yes / In order to study the mechanical behaviors of engineered cementitious composites (ECC) reinforced with various types of polyvinyl alcohol (PVA) fibers and different fiber volume fractions after the freeze-thaw cycles, the rapid freeze-thaw method was used to test the mass loss ratios, longitudinal relative dynamic elastic modulus, compressive strength and flexural strength. The results showed that specimens incurred more serious damage with the increasing of freeze-thaw cycles; however their performance would be improved by fiber type and dosage. Mass loss rate of JPA (specimen with 2% volume content of JP fiber) was lower than JPB (specimen with 1% volume content of JP fiber). Furthermore, the mass loss rate of JPB was lower than that of CPB (specimen with 1% volume content of CP fiber). The longitudinal relative dynamic elastic modulus of JPA was higher than that of JPB while the longitudinal relative dynamic elastic modulus of JPB was higher than that of CPB. In addition, the compressive strength and flexural strength decreased with the increasing of freeze-thaw cycles. Mechanical behaviors of specimens with fiber exhibited better strength than specimens without fiber. Based on the SL 211-2006 code for the design of hydraulic structures against ice and freezing action, JPA and JPB specimens are adequate for use in severe cold regions, while specimen CPA and CPB can be used in cold regions, specimen JPC only can be used in warm regions.

Cette thèse a pour objet la comparaison des procèdes de polymérisation en émulsion et en miniémulsion. L'influence de la combinaison de stabilisants moléculaires et macromoléculaires sur la cinétique réactionnelle et la distribution de tailles de particules sont les critères pertinents dans notre étude. Un stabilisant polymère, le poly (alcool vinylique-co-acétate de vinyle) (PVA), a été synthétisé avec différents taux d'hydrolyse par saponification directe du polyacétate de vinyle. Le taux d'hydrolyse de ce copolymère a été caractérisé par la Résonance Magnétique Nucléaire du proton (RMN 1H). Puis, nous avons étudié l'influence de la composition d'un mélange stabilisant [copolymères poly (alcool vinylique-co-acétate de vinyle) (PVA)/laurylsulfate de sodium (SDS)] et en particulier le taux d'hydrolyse du PVA. La présence de complexe (PVA/SDS) influence légèrement la cinétique de polymérisation. Par contre la capacité des complexes à stabiliser les particules de latex final dépend du taux d'hydrolyse du PVA, plus ce dernier est faible, plus l'agrégation est importante. Enfin, nous avons suivi en ligne par spectroscopie Raman des polymérisations en émulsion et en miniémulsion du styrène. Une exploitation du spectre a été réalisée et a permis d'attribuer les différents pics aux vibrations de certaines liaisons. La consommation du monomère et l'apparition du polymère a pu être suivi tout au long de la polymérisation / The aim of this work is to compare processes of emulsion and miniemulsion polymerization. The influence of the combination of molecular and macromolecular stabilizers on the reaction kinetics and particle size distribution are relevant factors in our study. A stabilizer polymer, poly (vinyl alcohol-co-vinyl acetate) (PVA), was synthesized with different degrees of hydrolysis by a direct saponification of polyvinyl acetate. The degree of hydrolysis of this copolymer was characterized by Nuclear Magnetic Resonance (1H NMR). Then, we studied the influence of the composition of a mixture stabilizer [poly (vinyl alcohol-co-vinyl acetate) (PVA)/sodium lauryl sulfate (SDS)], and particulary the degree of hydrolysis of PVA. The presence of complex (PVA/SDS) influences slightly the kinetic of polymerization. The ability of the complexes to stabilize the particles of latex depends on the degree of hydrolysis of PVA, the lower it is, the more the aggregation is important. Finally, we followed in situ emulsion and miniemulsion polymerizations of styrene by Raman spectroscopy. The exploitation of the spectrum allowed us to assign the different peaks to vibrations of certain bands. The consumption of the monomer and the appearance of the polymer could be followed throughout the polymerization

Les copolymères poly (acétate de vinyle-co-alcool vinylique), désignés par PVA, sont des tensioactifs macromoléculaires obtenus par hydrolyse partielle de poly (acétate de vinyle)(PVAc). Si les propriétés tensioactives des PVA ont pu être corrélées aux caractéristiques moléculaires il n'en est par de même en ce qui concerne les associats du type nanogels présents dans les solutions aqueuses. L'objectif de cette thèse était de caractériser les nanogels par des techniques telles que la diffusion dynamique de la lumière, la chromatographie d'exclusion stérique et la viscosimétrie. 