Abstract The industries that have polymers as an important raw material in their production, such as the construction, automotive, electrical and electronic sectors, always seek innovations to cut costs, reduce weight, easiness of processing, maximizing mechanical properties, and recyclability. In this context, this work presents the study of the kinetic parameters and viscoelastic behavior of a new thermoplastic system initially liquid. Through differential scanning calorimetry (DSC) analysis, Brookfield viscosimetry; dynamic-mechanical analysis (DMA) and mathematical modeling with consolidated and standardized methods, it was possible to evaluate the polymerization kinetics and viscoelastic behavior of the material in solutions with different concentrations. The generated equations allow the prediction of the kinetic and gelation behavior of the material reducing the need for laboratory tests to determine polymer properties. The found results showed that concentrations of benzoyl peroxide initiator with 1wt% in the methyl methacrylate (MMA) copolymer solution have the best viscoelastic and dynamic-mechanical properties with a less expensive polymerization cycle. production construction automotive sectors costs weight processing recyclability context liquid DSC (DSC viscosimetry dynamicmechanical dynamic DMA (DMA methods 1wt wt MMA (MMA cycle

Abstract Among the engineering thermoplastics, poly(phenylene sulfide) (PPS) stands out for its excellent properties and mainly for processing at lower temperatures. The requirements requested by industries can be made by improving mechanical strength, weight reduction, and durable components by reinforcing the PPS matrix with fiberglass (FG) and carbon fiber (CF). This review intends to present the most current research related to the physical, mechanical, and thermal properties of PPS and the PPS/FG and PPS/CF composites most currently used by the aerospace, automotive, and energy industries. In addition to presenting the feasibility of mechanical and thermal recycling processes for PPS-based waste to reinsert a high market value thermoplastic into the industrial production cycle, thus contributing to the minimization of waste destined for landfills and incinerated or even improperly disposed of in the environment.

Abstract Polyamide (PA) is a well-known and researched thermoplastic due to its excellent mechanical and physical properties, making it developed in the automotive sector, suitable for lighter vehicles, and, consequently, lower fuel consumption. This review manuscript presents the applications of PA-based materials in the manufacture of vehicle parts, with a description of their processing, a discussion about their thermal properties and the crystallization of polymer structure, the challenges of machining PA-based composite materials, and the feasibility of recyclability. This work aims to revise literature about the use of polyamide 6 (PA6), polyamide 66 (PA66), and polyamide 12 (PA12) and their composites reinforced with fiberglass (FG) and carbon fiber (CF) focused on the potential that these materials have as alternative materials for the automotive industry.

ABSTRACT The addition of expanded graphite (EG) on environmentally friendly polymer matrix was systematically studied to produce carbon-polymer porous composite. Firstly, an appropriate EG was produced by monitoring the time and temperature of intercalated graphite thermal expansion while poly(furfuryl alcohol) (PFA) resin was obtained from the furfuryl alcohol polymerization. After PFA synthesis, different EG amounts of 0.2, 0.5, and 1.0 wt% were added in the resin and evaluated by viscosimetry and differential scanning calorimetry that showed EG helped in the crosslink formations decreasing the onset and endset temperatures. PFA resin kept a good fluidity, even for 1.0 wt% EG ensuring its homogeneous impregnation on the polyurethane foams. FTIR analyses confirmed the presence of functional groups on EG, which would contribute to the resin impregnation on the foam porous structure without changing the thermal resistance of the final product.

Abstract Factors such as project and execution errors, lack of maintenance and inspection, and increases in loading can cause deficiencies to reinforced concrete structures. In this regard, there is the necessity of the application of structural reinforcement systems. This manuscript aims at the structural capacity analyses involving the bending of steel-reinforced concrete beams with additional reinforcement of polymer composites using glass and carbon fibers, and its comparison with regular reinforced concrete beams. Steel-reinforced concrete, polymeric composite, and hybrid beams (steel-reinforced concrete and polymeric composite combined) were submitted to the four-points bending test. Experimental and calculated results for the dimensioning of the beams were compared, allowing the validation of the calculation method and its implementation. It was possible to notice both the efficiency of the composite material applied as reinforcement, as well as the efficiency of the calculation models applied in this work.

