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Resistência e tolerância a impacto transversal de baixa energia de um laminado híbrido metal/fibra; Low-energy transverse impact resistance and tolerance of hybrid fiber/metal laminate

GUALBERTO, A.R.M.; GATT, M.C.A.; TARPANI, J.R.
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
46.16%
A energia absorvida no impacto transversal do laminado híbrido metal/fibra Glare® foi determinada por três diferentes métodos. O primeiro método utiliza um sofisticado aparato Laser-Doppler que registra a aceleração e a desaceleração do impactador ao longo do evento de choque mecânico por queda-de-peso, enquanto que o segundo se baseia apenas nos dados de carga de impacto contra o tempo de contato do impactador com o espécime. Já o terceiro método considera somente as velocidades do impactador pré- e pós-impacto. Concluiu-se que as duas primeiras metodologias geram resultados bastante similares entre si, com o material em geral absorvendo cerca de 70% da energia disponibilizada no impacto, enquanto que a terceira abordagem apresentou resultados excessivamente não-conservadores. As propriedades residuais em flexão dos laminados previamente danificados por impacto demonstraram que o módulo de elasticidade é o parâmetro mais confiável para a monitoração do grau de integridade estrutural do compósito híbrido.; The absorbed energy during the low-velocity transversal impact of hybrid metal/fiber GlareTM laminate was determined by three different analytical methods. The first method employs a sophisticated Laser-Doppler apparatus that registers the acceleration and deceleration of the impact tup along the drop-weight test...

Estudo da viabilidade de fabricação de um tubo para construção de uma prótese de membro inferior em composito híbrido epóxi carbono-vidro ; Viability of hybrid epoxi carbon-glass composite pipe manufacture for use in lower limb prosthesis

Lebrão, Guilherme Wolf
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/03/2007 PT
Relevância na Pesquisa
46.25%
Neste trabalho propôs-se a construção de um tubo de material compósito híbrido, com fibra de vidro e fibra de carbono, para utilização como prolongador de prótese de membro inferior a serem fabricadas pela AACD - Associação de Assistência à Criança Deficiente. O objetivo é avaliar as solicitações da prótese para otimizar custo e reduzir a massa. Fez-se inicialmente um levantamento das propriedades dos materiais comerciais utilizados para a fabricação do prolongador para referenciar o desenvolvimento do componente da prótese. Utilizou-se modelagem por elementos finitos para otimizar o componente em função dos esforços biomecânicos a que a prótese é submetida. Nesta modelagem, estudaram-se várias disposições, quantidade e material das camadas de forma a atender às solicitações e minimizar os custos. O levantamento bibliográfico permitiu encontrar uma rota de menor custo para a fabricação de compósito que utiliza um processo de transferência de resina auxiliado a vácuo e pré-formados de vidro e carbono. Como referência, foi fabricado um componente pelo processo de bobinagem filamentar que produz materiais compósitos de qualidade reconhecida. O processo de moldagem por transferência de resina assistido à vácuo...

Desenvolvimento e estudo físico-químico de compósitos de nanotubos de carbono; Physical chemical study and development of carbon nanotubes composites

Matsubara, Elaine Yoshiko
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 08/03/2010 PT
Relevância na Pesquisa
46.29%
Esta tese apresenta pela primeira vez a obtenção, a partir de alcoóis, de nanotubos de carbono do tipo cup-stacked nitrogenados sendo esses nanotubos hidrofílicos e semicondutores. Os compósitos híbridos de fibra de carbono/nanotubos de carbono possuem geometria tridimensional nanoestruturada e foram preparados em reator de deposição química de vapor de leito fixo. Neste processo nanotubos de carbono do tipo cup-stacked nitrogenados, de paredes múltiplas organizadas ou helicoidais são crescidos diretamente sobre as fibras de carbono com diferentes graus de grafitização. Os compósitos obtidos foram analisados principalmente por microscopia eletrônica de varredura e de transmissão de alta resolução que mostrou que o grau de grafitização do substrato de carbono tem influência sobre o crescimento. A densidade de NTC diminui com a redução da grafitização das fibras de carbono, o que produz um material com porosidade não observada quando as fibras são bem grafitizadas. O material compósito foi estudado como elemento filtrante, eletrodos de baterias de íons de lítio, emissor de elétrons e como reforço em compósitos de silicone. A constatação da eficiência na filtragem seletiva de uma série de compostos orgânicos voláteis presentes na fumaça do cigarro bem como a preparação de eletrodos de baterias de íons de lítio sem o uso de folhas metálicas de alumínio ou cobre resultaram no deposito de dois pedidos de patente.; This thesis presents for the first time nitrogen-cup-stacked carbon nanotubes with hydrophilic and semiconducting properties synthesized by alcohol precursor. The hybrid carbon fiber/carbon nanotubes composite have three-dimensional geometry and nanostructure. The material was prepared via fixed-bed chemical vapor deposition reactor. In this process nitrogen-cup-stacked...

