The Experts below are selected from a list of 7092 Experts worldwide ranked by ideXlab platform
Ali Dadrasi - One of the best experts on this subject based on the ideXlab platform.
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mechanical properties and Energy Absorption Capability of thin walled square columns of silica epoxy nanocomposite
Construction and Building Materials, 2015Co-Authors: Mahmoud Shariati, Gholamali Farzi, Ali DadrasiAbstract:Abstract In this paper, the effect of adding silica nanoparticle to epoxy, silica weight percent, particle size and various combinations of epoxy/silica on Young’s modulus, yield strength and Energy Absorption Capability of thin-walled square columns was investigated. Two different sizes of silica nanoparticles, nominally 17 nm and 65 nm in diameter, were used. Nanosilica particles were dispersed almost homogeneously in the epoxy resin from 1.5 wt.% to 6 wt.% in three series of composites. First and second series were composites reinforced with 17 nm and 65 nm particle size, respectively and third series were composites reinforced with combination of both particle sizes. All specimens were tested under quasi-static loading using a servohydraulic Instron machine. A scanning electron microscopy (SEM) was used for fracture surface studies. The results showed that when silica weight percent was increased, the Young’s modulus increased, yield strength remained constant and Energy Absorption Capability of columns decreased, and specimens collapsed under unstable and dangerous mode. It was observed that the reason for this type of collapse was initiation of axial cracks at an early stage of the loading and propagation along the specimen height. Energy Absorption Capability for columns with height of 60 mm and 90 mm was also investigated and results showed that this parameter for shorter specimens was higher in the same combination of a nanocomposite. Moreover, the effect of particle size on Young’s modulus, yield strength and Energy Absorption Capability was not considerable. Using both particles in a combination did not show any important synergy effect. And finally, fracture surfaces of the specimens showed that surface roughness was increased by increasing the silica nanoparticles.
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Mechanical properties and Energy Absorption Capability of thin-walled square columns of silica/epoxy nanocomposite
Construction and Building Materials, 2015Co-Authors: Mahmoud Shariati, Gholamali Farzi, Ali DadrasiAbstract:Abstract In this paper, the effect of adding silica nanoparticle to epoxy, silica weight percent, particle size and various combinations of epoxy/silica on Young’s modulus, yield strength and Energy Absorption Capability of thin-walled square columns was investigated. Two different sizes of silica nanoparticles, nominally 17 nm and 65 nm in diameter, were used. Nanosilica particles were dispersed almost homogeneously in the epoxy resin from 1.5 wt.% to 6 wt.% in three series of composites. First and second series were composites reinforced with 17 nm and 65 nm particle size, respectively and third series were composites reinforced with combination of both particle sizes. All specimens were tested under quasi-static loading using a servohydraulic Instron machine. A scanning electron microscopy (SEM) was used for fracture surface studies. The results showed that when silica weight percent was increased, the Young’s modulus increased, yield strength remained constant and Energy Absorption Capability of columns decreased, and specimens collapsed under unstable and dangerous mode. It was observed that the reason for this type of collapse was initiation of axial cracks at an early stage of the loading and propagation along the specimen height. Energy Absorption Capability for columns with height of 60 mm and 90 mm was also investigated and results showed that this parameter for shorter specimens was higher in the same combination of a nanocomposite. Moreover, the effect of particle size on Young’s modulus, yield strength and Energy Absorption Capability was not considerable. Using both particles in a combination did not show any important synergy effect. And finally, fracture surfaces of the specimens showed that surface roughness was increased by increasing the silica nanoparticles.
Mahmoud Shariati - One of the best experts on this subject based on the ideXlab platform.
