sur la structure, les composants et l’hydrophilicité des fibres, et les propriétés mécaniques de ces composites sont mis en évidence. Nous avons étudié ensuite l’effet de vieillissement sur leurs comportements mécaniques, notamment l'humidité, la température et le rayonnement ultraviolet. Les résultats ont montré que le traitement de fibres par l'eau et l’alcali a des effets considérables sur la structure de fibres, les propriétés mécaniques et la durabilité des composites renforcés. La modification par l'agent de silane a une influence moins importante sur la structure des fibres, pourtant son groupe fonctionnel a une influence significative sur les propriétés mécaniques et la résistance au vieillissement des composites renforcés / Using agro fiber as reinforcement of polymer com-posites attracts numerous investigations due to the good mechanical properties and environmental benefits. Prior to blend agro fiber with polymer, chemical treatment can be employed to treat agro fiber for the purpose of reducing the hydrophilicity of fiber and improving the interfacial adhesion fi-ber/polymer matrix. In this thesis, water and alkali are utilized to treat hemp fiber firstly and then three silane agent as 3-(Trimethoxysilyl)propyl methacry-late (MPS), N-[3-(Trimethoxysilyl)propyl]aniline (PAPS) and (3-Aminopropyl)-triethoxysilane (APS) are employed to modify the hemp fiber surface. These treated or modified fibers are blended respectively with polypropylene (PP) to fabricate the hemp fiber/PP composites. The effects of these different treatments on the structure, components and hydro-philicity of fiber, and the mechanical properties of the reinforced PP composites are studied. Moreover, the accelerated ageing experiments including humidity, temperature and ultraviolet of the reinforced PP composites are conducted. The results showed that the fiber treatment of water and alkali has a considerable effect on fiber structure, mechanical properties and durability of the reinforced compo-sites. The silane agent modification of fiber has less influence on the fiber structure but its functional group has great influence on the mechanical proper-ties and ageing resistance of the reinforced compo-sites.

Depuis quelques années les matériaux composites à base de fibres naturelles sont de plus en plus utilisés pour les nouvelles performances qu’ils proposent. C’est surtout au niveau des fibres naturelles que de nouvelles propriétés sont proposées. Dans ce travail, nous nous sommes essentiellement intéressés aux fibres naturelles de chanvre. Ces fibres sont déjà fortement utilisées dans l’automobile et la construction. En Europe, ces fibres sont produites principalement en France et plus particulièrement dans l’Aube. Pour développer des agro-composites hautes performances, c’est sous la forme de fibres longues et de tissus que nous avons choisi d’orienter ce travail de thèse. Nous avons choisi la thermocompression pour élaborer des plaques avec des tissus de chanvre et une matrice en polypropylène (PP). Ce travail permet de voir l’influence des conditions d’élaboration sur le comportement mécaniques de ces agro-composites. Cette thèse permet aussi de voir l’effet du vieillissement aux UV et à l’Humidité sur les performances de ces matériaux. Enfin une analyse des contraintes résiduelles par la méthode du trou incrémental permet de voir leurs effets sur ces agro-matériaux / In recent years composite materials based on natural fibers are more and more used for their new performances. Natural fibers propose attractive environmental, mechanical and thermal properties.In this work, we are firstly interested in hemp fibers. These fibers are already used in the automotive and construction industry. In Europe, these fibers are produced mainly in France and especially in Aube. To develop agro-composites with high performances, we have focused this thesis on hemp woven. We chose to elaborate the plates with hemp woven and a polypropylene matrix (PP) by compression molding. This work allows us to see the influence of elaboration conditions on the mechanical behavior of these agro-composites. This thesis also allows us to see the effect of aging conditions UV and humidity on the performance of these materials. Finally an analysis of residual stresses determined by the hole drilling method is proposed to see their effects on the agro-materials