Abstract In this study, the chemical interaction between functionalized carbon nanotuboes with carboxyl groups (CNT-f) and the subsequent addition of furfuryl alcohol (FA) and mixture with poly(furfuryl alcohol) (PFA) resin was evaluated. The FA with CNT-f was mixed in PFA resin to facilitate the chemical interaction of CNTs. The morphological and chemical interaction were studied by Transmission Electron Microcopies (MET), FTIR analyses, Raman Spectroscopy, viscosimetry and X-ray photoelectron spectroscopy (XPS). It was observed that a chemical interaction occurs through the opening of the hydroxyl polymer chain with a subsequent output of one water molecule. This interaction was evident from the FTIR and XPS data of the PFA composites. In this way, the mixture of functionalized carbon nanotubes with carboxyl groups in the FA, before adding this reinforcement into the PFA resin, can be considered a good procedure in order to obtain an appropriate chemical interaction between the CNT and PFA resin.

Abstract This review provides valuable information about the general characteristics, processing conditions and physical properties of carbon nanotube buckypaper (BP) and its polymer composites. Vacuum filtration is the most common technique used for manufacturing BP, since the carbon nanotubes are dispersed in aqueous solution with the aid of surfactant. Previous works have reported that mechanical properties of BP prepared by vacuum filtration technique are relatively weak. On the other hand, the incorporation of polymer materials in those nanostructures revealed a significant improvement in their mechanical behavior, since the impregnation between matrix and BP is optimized. Electrical conductivity of BP/polymer composites can reach values as high as 2000 S/m, which are several orders of magnitude greater than traditional CNT/polymer composites. Also, BP can improve remarkably the thermal stability of polymer matrices, opening new perspectives to use this material in fire retardant applications.

ABSTRACT: Multifunctional composites combine structural and other physicochemical properties, with major applications in aeronautical, space, telecommunication, automotive, and medical areas. This research evaluates electromagnetic properties of multifunctional composites based on glass fiber woven fabric pre-impregnated with epoxy resin laminated together carbon fiber non-woven veil metalized with Ni. In this way, searching for possible application as radar absorbing structures or electromagnetic interference shielding structures. The scattering parameters, in the frequency range of 8.2 to 12.4 GHz, show that the epoxy resin/glass fiber prepreg allows the transmission of the electromagnetic waves through its microstructure, independently of the glass fiber reinforcement orientation (98% transmission, S24 = −0.09 dB). However, the carbon fiber/Ni veil shows highly reflector behavior (91% reflection, S22 = −0.43 dB). Energy dispersive spectroscopy of the veil, before and after nitric acid attacks, confirmed the Ni coating removal from the carbon fiber surface. Still, the scattering parameters show reflector behavior (77% reflection, S22 = −1.13 dB), attributed to the electrical conductivity of carbon fibers. Multifunctional composites based on glass fiber/epoxy/carbon fiber/Ni veil laminates were processed by hot compression molding. The scattering parameters show that the laminates do not behave as good radar absorbing structures. Nevertheless, the laminates present promising results for application as light weight and low thickness structural composites with electromagnetic interference shielding effectiveness (91.4% reflection for 0.36 mm thickness and 100% for ∼ 1.1 mm) for buildings, aircraft, and space components.