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Experimental analysis of Energy Absorption Capability of thin-walled composite cylindrical shells by quasi-static axial crushing test
Thin-Walled Structures, 2018Co-Authors: Seyed Morteza Hosseini, Mahmoud ShariatiAbstract:Abstract The Energy Absorption Capability of thin-walled composite cylindrical shells is experimentally investigated. Effects of six parameters on Absorption Energy of composite shells are studied. These parameters including three geometric parameters of inner diameter, length and shell thickness and the other three parameters are layer orientation, reinforcing fibers and manufacturing process. The design of experiment was accomplished by applying Taguchi method and the axial crushing test was conducted on shells. The resulting data was statistically analyzed which led to the ranking of the six parameters and an optimized structure based on the selected parameters was proposed. Finally, different kinds of complicated failure modes controlling Absorption capacity were studied. In addition, effects of the six mentioned parameters on both stable and unstable crushing modes of shells were investigated. It is found that a good correspondence exists between statistical analysis results and crushing collapse mechanisms in experimental analysis results, which both of the analysis are accorded to specific Energy Absorption.
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mechanical properties and Energy Absorption Capability of thin walled square columns of silica epoxy nanocomposite
Construction and Building Materials, 2015Co-Authors: Mahmoud Shariati, Gholamali Farzi, Ali DadrasiAbstract:Abstract In this paper, the effect of adding silica nanoparticle to epoxy, silica weight percent, particle size and various combinations of epoxy/silica on Young’s modulus, yield strength and Energy Absorption Capability of thin-walled square columns was investigated. Two different sizes of silica nanoparticles, nominally 17 nm and 65 nm in diameter, were used. Nanosilica particles were dispersed almost homogeneously in the epoxy resin from 1.5 wt.% to 6 wt.% in three series of composites. First and second series were composites reinforced with 17 nm and 65 nm particle size, respectively and third series were composites reinforced with combination of both particle sizes. All specimens were tested under quasi-static loading using a servohydraulic Instron machine. A scanning electron microscopy (SEM) was used for fracture surface studies. The results showed that when silica weight percent was increased, the Young’s modulus increased, yield strength remained constant and Energy Absorption Capability of columns decreased, and specimens collapsed under unstable and dangerous mode. It was observed that the reason for this type of collapse was initiation of axial cracks at an early stage of the loading and propagation along the specimen height. Energy Absorption Capability for columns with height of 60 mm and 90 mm was also investigated and results showed that this parameter for shorter specimens was higher in the same combination of a nanocomposite. Moreover, the effect of particle size on Young’s modulus, yield strength and Energy Absorption Capability was not considerable. Using both particles in a combination did not show any important synergy effect. And finally, fracture surfaces of the specimens showed that surface roughness was increased by increasing the silica nanoparticles.
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Mechanical properties and Energy Absorption Capability of thin-walled square columns of silica/epoxy nanocomposite
Construction and Building Materials, 2015Co-Authors: Mahmoud Shariati, Gholamali Farzi, Ali DadrasiAbstract:Abstract In this paper, the effect of adding silica nanoparticle to epoxy, silica weight percent, particle size and various combinations of epoxy/silica on Young’s modulus, yield strength and Energy Absorption Capability of thin-walled square columns was investigated. Two different sizes of silica nanoparticles, nominally 17 nm and 65 nm in diameter, were used. Nanosilica particles were dispersed almost homogeneously in the epoxy resin from 1.5 wt.% to 6 wt.% in three series of composites. First and second series were composites reinforced with 17 nm and 65 nm particle size, respectively and third series were composites reinforced with combination of both particle sizes. All specimens were tested under quasi-static loading using a servohydraulic Instron machine. A scanning electron microscopy (SEM) was used for fracture surface studies. The results showed that when silica weight percent was increased, the Young’s modulus increased, yield strength remained constant and Energy Absorption Capability of columns decreased, and specimens collapsed under unstable and dangerous mode. It was observed that the reason for this type of collapse was initiation of axial cracks at an early stage of the loading and propagation along the specimen height. Energy Absorption Capability for columns with height of 60 mm and 90 mm was also investigated and results showed that this parameter for shorter specimens was higher in the same combination of a nanocomposite. Moreover, the effect of particle size on Young’s modulus, yield strength and Energy Absorption Capability was not considerable. Using both particles in a combination did not show any important synergy effect. And finally, fracture surfaces of the specimens showed that surface roughness was increased by increasing the silica nanoparticles.
Renaud Metz - One of the best experts on this subject based on the ideXlab platform.
