Reforço de elementos estruturais de madeira com materiais comp��sitos de matriz polim��rica

A necessidade de manuten����o e reabilita����o de estruturas de madeira antigas ��, nos dias de hoje, um aspeto bastante importante a n��vel mundial. Assim, o estudo da efic��cia de alguns sistemas de reforço torna-se fulcral. A presente disserta����o �� um estudo experimental sobre reforço de estruturas de madeira com materiais comp��sitos. Os materiais comp��sitos utilizados na componente experimental foram pol��meros refor��ados com fibras de carbono (CFRP ��� Carbon Fiber Reinforced Polymer) e estes foram colados ao substrato de madeira com resina epox��dica. O estudo experimental foi composto por duas fases. Na primeira fase realizaram-se ensaios de corte simples e na segunda fase ensaios de flexão. Os ensaios de corte simples foram realizados de modo a estudar a liga����o CFRP-madeira e a analisar a influ��ncia do comprimento colado de CFRP ao substrato de madeira. Para tal, utilizaram-se duas t��cnicas de reforço, a t��cnica EBR (Externally Bonded Reinforcement) em que os laminados de CFRP s��o colados exteriormente e a t��cnica NSM (Near Surface Mounted) em que os laminados de CFRP s��o colados numa ranhura feita no provete de madeira. Foram realizados 17 ensaios de corte simples, 10 com a t��cnica EBR e 7 com a t��cnica NSM. Na segunda fase, foram realizados 3 ensaios de flexão sobre pavimentos de madeira refor��ados com laminados de CFRP. Para estes ensaios tamb��m se utilizaram duas t��cnicas de reforço, a t��cnica EBR e uma t��cnica em que o laminado de FRP �� ancorado nas extremidades das vigas. Numa fase final os resultados foram analisados e comparados de modo a tirar conclus��es. Conclu��u-se que a t��cnica de reforço NSM apresenta um desempenho superior �� t��cnica EBR nos ensaios de corte simples. Comparativamente �� t��cnica EBR, os pavimentos de madeira com o laminado de CFRP ancorado nas extremidades das vigas apresentaram um melhor desempenho.

Estudo num��rico sobre o reforço de pilares de bet��o armado refor��ados com cantoneiras e presilhas met��licas. An��lise param��trica.

A presente comunica����o descreve o estudo param��trico desenvolvido com base no m��todo dos elementos finitos (MEF) para analisar a influ��ncia de factores geom��tricos e mec��nicos no comportamento �� flexo-compress��o de pilares de bet��o armado (BA) refor��ados com cantoneiras e presilhas de a��o (steel caging). Com base num modelo de elementos finitos 3D, levou-se a cabo um estudo num��rico sobre a influ��ncia de v��rios fatores no comportamento �� flexo-compress��o de pilares BA. Esses factores s��o: a dimens��o dos pilares, a dimens��o dos elementos que formam o reforço (cantoneiras e presilhas) e as propriedades mec��nicas dos materiais constituintes do pilar de bet��o armado e do reforço (cantoneiras e presilhas de a��o).

Estudo num��rico sobre o reforço de pilares de bet��o armado com cantoneiras e presilhas met��licas: an��lise param��trica e modelo de c��lculo

Disserta����o de mestrado integrado em Engenharia Civil

Fibras de licuri: um reforço vegetal alternativo de comp��sitos polim��ricos

This research is based, at first, on the seeking of alternatives naturals reinforced in place of polymeric composites, also named reinforced plastics. Therein, this work starts with a whole licuri fiber micro structural characterization, as alternative proposal to polymeric composites. Licuri fiber is abundant on the Bahia state flora, native from a palm tree called Syagrus Coronata (Martius) Beccari. After, it was done only licuri fiber laminar composite developing studies, in order to know its behavior when impregnated with thermofix resin. The composite was developed in laminar structure shape (plate with a single layer of reinforcement) and produced industrially. The layer of reinforcement is a fabric-fiber unidirectional of licuri up in a manual loom. Their structure was made of polyester resin ortofit��lica (unsaturated) only reinforced with licuri fibers. Fiber characterization studies were based on physical chemistry properties and their constitution. It was made by tension, scanning electron microscopy (SEM), x-ray diffraction (RDX) and thermal analyses (TG and DTA) tests, besides fiber chemistry analyses. Relating their mechanical properties of strength and hardness testing, they were determined through unit axial tension test and flexion in three points. A study in order to know fiber/matrix interface effects, in the final composites results, was required. To better understand the mechanical behavior of the composite, macroscopic and microscopic optical analysis of the fracture was performed

