ahmad almagableh | The Hashemite University (original) (raw)
Papers by ahmad almagableh
Journal of Composite Materials
This study models the mechanical performance of thermoset polyamide filled with various percentag... more This study models the mechanical performance of thermoset polyamide filled with various percentages of glass beads using a coupling agent. A micromechanical model is developed for polyamide glass-bead composite containing three-phase zones with imperfect bonding across interfaces. The micromechanical/interface model uses square sub-region arrays representing particle, matrix, and interface zones to obtain the stress transfer behavior across the cohesive zone for a given microstructure. Understanding the stress transfer tool and interfacial adhesion across multi-coated inclusions, and developing accurate material models will help in establishing upcoming design criteria in the engineering of polymer based composites. The impact of this study comes from the fact that the diffusion quality and non-uniform distribution of inclusions within the polymer matrix, and weak bonding of filler to the polymer matrix, may result in an ineffective stress transfer, which in turn degrades the mechan...
This paper discusses the viscoelastic behavior of 1.25 and 2.5 wt. % nanoclay and graphite platel... more This paper discusses the viscoelastic behavior of 1.25 and 2.5 wt. % nanoclay and graphite platelet reinforced vinyl ester under short term creep and relaxation tests using a Dynamic Mechanical Analyzer (DMA). Linear viscoelastic models are generally composed of one or more elements such as dashpots and springs that represent the viscous and elastic properties. Stress relaxation data from DMA was used to obtain the elastic parameters based on model constitutive equations. The Standard Linear Solid (SLS) model, which is a physical model, was used for predicting the creep deformation behavior of the vinyl ester nanocomposites over a wide temperature range. This model was chosen because it can describe the stress relaxation and creep behavior of polymers and can also explain the two main deformations of plastics [1]; with the spring representing deformations due to bending and stretching of intermolecular bonds and dashpot represents deformation due to the viscous effect. Some correlat...
A micromechanical model is applied to examine the tensile properties of composite materials fille... more A micromechanical model is applied to examine the tensile properties of composite materials filled with multi-wall CNT oriented in in-plane and out-of-plane direction and a quantitative micromechanical model for the mechanical behavior of CNT-composites has been developed. Digimat-MF is used to generate a realistic three-dimensional microstructure for the current carbon nanotube/ epoxy composite. The Digimat model simulates a system of aligned carbon nanotubes arranged in-plane and another one having out of plane arrangement of reinforcements. A second model shows a representative volume element for the current nano-composite, in which the carbon nanotubes were simulated as a randomly (fully) dispersed, where all particles have been separated from each other. The predicted mechanical properties are compared with experimental tensile properties of composite materials reinforced with multi-wall CNTs arranged in in-plane and out-of-plane direction. A good agreement between the micromec...
The creep resistance of thermoset vinyl ester-based nanocomposites is studied by adding different... more The creep resistance of thermoset vinyl ester-based nanocomposites is studied by adding different weight percents of exfoliated graphite filler, characterized at different temperatures under constant loading. The creep response of these nanocomposites was analyzed using the TA Instruments Model Q800- DMA. Results showed that the nano-filler at some temperatures may hinder slippage and reorientation of polymer chain that, in turn, shows higher creep resistance for nanocomposites than the neat matrix. At a lower temperature, poor creep resistance was observed for neat matrix as compared to nano materials tested; however, at elevated temperatures (beyond the glass transition temperature), creep resistance in nanocomposites becomes close to that of neat vinyl ester. To fully understand the complex creep deformation of polymeric based nanocomposites, a physical modeling is conducted to study the structure-property relationship as a function of filler content. Parametric studies for the s...
