• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 66
  • 30
  • 26
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 168
  • 168
  • 44
  • 38
  • 34
  • 29
  • 28
  • 27
  • 23
  • 22
  • 20
  • 19
  • 18
  • 18
  • 16
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Παρασκευή και χαρακτηρισμός ενισχυτικών νανοδομών και πολυμερών συνθέτων υλικών βασισμένων στους νανοσωλήνες άνθρακα

Καστάνης, Δημήτρης 13 April 2009 (has links)
Η χρήση επιφανειακά τροποποιημένων νανοσωλήνων ως ενισχυτικό μέσο σε πολυμερή σύνθετα υλικά έχει αναφερθεί σε εκτενώς στην βιβλιογραφία [53,77,80]. Στην μελέτη μας εφαρμόστηκαν οξειδωτικές διεργασίες σε νανοσωλήνες πολλαπλού τοιχίου (MWCNTs) για να βελτιωθεί η συμβατότητα τους με την πολυμερική μήτρα. Μελετήθηκε η επίδραση της οξείδωσης στην δομή των MWCNTs με όξινες διεργασίες (HΝΟ3 και ένα μείγμα H2SO4/H2O2) και με μια βασική (ΝΗ4ΟΗ/Η2Ο2). Για να καθαριστεί το πρωτογενές υλικό εφαρμόστηκε μια μη-οξειδωτική διεργασία (με HCl) επίσης . Η ηλεκτρονική μικροσκοπία και η θερμοσταθμική ανάλυση φανέρωσαν ότι το υλικό που είναι τροποποιημένο με HNO3 υπέστη τον υψηλότερο βαθμό υποβάθμισης, όπως τον τεμαχισμό των νανοσωλήνων και επιπρόσθετη παραγωγή ατελειών στο γραφιτικό δίκτυο. Η βασική οξειδωτική κατεργασία οδήγησε σε πλήρη απομάκρυνση του άμορφου άνθρακα και των προσμείξεων μεταλλικών οξειδίων αλλά η δομική ακεραιότητα φάνηκε να είναι ανέγγιχτη. Η φασματοσκοπία XPS χρησιμοποιήθηκε για να επιβεβαιώσουμε τις διαφορετικές λειτουργικές ομάδες καρβοξυλίων και υδροξυλίων που παράγει ο κάθε οξειδωτικός φορέας. Εξετάστηκε η πιθανότητα ελέγχου του απαιτούμενου ποσού δραστικών ομάδων, μέσω των διεργασιών οξείδωσης Οι οξειδωμένοι MWCNTs χρησιμοποιήθηκαν ως πρώτη ύλη για την παρασκευή ξηρών υμενίων. Τα υμένια MWCNTs παρασκευάστηκαν με διήθηση αιωρήματος νανοσωλήνων που προετοιμάστηκαν από διαφορετικές οξειδωτικές διεργασίες, και μελετήθηκαν οι τοπολογικές και μηχανικές ιδιότητες τους. Οι μηχανικές ιδιότητες των υμενίων έχουν βρεθεί να είναι ισχυρά εξαρτώμενες από τα τοπολογικά χαρακτηριστικά όπως το πορώδες και το μέγεθος των συσσωματωμάτων των νανοσωλήνων. Βρέθηκε ότι υμένια χαμηλού πορώδους που είναι προετοιμασμένα από υψηλά οξειδωμένους CNTs οδηγούν σε ενίσχυση των μηχανικών τους ιδιοτήτων, και εμφανίζουν μεταφορά φορτίου μεταξύ των νανοσωλήνων. Αυτό δίνει την δυνατότητα στα υμένια αυτά να χρησιμοποιηθούν ως ενισχυτικές νανοδομές που αποτελούν (μαζί με την ρητίνη) τις πρώτες ύλες για την παρασκευή πολυμερών συνθέτων υλικών. Τέλος επιχειρήθηκε η παρασκευή πολυμερών νανοσύνθετων με βάση τις ενισχυτικές νανοδομές οξειδωμένων MWCNTs χρησιμοποιώντας την τεχνική RFI (Resin Film Infusion). Τα παραγόμενα υλικά διαθέτουν βελτιωμένο μέτρο ελαστικότητας έναντι της καθαρής ρητίνης, κάτι το οποίο διαπιστώθηκε μέσω μηχανικού εφελκυσμού. Η τεχνική παρασκευής νανοσύνθετων χρήζει περαιτέρω διερεύνησης για την χρήση της σε βιομηχανική κλίμακα, ως μεθόδου παρασκευής προηγμένων υλικών. / The use of surface treated carbon nanotubes as a reinforcing media in polymer composites has been referred widely in literature [53,77,80]. In our work oxidative treatments to multi-walled carbon nanotubes (MWCNTs) was applied in order to improve their compatibility with the polymer matrix. The effect of oxidation on the structure of MWCNTs was studied by acidic treatments (HΝΟ3 and a mixture of H2SO4/H2O2) and by one basic (ΝΗ4ΟΗ/Η2Ο2). To purify the pristine material a non-oxidative treatment (by HCl) was carried out. Electron microscopy and thermogravimetric analysis revealed that HNO3 treated material got the highest degree of degradation, like cutting of nanotubes and extra production of defects on graphitic network. Basic oxidative treatment led to complete removal of amorhous carbon and metal oxide impurities but the structural integrity was kept intact. XPS spectroscopy was used to verify different functionalities, carboxyl and hydroxyl groups, that every oxidation agent produces. Also we examined the possibility of control the required amount of functionalities through different via these oxidation treatments. The oxidized MWCNTs used as raw material for the production of sheets. The MWCNTs sheets were produced by nanotube suspension filtration. The topological and mechanical properties of MWCNTs sheets were studied. Sheet’s mechanical properties were found to be strongly dependent to topological characteristics like porosity and nanotubes clusters’ size. Also was found that low porosity sheets that are prepared by highly oxidized MWCNTs lead to enhancement of their mechanical properties and reveal improved stress transfer between nanotubes. This provides the possibility to MWCNTs sheets to be used as reinforcing nanostructures that comprise (with resin) the main components for manufacturing of polymer composite materials. Finally, production of polymer nanocomposites based on oxidized MWCNTs reinforcing nanostructures was attempted, by using the RFI technique (Resin Film Infusion). The produced materials offer improved Young modulus against neat resin that was examined by tensile testing. The manufacturing technique requires further investigation in order to be applied in industrial grade, as a production method of advanced materials.
52

