Hygrothermal effects on damping behavior of metal/glass fiber/epoxy hybrid composites

Continuous fiber/metal laminates (FML) offer significant improvements over current available materials for aircraft structures due to their excellent fatigue endurance and low density. Glass fibers/epoxy laminae and aluminum foil (Glare) are commonly used to obtain these hybrid composites. The environmental factors can limit the applications of composites by deteriorating the mechanical properties during service. Usually, epoxy resins absorb moisture when exposed to humid environments and metals are prone to surface corrosion. Therefore, the combination of the two materials in Glare (polymeric composite and metal). can lead to differences that often turn out to be beneficial in terms of mechanical properties and resistance to environmental influences. In this work. The viscoelastic properties. such as storage modulus (E') and loss modulus (E'), were obtained for glass fiber/epoxy composite, aluminum 2024-T3 alloy and for a glass fiber/epoxy/aluminum laminate (Glare). It was found that the glass fiber/epoxy (G/E) composites decrease the E' modulus during hygrothermal conditioning up to saturation point (6 weeks). However, for Glare laminates the E' modulus remains unchanged (49GPa) during the cycle of hygrothermal conditioning. The outer aluminum sheets in the Glare laminate shield the G/E composite laminae from moisture absorption. which in turn prevent, in a certain extent, the material from hygrothermal degradation effects. (c) 2005 Elsevier B.V. All rights reserved.

A review on the development and properties of continuous fiber/epoxy/aluminum hybrid composites for aircraft structures

Weight reduction and improved damage tolerance characteristics were the prime drivers to develop new family of materials for the aerospace/ aeronautical industry. Aiming this objective, a new lightweight Fiber/ Metal Laminate (FML) has been developed. The combination of metal and polymer composite laminates can create a synergistic effect on many properties. The mechanical properties of FML shows improvements over the properties of both aluminum alloys and composite materials individually. Due to their excellent properties, FML are being used as fuselage skin structures of the next generation commercial aircrafts. One of the advantages of FML when compared with conventional carbon fiber/epoxy composites is the low moisture absorption. The moisture absorption in FML composites is slower when compared with polymer composites, even under the relatively harsh conditions, due to the barrier of the aluminum outer layers. Due to this favorable atmosphere, recently big companies such as EMBRAER, Aerospatiale, Boing, Airbus, and so one, starting to work with this kind of materials as an alternative to save money and to guarantee the security of their aircrafts.

The volumetric fraction of inorganic particles and the flexural strength of composites for posterior teeth

Objective. To evaluate the content of inorganic particles and the flexural strength of new condensable composites for posterior teeth in comparison to hybrid conventional composites.Method. The determination of the content of inorganic particles was performed by mass weighing of a polymerized composite before and after the elimination of the organic phase. The volumetric particle content was determined by a practical method based on Archimedes' principle, which calculates the volume of the composite and their particles by differential mass measured in the air and in water. The flexural. strength of three points was evaluated according to the norm ISO 4049:1988.Results. The results showed the following filter content: Alert, 67.26%; Z-100, 65.27%; Filtek P 60, 62.34%; Ariston pHc, 64.07%; Tetric Ceram, 57.22%; Definite, 54.42%; Solitaire, 47.76%. In the flexural strength test, the materials presented the following decreasing order of resistance: Filtek P 60 (170.02 MPa) > Z-100 (151.34 MPa) > Tetric Ceram (126.14 MPa) = Alert (124.89 MPa) > Ariston pHc (102.00 MPa) = Definite (93.63 MPa) > Solitaire (56.71 MPa).Conclusion. New condensable composites for posterior teeth present a concentration of inorganic particles similar to those of hybrid composites but do not necessarily present higher flexural strength. (C) 2003 Elsevier B.V. Ltd. Alt rights reserved.

Analysis of curaua/glass hybrid interlayer laminates

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Experimental Study on the Impact Behaviour of Metal-fiber Laminates

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeito do condicionamento ambiental nas propriedades de cisalhamento e viscoelásticas de compósitos híbridos metal-fibra

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento e caracterização de compósitos de fibras naturais modificadas e híbridos: fibras da coroa do abacaxi/polipropileno e fibras da coroa do abacaxi/fibras de vidro/polipropileno

The concern with the environment preservation has done with that researchers as well as industries invest in the search for materials that come from renewable sources. Natural fibers, because they are ecologically correct and have low cost, have been studied as a possible substitute, even if partial, of synthetic fibers in the development of polymeric composites. In this context, the hybrid composites (natural/synthetic) increase considerably the range of application of natural composites. The auto industry, in its constant quest for good mechanical properties materials which are developed with sustainability, has in composites with hybrid reinforcement a very viable alternative. In the present work, the nature Crown pineapple fibers and nature Crown pineapple fibers treated with alkaline solution were studied in order to evaluate the influence of chemical treatment in its properties. For this techniques were used x-ray diffractometry, Thermogravimetry and Infrared Spectroscopy (FTIR). Composites have been developed using polypropylene, reinforced with pineapple fibers and pineapple fibers hybrids/glass fibres, both with levels of 5 and 10%. These composites were analyzed by Thermogravimetry techniques and tested by traction. The realization of this work indicated that although the chemical treatment did not affect the thermal stability of the fibers, caused an increase in crystallinity index fibers and decreased its hydrophilic. The tests performed on composite indicated that the composites process was suitable because it provided good dispersion of the polymer matrix. The addition of natural fibers from the pineapple's Crown, in a proportion of 10%, provided the greatest increase in modulus of elasticity (27%) when compared to the pure polymer

Avaliação do efeito ambiental nas propriedades mecânicas e viscoelásticas de compósitos híbridos de titânio/fibra de carbono/resina epóxi

