Sasan Fooladpanjeh - Academia.edu (original) (raw)
Papers by Sasan Fooladpanjeh
Computational Materials Science, Dec 1, 2021
Abstract Graphene-like nanosheets are the key elements of advanced materials and systems. The mec... more Abstract Graphene-like nanosheets are the key elements of advanced materials and systems. The mechanical behavior of the structurally perfect 2D nanostructures is well documented, but that of polycrystalline ones is less understood. Herein, we applied molecular dynamics simulation (MDS) to take the fracture fingerprint of polycrystalline SiC nanosheets (PSiCNS), where monocrystalline SiC nanosheets (MSiCNS) was the reference nanosheet. The mechanical responses of defect-free and defective MSiCNS and PSiCNS having regular cracks and circular-shaped notches were captured as a function of temperature (100–1200 K), such that elevated temperatures were unconditionally deteriorative to the properties. Moreover, larger cracks and notches more severely decreased the strength of PSiCNS, e.g. Young’s modulus dropped to ca. 41% by the crack enlargement. The temperature rise similarly deteriorated the failure stress and Young's modulus of PSiCNS. However, the stress intensity factor increased by the enlargement of the crack length but decreased against temperature. We believe that the findings of the present study can shed some light on designing mechanically stable nanostructures for on-demand working conditions.
Journal of Molecular Graphics & Modelling, Sep 1, 2021
Boron carbide nanosheets (BC3NSs) are semiconductors possessing non-zero bandgap. Nevertheless, t... more Boron carbide nanosheets (BC3NSs) are semiconductors possessing non-zero bandgap. Nevertheless, there is no estimation of their thermal conductivity for practical circumstances, mainly because of difficulties in simulation of random polycrystalline structures. In the real physics world, BC3NS with perfect monocrystalline is rare, for the nature produces structures with disordered grain regions. Therefore, it is of crucial importance to capture a more realistic picture of thermal conductivity of these nanosheets. Polycrystalline BC3NS (PCBC3NSs are herein simulated by Molecular Dynamics simulation to take their thermal conductivity fingerprint applying ΔT of 40 K. A series of PCBC3NSs were evaluated for thermal conductivity varying the number of grains (3, 5, and 10). The effect of grain rotation was also modeled in terms of Kapitza thermal resistance per grain, varying the rotation angle (θ/2 = 14.5, 16, 19, and 25°). Overall, a non-linear temperature variation was observed for PCBC3NS, particularly by increasing grain number, possibly because of more phonon scattering (shorter phonon relaxation time) arising from more structural defects. By contrast, the heat current passing across the slab decreased. The thermal conductivity of nanosheet dwindled from 149 W m-1 K-1 for monocrystalline BC3NS to the values of 129.67, 121.32, 115.04, and 102.78 W m-1 K-1 for PCBC3NSs having 2, 3, 5, and 10 grains, respectively. The increase of the grain̛s rotation angle (randomness) from 14.5° to 16°, 19° and 25° led to a rise in Kapitza thermal resistance from 2⨯10-10 m2 K·W-1 to the values of 2.3⨯ 10-10, 2.9⨯10-10, and 4.7⨯ 10-10 m2 K·W-1, respectively. Thus, natural 2D structure would facilitate phonon scattering rate at the grain boundaries, which limits heat transfer across polycrystalline nanosheets.
Materials
Thermal control systems have been introduced as an important part of electronic devices, enabling... more Thermal control systems have been introduced as an important part of electronic devices, enabling thermal management of their electronic components. Loop heat pipe (LHP) is a passive two-phase heat transfer device with significant potential for numerous applications, such as aerospace applications, high-power LEDs, and solar central receivers. Its advantages are high heat transfer capability, low thermal resistance, long-distance heat transfer, and compact structure. The essential role of wick structures on the performance of LHPs has already been highlighted, but no comprehensive review is available that deals with different parameters such as LHP design and wick size, which are largely decisive and effective in achieving a practical level of thermal transmission governed by wick structures. To rely on this necessity, this article summarizes, analyzes, and classifies advancements in the design and fabrication of wick structures. The main conclusion to be drawn after careful monitor...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2020
In many industries, it is necessary to use structures that exhibit a proper stability against the... more In many industries, it is necessary to use structures that exhibit a proper stability against the design loads and depreciate the energy in a controlled manner. In this study, the energy absorption characteristics of thin-walled structures with rectangular cross sections are investigated under the quasi-static loading. The section of structures has a different aspect ratio, and in all of them, an elliptical cutout with a different diameter ratio exists on the larger side. In all instances, the area of the cross section and cutout is constant. Hence, an experimental design with two design parameters consisting of the shell aspect ratio and the diameter ratio of the cutout was conducted by applying the central composite design method. Energy absorption parameters were modeled using the artificial neural network and the response surface method. A systematic crashworthiness study was carried out with a multi-objective optimization design using the genetic algorithm. The results showed that the optimal amount of the specific energy absorption was 14.48 kJ/kg and the optimal amount of the peak crushing load was 37.77 kN which was obtained in the aspect ratio of 1 and the diameter ratio of 0.7. The validity of the results was confirmed by empirical experiments.
