Estudo do conteúdo de partículas inorgânicas, da contração de polimerização e da resistência à flexão de materiais restauradores estéticos diretos indicados para dentes posteriores

Recentemente, foram lançados no mercado odontológico novos materiais estéticos para restaurações diretas em dentes posteriores, aos quais são atribuídas propriedades mais adequadas para essa indicação. Entretanto, as informações disponíveis são ainda muito escassas, gerando dúvidas quanto à sua real eficácia, sobre quais as diferenças de suas composições e propriedades físicas e mecânicas em relação aos materiais até então disponíveis e se, de fato, apresentam melhor performance clínica. Em vista do exposto, nos propusemos a estudar contração de polimerização, resistência à flexão e concentração de partículas inorgânicas, por massa e volume, de sete resinas compostas (Alert, Ariston, Solitaire, Definite, Filtek P60, Z-100 e Tetric Ceram). A contração de polimerização foi medida nos materiais inseridos em um anel plástico, e o registro das alterações, durante a polimerização, foi feito por meio de instrumento eletrônico de medida linear, que registra as alterações dimensionais, com sensibilidade de 1 mm. A resistência à flexão foi medida na máquina de ensaios mecânicos MTS 810 e a confecção dos corpos-de-prova e dos dispositivos para o ensaio foi orientada pela norma ISO no 4049:1988. A determinação do conteúdo de partículas inorgânicas por massa foi feita através da pesagem de uma porção de resina composta polimerizada antes e após a eliminação da fase orgânica em forno, à temperatura de 700oC. O porcentual volumétrico de partículas inorgânicas foi calculado com base no Princípio de Arquimedes. Foi determinado o volume da resina composta polimerizada, antes e após a eliminação da fase orgânica, pela diferença da massa do material pesado ao ar e imerso em água. Os dados de conteúdo de partículas inorgânicas por massa e por volume, de contração de polimerização e resistência à flexão foram submetidos...(Resumo completo, clicar acesso eletrônico abaixo)

Determinação do fator de rigidez de junta aparafusada em tração utilizando o software Excel

When a bolted joint is loaded in tension with dynamically, part of this load is absorbed by the bolt and rest is absorbed by the joint material. What determines the portion that is to absorbed by the bolt is the joint stiffness factor. This factor influences the tension which corresponds to pre-load and the safety factor for fatigue failure, thus being an important factor in the design of bolted joints. In this work, three methods of calculating the stiffness factor are compared through a spreadsheet in Excel software. The ratio of initial pre-load and the safety factor for fatigue failure depending on the stiffness factor graph is generated. The calculations for each method show results with a small difference. It is therefore recommended that each project case is analyzed, and depending on its conditions and the range of stiffness values, the more or less rigid method about the safety factor for fatigue failure is chosen. In general, the approximation method provides consistent results and can be easily calculated

Processamento do compósito de fibra de capim-sapê / epóxi e avaliação da resistência à flexão “t” de Student

In recent years a great worldwide interest has arisen for the development of new technologies that enable the use of products with less environmental impact. The replacement of synthetic fiber plants is a possibility very important because this fiber is renewable, biodegradable and few cost and cause less environmental impact. Given the above, this work proposes to develop polymeric composites of epoxy resin and study the behavior of these materials. Both, the epoxy resin used as matrix in the manufacture of sapegrass fiber composite, as tree composites formed by: epoxy/unidirectional sapegrass long fiber, 75% epoxy/25% short fiber, by volume, and 80% epoxy/20% short fiber, by volume, were characterized by bending, and the composites produced with short fibers random were inspected by Optical Microscopy and Acoustics Inspection (C-Scan). For the analysis of the sapegrass fiber morphology, composites 75% epoxy/25% short fiber (sheet chopped) and 80% epoxy/20% short fiber images were obtained by optical microscope and the adhesion between polymer/fiber was visualized. As results, the flexural strength of composites epoxy/unidirectional long fibers, 75% epoxy/25% short fiber and 80% epoxy/20% short fiber were 70.36 MPa, 21.26 MPa, 25.07 MPa, respectively. Being that composite showed that the best results was made up of long fibers, because it had a value of higher flexural strength than other composites analyzed

Desempenho estrutural de vigas em madeira laminada colada armada

The objective of the present work was to evaluate Pinus’ glued laminated timber (glulam) beams and steel reinforced glulam beams, using PU mono-component adhesive in lamination step and epoxy adhesive to bond steel bars. The mechanical performance was verified through bending test, and the adopted method based on homogenized section, to considerate the differences between wood and steel mechanical properties. The homogenization section method proved itself effective in obtaining the stiffness of the parts in MLCA. The stiffness of reinforced beams increased 91% in comparison with glulam beams, differing only 5.5 % from value of stiffness calculated

Caracterização físico-mecânica de elementos estruturais roliços perfilados de Amaru