This paper describes investigations on dynamic mechanical analysis (DMA) of nylon 6,6 thermoplast... more This paper describes investigations on dynamic mechanical analysis (DMA) of nylon 6,6 thermoplastic reinforced with 1.25 and 2.5 wt. percent multi-wall carbon nano tubes (MWCNT), and Derakane 411-350 vinyl ester thermoset reinforced with 1.25 and 2.5 wt. percent Cloisite 30B nanoclay and exfoliated graphite nanoplatelets (xGnP). Visco-elastic materials exhibit the characteristics of both elastic solid and viscous liquid. This dual behavior which is both time and temperature dependent has been characterized by dynamic oscillation and creep experiments performed at various isothermal temperatures. Viscoelastic properties such as storage modulus (E’), loss modulus (E”), damping, glass transition temperature (Tg) and creep behavior were compared for the different nanocomposites. Short range creep tests were performed at isothermal conditions and the time-temperature superposition principle was utilized to generate creep-strain master curves at a reference temperature. An increase in sto...
... without the help and support of a great number of people. Perhaps the individual to whom I am... more ... without the help and support of a great number of people. Perhaps the individual to whom I am most indebted is Professor P. Raju Mantena, who has been my advisor, mentor and a source of support throughout my years of graduate study. His patience and willingness as ...
Journal of Composite Materials, 2014
Mechanical response of nano-based composites is generally influenced by interaction of filler and... more Mechanical response of nano-based composites is generally influenced by interaction of filler and matrix at interface. Increasing filler-loading within the composite may cause spatial limitation toward best dispersion of filler, and since synthesizing a totally agglomerated-free nanocomposite is difficult, filler and matrix interaction needs to be perfectly modeled. A micromechanical model is developed in this study based on the common Halpin–Tsai theory to predict the elastic stiffness of vinyl ester/exfoliated graphite platelet nanocomposites. The model considers near-rational ideal (uniformly dispersed) mixed with clustered filler-network to simulate filler-distribution conditions. A filler-dispersion level based on the filler concentration has been proposed mathematically in this study. Predictions of the proposed model considering filler morphology were compared with the predictions of the Halpin–Tsai model and the experimentally obtained results as well. The proposed model sho...
Journal of Applied Polymer Science, 2010
This article discusses the viscoelastic behavior of a vinyl ester (Derakane 411-350) reinforced w... more This article discusses the viscoelastic behavior of a vinyl ester (Derakane 411-350) reinforced with 1.25 and 2.5 wt % nanoclay and exfoliated graphite nanoplatelets during short-term creep and relaxation tests with a dynamic mechanical analyzer. Linear viscoelastic models are generally composed of one or more elements such as dashpots and springs that represent the viscous and elastic properties. Stress relaxation data from the dynamic mechanical analyzer have been used to obtain the elastic parameters based on model constitutive equations. The standard linear solid model, which is a physical model, has been used for predicting the creep deformation behavior of the vinyl ester nanocomposites over a wide temperature range. Some correlations have been made with the mechanical model, such as the effect of temperature on the deformation behavior, which is well explained by the dashpot mechanism. At lower temperatures, higher creep compliance has been observed for the vinyl ester versus the nanocomposites, whereas at temperatures near the glass-transition temperature of the vinyl ester, creep compliance in the nanocomposites is closer in magnitude to that for the vinyl ester. The creep response of the pure vinyl ester and its nanocomposites appears to be modeled reasonably well at temperatures lower than their glass-transition temperatures. A comparison of the predictions and experimental data from the creep tests has demonstrated that this model can represent the long-term deformation behavior of these nanoreinforced materials reasonably well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Journal of Applied Polymer Science, 2012