Hybrid composites combining metal plates and laminates with continuous fiber reinforced polymer, called fiber-metal (CHMF), have been particularly attractive for aerospace applications, due mainly to their high mechanical strength and stiffness associated with low density. These laminates (CHMF) consist of a sandwich structure consisting of layers of polymer composites and metal plates, stacked alternately. This setting allows you to combine the best mechanical performance of polymer composites reinforced with long fibers, to the high toughness of metals. Environmental effects should always be considered in the design of structural components, because these materials in applications are submitted to the effects of moisture in the atmosphere, the large cyclical variations of temperature around 82 ° C to -56 ° C, and high effort mechanical. The specimens of fibermetal composite were prepared at EMBRAER with titanium plates and laminates of carbon fiber/epoxy resin. This study aims to evaluate the effect of different environmental conditions (water immersion, hygrothermal chamber and thermal shock) of laminate hybrid titanium/carbon fiber/epoxy resin. The effects of conditioning were evaluated by interlaminar shear tests - ILSS, tensile, and vibration free

Quantificação eletroquímica de analitos de interesse ambiental e biológico, empregando novos materiais preparados a partir de silsesquioxanos funcionalizados

Pós-graduação em Ciência dos Materiais - FEIS

Surface roughness of enamel and four resin composites

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Small-angle X-ray scattering study of sol-gel-derived siloxane-PEG and siloxane-PPG hybrid materials

Hybrid organic-inorganic two-phase nanocomposites of siloxane-poly(ethylene glycol) (SiO3/2-PEG) and siloxane-poly(propylene glycol) (SiO3/2-PPG) have been obtained by the sol-gel process. In these composites, nanometric siloxane heterogeneities are embedded in a polymeric matrix with covalent bonds in the interfaces. The structure of these materials was investigated in samples with different molecular weights of the polymer using the smalt-angle X-ray scattering (SAXS) technique. The SAXS spectra exhibit a well-defined peak that was attributed to the existence of a strong spatial correlation of siloxane clusters. LiClO4-doped siloxane-PEG and siloxane-PPG hybrids, which exhibit good ionic conduction properties, have also been studied as a function of the lithium concentration [O]/[Li], O being the oxygens of ether type. SAXS results allowed us to establish a structural model for these materials for different basic compositions and a varying [Li] content. The conclusion is consistent with that deduced from ionic conductivity measurements that exhibit a maximum for [O]/[Li] =15.

Silica-PEG hybrid ormolytes: structure and properties

The effect of lithium salt doping on the structure and ionic conduction properties of silica-polyethyleneglycol composites is reported. These materials, so called ormolytes (organically modified electrolytes), were obtained by the sol-gel process. They have chemical stability due to the covalent bonds between the inorganic (silica) and organic (polymer) phase. The structure of these hybrid materials was investigated by small-angle X-ray scattering (SAXS) as a function of lithium concentration [O]/[Li] (O being the oxygens of the ether type). The spectra have a well-defined peak attributed to the existence of a liquid-like spatial correlation of silica clusters. The ionic conductivity was studied by AC impedance spectroscopy and is maximum for [O]/[Li] = 15. This result is consistent with SAXS and thermo-mechanical analysis measurements and is due to the formation of cross-linking between the polymer chains for the larger lithium concentrations. These materials are solid, transparent, flexible and have an ionic conductivity up to 10(-4) S/cm. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Gelation of siloxane-poly(oxypropylene) composites

The viscoelastic properties of siloxane-poly(oxypropylene) (PPO) nanocomposites prepared by the sol-gel process has been analyzed during gelation by dynamic rheological measurements. The changes of storage and loss moduli, complex viscosity and phase angle has been measured as a function of time showing the newtonian viscosity of the sol in the initial step of gelation, and its progressive transformation to a viscoelastic gel. The rheologic properties have been correlated to mass fractal, nearly linear growth models and percolation theory. This study, completed by quasi-elastic light scattering and Si-29 solid state nuclear magnetic resonance measurements, shows that the mechanisms of gelation of siloxane-PPO hybrids depend on the molecular weight of the polymer and on the pH of the hybrid sol. For hybrids prepared in acid medium, a polymerization involving silicon reactive species located at the extremity of the polymer chains and presenting a functionality f = 2 occurs, forming a fractal structure during the first stage of sol-gel transition. For samples prepared under neutral pH, the fractal growth is only observed for hybrids containing short polymer chains (M-w similar to 130 gmol(-1)). The fractal dimensionality determined from the change in the rheological properties, indicates that the fractal growth mechanism changes from reaction-limited to diffusion-limited aggregation when the molecular weight of the PPO increases from 130 to 4000 gmol(-1) and as catalyst conditions change from acidic to neutral. Near the gel point, these hybrid gels have the typical scaling behavior expected from percolation theory. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Processing and mechanical characterization of titanium-graphite hybrid laminates

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hybridization effect on the mechanical properties of curaua/glass fiber composites

The aim of this paper was to evaluate the effect of hybridizing glass and curaua fibers on the mechanical properties of their composites. These composites were produced by hot compression molding, with distinct overall fiber volume fraction, being either pure curaua fiber, pure glass fiber or hybrid. The mechanical characterization was performed by tensile, flexural, short beam, Iosipescu and also nondestructive testing. From the obtained results, it was observed that the tensile strength and modulus increased with glass fiber incorporation and for higher overall fiber volume fraction (%Vf). The short beam strength increased up to %Vf of 30 vol.%, evidencing a maximum in terms of overall fiber/matrix interface and composite quality. Hybridization has been successfully applied to vegetable/synthetic fiber reinforced polyester composites in a way that the various properties responded satisfactorily to the incorporation of a third component. © 2013 Published by Elsevier Ltd. All rights reserved.