Preparation and characterization of ramie-glass fiber reinforced polymer matrix hybrid composites

Romanzini, Daiane; Ornaghi Junior, Heitor Luiz; Amico, Sandro Campos; Zattera, Ademir José
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
Relevância na Pesquisa
46.16%
The use of ramie fibers as reinforcement in hybrid composites is justified considering their satisfactory mechanical properties if compared with other natural fibers. This study aims to verify changes in chemical composition and thermal stability of the ramie fibers after washing with distilled water. One additional goal is to study glass fiber and washed ramie fiber composites focusing on the effect of varying both the fiber length (25, 35, 45 and 55 mm) and the fiber composition. The overall fiber loading was maintained constant (21 vol.%). Based on the results obtained, the washed ramie fiber may be considered as an alternative for the production of these composites. The higher flexural strength presented being observed for 45 mm fiber length composite, although this difference is not significant for lower glass fiber volume fractions: (0:100) and (25:75). Also, by increasing the relative volume fraction of glass fiber until an upper limit of 75%, higher flexural and impact properties were obtained.

Charge injection in an LED with a hybrid composite as the emissive layer

Gozzi, G.; Chinaglia, D. L.; Schmidt, T. F.; Oliveira, O. N.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 969-974
ENG
Relevância na Pesquisa
66.28%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Understanding and controlling charge transport are crucial to achieve optimized organic devices, including light emitting diodes. In this study, we investigate the charge injection in devices made with a hybrid composite (HC) containing Zn(2)SiO(4):Mn (ZSP:Mn) in a polymeric blend consisting of poly(o-methoxyaniline) (POMA) and poly(vinylidene co-trifluorethylene) P(VDFTrFE), with the architecture ITO/HC/metallic electrode (ME). Charge injection was found to depend mainly on the POMA semiconducting phase. For ITO/HC/Au, an Ohmic junction was observed because the work function of ITO is close to that of Au, which also matches the energy levels of HC. Holes are injected through the HC/Au junction, as the highest occupied molecular orbital (HOMO) level of POMA matches the Fermi level of Au. The impedance spectroscopy data for the ITO/HC/ME devices were analyzed with a theoretical model where charge injection was assumed to occur via hopping with a distribution of potential energy barriers. The average hopping distance was estimated as 5.5 angstrom and only the device with the Al electrode had the current limited by the interface mechanism (charge injection). For ITO/HC/Cu and ITO/HC/Au devices the limiting factor for the charge transport was the bulk resistance of the samples...

Electric characterization of a hybrid composite based on POMA/P(VDF- TrFE)/Zn2SiO4 : Mn using impedance spectroscopy