9 PVA, de degrés d'hydrolyse de 73 à 88 mole% et de degrés de polymérisation de 650 à 2500 ont été étudiés. Il est apparu que les nanogels présent dans les PVA de DH =73 mole% et formés par interactions hydrophobe-hydrophobe entre séquences acétate ont des tailles entre 20-40 nm, avec des fractions volumiques de l'ordre de 20-30%. La désagrégation des nanogels par formation de complexes avec des tensioactifs anioniques du type SDS et SDBS a ensuite été démontrée. En faisant appel à la technique de fractionnement par « point de trouble » il est apparu que les chaînes les plus riches en acétate et en particulier celles ayant des longueurs des séquences acétate importantes complexent plus de SDS.Des « copolymères modèles » du type copolymères diblocs PVAc-b-PVOH comportant une séquence hydrophobe PVAc et une hydrophile PVOH ont pu être préparés par polymérisation RAFT, suivie par une réaction click. Une étude préliminaire de la micellisation de tels copolymères a permis de montrer la très grande analogie entre micelles de copolymères à blocs PVAc-b-PVOH et les nanogels de PVA examinés précédemment. / Poly (vinyl acetate-co-vinyl alcohol) copolymers, designated by PVA, are macromolecular surfactants obtained by partial hydrolysis of poly (vinyl acetate) (PVAc). If the surfactant properties of PVA have been correlated with molecular characteristics it is not the same for the colloidal aggregates in aqueous solutions so-called nanogels. The objective of this thesis was to characterize the nanogels using techniques such as dynamic light scattering, size exclusion chromatography and viscometry.9 PVA with degrees of hydrolysis between 73 and 88 mole% and polymerization degrees of 650 to 2500 were studied. It appeared that the nanogels, formed by hydrophobic-hydrophobic interactions between acetate sequences, are the size in the range of 20 to 40 nm with volume fractions between 20 and 30%. The disaggregation of nanogels by complex formation with anionic surfactants such as SDS and SDBS was further demonstrated. By using the "cloud point" fractionation technique it appeared that SDS is complexed by the sequences with high acetate content and in particular those with significant lengths of acetate sequences.As a model system diblock copolymers PVAc-b-PVOH containing a PVAc hydrophobie sequence and a PVOH hydrophilic sequence were prepared by RAFT polymerization, followed by a click reaction. A preliminary micellization study of these copolymers showed a very strong analogy between PVAc-b-PVOH block copolymer micelles and PVA nanogels discussed above.

A artrose, também chamada de osteoartrose ou osteoartrite (OA), é a terceira doença de maior incidência no Mundo. Nesse trabalho, buscou-se criar uma lesão osteocartilaginosa em joelhos de ratos Wistar machos com seis meses de vida, objetivando constituir um modelo animal para estudo da OA humana e, a partir desse modelo, avaliar biomateriais de forma isolada ou associados entre si e avaliados quanto à sua segurança biológica e potencial de reparação tecidual. Além disto, foi analisado o efeito reparador de células-tronco mesenquimais da polpa do dente de leite humano (MSC) isoladamente e em associação com o biomaterial formado por: Titânio + Poli Vinil Álcool + Ac. Hialurônico, nesse estudo denominado de TRIGEL (TRG). O Ac. Hialurônico (HA), por suas propriedades visco elásticas, o pó de Titânio (Ti), devido às suas propriedades biológicas únicas de ostoeintegração e o polímero Poli Vinil Álcool (PVA), com suas propriedades hidrofílicas, promovendo a formação do Hidrogel, os quais associados entre si formam um compósito, o TRG, que foi aplicado sobre uma lesão padrão no joelho da pata pélvica direita de ratos Wistar machos de seis meses de idade. Para a obtenção da lesão padrão, os animais foram divididos em três grupos de cincoanimais e cada grupo foi submetido a uma intervenção cirúrgica em seus joelhos direitos, utilizando três técnicas cirúrgicas diferentes, a saber: Grupo (I): Remoção cirúrgica dos meniscos medial e lateral mais perfuração do platô tibial seguido da aspiração da medula óssea através dessa perfuração por meio de seringa e agulha. Grupo (II): Remoção dos meniscos mais perfuração, sem aspiração, Grupo (III): Apenas a perfuração. Todos os animais foram autopsiados após 30 dias. Os joelhos dos quinze animais que constituíam os três grupos foram devidamente catalogados e enviados para a empresa Histotech, para a confecção das lâminas, tendo sido eleito, por análise histológica, o Grupo (I), por demonstrar menor reparo tecidual espontâneo. Em tese, o TRG teria as seguintes propriedades: Uma fonte de reparação tecidual (visco terapia) dada pelo HA e a capacidade amortecedora e carreadora de células-tronco do polímero PVA, que se hidrata, formando o hidrogel. O Ti, pela sua propriedade de osteointegração formaria um tampão sobre as áreas de matriz óssea exposta o que possibilitaria o afluxo de novos condrócitos, que também pode ocorrer pela ação das células-tronco. Livrar a superfície articular das áreas com exposição da matriz óssea é fundamental para o bloqueio das proteases que perpetuam a fisiopatologia da OA. Após tratamento estatístico dos diversos ensaios, utilizando-se os diversos biomateriais no tratamento da lesão, o TRG foi o biomaterial que apresentou o melhor resultado de força entre os grupos. No estudo histológico, foi evidenciada a presença de tecido cartilaginoso supra- lesional, o que só ocorreu nos animais dos grupos que receberam: apenas TRG, TRG associado com células-tronco e aquele que recebeu apenas MSCs. No entanto, mais estudos, com animais de maior porte e mais velhos, devem ser realizados para melhor analisar a segurança e o potencial terapêutico