Die Entwicklung von Geweben mit gestreckten Fadenlagen ist Gegenstand aktueller Forschungen, die vielfach Sondermaschinen für ganz spezielle Anwendungen hervorbringen. Eine systematische Analyse und Optimierung der unter Berücksichtigung der Verbundeigenschaften existiert nach bekanntem Stand des Wissens nicht. Ziel der Dissertation ist es, diese Lücke zu schließen und einen Beitrag zur Etablierung von Geweben mit gestreckten Fadenlagen in Faserverbundwerkstoffen zu leisten. Die Arbeit basiert zum Teil auf den Ergebnissen, die in der Zeit von 2006 – 2012 am Institut für Textilmaschinen und textile Hochleistungswerkstofftechnik der Technischen Universität Dresden im Rahmen verschiedener AiF und DFG Vorhaben entstanden sind. Weiterführende Überlegungen wurden 2015 – 2017 im Rahmen eines Promotionsstudiums an der Professur für Textile Technologien der Technischen Universität Chemnitz angefertigt. Wie anhand konkreter Ausführungsbeispiele gezeigt wird, stößt das Weben insbesondere für Anwendungen im Faserverbundleichtbau an technologisch bedingte Grenzen. Es erfolgt zunächst eine Gegenüberstellung konventioneller Flächenbildungsverfahren und der Anforderungen seitens der Endanwender, insbesondere aus dem Bereich der Verbundwerkstoffindustrie, gleichermaßen. Daraus wird ein Anforderungsprofil für ein anforderungsgerechtes Flächenbildungsverfahren abgeleitet und konstruktive Lösungsvorschläge zu dessen Umsetzung aufgezeigt. / The development of non-crimped-fabrics (NCF) is subject of current research activities. These often led to special machines for very special applications. There is no systematic analysis and optimization of the properties of composites based on the state of the art. The aim of this dissertation is to close this gap and to contribute to the establishment of woven NCF in fiber-reinforced composites. The work is based partially on the results obtained at the Institut für Textilmaschinen und textile Hochleistungswerkstofftechnik der Technischen Universität Dresden from 2006 to 2012 within the framework of various AiF and DFG projects. Further reflections were made between 2015 and 2017 as part of a doctoral study at the Chair of Textile Technologien der Technischen Universität Chemnitz. As shown from examples of the design, weaving is reaching technological limits, especially for applications in composite construction. First of all, conventional surface formation methods are compared with the requirements of end users, especially from the composites industry. From this, a requirement profile is derived for a requirements-based surface formation process and constructive proposals for solutions for its implementation are identified.

Orientador: João Sinezio de Carvalho Campos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-04T01:48:34Z (GMT). No. of bitstreams: 1 Liba_AdemirDonizeti_M.pdf: 4797015 bytes, checksum: 1351ff08893b1a29731246cf2e4cd3c8 (MD5) Previous issue date: 2004 / Resumo: A resina de poliéster insaturada (RPI) é um polímero termofixo de baixo peso molecular obtido por condensação, o processo inicia-se através da esterificação entre diálcoois e diácidos saturados e insaturados, com o aumento do peso molecular do polímero, a retirada da água, que é gerada como subproduto da reação, torna-se difícil e lança-se mão do uso do vácuo ou de um maior fluxo de gás inerte para finalização da reação. Quanto à produção em escala industrial, apesar de conhecerem-se métodos de produção contínua, esta na maioria das indústrias é conduzida em bateladas com tempo de duração em média de 20 horas, podendo variar de acordo com a escolha das matérias primas utilizadas. Para a obtenção do polímero dentro dos parâmetros especificados, se faz necessário o controle dos radicais carboxilas, medidos através do índice de acidez (IA) e do peso molecular médio numérico (Mn), sendo este último parâmetro obtido de maneira indireta através da viscosidade(n). Para a viscosidade pode-se utilizar a escala Gardner, ou o viscosímetro cone e placa. A marcha de execução destas técnicas envolve várias etapas, desde a retirada da amostra até a obtenção do resultado da medida, sendo que para a amostragem, dependendo do equipamento disponível, esta pode implicar na interrupção do processo produtivo. Neste trabalho apresenta-se uma alternativa para o controle da reação, através do infravermelho próximo (NIR), em substituição às técnicas convencionais, com a vantagem do acompanhamento e do controle ser passível de execução em tempo real e sem a necessidade da retirada de amostras. Utilizou-se