Gozzi, G.; Chinaglia, D. L.; Schmidt, T. F.; Walmsley, L.; Constantino, C. J. L.; Job, A. E.; Santos, L. F.; Oliveira, O. N.
Fonte: Iop Publishing Ltd Publicador: Iop Publishing Ltd
Tipo: Artigo de Revista Científica Formato: 3888-3894
ENG
Relevância na Pesquisa
46.29%
Understanding the microscopic origin of the dielectric properties of disordered materials has been a challenge for many years, especially in the case of samples with more than one phase. For polar dielectrics, for instance, the Lepienski approach has indicated that the random free energy barrier model of Dyre must be extended. Here we analyse the dielectric properties of a polymer blend made up with the semiconducting poly(o-methoxyaniline) and poly( vinylidene fluoride-trifluorethylene) POMA/P(VDF-TrFE), and of a hybrid composite of POMA/P(VDF-TrFE)/Zn2SiO4:Mn. For the blend, the Lepienski model, which takes into account the rotation or stretching of electric dipoles, provided excellent fitting to the ac impedance data. Because two phases had to be assumed for the hybrid composite, we had to extend the Lepienski model to fit the data, by incorporating a second transport mechanism. The two mechanisms were associated with the electronic transport in the polymeric matrix and with transport at the interfaces between Zn2SiO4: Mn microparticles and the polymeric matrix, with the relative importance of the interfacial component increasing with the percentage of Zn2SiO4: Mn in the composite. The analysis of impedance data at various temperatures led to a prediction of the theoretical model of a change in morphology at 190 +/- 40 K...

Hybrid composite rods for concrete reinforcement

Fangueiro, Raúl; Pereira, Cristiana Gonilho; Jalali, Said; Araújo, Mário Duarte de; Marques, P.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2010 ENG
Relevância na Pesquisa
56.27%
The current work is concerned with the development of braided composite rods for civil engineering applications, namely for concrete internal reinforcement, as a steel substitute. The research study aims at understanding the tensile behaviour of composite rods reinforced by a textile structure – braided structure with core reinforcement.Seven types of braided composite rods were produced, varying the type of fibres used as a core reinforcement of a polyester braided structure. E-glass, carbon and HT polyethylene fibres were used in different combinations. The tensile properties of the braided reinforced composite rods were evaluated in order to identify the type(s) of fibre(s) to be used as core reinforcement. Results are compared to those of conventional materials used for concrete reinforcement, such as steel.

Acoustical behavior of hybrid composite sandwich panels

Patinha, Sérgio; Cunha, Fernando Eduardo Macedo; Fangueiro, Raúl; Rana, Sohel; Prego, Fernando
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2015 ENG
Relevância na Pesquisa
56.37%
This paper deals with the characterization of acoustic insulation behaviour of hybrid sandwich composite panels for application in modular house construction. These sandwich panels are a sustainable, light-weight and durable solution, since are based on natural fibers structure impregnated with a thermosetting polymer. In this way, three different types of hybrid composite panels containing polyurethane core and laminated composite skins were produced and analyzed, varying the composition of laminates. The composite laminates of the prototypes were produced using a vacuum infusion technique and were composed of glass and jute fibers, impregnated with a polyester resin. The solutions developed were compared with a standard, composed of plasterboards having different thicknesses and used for thermal and acoustic insulation. Acoustic insulation characterization was performed on specimens with 220x220 mm size in a sound proof acoustic chamber. The tested sandwich panels showed promising results; however, their overall performance was lower as compared to the performance of standard solutions used for comparison. Nevertheless, the specific acoustic insulation performance, i.e. sound reduction per unit mass of material for the developed sandwich panels was significantly higher as compared to the standard materials...

In vitro evaluation of microleakage of a flowable composite in class V restorations

Cimello,Daniela Thomazatti; Chinelatti,Michelle Alexandra; Ramos,Renata Pereira; Palma Dibb,Regina Guenka
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2002 EN
Relevância na Pesquisa
46.39%
The aim of this study was to evaluate microleakage around class V restorations using a flowable composite compared to a hybrid composite. Forty class V cavities were prepared on buccal and lingual surfaces of 20 human teeth, with occlusal and cervical margins at the enamel and cementum/dentin levels, respectively. Specimens were divided into 2 groups with 10 samples each. Group 1: buccal cavities received Paama 2 (conventional bonding agent) + Wave (flowable composite); lingual cavities were restored with Paama 2 + Glacier (hybrid composite). Group 2: buccal cavities received Optibond Solo (self-priming bonding agent) + Wave; lingual cavities were restored with Optibond Solo + Glacier. After being stored in distilled water and finished, the teeth were thermocycled, immersed in a 50% silver nitrate solution and embedded in resin. They were sectioned and the depth of tracer penetration was scored. The results were analyzed using Kruskall-Wallis and Wilcoxon tests. The restorations with flowable composite and those with hybrid composite from the same group showed similar results of microleakage for both occlusal and cervical margins. Optibond Solo improved the sealing of the restorations when compared with Paama 2 (p<0.01). None of the restorative materials completely sealed the tooth/restoration interface at the cervical margins.