do compósito Trigel. / Osteoarthritis, or osteoarthritis (OA) is the third most debilitating disease in the world. In this study, we attempted to create an osteocartilaginous lesion in the knees of six months old male Wistar rats, aiming to constitute an animal model for the study of human OA and to use this model to evaluate the therapeutic potential of biomaterials, which are already well known for their biocompatibility properties in the clinical practice. The biomaterials were used in isolation or associated with each other and then evaluated for their biological safety and tissue repair capacity. Mesenchymal stem cells, obtained from human dental pulp from deciduous teeth (MSC) were evaluated alone and in association with the biomaterial formed by: Titanium + Poly Vinyl Alcohol + Ac. Hyaluronic, here called TRIGEL (TRG). Due to its visco-elastic properties, the Ti powder, due to its unique biological properties of ostointegration and the polymer PVA, with its hydrophylic properties, forming a hydrogel, were associated to form the composite named TRIGEL, (TRG), which was applied to a standard knee injury of the right hind leg of male Wistar rats. In order to elect the standard lesion, the animals were divided into three groups with five animals each and each group underwent a surgical intervention in their right knees, with three different surgical techniques being applied, namely: Group (1): Surgical removal ofmedial and lateral meniscus plus perforation of the tibial plateau, followed by aspiration of the bone marrow through this perforation using syringe and needle. Group (2): Removal of the meniscus plus perforation, without aspiration, Group (3): Drilling only. All groups were autopsied 30 days after the procedure and all groups were autopsied at 30 days post-procedure. The knees of the 15 animals that constituted the three groups were analyzed histologically and Group (1) (meniscus removed, perforated and aspirated), was elected as the standard lesion since it demonstrated less spontaneous tissue repair. TRG has the following properties: HA is used as a source of tissue repair (visco therapy) and hydration of the polymer; PVA, forms a hydrogel\", with damping action and as a stem cells carrier, whereas Ti was used due to its ósseo-integration, which would allow coating of the exposed bone matrix and this intra-osseous osteo-integration response would form an intercalating buffer. The healthy cartilage surfaces around this structural buffer would allow the reception of new chondrocytes or the action of the cells on TRG properties. Freeing the articular surface of the areas with bone matrix exposure is critical for blocking the proteases that perpetuate the pathophysiology of OA. In the various biomaterial tests in the treatment of the standard lesions, TRG was statistically shown to be the one that better mimicked the non-injured group. The histological study demonstrated the presence of a supra-lesional cartilagenous tissue, which only occurred in the groups which received: only TRG, mesenchymal stem cells associated with TRG and that which received only MSCs. However, further studies with larger and older animals should be pursued to better assess the safety and therapeutic potential of the Trigel composite.

Les vésicules géantes unilamellaires (GUV) permettent d’étudier efficacement les interactions entre les lipides et les peptides. Dans ce manuscrit, il a été montré que les interactions attractives lipides-peptides sont supprimées par l’attachement de polypeptides de type élastine (ELP) sur des peptides riches en arginine et peuvent être modulées par l’auto-assemblage en micelles ainsi que par le nombre de groupements arginine dans la séquence des peptides capables de pénétrer les cellules. De plus, une nouvelle méthode pour former des GUV à partir de systèmes complexes en seulement quelques minutes a été développée. Cette méthode est basée sur le gonflement d’un film de PVA sous une bicouche lipidique. Elle supprime la dégradation des molécules pendant la formation des GUV de lipides synthétiques, tels que des glycolipides et des phospholipides portant des groupements amides, où les méthodes traditionnelles ne réussissent pas à produire des vésicules non endommagées. / Giant Unilamellar Vesicles (GUVs) are a valuable tool to study lipid bilayer-biomolecule interactions in simplified cell-like model systems. In this work, a new method to efficiently form GUVs within minutes from more complex systems was developed. This method is based on swelling of a PVA-film under a lipid bilayer and minimizes damage of involved molecules during GUV formation. It also opens up many interesting perspectives for the formation of GUVs composed from new classes of synthetic lipids, such as glycolipids and amide-bearing phospholipids, where the traditional methods fail to efficiently produce “undamaged” vesicles. GUVs were also used for studying lipid-peptide interactions of a new class of elastin-like polypeptides functionalized with arginine-rich residues. It is shown that attractive interactions between lipids and peptides are suppressed by cargo-attachment and can be tuned by self-assembly into micelles and the arginine-amount of the cell penetrating residue.