T��cnicas de reforço estrutural para edifica����es antigas: estudo de caso na cidade de Rio Branco ��� Acre

Este trabalho visou a demonstrar o dimensionamento e verifica����o de c��lculo da NBR 6118 (ABNT, 2007) com as suas caracter��sticas geom��tricas, cobrimento da armadura, armaduras, flambagem e a resist��ncia de pilares �� compress��o centrada dos pilares em concreto armado, apresentando na revis��o bibliogr��fica as principais t��cnicas de reforço estrutural de pilares de concreto armado para edifica����es antigas, identificando as principais metodologias e t��cnicas utilizadas no Brasil e apresentando os pontos positivos e negativos de cada t��cnica:encamisamento de concreto, perfis met��licos, chapa de a��o colado, manta/tecido de carbono, aramida e vidro e pol��meros refor��ados com fibras de carbono (PRFC). Os pilares com aumento da se����o transversal retangular, com adi����o de arma����o e concreto, sendo mais usual e pr��tica a t��cnica apresenta dificuldades em obras antigas, geralmente devido �� necessidade arquitet��nica de permanecer o mais fiel a sua forma original. Justificando-se a necessidade de conhecimento das diversas t��cnicas de reforço estrutural descritas neste trabalho com aumento de capacidade de resist��ncia, sem que haja aumento substancial, na se����o transversal dos pilares e objetivando a an��lise do reforço proposto atrav��s dos c��lculos do projeto, programa ��� PDOP 2.0 e par��metros de c��lculo da NBR 6118 (ABNT, 2007). Os resultados obtidos atrav��s da an��lise comparativa do reforço executado no estudo de caso ���revitaliza����o do casar��o��� - com rela����o �� an��lise dos pilares retangulares submetidos �� flexão composta obl��qua, esfor��os cortantes e torsores quanto �� NBR 6118 (ABNT, 2007) utilizando o programa para dimensionamento otimizado de pilares ��� PDOP 2.0 - indicaram que a t��cnica de reforço estudada foi eficiente, pois todas as pe��as refor��adas tiveram uma capacidade portante maior que a do pilar original sem o reforço.

Estudo de comp��sitos de madeira com reforço em bambu para utiliza����o em mobili��rio

Bamboo has been studied because of its peculiar mechanical properties and numerous possibilities of use, besides being a fast-growing grass and short cutting cycle. This study aimed to analyze the mechanical characteristics of wood-bamboo composite material, where the samples were developed from the combination of layers of bamboo as a structural reinforcement in solid pieces of pine and EGP panel parts. The species of wood used was Pinus taeda, and the bamboo species Guadua angustifolia and Dendrocalamus giganteus. All work was conducted at the Universidade Estadual Paulista - UNESP in the laboratory of Physical and Mechanical Properties of Wood. Tests including the density and tension parallel to grain of the bamboo species used and the static bending of composites in order to use this in the furniture industry. For the tests have been used as a basis the requirements of the normative document NBR 7190/97. The values obtained in the tests showed a significant increase in strength and stiffness compared to unreinforced parts, where there was an increase in MOE and MOR in static bending in all specimens used in evidence. The results showed the possibility of reducing sections in furniture components and the possibility of improving the mechanical properties of parts with defects found in wood of Pinus Itapeva region of S��o Paulo

Flexão e an��lise din��mico-mec��nica de comp��sitos 5HS e NCF com resina ep��xi monocomponente produzidos por RTM