In the paper, we present results of stress analysis in domains which are a mixture of solid and l... more In the paper, we present results of stress analysis in domains which are a mixture of solid and liquid phases. Such mixtures occur in solidifying castings and are a result of forming a structure with solid skeleton and filling of a liquid phase. In this structure, stress occurs due to the appearance of temperature gradients, different values of material properties for the solid and liquid phase, and the appearance of friction forces between the solidified part of the casting and the mold on a macroscopic scale. This can lead to casting defects, such as hot cracking. The results are obtained with the use of a authors computer program based on the Finite Element Method. The stress analysis takes into account the elastic-plastic state of considered computational area. The presented results are focused on the microscopic scale, for which a finite element mesh is created which imitates the growing grains of the metal alloy in the casting, on the basis of macroscopic parameters.
Journal of Materials Engineering and Performance, 2021
In this work, an experimental study on the quasi-static collapse of thin-walled frusta of silica/... more In this work, an experimental study on the quasi-static collapse of thin-walled frusta of silica/epoxy nano-composites was conducted. The effect of nano-silica content and the particle size hybrid on the energy absorption capability of thin-walled frusta, the impact strength, Young’s modulus, and the yield strength was investigated. For this purpose, three various sizes of the silica particle with the mean diameter of 17, 25, and 65 nm were used. The results showed that by adding the silica nano-particles up to 6 wt.%, the impact strength and Young’s modulus increased, the yield strength remained constant, and the crashworthy capability of structures decreased. Also, two approaches including Fuzzy Neural Network, the hybrid of Particle Swarm Optimization (PSO), and Multivariate Nonlinear Regression (MNLR) were employed to determine the effect of the mentioned parameters. In comparison with the mentioned models and the experimental results, PSO/MNLR approach showed a better prediction for the parameters. Different parameters were optimized by Gene Expression Programming. Some fracture surfaces were studied by scanning the electron microscopy.
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2019
This study is focused on the role of hydroxyapatite (HA) nanoparticles and graphene oxide (GO) na... more This study is focused on the role of hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanoplates on the flexural and compression properties of epoxy-based hybrid nanocomposites. In the first step, epoxy-based hybrid nanocomposites were reinforced by different HA nanoparticles and GO nanoplates up to 7 wt% and 0.5 wt%, respectively. Filler’s weight fractions that used as design parameters have been achieved by central composite design method in Minitab software. The experimental results showed different combinations of HA- and GO-enhanced mentioned mechanical properties in various states. In the second step, a statistical modeling has been done by response surface method (RSM), artificial neural network (ANN) and decision tree methods. Modeling results showed that ANN and decision tree methods have the best fitness. Finally, the mechanical properties are optimized by genetic algorithm. The optimum values are 21.54 MPa for flexural strength in 5.17 wt% HA and 0.38 wt% Go and 25.7 GPa for flexural modulus in 2.73 wt% HA and 0.195 wt% GO. Also, the optimum results for compression strength are 23.95 MPa in 7 wt% HA and 0.289 wt% GO, and also 690.5 MPa for compression modulus in 6.89 wt% HA and 0.007 wt% GO. Effective mechanisms of fillers have been analyzed by SEM and observed that debonding, crack path deflection, plastic void growth and pullout were dominant.