Materials used in blast, penetration, and impact loaded structural applications require high stre... more Materials used in blast, penetration, and impact loaded structural applications require high strength and toughness under high strain rate loading. 510A-40 brominated bisphenol-A-based vinyl ester resin was developed and reinforced with different loadings of nanoclay and exfoliated graphite platelet to produce composites with optimal flexural rigidity, vibration damping, and enhanced energy absorption. As these reinforced polymeric materials are viscoelastic in principle, the mechanical behavior was characterized under two extremes of strain rate loading. In this article, the macroscopic response of brominated vinyl ester reinforced with 1.25 and 2.5 wt % nanoclay and exfoliated graphite platelet is considered. Air-blast experiment was conducted by subjecting these specimens to a high-transient pressure in a shock-tube with flexural loading configuration. The axial response was investigated quasi-statically in a uniaxial tension/compression test and dynamically in a compression Split-Hopkinson bar test. The servo-hydraulic MTS system was used to simulate the shock-tube testing in a flexural quasi-static loading configuration. High strain rate properties obtained from shock-tube experiment are compared with that of characterized under the simulated quasi-static flexural loading. Further, a computational finite element analysis model was developed in ANSYS LSDYNA to predict with reasonable accuracy the dynamic response of shock-loaded nanoreinforced specimens. Drop in both failure strain and energy absorption was observed with the addition of nanoparticles to pristine vinyl ester. However, an improvement in energy absorption was observed in case of shock-tube loading at high strain rates as compared to that loaded quasi-statically. V
Applied Mechanics and Materials, 2014
In this work, four Mg-Zn-Ce sheets were processed on an industrial scale by “Helholtz-ZentrumGree... more In this work, four Mg-Zn-Ce sheets were processed on an industrial scale by “Helholtz-ZentrumGreesthacht” company. To study the effect of alloying elements and annealing conditions on the rolled sheets, these sheets were annealed at different conditions. Mechanical properties of these rolled and annealed sheets were determined in rolling and transverse directions. Optical microscopy was used to investigate microstructure evolution and stability as well as grain size after annealing. Annealing at 450°C, 1 hr for A and D sheets provides microstructure stability of these sheets. Whereas, annealing B and C sheets for one hour at 400 and 350°C, respectively, provide the optimum annealing conditions. In the studied alloys, the highest zinc (Zn) presence alloyed with magnesium significantly increases the grain size and the amount of precipitates. Whereas, the highest cerium (Ce) presence alloyed with magnesium, refines the grain size during the recrystallization process.
... without the help and support of a great number of people. Perhaps the individual to whom I am... more ... without the help and support of a great number of people. Perhaps the individual to whom I am most indebted is Professor P. Raju Mantena, who has been my advisor, mentor and a source of support throughout my years of graduate study. His patience and willingness as ...
eXPRESS Polymer Letters, 2009
Fire, smoke and toxicity are of significant concern for composite materials used in marine applic... more Fire, smoke and toxicity are of significant concern for composite materials used in marine applications. Bromination of vinyl ester resin imparts fire retardancy as manifested by a reduction in the amount of smoke, carbon monoxide, and corrosive combustion products. In this research, the viscoelastic properties, modulus (stiffness) and damping (energy dissipation), of 1.25 and 2.5 wt. percent nanoclay and exfoliated graphite nanoplatelet (xGnP) reinforced non-brominated and brominated vinyl ester have been studied over a range of temperature and frequency. Effects of frequency on the viscoelastic behavior were investigated using a Dynamic Mechanical Analyzer (DMA) by sweeping the frequency over three decades: 0.01, 0.1, 1 and 10 Hz, and temperature range from 30-150°C at a step rate of 4°C per minute. Master curves were generated by time-temperature superposing the experimental data at a reference temperature. The nano reinforced composites showed a drop in initial storage modulus with bromination. Nanocomposites with 1.25 and 2.5 wt. percent graphite had the highest storage modulus among brominated specimens. Bromination was also found to significantly increase the glass transition temperature (Tg) and damping for all nanocomposites. Among the brominated specimens, 1.25 wt. percent graphite platelet reinforced vinyl ester exhibited the best viscoelastic response with high damping and glass transition temperature, along with superior storage modulus over a longer time period.