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The effect of lithium oxide on the threshold field of ZnO varistors
Ceramics International, 2009Co-Authors: Mourad Houabes, Renaud MetzAbstract:Lithium oxide in form of Li2CO3 solution is added with contents of 0–200 ppm to two ZnO-based varistors standard formulations, once with Sb2O3 and the other without. According to Li2CO3 concentration, both threshold field and Energy Absorption Capability evolution are studied. It is found that with the benefit of antimony, the lithium allows reaching high threshold field but concomitantly, low Energy Absorption Capability. Without antimony, threshold fields up to 300 V/mm are attained, associated with a fair Energy Absorption Capability. With 100 ppm of Li2CO3, optimum couple of values (315 V/mm; 115 J/cm3) is achieved. With 200 ppm of Li2CO3, threshold field exceeds 500 V/mm but Energy Absorption Capability falls below 50 J/cm3. Correlations with SEM microstructures observations suggest that lithium increases voltage barrier height by decreasing donor density and that spinel phases (Zn7Sb2O12) have detrimental effects on the electrical Absorption Capability by limiting the density of current, reducing the effective current path from one ZnO grain to another.
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rare earth oxides effects on both the threshold voltage and Energy Absorption Capability of zno varistors
Ceramics International, 2007Co-Authors: Mourad Houabes, Renaud MetzAbstract:Abstract Rare earth oxides: Pr6O11, Y2O3, La2O3, Ce2O3 and Nd2O3 are added with contents of 0.01–0.5 wt.% to ZnO standard and antimony-rich varistor compositions. It is found that the rare earth oxide: REO, allows reaching large Energy Absorption Capability value for the high threshold voltage ZnO-based varistors. A 30% maximum increase in threshold voltage is observed with the addition of 0.1 wt.% REO. However, degradation is accentuated with REO addition. Between 0 and 0.1 wt.% of REO the degradation remain still acceptable, but beyond 0.1% it becomes strong, up to 20% and Energy Absorption Capability remains more than 100 J/cm3. It is practically constant whatever the REO percentage. Results from standard composition are exploited for the second composition by optimization of Sb2O3 and REO concentrations in order to control the growth of the ZnO grains while maintaining the Energy Absorption Capability above 100 J/cm3. On the one hand, a high threshold voltage 300 V/mm ensured by antimony oxide, and on the other hand, a good capacity for Absorption in Energy 107 J/cm3 ensured by the REO, whereas it had fallen to 52 J/cm3 because of the great quantity of Sb2O3. Satisfactory values of non-linearity coefficient (α) between 40 and 52 are obtained. These results are explained by the presence of extra-pyrochlore phase suggesting less bismuth oxide in the ceramics, especially at grain boundaries. Varistors present more active grains and hence a larger conduction section which account for large Absorption Capability.
Martin Maier - One of the best experts on this subject based on the ideXlab platform.
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mechanical properties and Energy Absorption Capability of woven fabric composites under 45 off axis tension
Composite Structures, 2015Co-Authors: Tim Bergmann, Sebastian Heimbs, Martin MaierAbstract:Abstract Fibre-reinforced polymer composites are generally known for their brittle failure behaviour. Ductility of composites, in contrast, which may be of relevance for specific applications like for Energy-absorbing structures, can typically be obtained under ±45° off-axis tension using the in-plane shear effect. In order to provide an extensive database for the in-plane shear behaviour, a comprehensive experimental study of woven fabric composites under quasi-static and high strain-rate ±45° off-axis tensile loading is presented, assessing the non-linear stress–strain behaviour and weight-specific Energy Absorption Capability under different loading rates. The test campaign aims at characterising the influence of fibre material (carbon, glass, aramid, Vectran® and Dyneema®), matrix material (untoughened epoxy resin, toughened epoxy resin and thermoplastic PEEK), weave pattern (plain weave, twill weave, satin weave and braid) and fibre areal weight on the ±45° off-axis tensile mechanical properties. The results reveal failure strain values of up to 28% and significant strain rate effects, influencing stiffness, strength, strain-to-failure and Energy Absorption.