Made available in DSpace on 2014-12-17T15:42:15Z (GMT). No. of bitstreams: 1 FabioPF_TESE.pdf: 3376603 bytes, checksum: 15dfaa7fe12ca918fd7e1b98c4378dd9 (MD5) Previous issue date: 2011-09-16 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Enzymatic synthesis of peptides using proteases has attracted a great deal of attention in recent years. One key challenge in peptide synthesis is to find supports for protease immobilization capable of working in aqueous medium at high performance, producing watersoluble oligopeptides. At present, few reports have been described using this strategy. Therefore, the aim of this thesis was to immobilize proteases applying different methods (Immobilization by covalent bound, entrapment onto polymeric gels of PVA and immobilization on glycidil metacrylate magnetic nanoparticles) in order to produce water-soluble oligopeptides derived from lysine. Three different proteases were used: trypsin, α-chymotrypsin and bromelain. According to immobilization strategies associated to the type of protease employed, trypsin-resin systems showed the best performance in terms of hydrolytic activity and oligopeptides synthesis. Hydrolytic activities of the free and immobilized enzymes were determined spectrophotometrically based on the absorbance change at 660 nm at 25 ?C (Casein method). Calculations of oligolysine yield and average degree of polymerization (DPavg) were monitored by 1H-NMR analysis. Trypsin was covalently immobilized onto four different resins (Amberzyme, Eupergit C, Eupergit CM and Grace 192). Maximum yield of bound protein was 92 mg/g, 82 mg/g and 60 mg/g support for each resin respectively. The effectiveness of these systems (Trypsin-resins) was evaluated by hydrolysis of casein and synthesis of water-soluble oligolysine. Most systems were capable of catalyzing oligopeptide synthesis in aqueous medium, albeit at different efficiencies, namely: 40, 37 and 35% for Amberzyme, Eupergit C and Eupergit CM, respectively, in comparison with free enzyme. These systems produced oligomers in only 1 hour with DPavg higher than free enzyme. Among these systems, the Eupergit C-Trypsin system showed greater efficiency than others in terms of hydrolytic activity and thermal stability. However, this did not occur for oligolysine synthesis. Trypsin-Amberzyme proved to be more successful in oligopeptide synthesis, and exhibited excellent reusability, since it retained 90% of its initial hydrolytic and synthetic activity after 7 reuses. Trypsin hydrophobic interactions with Amberzyme support are responsible for protecting against strong enzyme conformational changes in the medium. In addition, the high concentration of oxirane groups on the surface promoted multi-covalent linking and, consequently, prevented the immobilized enzyme from leaching. The aforementioned results suggest that immobilized Trypsin on the supports evaluated can be efficiently used for oligopeptides synthesis in aqueous media / S?ntese enzim?tica de pept?deos usando proteases tem atra?do uma enorme aten??o nos ?ltimos anos. Um desafio chave na s?ntese de pept?deos ? encontrar suportes para imobiliza??o de proteases capazes de apresentar um alto desempenho em meio aquoso, produzindo oligopept?deos sol?veis em ?gua, j? que at? o presente momento, pouco tem sido descrito usando essa estrat?gia. Dessa forma, o objetivo dessa tese foi imobilizar proteases usando diferentes m?todos (imobiliza??o por liga??o covalente, aprisionamento em g?is polim?ricos de PVA e imobiliza??o em nanopart?culas magn?ticas de Glicidil) para a produ??o de oligopept?deos derivados da lisina. Tr?s proteases foram utilizadas: tripsina, α-quimotripsina e bromela?na. De acordo com as estrat?gias de imobiliza??o associadas ao tipo de protease empregada, foi provado que os sistemas tripsina-resinas mostraram os melhores desempenhos em termos de atividade hidrol?tica e s?ntese de oligopept?deos. A atividade hidrol?tica das enzimas livres e imobilizadas foi determinada por espectrofotometria com base na mudan?a de absorb?ncia em 660 nm ? temperatura de 25 ?C (Casein method). O rendimento de oligolisina e o c?lculo do grau de polimeriza??o m?dio foram monitorados por RMN H. A protease tripsina foi covalentemente imobilizada em quatro diferentes resinas (Amberzyme, Eupergit C, Eupergit CM and Grace 192). O m?ximo rendimento de prote?na imobilizada foi 92, 82, 60, e 71 mg/g de suporte para cada resina, respectivamente. A efici?ncia desses sistemas (Tripsina-resinas) foi avaliada pela hidr?lise do substrato case?na e a s?ntese de oligolisina em meio aquoso. A maioria dos sistemas foram capazes de catalisar a s?ntese de oligopept?deos, entretanto com diferentes efici?ncias, tais como: 40, 37 e 35% para os suportes Amberzyme, Eupergit C e Eupergit CM, respectivamente, em compara??o com a enzima livre. Esses sistemas produziram olig?meros em somente 1 hora com grau de polimeriza??o m?dio mais alto que a enzima livre. Dentre esses sistemas, Eupergit