Papers by Keyword: Particulate Composite

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Authors: Leila Figueiredo de Miranda, Antônio Hortêncio Munhoz Jr., Terezinha Jocelen Masson, Virgínia Carolina Naime, Gustavo Camargo Costa
Abstract: The properties of composites based on thermosetting polyester and barite for use in the radiological protection area have been investigated with the objective to study the effect of different variables in the attainment of composites. To verify the efficiency of the composites produced in relation to radiological protection, lead was adopted as reference. A factorial experimental design was carried out and the studied variables were: type of polyester resin (orthophthalic or isophthalic), coupling agent (titanate or organosilane) and the ratio of resin to accelerator, catalyst and barite. The variables analyzed were: efficiency for barring the X-radiation, apparent density and mechanical properties. The effect, obtained from the experimental design, due to ratio of resin to barite in the apparent density was 0.036. The average apparent density of the samples produced with barite/resin value equal 2.0 (weight ratio) was 2.16g/cm3, while the average density of the samples produced with the weight ratio of barite/resin equal 3.0 was 2.2g/cm3. It was observed same trend for the density to mechanical properties. It was observed that the samples attenuated X-ray radiation adequately up to 116 kV.
Authors: Masuo Hagiwara, Satoshi Emura
Abstract: Titanium alloys and Titanium alloy-based particulate composites were synthesized using the blended elemental P/M route. First, processing conditions such as the fabrication of master alloy powder were investigated. Ti-6Al-4V, Ti-5Al-2.5Fe, Ti-6Al-2Sn-4Zr-2Mo, IMI685, IMI829, Timetal 1100 and Timetal 62S, and Ti-6Al-2Sn-4Zr-2Mo/10%TiB and Timetal 62S/10%TiB were then synthesized using the optimal processing conditions obtained. The microstructures and mechanical properties such as tensile strength and high cycle fatigue strength were evaluated.
Authors: Anthony Kelly
Abstract: A description is given of a possible solution of an important practical problem in microelectronics, namely producing a material of thermal expansion coeffiecient to equal that of silicon.
Authors: E. Fénard, J.L. Besson, Martine Desmaison-Brut
Authors: Satoshi Emura, Masuo Hagiwara
Abstract: A TiB particulate-reinforced Ti-22Al-27Nb (mol%) alloy, based on the orthorhombic intermetallic phase, was prepared using gas atomization powder metallurgy method. In the as-atomized condition, extremely fine TiB particulates of less than 1-μm diameter and 5-μm length were dispersed in the matrix. After annealing heat treatment (heat treated at 1423 K with subsequent furnace cooling), this composite exhibited a lamellar matrix microstructure and showed better creep properties than a composite produced using conventional ingot metallurgy method, with coarse TiB particulates of 5-μm diameter and 40-μm length. Coarsening of the matrix microstructure and growth of TiB particulates occurred after annealing heat treatment at higher temperature (ca. 1473 K). Creep-resistance improvement was also observed, which seemed to be mainly attribute to the effect of the matrix microstructure. From measurements of stress components and activation energy, all composites showed an identical creep mechanism: dislocation-controlled creep.
Authors: Hong Chang Qu, Xiao Zhou Xia, Zhi Qiang Xiong
Abstract: The crack tip region in an elastic composite can be separated into three different regions. based on a simple rate-independent phenomenological constitutive model, the path independence of the J-integral and the concept of cracktip shielding, the maximum radii R of the damage saturation zone is obtained. Damage isotropy in the largest saturated damage zone is expressed by utilizing the Monte-Carlo technique to create the uniform distributions of microcrack location and orientation. With the assumption of dilute microcrack concentration, interaction among microcracks are neglected, and the stress intensity factor produced by interaction between main-crack and each microcrack can be superposed. Two sources of loading are analyzed, one is for the main-crack microcrack interaction under an applied remote load, and the other is for the main-crack microcrack interaction accompanied by the relief of residual stresses on the microcrack surfaces. The results show that two sources of loading can shield the main-crack tip, and microcracks behind the main-crack tip can make the most shielding whereas microcracks ahead of the main-crack tip play no role in shielding.
Authors: Akihiro Wada, Yusuke Nagata, Shi Nya Motogi
Abstract: In this study, partially debonded spherical particles in a particulate composite are analyzed by three-dimensional finite element method to investigate their load carrying capacities, and the way to replace a debonded particle with an equivalent inclusion is examined. The variation in Young’s modulus and Poisson’s ratio of a composite with the debonded angle was evaluated for different particle arrangements and particle volume fractions, which in turn compared with the results derived from the equivalent inclusion method. Consequently, it was found that by replacing a debonded particle with an equivalent orthotropic one, the macroscopic behavior of the damaged composite could be reproduced so long as the interaction between neighboring particles is negligible.
Authors: Chang Jun He, Hui Jian Li, Wei Yu, Xi Liang, Hai Yan Peng
Abstract: . The Young’s modulus of syntactic foams were studied both the experiment and the theory. The compressive test and dynamic mechanical analysis were progressed for a few of specimens, which were made of the syntactic foams with the epoxy resin and hollow glass microspheres (HGMs). the equations for Young’s modulus of concentrated particulate composites were derived using a differential scheme of an infinitely dilute system, and were employed to prediction the Young’s modulus of syntactic foams. The computed effective Young’s moduli were compared with the experimental results, the prediction values were between the lower and upper bounds of the experimental data, and the prediction model was acceptable and can estimate the Young’s modulus of syntactic foams.
Authors: Sabbah Ataya, Marcus Korthäuer, Essam El Magd
Abstract: Copper reinforced by tungsten particles has high potential applications in the fields of electronics and electric contacts where high strength accompanied with good electrical conductivity is required. The effects of different scaling parameters (deformed volume, tungsten volume fraction and the tungsten particle size) affect the force needed for the machining of the W/Cu particle reinforced composites. W/Cu composites with different weight percentages of tungsten (80, 70 and 60 wt.%) were tested under compression loading. Different sizes of the compression specimens were tested; the specimen diameter DS was varied to be 1, 2, 4, 6 and 8 mm. The effect of the tungsten particle size was varied to be 10 and 30-m. The compression tests were done at strain rates of 0.1s-1. The experiments were carried out within a temperature range from 20 °C to 800°C. The mechanically tested specimens were metallographically investigated to determine the degree of deformation of the tungsten particles in different specimen geometries. A clear dependence of the flow stress on the volume of the deformed specimens and the tungsten volume fraction was found. This size effects were more obvious with increase of the tungsten volume fraction at lower temperatures. The metallographic investigation was helped to understand the observed size effect of the composites in relation to the volume fraction and the specimen size
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