The study of physical and mechanical properties of wood is essential for its structural use and it is of great importance to the construction industry. Thus, this study aimed to determine the physical and mechanical properties of the wood Amaru - a hybrid of Eucalyptus, developed by Plantar Projects and Forest Products Ltda. In order to determine the properties of Amaru, round samples were used, which were provided to the Laboratory of Wood and Wooden Structures of the School of Engineering of São Carlos, University of São Paulo - LaMEM / EESC / USP. For the characterization of the physical properties, the apparent specific gravity and moisture content of the samples were determined. To the mechanical characterization, the following properties were evaluated: strength and stiffness in compression, strength and stiffness in bending, shear and tension. The procedures of the tests performed in this study were done according to the recommendations of the Brazilian Wood Standard ABNT NBR 7190:1997. The specimen used were confectioned in actual dimensions, according to as those used in the construction system proposed by Plantar. The results obtained from the tests performed showed that the mechanical properties approached the values proposed by the Wood Standard NBR 7190. The visual grading was important to provide a primary idea about the failure modes to be obtained from the tests performed. The bending test showed the modulus of elasticity (MOE) and Modulus of Rupture (MOR), which resulted in 15822 MPa and 101,7 MPa, respectively. The compression test resulted in values Ec0,m and fc0, 15698 MPa and 50,7 MPa. The tensile strength (ft0) of this hybrid was calculated and its value obtained was 60,8 MPa. The shear strength (fv0) was 8,2 MPa. The results obtained from the tests are the basis for engineers and architects to design structures using wood species Amaru

Estudo de compósitos de madeira com reforço em bambu para utilização em mobiliário

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

Flexão e análise dinâmico-mecânica de compósitos 5HS e NCF com resina epóxi monocomponente produzidos por RTM

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

Efeito de protocolos de jateamento na resistência à flexão e transformação de fase cristalina em cerâmicas de Y-TZP

Pós-graduação em Odontologia Restauradora - ICT

Resistência à flexão em porcelana feldspática: efeito da ciclagem mecânica e limite de fadiga pelo método escada

This study evaluated the fatigue limit (FL) by the staircase method and the effect of mechanical cycling on the flexural strength (FS) of Duceragold feldspathic porcelain. Specimens (25 x 5 x 2 mm) were made according to manufacturer’s directions and submitted to three-point flexural strength test (n = 10). To determine FL (n = 30; 10,000 cycles; 2 Hz), an initial loading of 60% of the FS and an incremental loading (step) of 3% of the FS were used. Data were analyzed by Anova and Tukey´s test (p < 0.05). Although the proposed cycles have not reduced FS significantly, fractography analysis showed striation, characteristic signs of mechanical fatigue.

Caracterização química e resistência à flexão de uma resina acrílica após a incorporação de um polímero com atividade antimicrobiana

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efeito das dimensões dos corpos de prova na resistência à flexão de compósitos restauradores

The aim of this study was to evaluate the influence of specimen size, in comparison with the ISO Standard, on the three point flexural strength of resin composite restorative materials Filtek Supreme and Filtek Z-250. Forty specimens were fabricated for each material with the following length, width and thickness measurements (n = 10): 1) 20 × 2 × 2 mm (ISO 4049); 2) 10 × 2 × 1 mm; 3) 10 × 1 × 1 mm; 4) 8 × 0.8 × 0.8 mm. The composites were inserted in a single increment into two-piece metal device and light-polymerized. The specimens were dry stored at 37 ± 1 °C and protected from light for 7 days. After this period, flexural strength was measured by three-point flexure test using MTS 810 equipment, with a load cell of 10 kN at a speed of 0.5 mm/min. For the evaluated sizes, the results showed significant variability (p = 0.00) with values when compared with the ISO Standard (116.700 MPa), being statistically higher for the test specimens measuring 10 × 1 × 1 mm (142.530 MPa), similar for those of 10  ×  2  ×  1  mm (115.815 MPa) and lower for those of 8 × 0.8 × 0.8 mm (86.650 MPa). There was statistical equality (p = 0.08) for the studied composites (Filtek Supreme, 125.270 MPa; Filtek Z-250, 108.130 MPa). Specimens measuring 10 × 2 × 1 mm provided flexural strength values equivalent to those obtained in the sizes recommended by the ISO 4049 standard, with lower consumption of material, energy and time.

Resistência à flexão de uma resina acrílica após a incorporação de um polímero antimicrobiano

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efeito da infiltração de sílica pelo método sol-gel na resistência à flexão de bicamadas de porcelana e Y-TZP

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Evaluation of femur of orchiectomized guinea pigs by bone densitometry using dual-energy x-ray absortiometry (DXA) and mechanical testing

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efeito da inibição dos receptores canabinóides CB₁ ou CB₂ durante o período neonatal sobre o dimorfismo sexual esquelético ao longo do desenvolvimento

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)