A Viscoelastic-Viscoplastic Analysis of Fiber Reinforced Polymer Composites Undergoing Mechanical Loading and Temperature Changes

Jeon, Jaehyeuk 16 December 2013 (has links)
This study presents a combined viscoelastic (VE)-viscoplastic (VP) analysis for Fiber Reinforced Polymer (FRP) composites subject to simultaneous mechanical load and conduction of heat. The studied FRP composites consist of unidirectional fibers, which are considered as linearly elastic with regards to their mechanical response, and isotropic polymeric matrix, which shows viscoelastic-viscoplastic response under various stresses and temperatures. Due to the viscoelastic and viscoplastic behavior of the polymeric matrix, the overall FRP composites exhibit a combined time-dependent and inelastic behavior. A simplified micromechanical model, consisting of a unit-cell with four fiber and matrix subcells, is formulated to homogenize the overall heat conduction and viscoelastic-viscoplastic responses of the FRP composites. The micromechanical model is compatible with a displacement based finite element (FE) and is implemented at the Gaussian integration points within the continuum finite elements, which is useful for analyzing the overall time-dependent response of FRP composite structures under various boundary conditions. The Schapery nonlinear integral model combined with the Perzyna viscoplastic model is used to describe the viscoelastic-viscoplastic response of the polymer constituents. An integrated time integration algorithm is formulated at the micromechanics level in order to solve the nonlinear viscoelastic-viscoplastic constitutive model at the matrix subcells and obtain the overall nonlinear response of the FRP. The viscoelastic-viscoplastic micromechanical model is validated usingexperimental data on off-axis glass/epoxy FRP composites available in literature. The overall response of the FRP composites determined from the simplified micromechanical model is also compared with the ones generated from microstructures of FRP with various fiber arrangements dispersed in homogeneous polymer matrix. The microstructural models of the FRP with detailed fiber arrangements are generated using FE. The effects of thermal stresses, due to the mismatches in the coefficient of thermal expansions of the fibers and polymeric matrix, and stress concentrations/discontinuities near the fiber and matrix interfaces on the overall thermo-mechanical deformation of FRP composites are studied using the two micromechanical models discussed above. Finally, an example of structural analysis is performed on a polymeric smart sandwich composite beam, having FRP skins and polymeric foam core with piezoelectric sensors integrated to the FRP skins, undergoing three point bending at an elevated temperature. The creep displacement is compared to experimental data available in literature.
53