Transactions of the Indian Institute of Metals, 2018
In this paper, the crashworthiness of steel thin-walled square columns was investigated. These st... more In this paper, the crashworthiness of steel thin-walled square columns was investigated. These structures were reinforced with three types of reinforcers. The first type was aluminum shells which were placed inside the steel columns based on a specific fractal geometry, and two other types were aluminum and polyurethane foams. All samples were placed under axial loading, and fractals were thinned out up to three stages. At each stage, the effectiveness of aluminum shells alone and also in the presence of polyurethane and aluminum foams has been investigated. Also, the effect of foams' location and in or out of fractal geometry, was studied. The results showed that the presence of reinforcers with different geometries and materials improved the energy absorption. As the fractal geometry of the reinforcers becomes smaller, the energy absorption capacity increases. The presence of the foams well compensated the load–displacement diagram drop after the initial peak and made the energy absorption behavior more ideal. On the other hand, polyurethane foam showed a significant effect on buckling control so that in one of the samples it prevented buckling. Comparison of the studied samples showed that the energy absorption was better when polyurethane foam prevailed. The effect of the second-stage fractal geometry was almost twice the fractal geometry of the first stage. The best choice among the discussed examples was an absorbent in the second stage with foam, in which the polyurethane foam predominated. Finally, some results were validated.
Engineering Fracture Mechanics, 2020
Abstract The main purpose of this study was to examine, modelling and optimization the fracture t... more Abstract The main purpose of this study was to examine, modelling and optimization the fracture toughness and the fracture energy of bisphenol-A epoxy resin reinforced by silica nano-particles. Three different approaches including Gene Expression Programming (GEP), Response Surface Method (RSM) and, Decision Tree Method (DTM) have been employed to predict the effects of particle size and the weight fraction of nano-particles on the mentioned parameters. Three sizes of the nano-particles with the mean diameters of 17 nm, 25 nm and 65 nm up to 6 wt% have been used. The two general series of the nano-composites consisting of unimodal and bimodal particle size systems have been investigated. Experimental and modelling results showed that the Young’s modulus, the fracture toughness and the fracture energy increased in all composites by the addition of the silica nano-particles and also by increasing the silica weight percent. In addition, it was observed that the particle size had no considerable effect on the properties. Mixed use of particles with different sizes in a composite also showed a negligible synergy effect on the Young’s modulus and the fracture characteristics. The addition of these nano-particles did not have a significant effect on the yield strength of composites. Moreover, the best modelling approach is selected and optimized values resulted by Particle Swarm Optimization (PSO). The fracture surface was examined to understand the role of nanoparticles on toughening mechanisms by SEM.
A modelling of fracture toughness (KIC), fracture energy (GIC) and Young's modulus of styrene... more A modelling of fracture toughness (KIC), fracture energy (GIC) and Young's modulus of styrene acrylonitrile composites by two volume content of 24% and 34% acrylonitrile has been conducted. ZnO nanoparticles were added to composites up to 1 vt%. Volume percent of nanoparticles and acrylonitrile’s content has been used as input parameters for ANN, RSM and regression tree modelling. The results of modeling showed that the second order response surface method makes the best prediction. Additionally, the selected model optimized by binary GA. Based on this optimization, the best value for Fracture toughness is 2.283 MPa.m1/2 when the volume percent of styrene acrylonitrile is 34% and volume percent of ZnO is 0.1%. Also, the best value for fracture energy is equal to 1101 J/m2, when the volume percent of styrene acrylonitrile is 34% and the volume percent of ZnO is 0.33%. And finally, this method shows that the best value for Young's modulus is 4.281 GPa when the volume percent o...
One way to enhance the mechanical properties of nanocomposites has been to use different fillers.... more One way to enhance the mechanical properties of nanocomposites has been to use different fillers. In this study, ternary hybrid composites of graphene oxide/hydroxyapatite/epoxy resin were investig...
Journal of Molecular Graphics and Modelling
Computational Materials Science
Computational Materials Science
Journal of Molecular Graphics and Modelling
This study is focused on the role of hydroxyapatite (HA) nanoparticles and graphene oxide (GO) na... more This study is focused on the role of hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanoplates on the flexural and compression properties of epoxy-based hybrid nanocomposites. In the first step, epoxy-based hybrid nanocomposites were reinforced by different HA nanoparticles and GO nanoplates up to 7 wt% and 0.5 wt%, respectively. Filler's weight fractions that used as design parameters have been achieved by central composite design method in Minitab software. The experimental results showed different combinations of HA-and GO-enhanced mentioned mechanical properties in various states. In the second step, a statistical modeling has been done by response surface method (RSM), artificial neural network (ANN) and decision tree methods. Modeling results showed that ANN and decision tree methods have the best fitness. Finally, the mechanical properties are optimized by genetic algorithm. The optimum values are 21.54 MPa for flexural strength in 5.17 wt% HA and 0.38 wt% Go and 25.7 GPa for flexural modulus in 2.73 wt% HA and 0.195 wt% GO. Also, the optimum results for compression strength are 23.95 MPa in 7 wt% HA and 0.289 wt% GO, and also 690.5 MPa for compression modulus in 6.89 wt% HA and 0.007 wt% GO. Effective mechanisms of fillers have been analyzed by SEM and observed that debonding, crack path deflection, plastic void growth and pullout were dominant.