Effectiveness of composite resin polymerization using light-emitting diodes (LEDs) or halogen-based light-curing units

Micali,Bianca; Basting,Roberta Tarkany
Fonte: Sociedade Brasileira de Pesquisa Odontológica - SBPqO Publicador: Sociedade Brasileira de Pesquisa Odontológica - SBPqO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2004 EN
Relevância na Pesquisa
46.31%
The clinical performance of composite resins is greatly influenced by the quality of the light-curing unit used. The aim of this study was to compare the efficiency of a commercial light-emitting diode (LED) with that of a halogen-based light-curing unit by means of dye penetration of a micro hybrid composite resin. The composite resin evaluated was Filtek Z250 (3M Dental). The composite was filled into acrylic moulds that were randomly polymerized for 40 seconds by each of the light-emitting systems: light-emitting diode Ultraled (Dabi Atlante) or halogen light Degulux (Degussa Hüls) curing units. Immediately after polymerization, each specimen was individually immersed in 1 ml of 2% methylene blue solution at 37°C ± 2°C. After 24 hours, the specimens were rinsed under running distilled water for 1 minute and stored at 37°C ± 2°C at relative humidity for 24 hours. The composite resins were removed from the moulds and individually triturated before being immersed in new test tubes containing 1 ml of absolute alcohol for 24 hours. The solutions were filtered and centrifuged for 3 minutes at 4,000 rpm and the supernatant was used to determine absorbance in a spectrophotometer at 590 nm. To verify the differences between groups polymerized by LED or halogen light t-test was applied. No significant differences were found between composite resins light-cured by LED or halogen light-curing unit (p > 0.05). The commercially LED-based light-curing unit is as effective to polymerize hybrid composite resins as the halogen-based unit.

Effect of light-activation methods and water storage on the flexural strength of two composite resins and a compomer

Rodrigues Filho,Leonardo Eloy; Burger,Luis Antônio dos Santos; Kenshima,Silvia; Bauer,José Roberto de Oliveira; Medeiros,Igor Studart; Muench,Antonio
Fonte: Sociedade Brasileira de Pesquisa Odontológica - SBPqO Publicador: Sociedade Brasileira de Pesquisa Odontológica - SBPqO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2006 EN
Relevância na Pesquisa
46.17%
The present study evaluated the flexural strength of three composite resins recommended for direct esthetic restorations: a polyacid modified composite (Dyract AP), a unimodal composite resin (Filtek Z250) and a hybrid composite resin (Point 4). The variation factors, apart from the type of composite resin, were the light activation method and the water storage period. The composite resins were light-cured in continuous mode (40 s, 500 mW/cm²) or in ramp mode (0-800 mW/cm² for 10 s followed by 30 s at 800 mW/cm²) and stored for 24 hours or 30 days in distilled water at 37°C. The data were analyzed by ANOVA and Tukey test for multiple comparisons (alpha = 0.05). The composite resin Z250 presented the highest mean flexural strength (166.74 MPa) and Dyract AP presented the lowest one (129.76 MPa). The storage for 30 days decreased the flexural strength in ramp mode (24 h: 156.64 MPa; 30 days: 135.58 MPa). The light activation method alone did not lead to different flexural strength values.

Three-year randomised clinical trial to evaluate the clinical performance, quantitative and qualitative wear patterns of hybrid composite restorations