In order to study resin distribution and homogeneity of composite laminates manufactured by RTM, it was used CYCOM 890 monolithic toughened epoxy as a matrix with two different configurations of intermediated modulus (IM) carbon fibers: Satin Weave (5HS) and non crimp fabric (NCF). The injection parameters were defined based on Thermo Gravimetric Analysis (TG), Differential Scanning Calorimetry (DSC) and rheological analysis. After processing the material, the resin/fiber impregnation was studied using ultrasonic test, Thermo Gravimetric Analysis, Differential Scanning Calorimetry, Dynamic Mechanical Analysis (DMA) and flexural tests. Therefore, it was able to observe an internal residual stress during the cooling process in both laminates, higher in the composite using NCF fabric due to the lack of symmetry, although a good proportion of fiber/matrix has been verified by the lower values of flexural modulus deviation. The DMA enabled the visualization of glass transition and its association with the inter and intra molecular interaction and movement, in which the NCF composite presented better permeability due to the lowest temperature of glass transition, when compared to the Satin Weave composite

Influ��ncia da incorpora����o de nanofibras de poliamida 6 com e sem nanotubos de carbono como reforço de pr��tese parcial fixa adesiva

The aim of this study was to evaluate the behavior of reinforced composites with polyamide 6 fibers aligned (6000 rpm) and alignment (120 rpm) with or without CNT using the flexural strength test. After preparation of nanofibers aligned nylon 6 (6000 rpm) and alignment (120 rpm) with and without incorporation of nanotube carbon by the method of electrospinning, were performed one control group (n = 10) and 4 experimental groups (n = 40) G1: Control (just resin Charisma - Heraeus Kulzer) ;G2 Resin + N6 aligned (6000 rpm) + CNT; G3:Resin + N6 alignment (120 rpm) + CNT; G4: Resin + aligned ( 6000 rpm) N6. G5: Resin + N6 alignment (120 rpm). The fibers were cut to the dimensions of 0,3 x 15 mm and were applied an adhesive at the surface (Single Bond 2) for 5 min and cured. In the matrix, was added resin in the proximal box (Charisma A2, Heraeus Kulzer) and cured for 40 s. (power 1100 mW / cm��). A first layer of resin and on the resin was deposited. The resin layers specimens were light irradiated with three overlapping exposures delivered. For each resin layer were light irradiated for 40 sec. The samples were tested with a cross-speed of 1 mm / min, and a 50 Kgf at Universal testing machine (EMIC mod.DL2000). The Dunnet test showed that only the nanotube group was significantly different from the control group. The ANOVA two-way indicates that the nanotube factor was statistically significant (p < 0.05) and there is no interaction between factors and orientation nanotube. The presence of nanotube showed lower fracture resistance values for aligned and unaligned groups. The results of this study showed that the orientation of the fibers does not influence the strength of composite resins and the incorporation of nylon nanofibers with carbon nanotubes decreased the fracture resistance values. The presence of the fibers has not been able to improve the strength of the material in any of the...

Influ��ncia da incorpora����o de nanofibras de poliamida 6 com e sem nanotubos de carbono como reforço de pr��tese parcial fixa adesiva

The aim of this study was to evaluate the behavior of reinforced composites with polyamide 6 fibers aligned (6000 rpm) and alignment (120 rpm) with or without CNT using the flexural strength test. After preparation of nanofibers aligned nylon 6 (6000 rpm) and alignment (120 rpm) with and without incorporation of nanotube carbon by the method of electrospinning, were performed one control group (n = 10) and 4 experimental groups (n = 40) G1: Control (just resin Charisma - Heraeus Kulzer) ;G2 Resin + N6 aligned (6000 rpm) + CNT; G3:Resin + N6 alignment (120 rpm) + CNT; G4: Resin + aligned ( 6000 rpm) N6. G5: Resin + N6 alignment (120 rpm). The fibers were cut to the dimensions of 0,3 x 15 mm and were applied an adhesive at the surface (Single Bond 2) for 5 min and cured. In the matrix, was added resin in the proximal box (Charisma A2, Heraeus Kulzer) and cured for 40 s. (power 1100 mW / cm��). A first layer of resin and on the resin was deposited. The resin layers specimens were light irradiated with three overlapping exposures delivered. For each resin layer were light irradiated for 40 sec. The samples were tested with a cross-speed of 1 mm / min, and a 50 Kgf at Universal testing machine (EMIC mod.DL2000). The Dunnet test showed that only the nanotube group was significantly different from the control group. The ANOVA two-way indicates that the nanotube factor was statistically significant (p < 0.05) and there is no interaction between factors and orientation nanotube. The presence of nanotube showed lower fracture resistance values for aligned and unaligned groups. The results of this study showed that the orientation of the fibers does not influence the strength of composite resins and the incorporation of nylon nanofibers with carbon nanotubes decreased the fracture resistance values. The presence of the fibers has not been able to improve the strength of the material in any of the...