Processing, structure and properties of composites based on natural fillers and strereoregular polyolefins : environmentally benign concept

Berková, Kristýna 18 October 2013 (has links) (PDF)
This doctoral thesis is focused on composites based on polypropylene and wood flour. Firstly, the experimental work deals with preparation of composites based on wood flour with various concentrations and isotactic polypropylene with various melt flow indexes. In terms of this study, one polypropylene, which can have also practical use, was chosen. Further, this polypropylene is investigated with various types and concentrations of wood flour. Also, the attention is devoted to the modification of polypropylene by a specific β-nucleating agent. The differences are compared and described between the composites with neat and nucleated polypropylene. Further, the work is focused on solvent extraction of wood flour. The effect of extraction and solvent of wood flour is also examined in composites with neat and nucleated polypropylene. On prepared composites, the rheological, structural and thermal properties are studied. These properties differ depending on specific type of wood flour, its concentration and specific type of polypropylene.
54

Dispersion and alignment of carbon nanotube polymer based composites

Camponeschi, Erin L. 23 October 2007 (has links)
The goal of this research is to develop new approaches for the improvement of the properties of polymer carbon nanotube composites by effectively aligning and dispersing the CNT's in the polymer matrix. Specifically, this researched explored at how to mediate the problem of carbon nanotube insolubility in a matrix material. This was accomplished by assessing the effects of three different dispersing agents and two different alignment methods on the final composite properties. In previous research, the dispersing agents were found to either adequately disperse the carbon nanotubes or improve the mechanical properties of the composite material.4-6 Thus, comparing the three dispersing agents in different matrix materials and different processing methods can lead to a new understanding of interfacial interactions within the different composite materials. This understanding can then lead to the creation of more effective carbon nanotube composites that both adequately disperse the carbon nanotubes and improve the mechanical properties.
55

Influência das variáveis de processo nas propriedades de barras sólidas pultrudadas

Borges, Sandro Gasparetto January 2016 (has links)
Pultrusão é um de vários processos de fabricação de compósitos poliméricos. Seu princípio de funcionamento envolve a utilização de um conjunto de fibras de reforço, impregnadas previamente por uma resina polimérica termorrígida, que percorre o interior de uma matriz aquecida a fim curar a resina e dar o formato a um perfil sólido. Muitas variáveis de processo, tais como a temperatura das zonas de aquecimento sobre a matriz, a velocidade de tracionamento, a impregnação das fibras, a viscosidade da resina, entre outras, afetam a eficiência do processo assim como a qualidade e o desempenho dos compósitos. Neste estudo, foi investigada a influência do teor de fibra de vidro, do teor de carbonato de cálcio e da temperatura do reservatório de resina nas propriedades mecânicas, como a resistência à tração, o módulo de elasticidade, o alongamento até a ruptura e a dureza de barras sólidas circulares que foram fabricadas utilizando uma resina poliéster insaturada e um único peróxido orgânico. Foi constatado que o processo de pultrusão pode ser realizado utilizando um único iniciador de reação. Além disto, os resultados mostraram que a temperatura do reservatório de resina, o teor de carbonato de cálcio e o teor de fibra de vidro influenciaram de forma significativa nas propriedades das barras pultrudadas. Por fim, este estudo mostrou que é possível melhorar as características destes compósitos e, desta forma, desenvolver materiais que apresentem melhor qualidade e desempenho. / Pultrusion is one of several manufacturing processes of polymer composites. Its operating principle involves the use of a set of reinforcing fibers pre-impregnated with a thermoset resin which run through the interior of a heated die in order to cure the resin and to form a solid profile. Many processing variables such as die temperature, pulling speed, fiber impregnation, resin viscosity, among others, affect the process efficiency as well as the quality and performance of the pultruded composites. In this research, the influence of the glass fiber content, calcium carbonate content and the temperature of the resin bath on the mechanical properties, such as tensile strength, elastic modulus, elongation at break and superficial hardness of solid rods made with an unsaturated polyester resin and a single organic peroxide were investigated. It was observed that pultrusion process can be carried out using a single reaction initiator. In addition, the results showed that the temperature of the resin bath, the calcium carbonate and the glass fiber content have influenced significantly in the properties of the solid rods. Finally, this study showed that it is possible to improve the characteristics of such composites and, therefore, to develop materials that have good quality and performance.
56