Green Energy and Technology, 2017
International Journal of Engineering Science
International Journal of Engineering Science
Green Energy and Technology, 2017
Research Journal of Applied Sciences, Engineering and Technology, 2014
This paper describes investigations on dynamic mechanical analysis (DMA) of nylon 6,6 thermoplast... more This paper describes investigations on dynamic mechanical analysis (DMA) of nylon 6,6 thermoplastic reinforced with 1.25 and 2.5 wt. percent multi-wall carbon nano tubes (MWCNT), and Derakane 411-350 vinyl ester thermoset reinforced with 1.25 and 2.5 wt. percent Cloisite 30B nanoclay and exfoliated graphite nanoplatelets (xGnP). Visco-elastic materials exhibit the characteristics of both elastic solid and viscous liquid. This dual behavior which is both time and temperature dependent has been characterized by dynamic oscillation and creep experiments performed at various isothermal temperatures. Viscoelastic properties such as storage modulus (E'), loss modulus (E"), damping, glass transition temperature (T g) and creep behavior were compared for the different nanocomposites. Short range creep tests were performed at isothermal conditions and the time-temperature superposition principle was utilized to generate creep-strain master curves at a reference temperature. An increase in storage modulus was observed with increasing reinforcements in all the cases. Glass transition temperature and loss factor also showed an increase for vinyl ester with nano clay and graphite platelets. For MWCNT /nylon 6,6 nanocomposites, a marginal decrease in loss factor was observed with increasing reinforcement of MWCNT while glass transition temperature remained almost the same. The effect of reinforcement greatly improved the creepresistance of both nylon 6,6 and vinyl ester, with 2.5 wt. percent nano clay /vinyl ester exhibiting the maximum creep-resistance. The extent of creep-strain increased with increasing temperature, with 2.5 wt. percent graphite /vinyl ester exhibiting the maximum relative creep at its glass transition temperature.
IET Science, Measurement & Technology, 2015
Thermodynamic modelling of Mn-Sn and Mn-Sr binary systems is carried out using the reliable data ... more Thermodynamic modelling of Mn-Sn and Mn-Sr binary systems is carried out using the reliable data from the literature. Thermodynamic properties of the binary liquid solutions are described using the modified quasi-chemical model. The calculated phase diagrams and the thermodynamic properties are found to be in good agreement with the experimental data from the literature. A self-consistent thermodynamic database for the Mg-Mn-{Sn, Sr} systems is constructed by combining the thermodynamic descriptions of their constituent binaries. The constructed database is used to calculate and predict liquidus projection and invariant reactions of these ternary systems. The Mg-Mn-Sr system has nine ternary eutectic reactions, two saddle points and eleven crystallisation fields. Mg-Mn-Sn has four saddle points, two quasi-peritectic and six ternary eutectic reactions.
Journal of Reinforced Plastics and Composites, 2015
Journal of Composite Materials
This study models the mechanical performance of thermoset polyamide filled with various percentag... more This study models the mechanical performance of thermoset polyamide filled with various percentages of glass beads using a coupling agent. A micromechanical model is developed for polyamide glass-bead composite containing three-phase zones with imperfect bonding across interfaces. The micromechanical/interface model uses square sub-region arrays representing particle, matrix, and interface zones to obtain the stress transfer behavior across the cohesive zone for a given microstructure. Understanding the stress transfer tool and interfacial adhesion across multi-coated inclusions, and developing accurate material models will help in establishing upcoming design criteria in the engineering of polymer based composites. The impact of this study comes from the fact that the diffusion quality and non-uniform distribution of inclusions within the polymer matrix, and weak bonding of filler to the polymer matrix, may result in an ineffective stress transfer, which in turn degrades the mechan...
This paper discusses the viscoelastic behavior of 1.25 and 2.5 wt. % nanoclay and graphite platel... more This paper discusses the viscoelastic behavior of 1.25 and 2.5 wt. % nanoclay and graphite platelet reinforced vinyl ester under short term creep and relaxation tests using a Dynamic Mechanical Analyzer (DMA). Linear viscoelastic models are generally composed of one or more elements such as dashpots and springs that represent the viscous and elastic properties. Stress relaxation data from DMA was used to obtain the elastic parameters based on model constitutive equations. The Standard Linear Solid (SLS) model, which is a physical model, was used for predicting the creep deformation behavior of the vinyl ester nanocomposites over a wide temperature range. This model was chosen because it can describe the stress relaxation and creep behavior of polymers and can also explain the two main deformations of plastics [1]; with the spring representing deformations due to bending and stretching of intermolecular bonds and dashpot represents deformation due to the viscous effect. Some correlat...