CTripsina mostrou ser mais eficiente que os outros sistemas em termos de atividade hidrol?tica e estabilidade t?rmica, ao passo que n?o exibiu a mesma efici?ncia como era esperado para a s?ntese de oligolisina. Tripsina-amberzyme provou ser mais eficiente para a s?ntese de oligopept?deos, al?m de exibir um excelente reuso, mantendo 90% de sua atividade hidrol?tica e sint?tica ap?s sete reusos. As intera??es hidrof?bicas da tripsina com o suporte Amberzyme s?o respons?veis por proteger a enzima contra as fortes mudan?as conformacionais no meio reacional. Al?m disso, a alta concentra??o de grupos oxiranos na superf?cie da resina promoveu liga??es covalentes multipontuais e, consequentemente, preveniu a enzima imobilizada do processo de desor??o (Leaching process). Os resultados acima mencionados sugerem que a tripsina imobilizada nesses suportes pode ser eficientemente usada para a s?ntese de oligopept?deos em meio aquoso

A artrose, também chamada de osteoartrose ou osteoartrite (OA), é a terceira doença de maior incidência no Mundo. Nesse trabalho, buscou-se criar uma lesão osteocartilaginosa em joelhos de ratos Wistar machos com seis meses de vida, objetivando constituir um modelo animal para estudo da OA humana e, a partir desse modelo, avaliar biomateriais de forma isolada ou associados entre si e avaliados quanto à sua segurança biológica e potencial de reparação tecidual. Além disto, foi analisado o efeito reparador de células-tronco mesenquimais da polpa do dente de leite humano (MSC) isoladamente e em associação com o biomaterial formado por: Titânio + Poli Vinil Álcool + Ac. Hialurônico, nesse estudo denominado de TRIGEL (TRG). O Ac. Hialurônico (HA), por suas propriedades visco elásticas, o pó de Titânio (Ti), devido às suas propriedades biológicas únicas de ostoeintegração e o polímero Poli Vinil Álcool (PVA), com suas propriedades hidrofílicas, promovendo a formação do Hidrogel, os quais associados entre si formam um compósito, o TRG, que foi aplicado sobre uma lesão padrão no joelho da pata pélvica direita de ratos Wistar machos de seis meses de idade. Para a obtenção da lesão padrão, os animais foram divididos em três grupos de cincoanimais e cada grupo foi submetido a uma intervenção cirúrgica em seus joelhos direitos, utilizando três técnicas cirúrgicas diferentes, a saber: Grupo (I): Remoção cirúrgica dos meniscos medial e lateral mais perfuração do platô tibial seguido da aspiração da medula óssea através dessa perfuração por meio de seringa e agulha. Grupo (II): Remoção dos meniscos mais perfuração, sem aspiração, Grupo (III): Apenas a perfuração. Todos os animais foram autopsiados após 30 dias. Os joelhos dos quinze animais que constituíam os três grupos foram devidamente catalogados e enviados para a empresa Histotech, para a confecção das lâminas, tendo sido eleito, por análise histológica, o Grupo (I), por demonstrar menor reparo tecidual espontâneo. Em tese, o TRG teria as seguintes propriedades: Uma fonte de reparação tecidual (visco terapia) dada pelo HA e a capacidade amortecedora e carreadora de células-tronco do polímero PVA, que se hidrata, formando o hidrogel. O Ti, pela sua propriedade de osteointegração formaria um tampão sobre as áreas de matriz óssea exposta o que possibilitaria o afluxo de novos condrócitos, que também pode ocorrer pela ação das células-tronco. Livrar a superfície articular das áreas com exposição da matriz óssea é fundamental para o bloqueio das proteases que perpetuam a fisiopatologia da OA. Após tratamento estatístico dos diversos ensaios, utilizando-se os diversos biomateriais no tratamento da lesão, o TRG foi o biomaterial que apresentou o melhor resultado de força entre os grupos. No estudo histológico, foi evidenciada a presença de tecido cartilaginoso supra- lesional, o que só ocorreu nos animais dos grupos que receberam: apenas TRG, TRG associado com células-tronco e aquele que recebeu apenas MSCs. No entanto, mais estudos, com animais de maior porte e mais velhos, devem ser realizados para melhor analisar a segurança e o potencial terapêutico do compósito Trigel. / Osteoarthritis, or osteoarthritis (OA) is the third most debilitating disease in the world. In this study, we attempted to create an osteocartilaginous lesion in the knees of six months old male Wistar rats, aiming to constitute an animal model for the study of human OA and to use this model to evaluate the therapeutic potential of biomaterials, which are already well known for their biocompatibility properties in the clinical practice. The biomaterials were used in isolation or associated with each other and then evaluated for their biological safety and tissue repair capacity. Mesenchymal stem cells, obtained from human dental pulp from deciduous teeth (MSC) were evaluated alone and in association with the biomaterial formed by: Titanium + Poly Vinyl Alcohol + Ac. Hyaluronic, here called TRIGEL (TRG). Due to its visco-elastic properties, the Ti powder, due to its unique biological