Resumo O contínuo crescimento na utilização de compósitos termoplásticos em componentes estruturais na indústria aeroespacial deve-se, primordialmente, à flexibilidade de projeto, excelência de suas propriedades mecânicas e baixa massa específica, aliadas aos elevados valores de resistência mecânica e rigidez e baixa incidência de corrosão. No entanto, componentes que requerem exigências estruturais, quando expostos a ambientes agressivos como elevada temperatura e umidade, podem ter suas propriedades mecânicas sensibilizadas por esses fatores ambientais, e devem ser cuidadosamente avaliados antes de serem colocados em serviço. Embora existam diversos trabalhos na literatura reportando este problema para compósitos estruturais, poucos estudos relacionam, de maneira sistemática, a avaliação da absorção de umidade com o comportamento viscoelástico de matrizes de PPS reforçadas com fibras de carbono, quando este compósito é utilizado em aplicações aeronáuticas. Sendo assim, o objetivo deste trabalho é avaliar a influência do condicionamento higrotérmico nas propriedades viscoelásticas de laminados PPS/fibras de carbono. Os resultados mostram que os laminados condicionados em câmara higrotérmica apresentaram absorção de umidade segundo as leis de Fick, porém, não foram observadas variações significativas na temperatura de transição vítrea quando comparado compósitos condicionados e não condicionados.

Abstract Continued growth in the use of thermoplastic composites for structural components in the aerospace industry due, primarily, to the design flexibility, excellent mechanical properties and low density, combined with the high values of strength and stiffness and low incidence of corrosion meeting the stringent performance requirements of these structures while in service. However, components that requires structural requirements when exposed to harsh environments such as high temperature and moisture, can have their mechanical properties reduced by these environmental factors, and should be carefully evaluated before being placed in service. Although there are several studies in the literature reporting this problem for structural composites, few studies relate in a systematic way, assessing the moisture absorption with the viscoelastic behavior of PPS matrix reinforced with carbon fibers, when the composite is used in aeronautical applications. Thus, the aim of this study is to evaluate the influence of hygrothermal conditioning on the viscoelastic properties of PPS/carbon fiber composites. The results show that the laminates conditioned in a hygrothermal chamber had moisture absorption according to Fick laws, but it was not observed a significant glass transition temperature variation when compared conditioned and not conditioned specimens.

Resumo Neste estudo, foram avaliadas as propriedades dinâmico mecânicas e a viscosidade de compósitos nanoestruturados de poli(sulfeto de fenileno) (PPS) reforçado com nanotubos de carbono de paredes múltiplas (MWCNT) obtidos através da técnica de mistura em fusão. O módulo de armazenamento (E') e a temperatura de transição vítrea (Tg) apresentaram aumentos de até 130% e 11 °C em relação ao PPS puro quando 2,0 m/m% do nanoreforço foi considerado. Além disso, para concentrações superiores a 1,0% em massa foi observado um aumento nos valores da viscosidade complexa (η*), o que sugere a formação de uma estrutura interconectada de nanotubos no interior da matriz polimérica.

Abstract In this work, dynamic mechanical properties and viscosity of multiwalled carbon nanotubes reinforced poly (phenylene sulfide) nanostructured composites obtained by melt mixing techinique were investigated. The storage modulus (E') and the glass transition temperature (Tg) showed increases up to 130% and 11 °C for concentrations of 2.0 wt% compared to neat PPS. In Addition, it was observed for concentrations above 1.0 wt% an increment of complex viscosity (η*), suggesting the formation of an interconnected nanotube structure within the polymeric matrix.

Carbon fiber composites are used in several industries such as, aerospace, automotive, civil engineering, sports goods and technical applications due to its low-weight, strength and stiffness. However, the technology of recycling of these thermosetting polymer composites remains an engineering challenge because of their cross-linked structures that impede their reprocessing by simple heating. The aim of this work was to study the influence of the amount and dimensions of carbon fibers arising from composite waste into a new composite of polypropylene matrix. In order to carry out the study, the carbon fiber composite waste has been mechanically processed for the production of chopped fibers with two different lengths (4.5 mm and 3.0 mm). Thermoplastic composites made of chopped carbon fiber/ polypropylene at proportions 1%, 5% and 7% in fiber weight content were obtained by extrusion and injection process. Then, a series of laboratory test (mechanical, thermal and morphological) were performed in order to characterize the composite material obtained. The results showed that the fibers were capable of causing a reinforcing, even though the new composite presents a complex phase system with low adhesion between the recycled carbon fibers and the polypropylene matrix.