In this paper, the crashworthiness of steel thin-walled square columns was investigated. These st... more In this paper, the crashworthiness of steel thin-walled square columns was investigated. These structures were reinforced with three types of reinforcers. The first type was aluminum shells which were placed inside the steel columns based on a specific fractal geometry, and two other types were aluminum and polyurethane foams. All samples were placed under axial loading, and fractals were thinned out up to three stages. At each stage, the effectiveness of aluminum shells alone and also in the presence of polyurethane and aluminum foams has been investigated. Also, the effect of foams' location and in or out of fractal geometry, was studied. The results showed that the presence of reinforcers with different geometries and materials improved the energy absorption. As the fractal geometry of the reinforcers becomes smaller, the energy absorption capacity increases. The presence of the foams well compensated the load-displacement diagram drop after the initial peak and made the energy absorption behavior more ideal. On the other hand, polyurethane foam showed a significant effect on buckling control so that in one of the samples it prevented buckling. Comparison of the studied samples showed that the energy absorption was better when polyurethane foam prevailed. The effect of the second-stage fractal geometry was almost twice the fractal geometry of the first stage. The best choice among the discussed examples was an absorbent in the second stage with foam, in which the polyurethane foam predominated. Finally, some results were validated.
In this paper, Structures are investigated by collapse test and loading will be quasi-static. As ... more In this paper, Structures are investigated by collapse test and loading will be quasi-static. As is evident, doing an experiment always containing cost and time. So by designing the experiment can be spending the minimum cost and time،get the most information about the process. This structure was investigated by two parameters side's ratio and slot location. The results showed that the maximum value of energy absorption parameters were achieved in side's ratio 2 and perforation's diameter 0.5. The reported results are 1.47 KJ for absorbed energy, 19.61 KN for mean crushing load, 15.05 KJ/Kg for specific energy absorption and 37.5 KN for peak load.
In this paper, the energy absorption parameters of walls with rectangular cross section are inves... more In this paper, the energy absorption parameters of walls with rectangular cross section are investigated. The ratio of the sides and sides of the diameters are two main parameters for conducting the analysis. Analysis has been done by ABAQUS software and the obtained result indicates that the best values of the energy absorption parameters are 39.88 KN for peak load and sample D; 19.61 KN for mean load crushing and sample A; 1.47 KJ for energy absorption and sample A and 15.05 KJ/Kg for the specific absorbed energy and sample A reported. Also, according to the modeling results, the response surface method was choosing as the selected model. The results of optimization using the genetic algorithm showed an optimal amount of specific energy absorption was equal to 14.51 KJ/Kg, in the ratio of the sides 2 and side's diameter 0.67 was achieved.
Computational Materials Science, Dec 1, 2021
Abstract Graphene-like nanosheets are the key elements of advanced materials and systems. The mec... more Abstract Graphene-like nanosheets are the key elements of advanced materials and systems. The mechanical behavior of the structurally perfect 2D nanostructures is well documented, but that of polycrystalline ones is less understood. Herein, we applied molecular dynamics simulation (MDS) to take the fracture fingerprint of polycrystalline SiC nanosheets (PSiCNS), where monocrystalline SiC nanosheets (MSiCNS) was the reference nanosheet. The mechanical responses of defect-free and defective MSiCNS and PSiCNS having regular cracks and circular-shaped notches were captured as a function of temperature (100–1200 K), such that elevated temperatures were unconditionally deteriorative to the properties. Moreover, larger cracks and notches more severely decreased the strength of PSiCNS, e.g. Young’s modulus dropped to ca. 41% by the crack enlargement. The temperature rise similarly deteriorated the failure stress and Young's modulus of PSiCNS. However, the stress intensity factor increased by the enlargement of the crack length but decreased against temperature. We believe that the findings of the present study can shed some light on designing mechanically stable nanostructures for on-demand working conditions.