Mechanical and laser drilling of thick carbon fibre reinforced polymer composites (CFRP)

Bin Ahmad Sobri, Sharizal January 2018 (has links)
Carbon fibre reinforced polymer, or CFRP composite materials, play an increasingly important role in modern manufacturing. They are widely used in aerospace, and their use is currently spreading to other industries where high strength-to-weight ratios are required. However, machining of composites is still a challenging task and often hampered by poor quality. Despite the extensive research that was conducted on the machining of composite materials over the last few years, mechanical drilling still suffers from delamination, fibre pull-out and poor surface finish, whereas laser cutting produces microstructured defects and a taper problem. This thesis reports on the drilling of CFRP composites by demonstrating the possibility of drilling small diameter holes (i.e. 8mm) into 25.4mm thick carbon fibre reinforced polymer composites (CFRPs) using mechanical drilling and laser drilling as stand-alone processes and as a sequential combination. The research involved four main phases of experimental testing. The first part of Phase 1 involved!preliminary experiments of drilling thick CFRP to identify the most suitable drilling strategy. Three mechanical drilling strategies conducted in the same parameter by using a 2-flute uncoated WC twist drill that was assessed with respect to feasibility of drilling thick CFRP. The results showed that the single-step strategy was the most feasible strategy to drill thick CFRP compared to 2- and 4-peck drilling strategies. The second part of Phase 1 concerned the influence of speed-feed combinations on hole quality by utilising three twist drills with different materials and geometries in both an uncoated and coated condition. The results indicated that a significant increase in peel-up delamination was found with increasing feed rate. In contrast, using a constant feed rate but increasing the spindle speed seemed to reduce peel-up delamination. Furthermore, the hole entry for 2-flute uncoated WC drill bits was an uncommon study finding because most of the previous researchers experienced more damages at the hole exit and their investigation focused on the hole exit only. Currently, implementation of laser technology in cutting and drilling composites is becoming popular as an alternative solution. Various experiments were conducted with the goal of identifying the effects of machining parameters on key output measures (i.e. heat affected zone (HAZ), hole depth and other damages) in drilling of 25.4 mm thick CFRP by using a fibre laser. Phase 2 involved a number of machining parameters selected to identify the potential of a fibre laser in drilling thick CFRP composites (i.e. laser power, scanning speed, focal point plane position (FPP), assisted-gas type and gas pressure). The results proved that a fibre laser could penetrate thick CFRP to a 22mm depth only. Moreover, the spiral trepanning strategy was able to penetrate 80% out of the total thickness of the CFRP in continuous wave (CW) mode, whereas the modulated laser beam (i.e. laser pulse mode) can penetrate 67% only. This result was a major recorded breakthrough because previous research attempts cut up to 5mm only. Laser power proved to be the most influential factor for hole depth in laser drilling of thick CFRP when the spiral trepanning strategy was applied. Machining trials were conducted in Phase 3 by using a 16kW fibre laser in modulated pulsed laser mode. In this phase, laser power of more than 1kW was attempted to cut the whole thickness of CFRP composites in CW mode, but it was unsuccessful. However, a new parameter was discovered (i.e. the cooling time between passes in modulated pulsed mode), which proved a considerable reduction of HAZ when the higher cooling time was imposed. Finally, phase 4 involved the experiments of sequential laser-mechanical drilling. A 1kW fibre laser was selected as a pre-drilling or initial step and followed by mechanical drilling as the final step. The sequential drilling method successfully reduced thrust force and torque for mechanical drilling by an overall average of 61%, resulting in high productivity and decreasing the thermal and mechanical stresses in the cutting tool and, in turn, promoting higher tool life. The highest delamination factor (Fda) ratio was experienced by the sequential laser 8mm – mechanical 8mm for both tools (i.e. 2- and 3-flute uncoated tungsten carbide) and laser pre-drilling strategies (i.e. single- and double-side). Thus, a novel laser-mechanical sequential drilling technique was developed, evaluated and tested in the drilling of thick CFRP composites; this is the first time ever in drilling thick CFRP (i.e. 25.4mm).
57