Palaniappan, Senthamaraiselvi; Elsen, Liesbeth; Lijnen, Inge; Peumans, Marleen; Van Meerbeek, Bart; Lambrechts, Paul
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.44%
The aim of the study was to compare the clinical performance, quantitative and qualitative wear patterns of conventional hybrid (Tetric Ceram), micro-filled hybrid (Gradia Direct Posterior) and nano-hybrid (Tetric EvoCeram, TEC) posterior composite restorations in a 3-year randomised clinical trial. Sixteen Tetric Ceram, 17 TEC and 16 Gradia Direct Posterior restorations were placed in human molars and evaluated at baseline, 6, 12, 24 and 36 months of clinical service according to US Public Health Service criteria. The gypsum replicas at each recall were used for 3D laser scanning to quantify wear, and the epoxy resin replicas were observed under scanning electron microscope to study the qualitative wear patterns. After 3 years of clinical service, the three hybrid restorative materials performed clinically well in posterior cavities. Within the observation period, the nano-hybrid and micro-hybrid restorations evolved better in polishability with improved surface gloss retention than the conventional hybrid counterpart. The three hybrid composites showed enamel-like vertical wear and cavity-size dependant volume loss magnitude. Qualitatively, while the micro-filled and nano-hybrid composite restorations exhibited signs of fatigue similar to the conventional hybrid composite restorations at heavy occlusal contact area...

Colour changes in nano-filled and micro-hybrid composite resins on exposure to spices.

Yew, Hsu Zenn
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
66.48%
Colour changes in composite resins after immersion in beverages such as coffee, tea, alcohol beverage and carbonated drinks have been reported. Although much work has been done to determine the staining susceptibility of composite resins to various liquid beverages, effects of spices on colour stability of composite resins have not been fully researched. Objectives: The aim of this study is to evaluate the colour stability of nano-filled (Filtek Supreme™) and micro-hybrid (Gradia Direct™) composite resins finished with either Sof-Lex™ discs or mylar strips upon exposure to turmeric, paprika and tamarind. Materials and methods: Twenty cylindrical specimens were fabricated from two commercially available composite resins; Filtek Supreme XT™ (3M ESPE, St Paul, MN) and Gradia Direct X™(GC AMERICA). The top surfaces of the specimen were polished with Sof–Lex™ aluminium oxide discs (3M/ESPE, St Paul, MN USA) while the bottom surfaces were mylar strips finished. All samples were subjected to 500 thermocycling rounds between 5 and 55 ºC with 20 seconds dwell time prior to immersion in staining solution. Twenty specimens from each type of composite were then randomly divided into 4 groups (n=5) and immersed in each staining solutions (0.1% turmeric...

Klinische Studie zur Verschleißmessung von zwei Kompositfüllungsmaterialien; Wear resistance of two composite resins- a clinical study

Angele, Raphaela Maria
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
56.34%
Füllergehalt, Füllergröße und die Verteilung der Füllerpartikel haben entscheidenden Einfluss auf die physikalischen und mechanischen Eigenschaften von Kompositmaterialien. Ziel der Arbeit war es im Rahmen einer in vivo Studie, das Feinpartikelhybridkomposit Tetric Ceram mit dem Nanohybridkomposit Tetric EvoCeram, einer Weiterentwicklung aus der Tetric-Produktlinie, hinsichtlich des Abrasionsverhaltens im Seitenzahnbereich zu vergleichen. Hierzu wurden 31 Patienten mit insgesamt 57 Kompositfüllungen der Klasse-I und/ oder Klasse-II versorgt und über ein Jahr hinweg alle 3 Monate, sowohl mittels eines Abdruckes und dessen Umsetzung in Gips, als auch durch das Abtasten mit einer Sonde, kontrolliert und verglichen. Dabei sollten primär messbare Veränderungen mittels eines 3D-Laserscanners (ETKON) ermittelt und hierzu stützend die visuellen Veränderungen (Beurteilung der Randkonfiguration) festgehalten werden. Bezüglich der subjektiv vergebenen Noten für die Randbeschaffenheit der Füllungen sind beide Materialien nach 12 Monaten als gut (Tetric Ceram mit Note 2,0) bis deutlich gut (Tetric EvoCeram mit Note 1,83) einzustufen, zumal die Noten äußerst kritisch vergeben wurden und die Randbeschaffenheit meist durch eine erneute Politur verbessert werden konnte. Ein Vergleich mit anderen Studien ist nur eingeschränkt möglich. Die meisten Studien arbeiten mit der USPHS-Methode...