Journal of Molecular Graphics & Modelling, Sep 1, 2021
Boron carbide nanosheets (BC3NSs) are semiconductors possessing non-zero bandgap. Nevertheless, t... more Boron carbide nanosheets (BC3NSs) are semiconductors possessing non-zero bandgap. Nevertheless, there is no estimation of their thermal conductivity for practical circumstances, mainly because of difficulties in simulation of random polycrystalline structures. In the real physics world, BC3NS with perfect monocrystalline is rare, for the nature produces structures with disordered grain regions. Therefore, it is of crucial importance to capture a more realistic picture of thermal conductivity of these nanosheets. Polycrystalline BC3NS (PCBC3NSs are herein simulated by Molecular Dynamics simulation to take their thermal conductivity fingerprint applying ΔT of 40 K. A series of PCBC3NSs were evaluated for thermal conductivity varying the number of grains (3, 5, and 10). The effect of grain rotation was also modeled in terms of Kapitza thermal resistance per grain, varying the rotation angle (θ/2 = 14.5, 16, 19, and 25°). Overall, a non-linear temperature variation was observed for PCBC3NS, particularly by increasing grain number, possibly because of more phonon scattering (shorter phonon relaxation time) arising from more structural defects. By contrast, the heat current passing across the slab decreased. The thermal conductivity of nanosheet dwindled from 149 W m-1 K-1 for monocrystalline BC3NS to the values of 129.67, 121.32, 115.04, and 102.78 W m-1 K-1 for PCBC3NSs having 2, 3, 5, and 10 grains, respectively. The increase of the grain̛s rotation angle (randomness) from 14.5° to 16°, 19° and 25° led to a rise in Kapitza thermal resistance from 2⨯10-10 m2 K·W-1 to the values of 2.3⨯ 10-10, 2.9⨯10-10, and 4.7⨯ 10-10 m2 K·W-1, respectively. Thus, natural 2D structure would facilitate phonon scattering rate at the grain boundaries, which limits heat transfer across polycrystalline nanosheets.
Materials
Thermal control systems have been introduced as an important part of electronic devices, enabling... more Thermal control systems have been introduced as an important part of electronic devices, enabling thermal management of their electronic components. Loop heat pipe (LHP) is a passive two-phase heat transfer device with significant potential for numerous applications, such as aerospace applications, high-power LEDs, and solar central receivers. Its advantages are high heat transfer capability, low thermal resistance, long-distance heat transfer, and compact structure. The essential role of wick structures on the performance of LHPs has already been highlighted, but no comprehensive review is available that deals with different parameters such as LHP design and wick size, which are largely decisive and effective in achieving a practical level of thermal transmission governed by wick structures. To rely on this necessity, this article summarizes, analyzes, and classifies advancements in the design and fabrication of wick structures. The main conclusion to be drawn after careful monitor...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2020
In many industries, it is necessary to use structures that exhibit a proper stability against the... more In many industries, it is necessary to use structures that exhibit a proper stability against the design loads and depreciate the energy in a controlled manner. In this study, the energy absorption characteristics of thin-walled structures with rectangular cross sections are investigated under the quasi-static loading. The section of structures has a different aspect ratio, and in all of them, an elliptical cutout with a different diameter ratio exists on the larger side. In all instances, the area of the cross section and cutout is constant. Hence, an experimental design with two design parameters consisting of the shell aspect ratio and the diameter ratio of the cutout was conducted by applying the central composite design method. Energy absorption parameters were modeled using the artificial neural network and the response surface method. A systematic crashworthiness study was carried out with a multi-objective optimization design using the genetic algorithm. The results showed that the optimal amount of the specific energy absorption was 14.48 kJ/kg and the optimal amount of the peak crushing load was 37.77 kN which was obtained in the aspect ratio of 1 and the diameter ratio of 0.7. The validity of the results was confirmed by empirical experiments.
In the paper, we present results of stress analysis in domains which are a mixture of solid and l... more In the paper, we present results of stress analysis in domains which are a mixture of solid and liquid phases. Such mixtures occur in solidifying castings and are a result of forming a structure with solid skeleton and filling of a liquid phase. In this structure, stress occurs due to the appearance of temperature gradients, different values of material properties for the solid and liquid phase, and the appearance of friction forces between the solidified part of the casting and the mold on a macroscopic scale. This can lead to casting defects, such as hot cracking. The results are obtained with the use of a authors computer program based on the Finite Element Method. The stress analysis takes into account the elastic-plastic state of considered computational area. The presented results are focused on the microscopic scale, for which a finite element mesh is created which imitates the growing grains of the metal alloy in the casting, on the basis of macroscopic parameters.