Influência das variáveis de processo nas propriedades de barras sólidas pultrudadas

Borges, Sandro Gasparetto January 2016 (has links)
Pultrusão é um de vários processos de fabricação de compósitos poliméricos. Seu princípio de funcionamento envolve a utilização de um conjunto de fibras de reforço, impregnadas previamente por uma resina polimérica termorrígida, que percorre o interior de uma matriz aquecida a fim curar a resina e dar o formato a um perfil sólido. Muitas variáveis de processo, tais como a temperatura das zonas de aquecimento sobre a matriz, a velocidade de tracionamento, a impregnação das fibras, a viscosidade da resina, entre outras, afetam a eficiência do processo assim como a qualidade e o desempenho dos compósitos. Neste estudo, foi investigada a influência do teor de fibra de vidro, do teor de carbonato de cálcio e da temperatura do reservatório de resina nas propriedades mecânicas, como a resistência à tração, o módulo de elasticidade, o alongamento até a ruptura e a dureza de barras sólidas circulares que foram fabricadas utilizando uma resina poliéster insaturada e um único peróxido orgânico. Foi constatado que o processo de pultrusão pode ser realizado utilizando um único iniciador de reação. Além disto, os resultados mostraram que a temperatura do reservatório de resina, o teor de carbonato de cálcio e o teor de fibra de vidro influenciaram de forma significativa nas propriedades das barras pultrudadas. Por fim, este estudo mostrou que é possível melhorar as características destes compósitos e, desta forma, desenvolver materiais que apresentem melhor qualidade e desempenho. / Pultrusion is one of several manufacturing processes of polymer composites. Its operating principle involves the use of a set of reinforcing fibers pre-impregnated with a thermoset resin which run through the interior of a heated die in order to cure the resin and to form a solid profile. Many processing variables such as die temperature, pulling speed, fiber impregnation, resin viscosity, among others, affect the process efficiency as well as the quality and performance of the pultruded composites. In this research, the influence of the glass fiber content, calcium carbonate content and the temperature of the resin bath on the mechanical properties, such as tensile strength, elastic modulus, elongation at break and superficial hardness of solid rods made with an unsaturated polyester resin and a single organic peroxide were investigated. It was observed that pultrusion process can be carried out using a single reaction initiator. In addition, the results showed that the temperature of the resin bath, the calcium carbonate and the glass fiber content have influenced significantly in the properties of the solid rods. Finally, this study showed that it is possible to improve the characteristics of such composites and, therefore, to develop materials that have good quality and performance.
58