Obten����o e caracteriza����o de um comp��sito polim��rico de matriz poli��ster e reforço/carga de tecido plano de algod��o

He was obtained and studied the feasibility of using TPA (Tissue Cotton Plan) screen type, for bagging, with a weight of 207.9 g / m2 in a composite of orthophthalic crystal polyester resin matrix. The process for obtaining the composite was tested against the maximum number of layers that could be used without compromising the processability and manufacturing of CPs in compression mold. Five configurations / formulations were selected and tested at 1, 4, 8, 10 and 12 layers of cotton tissue - TPA. TPA was not subjected to chemical treatment, only by passing a mechanical washing process. The composite in its various configurations / formulations was characterized to determine its physical properties. The properties of the composite were higher viability resistance to bending, approaching the matrix and impact resistance, superiority in relation to the polyester resin. Another property that has shown good result compared to other composite has water absorption. Analyzing all the properties set the settings / formulations with higher viability were TA8 and TA10, by combining good processability and higher mechanical strength, with lower loss compared to polyester resin matrix. The composite showed lower mechanical behavior of the resin matrix for all the formulations studied except the impact resistance. The SEM showed a good adhesion between the layers of TPA and polyester resin matrix, without the presence of micro voids in the matrix confirming the efficient manufacturing process of the samples for characterization. The composite proposed proved to be viable for the fabrication of structures with low requests from mechanical stresses, and as demonstrated for the manufacture of solar and wind prototypes, and packaging, shelving, decorative items, crafts and shelves, with good visual appearance.

Obten����o e caracteriza����o de um comp��sito polim��rico de matriz poli��ster e reforço/carga de tecido plano de algod��o

He was obtained and studied the feasibility of using TPA (Tissue Cotton Plan) screen type, for bagging, with a weight of 207.9 g / m2 in a composite of orthophthalic crystal polyester resin matrix. The process for obtaining the composite was tested against the maximum number of layers that could be used without compromising the processability and manufacturing of CPs in compression mold. Five configurations / formulations were selected and tested at 1, 4, 8, 10 and 12 layers of cotton tissue - TPA. TPA was not subjected to chemical treatment, only by passing a mechanical washing process. The composite in its various configurations / formulations was characterized to determine its physical properties. The properties of the composite were higher viability resistance to bending, approaching the matrix and impact resistance, superiority in relation to the polyester resin. Another property that has shown good result compared to other composite has water absorption. Analyzing all the properties set the settings / formulations with higher viability were TA8 and TA10, by combining good processability and higher mechanical strength, with lower loss compared to polyester resin matrix. The composite showed lower mechanical behavior of the resin matrix for all the formulations studied except the impact resistance. The SEM showed a good adhesion between the layers of TPA and polyester resin matrix, without the presence of micro voids in the matrix confirming the efficient manufacturing process of the samples for characterization. The composite proposed proved to be viable for the fabrication of structures with low requests from mechanical stresses, and as demonstrated for the manufacture of solar and wind prototypes, and packaging, shelving, decorative items, crafts and shelves, with good visual appearance.