Resumo: O presente trabalho tem como principal objetivo avaliar a efetividade do processo de soldagem por resistência elétrica em compósitos de matriz poli (éterimida) reforçados com fibras contínuas de carbono, a partir do estudo das propriedades térmicas e mecânicas da junta soldada. Para a avaliação das propriedades térmicas, as amostras do material soldado foram submetidas às análises por termogravimetria e por análise termomecânica. Já com o intuito de se estudar a interface resultante da soldagem, estudos foram realizados a partir dos ensaios de cisalhamento ILSS e Iosipescu, assim como por End-Notched Flexure (ENF). Os resultados das análises térmicas em laminados de PEI/fibras de carbono não soldados mostram que o início da degradação para estes compósitos ocorre a 460 °C, e ainda é evidenciado que a temperatura de transição vítrea para amostras soldadas é aproximadamente 15% superior aos resultados provenientes de amostras não soldadas. Nos ensaios mecânicos mostram que houve um aumento de 32% e de 20%, respectivamente, nos resultados de cisalhamento interlaminar por ILSS e por Iosipescu nas amostras soldadas, quando estas são comparadas a amostras não soldadas. Os resultados do ensaio de ENF apresentam valores satisfatórios de tenacidade à fratura interlaminar nos compósitos soldados em relação aos valores encontrados em literatura.

Abstract: This study has as main objective to evaluate the effectiveness of the welding process by electrical resistance in composite poly (éterimida) matrix reinforced with continuous fibers of carbon, from the study of the thermal and mechanical properties of the welded joint. To evaluate the thermal properties of the welded material samples were subjected to analysis by thermogravimetry and by thermomechanical analysis. With the intention to study the resulting weld interface, studies were made from the shear tests ILSS and Iosipescu, as well as end-Notched Flexure (ENF). The results of the thermal analysis in laminated PEI / carbon fiber non-welded show that the beginning of degradation for these composites is 460 °C, and it is also evident that the glass transition temperature of welded samples is about 15% higher than the results from samples not welded. In the mechanical tests show that there was an increase of 32% and 20% respectively in interlaminar shear results for the ILSS and Iosipescu welded samples, when they are compared to samples not welded. The ENF test results show satisfactory values of interlaminar fracture toughness in the composite welded from the values found in literature.

The crystallization degree in semi-crystalline thermoplastics plays an important role in determining the final properties of structural composite material (e.g. toughness, stiffness and solvent resistance). The main purpose of this work is to study different induced degrees of crystallinity in carbon fiber (CF) reinforced polyphenylene sulfide (PPS) composites, by using three different cooling rates during hot compression molding processing (51%, 58% and 62% of crystallinity). In this study, the morphology, thermal and mechanical properties of the produced laminates were investigated and compared. The results showed an increase in the storage modulus (9.8%), Young's modulus (9.2%) and ILSS (14.2%) for the lower cooling rates. Evidences of fiber/interface improvement and crystallites nucleation on the fiber reinforcement surface were also identified.

RESUMO Frente à crescente necessidade de recuperar o meio ambiente e seus recursos naturais, atualmente a reciclagem e reutilização dos materiais torna-se uma das soluções sustentáveis mais visadas. Neste cenário, o processamento de compósitos particulados de alumínio em matriz termoplástica de polietileno de baixa densidade (PEBD), provenientes da reciclagem de embalagens longa vida, apresenta-se de maneira atrativa para a obtenção de matéria prima para a construção civil, na fabricação de telhas de baixo peso, associado a baixo custo e elevada disponibilidade, dentre outras aplicações. Este trabalho tem por objetivo estudar as propriedades e o comportamento do compósito de polietileno de baixa densidade/alumínio reciclados. Com este objetivo, foi realizada a avaliação morfológica do compósito a partir de microscopia óptica (MO), microscopia eletrônica de varredura (MEV) e espectroscopia por energia dispersiva de raios X (EDS), bem como avaliados os comportamentos térmico e mecânico deste material após estes terem sido submetidos à climatização higrotérmica e por radiação ultravioleta (UV). Para a avaliação térmica foram empregadas técnicas de análise termogravimétrica (TGA) e calorimetria exploratória diferencial (DSC). As propriedades mecânicas foram avaliadas por análise dinâmico-mecânica (DMA) e ensaios de tração e impacto. A partir dos resultados obtidos por meio deste trabalho pode-se concluir que o intemperismo envolvendo umidade e radiação UV pode influenciar nos desempenhos térmico e mecânico do compósito de Alumínio/PEBD, porém, foi observado que esta influência não é suficiente para inviabilizar a utilização destes materiais na construção civil, garantindo este mercado para o compósito de PEBD/Al.