properties of ostointegration and the polymer PVA, with its hydrophylic properties, forming a hydrogel, were associated to form the composite named TRIGEL, (TRG), which was applied to a standard knee injury of the right hind leg of male Wistar rats. In order to elect the standard lesion, the animals were divided into three groups with five animals each and each group underwent a surgical intervention in their right knees, with three different surgical techniques being applied, namely: Group (1): Surgical removal ofmedial and lateral meniscus plus perforation of the tibial plateau, followed by aspiration of the bone marrow through this perforation using syringe and needle. Group (2): Removal of the meniscus plus perforation, without aspiration, Group (3): Drilling only. All groups were autopsied 30 days after the procedure and all groups were autopsied at 30 days post-procedure. The knees of the 15 animals that constituted the three groups were analyzed histologically and Group (1) (meniscus removed, perforated and aspirated), was elected as the standard lesion since it demonstrated less spontaneous tissue repair. TRG has the following properties: HA is used as a source of tissue repair (visco therapy) and hydration of the polymer; PVA, forms a hydrogel\", with damping action and as a stem cells carrier, whereas Ti was used due to its ósseo-integration, which would allow coating of the exposed bone matrix and this intra-osseous osteo-integration response would form an intercalating buffer. The healthy cartilage surfaces around this structural buffer would allow the reception of new chondrocytes or the action of the cells on TRG properties. Freeing the articular surface of the areas with bone matrix exposure is critical for blocking the proteases that perpetuate the pathophysiology of OA. In the various biomaterial tests in the treatment of the standard lesions, TRG was statistically shown to be the one that better mimicked the non-injured group. The histological study demonstrated the presence of a supra-lesional cartilagenous tissue, which only occurred in the groups which received: only TRG, mesenchymal stem cells associated with TRG and that which received only MSCs. However, further studies with larger and older animals should be pursued to better assess the safety and therapeutic potential of the Trigel composite.

Concrete is undoubtedly the most important construction material, with widespread applications worldwide. Despite its many advantages, however, concrete exhibits low tensile strength and tends toward brittle failure. The most promising approach for improvement of its tensile properties is the addition of fibres. By addition of only one or two percent of high-performance polymer fibres to a cementitious matrix, strain-hardening can be developed under uniaxial tensile loading. Such materials yield multiple cracking and permit large inelastic deformation in a hardening regime, for which they are usually called Strain-Hardening Cement-based Composites (SHCC). However, the behaviour of SHCC depends on loading conditions, where the most critical case is cyclic loading in tension-compression regimes, in which the ductile properties of the composite can be lost after only several hundred cycles due to degradation of the fibre bridging capacity. The thesis at hand presents the results of experimental investigations into the crack-bridging behaviour of polymer fibres in SHCC subject to alternating tension-compression loading regimes. The investigations covered monotonic loading as well. The experimental programme included fibre tension tests; single-sided, single fibre pull-out tests; double-sided, single and multiple fibre pull-out tests; and microscopic analysis of the specimens after testing. The bridging and pull-out behaviour of single PVA fibres embedded in cement-based matrices were comprehensively characterised and described by a new model. The Locking Front Model explains different interaction phenomena between fibre and matrix after full de-bonding. Furthermore, the interaction and damage mechanisms under cyclic loading were understood. The damage types depend on various parameters such as fibre inclination angle to the crack plane. Above all, however, the deterioration of bridging capacity results from the damage of the fibres between the crack faces in alternating tension-compression regime. The severity of damage is mostly determined by the number of cycles, compressive stress level, and crack width. The results of the experimental investigations at the micro- and meso-levels were analysed further to establish a multi-scale approach for describing the behaviour of a single crack in the composite. The Non-Simultaneity Hypothesis is proposed, which suggests that the crucial events of fibre bridging action may occur non-simultaneously with increasing crack opening displacement, and the bridging parameters may be reliably determined based on the overall behaviour of a group of