Torque articular e ativa����o dos musculos biceps femoral e semi-tendineo durante movimentos isocineticos de flexão do joelho em atletas de futebol

Universidade Estadual de Campinas . Faculdade de Educa����o F��sica

Avalia����o in vitro da resist��ncia �� flexão de um prot��tipo de mini-implante desenvolvido para ancoragem do aparelho de Herbst

OBJETIVO: o prop��sito do presente estudo �� avaliar o limite de resist��ncia �� flexão de um prot��tipo de mini-implante desenvolvido para ancoragem do aparelho de Herbst. M��TODOS: ap��s a realiza����o de um c��lculo do tamanho da amostra, quatro corpos de prova contendo os prot��tipos de mini-implantes foram submetidos a uma for��a de flexão por engastamento simples, utilizando-se uma m��quina universal de ensaios mec��nicos, sendo calculado o limite de resist��ncia �� for��a de flexão. RESULTADOS: ap��s os ensaios mec��nicos, os novos mini-implantes apresentaram o limite de resist��ncia �� for��a de flexão de 98,2kgf, que foi o menor valor encontrado. CONCLUS��O: os prot��tipos de mini-implantes desenvolvidos para ancoragem do aparelho de Herbst foram capazes de suportar for��as de flexão maiores do que as for��as de mordida descritas na literatura.

Res��duos de sisal como reforço em comp��sitos de polipropileno virgem e reciclado

Foram estudadas as propriedades t��rmicas e mec��nicas de comp��sitos de polipropileno, virgem e reciclado, refor��ados com 30% em massa de fibras residuais de sisal, assim como o perfil de processamento e a morfologia da matriz polim��rica. Para tanto, foram determinadas a resist��ncia �� tra����o, o m��dulo de Young, alongamento na ruptura, e energia de impacto. As amostras tamb��m foram caracterizadas por MEV, DMTA e TG. Para ambos os comp��sitos de polipropileno, virgem e reciclado, com a adi����o das fibras, o alongamento na ruptura mostrou uma queda significativa, enquanto que a resist��ncia �� tra����o n��o sofreu grandes varia����es. Houve um aumento significativo nos valores de tra����o na ruptura e de energia de impacto com a adi����o das fibras de sisal na matriz de polipropileno. As an��lises t��rmicas mostraram liga����es secund��rias, como as liga����es polares, entre as fibras e a matriz, concordando com o comportamento mec��nico dos comp��sitos. Constatou-se que a temperatura de transi����o v��trea n��o variou ap��s a adi����o da fibra.

Avalia����o da cicatriza����o de feridas em dorso de ratos tratados com mitomicina C t��pica e posterior reforço com injet��vel

Estudo experimental em animais. A mitomicina C vem sendo usada como inibidor de fibroblastos, acarretando, com isso, diminui����o do processo cicatricial em feridas cir��rgicas. OBJETIVO: Este trabalho visa avaliar o uso de Mitomicina C para diminuir o processo cicatricial, atrav��s de seu uso t��pico com reforços posteriores injet��veis. MATERIAL E M��TODOS: Foi usado um modelo de feridas em dorso de ratos, com retirada circular da pele e cicatriza����o por segunda inten����o. Foram usados 18 ratos, divididos em tr��s grupos: controle; com uso t��pico; e com reforço de mitomicina C injet��vel, mensalmente e por 2 meses. Ap��s 3 meses os animais foram sacrificados e as cicatrizes retiradas cirurgicamente e submetidas a estudo histol��gico. RESULTADOS: Notou-se sob v��rios crit��rios que a cicatriza����o com o uso t��pico �� menos intensa, mas ao se usar o reforço injet��vel os par��metros voltam a ser comparados ao do grupo controle. DISCUSS��O: Acreditamos que a administra����o injet��vel de mitomicina C nas cicatrizes, pela sua elevada caracter��stica t��xica, acarreta destrui����o tecidual e neoforma����o cicatricial. CONCLUS��ES: A mitomicina C diminui o processo cicatricial quando usada topicamente, mas acarreta aumento da cicatriza����o quando nestas feridas s��o feitos reforços injet��veis.