Damage sensing in CFRP composites using electrical potential techniques

Angelidis, Nikolaos January 2004 (has links)
This Thesis investigates the damage sensing capabilities of the electrical potential measurement technique in carbon fibre reinforced polymer composites. Impact damage was introduced in multidirectional laminates and its effect on potential distribution studied. It was found that delaminations and fibre breakages within the laminate can be detected and located by measuring potential changes on the external composite surface. The extent and size of potential changes were significantly affected by the position of the current electrodes in relation to the potential measurement probes. A numerical model was developed investigating the effect of different size delaminations, located in various positions within the lamina, on electrical potential distributions on the external ply, and a quantitative analysis of the numerical results is presented. The numerical simulations demonstrated that the measured potential changes on the external ply were in proportion to the delamination size. The numerical and experimental results were compared and the optimum configuration of current electrodes and potential probes for damage detection selected. The response of electrical potential to mechanical strain, in unidirectional and multidirectional samples was also investigated. It was found that the conductive medium, used for introducing the current, defines the piezo-resistance performance of the composite. A finite element model was developed able to predict the effect of inhomogeneous current introduction in unidirectional specimens on electrical potential and piezo-resistance. The effects of temperature and water absorption on potential measurements were also presented.
59

Estudo da usinagem dos compósitos plástico madeira e madeira plástica /

David Müzel, Sarah. January 2017 (has links)
Orientador: Manoel Cléber de Sampaio Alves / Coorientador: Júlio Cesar Molina / Banca: Marcos Valério Ribeiro / Banca: Fábio Minoru Yamaji / Resumo: O compósito plástico madeira e a madeira plástica são materiais utilizados em diversos setores como automotivo, movelaria e principalmente na construção civil. Eles se tornaram tendência em construções ecológicas, sendo adequado para a construção de pisos, decks, brises, escadas, esquadrias, píeres e cercas. Tanto a produção da madeira plástica quanto do plástico madeira, em geral, é realizada via extrusão de perfis pré-definidos, porém, através da usinagem seria possível a produção de peças mais complexas em termos geométricos, dimensionais e superficiais, bem como, ampliar a utilização desses materiais na construção civil e na movelaria. Sendo assim, a presente proposta teve por objetivo o estudo da usinagem destes materiais. Para o estudo da usinagem da madeira plástica e do plástico madeira, foram realizados os processos de furação e de fresamento, nas modalidades tangencial e frontal, utilizando o método de Taguchi, tendo como fatores estudados as velocidades de corte e de avanço, o sentido de corte (concordante e discordante), a profundidade de corte e o tipo de material. As variáveis de saída analisadas foram o consumo de potência, a vibração média, o aquecimento das peças, a rugosidade, o desvio dimensional dos furos, a topografia das superfícies usinadas, o desgaste das ferramentas e os tipos e formas de cavacos gerados. Após os dados serem coletados foi realizada uma análise de variância (ANOVA) com nível de significância de 5%, para testar a existência de diferenç... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The wood plastic composite and the plastic lumber are materials used in the serveral sectors like automotive, furnitiures and mainly in the construction. They have become a tendency in ecological constructions, being appropried for floors, decks, strairs, frames, piers and fances. Both the production of the plastic lumber and the wood plastic composite, in general, is carried out by extrusion of predefined profiles, however, with the machining it would be possible to produce more complex pieces in geometric, dimensional and superficial terms, as well as to extend the use of these materials in construction and furniture. Therefore, the purpose of this proposal was to study the machining of these materials. To the machining study of the plastic lumber and the wood plastic composite, drilling processes and milling, the tangential and front procedures were performed using the Taguchi method, with the factors studied cutting speeds and feed the cutting direction (concordant and discordant ), depth of cut and the type of material and as output variable power consumption, the average vibration, heating the parts, the roughness, the dimensional tolerance of the holes, the topography of the machined surface, wear of tool types and shapes of chips generated. After the data is collected was carried out an analysis of variance (ANOVA) with 5% significance level to test the existence of significant differences between the means. The results obtained can be concluded that the materials stu... (Complete abstract click electronic access below) / Mestre
60

Revestimento a frio e a quente de laminados compósitos poliméricos de fibra de carbono para resistência a abrasão severa / Cold and hot coating of polymeric carbon fiber compositions for severe abrasion resistance