Development of innovative hybrid sandwich panel slabs: Experimental results

Mastali, Mohammad; Valente, Isabel B.; Barros, Joaquim A. O.; Gonçalves, Delfina
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /12/2015 ENG
Relevância na Pesquisa
46.33%
The authors appreciate the collaboration of the following labs: Civitest for developing DHCC materials, PIEP for conducting VARTM process (Eng. Luis Oliveira) and Department of Civil Engineering of Minho University to perform the tests (Mr. Antonio Matos and Eng. Marco Jorge).; In this paper, a new generation of composite sandwich slab is proposed as a solution for the rehabilitation of slabs in old masonry buildings. An innovative solution was developed during this research formed by four components: a Deflection Hardening Cement Composite (DHCC) layer on the top compression skin, a glass fiber reinforced polymer (GFRP) skin at the bottom tension surface, GFRP ribs to transfer shear from top to bottom layers, and foam core for thermal-insolation purposes. The DHCC layer contributes significantly for the load carrying and deflection capacity due to its stiffness, compressive strength and toughness, offers resistance to the occurrence of buckling phenomena in the GFRP ribs, improves the performance of this structural concept against impact and fire, and constitutes an excellent medium for the application of finishing materials, like ceramics or timber. Two different hybrid composite slabs were developed and tested, and their behavior was assessed under flexural loading. The results showed that the developed hybrid sandwich slabs accomplish all design requisites for serviceability and ultimate limit states...

Effect of Acidic Solutions on the Surface Degradation of a Micro-Hybrid Composite Resin

Münchow,Eliseu A.; Ferreira,Ana Cláudia A.; Machado,Raissa M. M.; Ramos,Tatiana S.; Rodrigues-Junior,Sinval A.; Zanchi,Cesar H.
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
Relevância na Pesquisa
56.25%
Composite resins may undergo wear by the action of chemical substances (e.g., saliva, alcohol, bacterial acids) of the oral environment, which may affect the material's structure and surface properties. This study evaluated the effect of acidic substances on the surface properties of a micro-hybrid composite resin (Filtek Z-250). Eighty specimens were prepared, and baseline hardness and surface roughness (KMN0 and Ra0, respectively) were measured. The specimens were subjected to sorption (SO) and solubility (SL) tests according to ISO 4049:2009, but using different storage solutions: deionized water; 75/25 vol% ethanol/water solution; lactic acid; propionic acid; and acetic acid. The acids were used in two concentrations: PA and 0.02 N. pH was measured for all solutions and final hardness (KMN1) and surface roughness (Ra1) were measured. Data were analyzed with paired t-tests and one-way ANOVA and Tukey's test (a=5%). All solutions decreased hardness and increased the Ra values, except for the specimens stored in water and 0.02 N lactic acid, which maintained the hardness. All solutions produced similar SO and SL phenomena, except for the 0.02 N lactic acid, which caused lower solubility than the other solutions. Ethanol showed the highest pH (6.6) and the 0.02 N lactic acid the lowest one (2.5). The solutions affected negatively the surface properties of the composite resin; in addition...

Relationship between the degree of conversion, solubility and salivary sorption of a hybrid and a nanofilled resin composite

Silva,Eduardo Moreira da; Almeida,Giselle Soares; Poskus,Laiza Tatiana; Guimarães,José Guilherme Antunes
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2008 EN
Relevância na Pesquisa
46.44%
This study analyzed the relationship between the degree of conversion (DC), solubility, and salivary sorption of a hybrid (Filtek P 60) and a nanofilled resin composite (Filtek Supreme), and evaluated the influence of the light-activation mode on these properties. Two light-activation modes were used: Conventional (C; 850 mW/cm² for 20 s) and Soft-start (SS; 100-1,000 mW/cm² for 10 s + 1,000 mW/cm² for 10 s). The DC (%) was evaluated by FT-Raman spectroscopy. The solubility and salivary sorption were measured after immersion in artificial saliva for 7 days. Data were analyzed by ANOVA and Student-Newman-Keuls' test and linear regression analysis (a = 0.05). The DC varied from 50.52% (nanofilled composite) to 57.15% (hybrid composite), and was influenced by the light-activation mode: C > SS. The solubility (0.45 mg/mm³) and salivary sorption (8.04 mg/mm³) of the nanofilled composite were greater than those of the hybrid composite (0.40 mg/mm³ / 6.87 mg/mm³), and were influenced by the light-activation mode: SS > C. Correlation was found between DC and solubility (r = - 0.89, p<0.05), as well as between solubility and salivary sorption (r = 0.95). These findings suggest that nanofilled composites may present higher degradation in the oral environment than hybrid ones. Soft-start light-activation mode may increase the solubility of resin composites.