A micromechanical model is applied to examine the tensile properties of composite materials fille... more A micromechanical model is applied to examine the tensile properties of composite materials filled with multi-wall CNT oriented in in-plane and out-of-plane direction and a quantitative micromechanical model for the mechanical behavior of CNT-composites has been developed. Digimat-MF is used to generate a realistic three-dimensional microstructure for the current carbon nanotube/ epoxy composite. The Digimat model simulates a system of aligned carbon nanotubes arranged in-plane and another one having out of plane arrangement of reinforcements. A second model shows a representative volume element for the current nano-composite, in which the carbon nanotubes were simulated as a randomly (fully) dispersed, where all particles have been separated from each other. The predicted mechanical properties are compared with experimental tensile properties of composite materials reinforced with multi-wall CNTs arranged in in-plane and out-of-plane direction. A good agreement between the micromec...
The creep resistance of thermoset vinyl ester-based nanocomposites is studied by adding different... more The creep resistance of thermoset vinyl ester-based nanocomposites is studied by adding different weight percents of exfoliated graphite filler, characterized at different temperatures under constant loading. The creep response of these nanocomposites was analyzed using the TA Instruments Model Q800- DMA. Results showed that the nano-filler at some temperatures may hinder slippage and reorientation of polymer chain that, in turn, shows higher creep resistance for nanocomposites than the neat matrix. At a lower temperature, poor creep resistance was observed for neat matrix as compared to nano materials tested; however, at elevated temperatures (beyond the glass transition temperature), creep resistance in nanocomposites becomes close to that of neat vinyl ester. To fully understand the complex creep deformation of polymeric based nanocomposites, a physical modeling is conducted to study the structure-property relationship as a function of filler content. Parametric studies for the s...
This paper describes investigations on dynamic mechanical analysis (DMA) of nylon 6,6 thermoplast... more This paper describes investigations on dynamic mechanical analysis (DMA) of nylon 6,6 thermoplastic reinforced with 1.25 and 2.5 wt. percent multi-wall carbon nano tubes (MWCNT), and Derakane 411-350 vinyl ester thermoset reinforced with 1.25 and 2.5 wt. percent Cloisite 30B nanoclay and exfoliated graphite nanoplatelets (xGnP). Visco-elastic materials exhibit the characteristics of both elastic solid and viscous liquid. This dual behavior which is both time and temperature dependent has been characterized by dynamic oscillation and creep experiments performed at various isothermal temperatures. Viscoelastic properties such as storage modulus (E’), loss modulus (E”), damping, glass transition temperature (Tg) and creep behavior were compared for the different nanocomposites. Short range creep tests were performed at isothermal conditions and the time-temperature superposition principle was utilized to generate creep-strain master curves at a reference temperature. An increase in sto...
... without the help and support of a great number of people. Perhaps the individual to whom I am... more ... without the help and support of a great number of people. Perhaps the individual to whom I am most indebted is Professor P. Raju Mantena, who has been my advisor, mentor and a source of support throughout my years of graduate study. His patience and willingness as ...
Journal of Composite Materials, 2014
Mechanical response of nano-based composites is generally influenced by interaction of filler and... more Mechanical response of nano-based composites is generally influenced by interaction of filler and matrix at interface. Increasing filler-loading within the composite may cause spatial limitation toward best dispersion of filler, and since synthesizing a totally agglomerated-free nanocomposite is difficult, filler and matrix interaction needs to be perfectly modeled. A micromechanical model is developed in this study based on the common Halpin–Tsai theory to predict the elastic stiffness of vinyl ester/exfoliated graphite platelet nanocomposites. The model considers near-rational ideal (uniformly dispersed) mixed with clustered filler-network to simulate filler-distribution conditions. A filler-dispersion level based on the filler concentration has been proposed mathematically in this study. Predictions of the proposed model considering filler morphology were compared with the predictions of the Halpin–Tsai model and the experimentally obtained results as well. The proposed model sho...