specimens. Additionally, the Three-Stage Micromechanics-based Model is developed to describe the bridging behaviour of the fibres with different embedded lengths. The parameters of the model were obtained according to the overall bridging behaviour and the Non-Simultaneity Hypothesis. The parameters were validated by comparing prediction with experiment and observation of bridging behaviour in the tests with varied embedded lengths and multiple fibres. In the framework of the novel concept Criterion-Dependent Reference Volume (CDRV), the effective volume fractions of the fibres assuming non-uniform distribution of the fibres were determined over the length of a hypothetical specimen. The behaviour of a single crack was then predicted at the composite level and compared to the equivalent experimental results. The whole multi-scale approach manifests a considerable capability for analysing the behaviour of Fibre-Reinforced, Cement-based Composite (FRCC). Finally, the concept of Representative Continuum with Predetermined Cracking Sequence (RCPCS) is briefly explained for describing the stress-strain behaviour of SHCC in further development of the multi-scale approach. / Beton ist weltweit mit seinen vielfältigen Anwendungsmöglichkeiten zweifelsohne der wichtigste Baustoff. Trotz der vielen Vorteile weist der Beton eine niedrige Zugfestigkeit und ein sprödes Versagen auf. Eine vielversprechende Methode zur Verbesserung dieser stellt seine Bewehrung mit Kurzfasern dar. Mit lediglich ein oder zwei Volumengehalt Prozent von Hochleistungspolymerfasern könnte das Dehnungs-Verfestigungsverhalten (engl.: Strain-hardening behaviour) unter einachsiger Zugbelastung erreicht werden. Allerdings ist das Verhalten des SHCC (engl.: Strain-Hardening Cementitious Composite) abhängig von dem Belastungsregime. Am kritischsten ist das zyklische Zug-Druck-Wechselbelastungsregime, denn dadurch wird kein duktiles Verhalten nach nur mehreren hundert Zyklen möglich sein, weil eine starke Degradation des Faserüberbrückungsvermögens stattfindet. Diese Dissertation beschreibt die Ergebnisse von experimentellen Untersuchungen des Überbrückungsverhaltens der Polymerfasern in SHCC mit dem Schwerpunkt Zug-Druck-Wechselbelastung. Außerdem umfassen die Untersuchungen monotone Belastung. Das experimentelle Programm enthält Faserzugversuche, einseitige- und zweiseitige Einzelfaserauszugsversuche sowie mikroskopische Analysen an den Probekörpern nach den Experimenten. Das Überbrückungs- und Auszugsverhalten der einzelnen PVA-Faser eingebettet in einer zementbasierten Matrix wurden ausführlich charakterisiert und mit einem neuen Modell beschrieben. Das „Locking Front Model“ erläutert spezifische Phänomene des Zusammenspiels der PVA-Faser und Matrix nach der vollen Ablösung. Zusätzlich wurden die Mechanismen der Zusammenwirkung und Schädigungen unter zyklischer Belastung dargestellt. Die Schädigungsarten sind abhängig von den verschiedenen Parametern wie z. B. Faserwinkel zur Rissebene. Vor allem resultierte die Verschlechterung der Überbrückungseigenschaften aus den Schädigungen der Faser zwischen den Rissebenen im Zug-Druck-Wechselbelastungsregime. Die Intensität der Schädigungen ist meistens mit Zyklenanzahl, zyklischer Druckbelastung und Rissbreiten korreliert. Die Ergebnisse der experimentellen Untersuchungen auf der Mikro- sowie Mesoebene wurden weiter ausgewertet, um einen Multiskalenansatz zur Bestimmung des Verhaltens eines einzelnen Risses im Werkstoff zu schaffen. Die „Non-Simultaneity Hypothese“ wurde vorgeschlagen, welche aussagt, den entscheidenden Vorgänge des Überbrückungsverhaltens der Fasern möglicherweise nicht gleichzeitig bei Vergrößerung der Rissöffnung auftreten. Deswegen sollten die Überbrückungsparameter am besten basierend auf dem allgemeinen Verhalten von vielen Proben in einer Gruppe bestimmt werden. Außerdem wurde das „Three-Stage Model“ zur Bestimmung des Überbrückungsverhaltens der Fasern mit verschiedenen Einbettungslängen entwickelt. Die Parameter des Modells wurden basierend auf dem allgemeinen Überbrückungsverhalten und der „Non-Simultaneity Hypothese“ bestimmt. Dann werden diese Parameter mit dem Überbrückungsverhalten anderer Einbettungslängen oder multipellen Fasern validiert. Im Rahmen des neuen Konzeptes, „Criterion-Dependent Reference Volume (CDRV)“, werden der effektive Volumenanteil der Faser in der Länge einer hypothetischen Probe aus Faserbeton mit ungleichmäßiger Faserverteilung bestimmt. Das Verhalten eines einzelnen Risses wird dann auf der Werkstoffebene bestimmt und mit den experimentellen Ergebnissen verglichen. Der gesamte Multiskalenansatz manifestiert wesentliche Fähigkeit zur Analyse des Verhaltens von Faserbeton. Schließlich wird ein neues Konzept, „Representative Continuum with Predetermined Cracking Sequence (RCPCS)“, zur Bestimmung der Spannungs-Dehnungsbeziehung des hochduktilen Betons (SHCC) als zukünftige Entwicklungsmöglichkeit des vorliegenden Multiskalenansatzes kurz vorgestellt.