Free vibration response of a multilayer smart hybrid composite plate with embedded SMA wires

Malekzadeh,K.; Mozafari,A.; Ghasemi,Faramarz Ashenai
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
Relevância na Pesquisa
66.49%
In this paper, free vibration response of a hybrid composite plate was studied. Effects of some geometrical, physical and material parameters on response of the composite plates embedded with shape memory alloy (SMA) wires were investigated, which have not been reported in the literature thus far. Some of these parameters included important factors affecting free vibration response of the smart hybrid composite plates. The SMA wires were embedded within the layers of the composite laminate. First-order shear deformation theory (FSDT) was utilized to obtain the governing equations of hybrid composite plates. Transverse shear and rotary inertia effects of the plate were taken into consideration. For simply-supported boundary conditions, systematic closed form solutions were obtained by Navier's technique. It was established that dynamic behavior of the smart hybrid composite plate depended on various parameters such as volume fraction, temperature dependent recovery stress and tensile pre-strain of SMA wires and aspect ratio of the laminated hybrid plate.

Effect of different finishing and polishing techniques on the surface roughness of microfilled, hybrid and packable composite resins

Barbosa,Silvia Helena; Zanata,Régia Luzia; Navarro,Maria Fidela de Lima; Nunes,Osvaldo Benoni
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2005 EN
Relevância na Pesquisa
46.34%
This study examined the average surface roughness (Ra, µm) of 2 microfilled (Durafill and Perfection), 1 hybrid (Filtek Z250) and 2 packable composite resins (Surefil and Fill Magic), before (baseline) and after eight different finishing and polishing treatments. The surface roughness was assessed using a profilometer. Ten specimens of each composite resin were randomly subjected to one of the following finishing/polishing techniques: A - carbide burs; B - fine/extrafine diamond burs; C - Sof-Lex aluminum oxide discs; D - Super-Snap aluminum oxide discs; E - rubber polishing points + fine/extrafine polishing pastes; F - diamond burs + rubber polishing points + fine/extrafine polishing pastes; G - diamond burs + Sof-Lex system; H - diamond burs + Super-Snap system. Data were analyzed using two-way ANOVA and Tukey's HSD test. Significant differences (p<0.05) were detected among both the resins and the finishing/polishing techniques. For all resins, the use of diamond burs resulted in the greatest surface roughness (Ra: 0.69 to 1.44 µm). The lowest Ra means were obtained for the specimens treated with Sof-Lex discs (Ra: 0.11 to 0.25 µm). The Ra values of Durafill were lower than those of Perfection and Filtek Z250, and these in turn had lower Ra than the packable composite resins. Overall...

In-service performance and behavior characterization of the hybrid composite bridge system - a case study

Civitillo, John M.; Harris, Devin K.; Gheitasi, Amir; Saliba, Mark; Kassner, Bernard L.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/09/2014
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The Hybrid Composite Beam (HCB) system is an innovative structural technology that has been recently used in bridge construction within the U.S. transportation network. In this system, the superstructure consists of a conventional reinforced concrete deck supported by Hybrid Composite Beams. Each beam is comprised of a glassfiber reinforced polymer (FRP) box shell containing a tied parabolic concrete arch. Inclined stirrups provide shear integrity and enforce composite action between the HCBs and the concrete deck. This paper focuses on evaluating the in-service performance of a newly constructed HCB bridge superstructure located on Route 205 in Colonial Beach, Virginia. A live load test was conducted using tandem axle dump trucks under both quasi-static and dynamic conditions. Results obtained from the experimental investigation were used to determine three key behavior characteristics. Dynamic amplification and lateral load distribution were found to be reasonable in comparison to the assumed design values. The testing program also included internal and external measurement systems to help characterize the load sharing behavior of the HCB on an element level. The main load carrying elements are the deck in compression and the steel ties in tension...