Journal of Applied Polymer Science, 2010
This article discusses the viscoelastic behavior of a vinyl ester (Derakane 411-350) reinforced w... more This article discusses the viscoelastic behavior of a vinyl ester (Derakane 411-350) reinforced with 1.25 and 2.5 wt % nanoclay and exfoliated graphite nanoplatelets during short-term creep and relaxation tests with a dynamic mechanical analyzer. Linear viscoelastic models are generally composed of one or more elements such as dashpots and springs that represent the viscous and elastic properties. Stress relaxation data from the dynamic mechanical analyzer have been used to obtain the elastic parameters based on model constitutive equations. The standard linear solid model, which is a physical model, has been used for predicting the creep deformation behavior of the vinyl ester nanocomposites over a wide temperature range. Some correlations have been made with the mechanical model, such as the effect of temperature on the deformation behavior, which is well explained by the dashpot mechanism. At lower temperatures, higher creep compliance has been observed for the vinyl ester versus the nanocomposites, whereas at temperatures near the glass-transition temperature of the vinyl ester, creep compliance in the nanocomposites is closer in magnitude to that for the vinyl ester. The creep response of the pure vinyl ester and its nanocomposites appears to be modeled reasonably well at temperatures lower than their glass-transition temperatures. A comparison of the predictions and experimental data from the creep tests has demonstrated that this model can represent the long-term deformation behavior of these nanoreinforced materials reasonably well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Journal of Applied Polymer Science, 2012
Materials used in blast, penetration, and impact loaded structural applications require high stre... more Materials used in blast, penetration, and impact loaded structural applications require high strength and toughness under high strain rate loading. 510A-40 brominated bisphenol-A-based vinyl ester resin was developed and reinforced with different loadings of nanoclay and exfoliated graphite platelet to produce composites with optimal flexural rigidity, vibration damping, and enhanced energy absorption. As these reinforced polymeric materials are viscoelastic in principle, the mechanical behavior was characterized under two extremes of strain rate loading. In this article, the macroscopic response of brominated vinyl ester reinforced with 1.25 and 2.5 wt % nanoclay and exfoliated graphite platelet is considered. Air-blast experiment was conducted by subjecting these specimens to a high-transient pressure in a shock-tube with flexural loading configuration. The axial response was investigated quasi-statically in a uniaxial tension/compression test and dynamically in a compression Split-Hopkinson bar test. The servo-hydraulic MTS system was used to simulate the shock-tube testing in a flexural quasi-static loading configuration. High strain rate properties obtained from shock-tube experiment are compared with that of characterized under the simulated quasi-static flexural loading. Further, a computational finite element analysis model was developed in ANSYS LSDYNA to predict with reasonable accuracy the dynamic response of shock-loaded nanoreinforced specimens. Drop in both failure strain and energy absorption was observed with the addition of nanoparticles to pristine vinyl ester. However, an improvement in energy absorption was observed in case of shock-tube loading at high strain rates as compared to that loaded quasi-statically. V
Applied Mechanics and Materials, 2014
In this work, four Mg-Zn-Ce sheets were processed on an industrial scale by “Helholtz-ZentrumGree... more In this work, four Mg-Zn-Ce sheets were processed on an industrial scale by “Helholtz-ZentrumGreesthacht” company. To study the effect of alloying elements and annealing conditions on the rolled sheets, these sheets were annealed at different conditions. Mechanical properties of these rolled and annealed sheets were determined in rolling and transverse directions. Optical microscopy was used to investigate microstructure evolution and stability as well as grain size after annealing. Annealing at 450°C, 1 hr for A and D sheets provides microstructure stability of these sheets. Whereas, annealing B and C sheets for one hour at 400 and 350°C, respectively, provide the optimum annealing conditions. In the studied alloys, the highest zinc (Zn) presence alloyed with magnesium significantly increases the grain size and the amount of precipitates. Whereas, the highest cerium (Ce) presence alloyed with magnesium, refines the grain size during the recrystallization process.