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Mechanical properties and Energy Absorption Capability of woven fabric composites under ±45° off-axis tension
Composite Structures, 2015Co-Authors: Tim Bergmann, Sebastian Heimbs, Martin MaierAbstract:Abstract Fibre-reinforced polymer composites are generally known for their brittle failure behaviour. Ductility of composites, in contrast, which may be of relevance for specific applications like for Energy-absorbing structures, can typically be obtained under ±45° off-axis tension using the in-plane shear effect. In order to provide an extensive database for the in-plane shear behaviour, a comprehensive experimental study of woven fabric composites under quasi-static and high strain-rate ±45° off-axis tensile loading is presented, assessing the non-linear stress–strain behaviour and weight-specific Energy Absorption Capability under different loading rates. The test campaign aims at characterising the influence of fibre material (carbon, glass, aramid, Vectran® and Dyneema®), matrix material (untoughened epoxy resin, toughened epoxy resin and thermoplastic PEEK), weave pattern (plain weave, twill weave, satin weave and braid) and fibre areal weight on the ±45° off-axis tensile mechanical properties. The results reveal failure strain values of up to 28% and significant strain rate effects, influencing stiffness, strength, strain-to-failure and Energy Absorption.
Mourad Houabes - One of the best experts on this subject based on the ideXlab platform.
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The effect of lithium oxide on the threshold field of ZnO varistors
Ceramics International, 2009Co-Authors: Mourad Houabes, Renaud MetzAbstract:Lithium oxide in form of Li2CO3 solution is added with contents of 0–200 ppm to two ZnO-based varistors standard formulations, once with Sb2O3 and the other without. According to Li2CO3 concentration, both threshold field and Energy Absorption Capability evolution are studied. It is found that with the benefit of antimony, the lithium allows reaching high threshold field but concomitantly, low Energy Absorption Capability. Without antimony, threshold fields up to 300 V/mm are attained, associated with a fair Energy Absorption Capability. With 100 ppm of Li2CO3, optimum couple of values (315 V/mm; 115 J/cm3) is achieved. With 200 ppm of Li2CO3, threshold field exceeds 500 V/mm but Energy Absorption Capability falls below 50 J/cm3. Correlations with SEM microstructures observations suggest that lithium increases voltage barrier height by decreasing donor density and that spinel phases (Zn7Sb2O12) have detrimental effects on the electrical Absorption Capability by limiting the density of current, reducing the effective current path from one ZnO grain to another.
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rare earth oxides effects on both the threshold voltage and Energy Absorption Capability of zno varistors
Ceramics International, 2007Co-Authors: Mourad Houabes, Renaud MetzAbstract:Abstract Rare earth oxides: Pr6O11, Y2O3, La2O3, Ce2O3 and Nd2O3 are added with contents of 0.01–0.5 wt.% to ZnO standard and antimony-rich varistor compositions. It is found that the rare earth oxide: REO, allows reaching large Energy Absorption Capability value for the high threshold voltage ZnO-based varistors. A 30% maximum increase in threshold voltage is observed with the addition of 0.1 wt.% REO. However, degradation is accentuated with REO addition. Between 0 and 0.1 wt.% of REO the degradation remain still acceptable, but beyond 0.1% it becomes strong, up to 20% and Energy Absorption Capability remains more than 100 J/cm3. It is practically constant whatever the REO percentage. Results from standard composition are exploited for the second composition by optimization of Sb2O3 and REO concentrations in order to control the growth of the ZnO grains while maintaining the Energy Absorption Capability above 100 J/cm3. On the one hand, a high threshold voltage 300 V/mm ensured by antimony oxide, and on the other hand, a good capacity for Absorption in Energy 107 J/cm3 ensured by the REO, whereas it had fallen to 52 J/cm3 because of the great quantity of Sb2O3. Satisfactory values of non-linearity coefficient (α) between 40 and 52 are obtained. These results are explained by the presence of extra-pyrochlore phase suggesting less bismuth oxide in the ceramics, especially at grain boundaries. Varistors present more active grains and hence a larger conduction section which account for large Absorption Capability.