Campos, Marcelo Capella de 26 January 2018 (has links)
Submitted by marcelo capella de campos (kapellla@yahoo.com.br) on 2018-03-16T15:03:39Z No. of bitstreams: 1 Campos_MC - tese corrigida.pdf: 3583190 bytes, checksum: 1db0dbc48ebc01935b750b73717116dc (MD5) / Approved for entry into archive by Maria Marlene Zaniboni null (zaniboni@bauru.unesp.br) on 2018-03-16T19:03:37Z (GMT) No. of bitstreams: 1 campos_mc_dr_bauru.pdf: 3583190 bytes, checksum: 1db0dbc48ebc01935b750b73717116dc (MD5) / Made available in DSpace on 2018-03-16T19:03:37Z (GMT). No. of bitstreams: 1 campos_mc_dr_bauru.pdf: 3583190 bytes, checksum: 1db0dbc48ebc01935b750b73717116dc (MD5) Previous issue date: 2018-01-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os laminados de compósitos poliméricos possuem um valor já consagrado dentro das aplicações mecânicas e industriais. Sua versatilidade aliada a suas propriedades mecânicas, incentivam o aumento das aplicações, devido em partes pela facilidade de construção, tornando-os competitivos com relação a outros materiais. O conhecimento sobre a matriz polimérica, que possui inúmeras variações e aplicações, neste trabalho contou com o estudo de três tipos, sendo duas do grupo bisfenol “a” e uma do grupo bisfenol “f”. A caracterização destas matrizes através das técnicas de TG e DSC, influenciaram na escolha em virtude da aplicação a qual seriam submetidas. E sobre o reforço, que neste estudo, utilizou tecidos de fibra de carbono em trama de tela. O processo de fabricação dos laminados através de infusão a vácuo contribuiu para um resultado satisfatório, demonstrando vantagens com relação à melhor impregnação e minimizando os possíveis vazios na matriz. Os dois tipos de revestimento aplicados nestes laminados, sendo um chamado de revestimento a frio, que é um produto composto por três tipos de materiais distintos, metal, cerâmica e polímeros e o segundo a aspersão térmica, através da técnica de aspersão por chama de arames, contendo carbeto de tungstênio, recobriram o material de forma eficiente, mantendo boa adesão superficial. Estes laminados recobertos tem a finalidade de terem a vida útil aumentada e proporcionar uma maior resistência a abrasão severa. Os ensaios mecânicos aplicados demonstram as boas características destes materiais, juntamente com a caracterização por microscopia óptica e microscopia eletrônica de varredura, revelaram a boa adesão entre laminados e revestimentos, concluindo que existe uma boa identidade para estes materiais, sendo uma das principais conclusões. / The laminates of polymeric composites have an already established value within the mechanical and industrial applications. Its versatility combined with its mechanical properties, encourage the increase the applications, due in part for the ease of construction, making them competitive with respect to other materials. The knowledge about the polymer matrix, which has numerous variations and applications, in this work had the study of three types, two of the bisphenol group "a" and one of the bisphenol "f" group. The characterization of these matrices through TG and DSC techniques influenced the choice by virtue of the application to which they would be submitted. And on the reinforcement, which in this study, used carbon fiber fabrics in screen fabric. The process of manufacturing the laminates through vacuum infusion contributed to a satisfactory result, demonstrating advantages in relation to the better impregnation and minimizing voids in the matrix. The two types of coating applied on these laminates, one called cold coating, which is a product composed of three different types of materials, metal, ceramic and polymers and the second the thermal spray, by the flame spray technique of wires , Containing tungsten carbide, coated the material efficiently, maintaining good surface adhesion. These coated laminates have the purpose of having increased shelf life and providing greater resistance to severe abrasions. The applied mechanical tests demonstrate the good characteristics of these materials, together with the characterization by optical microscopy and scanning electron microscopy, revealed the good adhesion between laminates and coatings, concluding that there is a good identity for these materials.

Page generated in 0.0344 seconds