como base para o trabalho, a utilização anterior do NIR em processos envolvendo outros polímeros, tais como o policloreto de vinila (PVC), o policarbonato, o poliuretano e outros. Para verificar-se a viabilidade da utilização do NIR em substituição as técnicas convencionais, os valores obtidos para o IA e a viscosidade através destas técnicas foram comparados estatisticamente aos valores obtidos pelo NIR, obtendo-se forte correlação, com confiabilidade estatística de 95%. Com os resultados obtidos concluiu-se que o NIR pode ser utilizado com vantagens para o controle do processo de obtenção da resina de poliéster insaturada / Abstract: The unsaturated polyester resin (UPR) is a thermosetting polymer of low molecular weight obtained by condensation, the process begins through a esterification, between glycols and a mix of saturated and unsaturated acids, when the molecular weight of the polymer increase, the retreat of the water, generated as by-product of the reaction, if it turns more difficult and are necessary to use a vacuum or a larger flow of inert gas for finalization of the reaction. The production in industrial scale, in spite of they know each other methods of continuous production, are made in a batch with 20 hours long, could vary in agreement with the choice of the raw materials. For the obtaining of the polymer in the specified parameters, are necessary the control of the acid number (AN) and of the molecular weight (Mn), being this last obtained parameter in an indirect way through the viscosity. For measures those properties, are used as tools for the measure of the acidity number by titrimetric methods, and for the viscosity are use the Gardner scale, or the cone and plate viscometer. These techniques involves several stages, from the take of the sample to the obtaining of the result of the measure, and for obtain the sampling, depending on the available equipment, this can implicate in the interruption of the productive process. In this work we propose an alternative for the control of the reaction, by near infrared spectrometer (NIR), in substitution to the conventional techniques, with the advantage of the attendance and of the control to be susceptible to execution in real time and without the need of take samples. It was used as base for the work, the previous work of NIR in processes involving other polymeric materials, such as polyvinyl chloride (PVC), polycarbonate, the polyurethane and others. To verify the viability of the use of NIR in substitution of the conventional techniques, the values obtained for acid number and viscosity through these techniques were compared to the values obtained by NIR, being obtained strong correlation, with statistical reliability of 95%. With the obtained results it was ended that NIR can be used with advantages for the process control of unsaturated polyester resin / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

Im Luftfahrtbereich haben sich kohlenstofffaserverstärkte Kunststoffe (CFK) wegen ihrer hohen spezifischen Festigkeiten und Steifigkeiten längst als Konstruktionswerkstoffe etabliert. In der Großserienfertigung von Automobilkarosserien kommt diese Materialgruppe jedoch nur zögerlich zum Einsatz. Offensichtlich sprechen noch viele Argumente für den Einsatz von metallischen Werkstoffen: Denn auch Leichtmetalle und pressgehärtete Stähle ermöglichen immer höhere Leichtbaugrade, ohne dabei signifikante Kostensteigerungen zu generieren. Zudem sind Fertigungs- und Montageabläufe für Metallkarosserien etabliert und weitgehend frei von Entwicklungsrisiken. Vor diesem Hintergrund erscheint es schwer, mit neuen Leichtbaumaterialien und den zugehörigen Bauweisen einen Durchbruch erzielen zu können. Dabei zeigt das Produktsegment der Supersportwagen schon deutlich, dass zusätzliche Leichtbaupotentiale durch beanspruchungsgerecht gestaltete und optimierte CFK-Strukturen für den Automobilbau eröffnet werden. Bislang lassen sich derartig optimierte CFK-Strukturen jedoch kaum wettbewerbsfähig in Großserie realisieren. An dieser Stelle ergeben sich Chancen und zugleich neue Herausforderungen für die Produktentwickler: Zum einen sind Faserverbundbauweisen zu erarbeiten, mit denen die Leichtbaupotentiale von CFK weitgehend ausgereizt werden. Zum anderen ist die automatisierte Fertigung bei hohen Taktraten zu ermöglichen. Die Lösung beider Teilaufgaben setzt den Einsatz geeigneter materialspezifischer Konstruktionsmethoden voraus.