ABSTRACT Face the growing need to restore the environment and its natural resources, currently the recycling and reuse of materials becomes one of the most important sustainable solution. In this scenario, the processing of aluminum particulate composite with low density polyethylene thermoplastic matrix (LDPE) from recycling packages, presents an attractive way to obtain raw materials for the building industry, in the manufacturing of lightweight roof tiles, associated with low cost and high availability, among other applications. This work aims to study the properties and behavior of recycled low density polyethylene/aluminum composite. In order to do this, they were performed composite morphology assessment through optical microscopy (OM), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS), as well as were evaluated the thermal and mechanical behavior of this material after being subjected to hygrothermal and ultraviolet conditioning (UV). For the thermal evaluation was performed thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The mechanical properties were evaluated by dynamic mechanical analysis (DMA) and tensile and impact tests. From the results obtained from this study it can be concluded that the moisture involving weathering and UV radiation can influence the thermal and mechanical performance of the composite aluminum / LDPE, but it was observed that this influence was not enough to prevent the use of these materials in construction, ensuring this market for LDPE / Al composite.

Atualmente, muitos componentes destinados à indústria aeronáutica, que anteriormente utilizavam compósitos com matriz termorrígida, vêm sendo substituídos por aqueles que apresentam matriz termoplástica, devido principalmente às melhores propriedades mecânicas obtidas, possibilidade de reaproveitamento do mesmo e a facilidade na fabricação de peças grandes e complexas, que serão integradas para formar o componente final desejado, assim como a sua temperatura de serviço mais elevada. Entretanto, um dos principais problemas da utilização de compósitos poliméricos em aplicações estruturais consiste em sua união efetiva para a integração de componentes. Nos últimos anos, a soldagem por resistência elétrica vem sendo considerada como uma das mais promissoras técnicas para a união de compósitos, pois se trata de um processo com pouca preparação de superfície e com qualidade aceitável no setor industrial. O principal objetivo deste trabalho consiste no estudo de parâmetros de soldagem por resistência elétrica para o compósito polimérico PEI poli (éter-imida) reforçado com fibras de carbono e de vidro (sistema híbrido) para aplicações aeronáuticas. As amostras do compósito foram soldadas e submetidas ao ensaio de lap shear para obtenção de tensão de ruptura ao cisalhamento de juntas simples. A partir deste ensaio foram estabelecidas as variáveis mais adequadas para utilização neste processo. O método utilizado foi um planejamento experimental fatorial completo que permitiu, com um número menor de experimentos, explorar todo o espaço experimental de interesse, estabelecendo os valores mais adequados de corrente elétrica, pressão e tempo para o processo de soldagem estudado.

Nowadays, many components applied in the aerospace industry, which had been previously used with thermoset matrix composites, are being replaced by those with thermoplastic matrix, which is mainly due to having better mechanical properties, the possibility of reuse and ease in manufacturing large and complex parts which will be integrated to form the desired component with higher service temperature. However, a major problem concerning the use of polymer composites for structural applications consists in its effective integration of components. Electrical resistance welding has been considered as one of the most promising techniques for bonding thermoplastic composites because it is a quick process with little surface preparation. The main objective of this work is to study the resistance welding parameters for PEI (polyether imide), and carbon and glass (hybrid) fibers laminates for aeronautical applications. The composite specimens were welded and subjected to the lap shear test in order to establish the most suitable variable in this process. It was used a full factorial design that allowed, with fewer experiments, exploring the whole experimental area of interest, establishing values of electric current, pressure and time for the studied welding process.