[pt] A história do solo como material de construção tem cerca de 10.000 anos. Grandes civilizações como a persa e a egípcia, construíram cidade inteiras com terra crua. As construções apresentam como principais vantagens a baixa geração e emissão de poluentes, o reduzido consumo energético e consequentemente o baixo custo, contudo, o principal inconveniente é sua baixa resistência na presença de água, que conduz para a maioria das patologias encontradas. Neste trabalho, a durabilidade de uma matriz de solo estabilizada com acetato de polivinila (PVA) e resina poliuretana derivada do óleo de mamona (RPM) foi avaliada, e ensaios mecânicos foram executados para aferição das resistências. O PVA, diluído em água nas proporções de 50 por cento e 70 por cento, e a RPM foram adicionados ao solo na proporção de 26 por cento, em peso de solo seco. Fibras de Pupunha (Bactris gasipaes K.) e Sisal (Agave sisalana), com comprimento de 25 mm e fração de 0,5 por cento, em peso de solo seco, foram inseridas no solo/RPM e sua resistência à compressão simples, tração por compressão diametral e absorção de água por imersão foram avaliados. A resistência à compressão simples dos corpos de prova de PVA se manteve abaixo do mínimo exigido por norma, e a absorção de água por imersão foi superior ao máximo recomendado, por sua vez, os ensaios de durabilidade para as misturas solo/RPM demonstraram, em todos os casos, a superioridade do aglomerante em comparação ao cimento e PVA. A absorção de umidade, após 24 horas imerso em água, foi de 5 por cento em contraste com os 23 por cento de absorção da matriz solo/cimento. A absorção por capilaridade se manteve abaixo dos demais compósitos. Nos ciclos de molhagem e secagem observou-se uma menor perda de massa e uma maior resistência à abrasão. A adição de fibras vegetais aumentou sua resistência mecânica não influenciando na absorção d água. / [en] The history of earth construction has about 10,000 years. Great civilizations, Egyptian and Persian, built cities with soil. The main advantages of this construction material are a low cost, low energy consumption and emission of pollutants, however, the disadvantage is its low water resistance, which leads to most structural pathologies. In this work, the durability of a matrix of soil stabilized with polyvinyl acetate (PVA) and castor oil resin (RPM) was assessed, and mechanical strength was measured. The PVA (50 per cent and 70 per cent solutions), and RPM were added to the soil in a proportion of 26 per cent in relation to soil dry weight. The performance of two types of vegetable fibers as reinforcement of soil/RPM matrix, Pupunha and Sisal, were investigated. The considered fibers were of 25 mm length, with weight fractions of 0,5 per cent in relation to soil dry weight. The compressive strength of the specimens stabilized with PVA remained below the minimum required by the standard, and water absorption by immersion was higher than the recommended maximum. The results demonstrate the potentiality of the use of castor oil resin. A significant decrease of the mechanical properties (results of unconfined compression and Brazilian test) compared to the mixture soil/cement was not observed. The durability tests showed, in all cases, the superior performance of resin compared to cement and PVA. Moisture absorption rate of soil/resin was 5 per cent in contrast to 23 per cent of the soil/cement matrix. The capillary absorption was lower when compared to other composites studied. There was less weight loss and a higher abrasion resistance after wetting and drying cycles. It was found that the vegetable fibers improved the post-cracking behavior of the composites.

abstract: Polymer fibers have broad applications in wearable electronics, bulletproof vests, batteries, fuel cells, filters, electrodes, conductive wires, and biomedical materials. Polymer fibers display light density and flexibility but are mostly weak and compliant. The ceramic, metallic, and carbon nanoparticles have been frequently included in polymers for fabricating continuous, durable, and functional composite fibers. Nanoparticles display large specific areas, low defect density and can transfer their superior properties to polymer matrices. The main focus of this thesis is to design, fabricate and characterize the polymer/nanocarbon composite fibers with unique microstructures and improved mechanical/thermal performance. The dispersions and morphologies of graphene nanoplatelets (GNPs), the interactions with polyvinyl alcohol (PVA) molecules and their influences on fiber properties are studied. The fibers were fabricated using a dry-jet wet spinning method with engineered spinneret design. Three different structured fibers were fabricated, namely, one-phase polymer fiber (1-phase), two-phase core-shell composite fiber (2-phase), and three-phase co-axial composite fiber (3-phase). These polymer or composite fibers were processed at three stages with drawing temperatures of 100˚C, 150˚C, and 200˚C. Different techniques including the mechanical tester, wide-angle X-Ray diffraction (WAXD), scanning electron microscope (SEM), thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC) have been used to characterize the fiber microstructures and properties. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2018