... without the help and support of a great number of people. Perhaps the individual to whom I am... more ... without the help and support of a great number of people. Perhaps the individual to whom I am most indebted is Professor P. Raju Mantena, who has been my advisor, mentor and a source of support throughout my years of graduate study. His patience and willingness as ...
eXPRESS Polymer Letters, 2009
Fire, smoke and toxicity are of significant concern for composite materials used in marine applic... more Fire, smoke and toxicity are of significant concern for composite materials used in marine applications. Bromination of vinyl ester resin imparts fire retardancy as manifested by a reduction in the amount of smoke, carbon monoxide, and corrosive combustion products. In this research, the viscoelastic properties, modulus (stiffness) and damping (energy dissipation), of 1.25 and 2.5 wt. percent nanoclay and exfoliated graphite nanoplatelet (xGnP) reinforced non-brominated and brominated vinyl ester have been studied over a range of temperature and frequency. Effects of frequency on the viscoelastic behavior were investigated using a Dynamic Mechanical Analyzer (DMA) by sweeping the frequency over three decades: 0.01, 0.1, 1 and 10 Hz, and temperature range from 30-150°C at a step rate of 4°C per minute. Master curves were generated by time-temperature superposing the experimental data at a reference temperature. The nano reinforced composites showed a drop in initial storage modulus with bromination. Nanocomposites with 1.25 and 2.5 wt. percent graphite had the highest storage modulus among brominated specimens. Bromination was also found to significantly increase the glass transition temperature (Tg) and damping for all nanocomposites. Among the brominated specimens, 1.25 wt. percent graphite platelet reinforced vinyl ester exhibited the best viscoelastic response with high damping and glass transition temperature, along with superior storage modulus over a longer time period.
Green Energy and Technology, 2017
International Journal of Engineering Science
International Journal of Engineering Science
Green Energy and Technology, 2017
Research Journal of Applied Sciences, Engineering and Technology, 2014
This paper describes investigations on dynamic mechanical analysis (DMA) of nylon 6,6 thermoplast... more This paper describes investigations on dynamic mechanical analysis (DMA) of nylon 6,6 thermoplastic reinforced with 1.25 and 2.5 wt. percent multi-wall carbon nano tubes (MWCNT), and Derakane 411-350 vinyl ester thermoset reinforced with 1.25 and 2.5 wt. percent Cloisite 30B nanoclay and exfoliated graphite nanoplatelets (xGnP). Visco-elastic materials exhibit the characteristics of both elastic solid and viscous liquid. This dual behavior which is both time and temperature dependent has been characterized by dynamic oscillation and creep experiments performed at various isothermal temperatures. Viscoelastic properties such as storage modulus (E'), loss modulus (E"), damping, glass transition temperature (T g) and creep behavior were compared for the different nanocomposites. Short range creep tests were performed at isothermal conditions and the time-temperature superposition principle was utilized to generate creep-strain master curves at a reference temperature. An increase in storage modulus was observed with increasing reinforcements in all the cases. Glass transition temperature and loss factor also showed an increase for vinyl ester with nano clay and graphite platelets. For MWCNT /nylon 6,6 nanocomposites, a marginal decrease in loss factor was observed with increasing reinforcement of MWCNT while glass transition temperature remained almost the same. The effect of reinforcement greatly improved the creepresistance of both nylon 6,6 and vinyl ester, with 2.5 wt. percent nano clay /vinyl ester exhibiting the maximum creep-resistance. The extent of creep-strain increased with increasing temperature, with 2.5 wt. percent graphite /vinyl ester exhibiting the maximum relative creep at its glass transition temperature.
IET Science, Measurement & Technology, 2015
Thermodynamic modelling of Mn-Sn and Mn-Sr binary systems is carried out using the reliable data ... more Thermodynamic modelling of Mn-Sn and Mn-Sr binary systems is carried out using the reliable data from the literature. Thermodynamic properties of the binary liquid solutions are described using the modified quasi-chemical model. The calculated phase diagrams and the thermodynamic properties are found to be in good agreement with the experimental data from the literature. A self-consistent thermodynamic database for the Mg-Mn-{Sn, Sr} systems is constructed by combining the thermodynamic descriptions of their constituent binaries. The constructed database is used to calculate and predict liquidus projection and invariant reactions of these ternary systems. The Mg-Mn-Sr system has nine ternary eutectic reactions, two saddle points and eleven crystallisation fields. Mg-Mn-Sn has four saddle points, two quasi-peritectic and six ternary eutectic reactions.
Journal of Reinforced Plastics and Composites, 2015