Journal of Materials Engineering and Performance, 2021
In this work, an experimental study on the quasi-static collapse of thin-walled frusta of silica/... more In this work, an experimental study on the quasi-static collapse of thin-walled frusta of silica/epoxy nano-composites was conducted. The effect of nano-silica content and the particle size hybrid on the energy absorption capability of thin-walled frusta, the impact strength, Young’s modulus, and the yield strength was investigated. For this purpose, three various sizes of the silica particle with the mean diameter of 17, 25, and 65 nm were used. The results showed that by adding the silica nano-particles up to 6 wt.%, the impact strength and Young’s modulus increased, the yield strength remained constant, and the crashworthy capability of structures decreased. Also, two approaches including Fuzzy Neural Network, the hybrid of Particle Swarm Optimization (PSO), and Multivariate Nonlinear Regression (MNLR) were employed to determine the effect of the mentioned parameters. In comparison with the mentioned models and the experimental results, PSO/MNLR approach showed a better prediction for the parameters. Different parameters were optimized by Gene Expression Programming. Some fracture surfaces were studied by scanning the electron microscopy.
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2019
This study is focused on the role of hydroxyapatite (HA) nanoparticles and graphene oxide (GO) na... more This study is focused on the role of hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanoplates on the flexural and compression properties of epoxy-based hybrid nanocomposites. In the first step, epoxy-based hybrid nanocomposites were reinforced by different HA nanoparticles and GO nanoplates up to 7 wt% and 0.5 wt%, respectively. Filler’s weight fractions that used as design parameters have been achieved by central composite design method in Minitab software. The experimental results showed different combinations of HA- and GO-enhanced mentioned mechanical properties in various states. In the second step, a statistical modeling has been done by response surface method (RSM), artificial neural network (ANN) and decision tree methods. Modeling results showed that ANN and decision tree methods have the best fitness. Finally, the mechanical properties are optimized by genetic algorithm. The optimum values are 21.54 MPa for flexural strength in 5.17 wt% HA and 0.38 wt% Go and 25.7 GPa for flexural modulus in 2.73 wt% HA and 0.195 wt% GO. Also, the optimum results for compression strength are 23.95 MPa in 7 wt% HA and 0.289 wt% GO, and also 690.5 MPa for compression modulus in 6.89 wt% HA and 0.007 wt% GO. Effective mechanisms of fillers have been analyzed by SEM and observed that debonding, crack path deflection, plastic void growth and pullout were dominant.
Transactions of the Indian Institute of Metals, 2018
In this paper, the crashworthiness of steel thin-walled square columns was investigated. These st... more In this paper, the crashworthiness of steel thin-walled square columns was investigated. These structures were reinforced with three types of reinforcers. The first type was aluminum shells which were placed inside the steel columns based on a specific fractal geometry, and two other types were aluminum and polyurethane foams. All samples were placed under axial loading, and fractals were thinned out up to three stages. At each stage, the effectiveness of aluminum shells alone and also in the presence of polyurethane and aluminum foams has been investigated. Also, the effect of foams' location and in or out of fractal geometry, was studied. The results showed that the presence of reinforcers with different geometries and materials improved the energy absorption. As the fractal geometry of the reinforcers becomes smaller, the energy absorption capacity increases. The presence of the foams well compensated the load–displacement diagram drop after the initial peak and made the energy absorption behavior more ideal. On the other hand, polyurethane foam showed a significant effect on buckling control so that in one of the samples it prevented buckling. Comparison of the studied samples showed that the energy absorption was better when polyurethane foam prevailed. The effect of the second-stage fractal geometry was almost twice the fractal geometry of the first stage. The best choice among the discussed examples was an absorbent in the second stage with foam, in which the polyurethane foam predominated. Finally, some results were validated.
Engineering Fracture Mechanics, 2020
Abstract The main purpose of this study was to examine, modelling and optimization the fracture t... more Abstract The main purpose of this study was to examine, modelling and optimization the fracture toughness and the fracture energy of bisphenol-A epoxy resin reinforced by silica nano-particles. Three different approaches including Gene Expression Programming (GEP), Response Surface Method (RSM) and, Decision Tree Method (DTM) have been employed to predict the effects of particle size and the weight fraction of nano-particles on the mentioned parameters. Three sizes of the nano-particles with the mean diameters of 17 nm, 25 nm and 65 nm up to 6 wt% have been used. The two general series of the nano-composites consisting of unimodal and bimodal particle size systems have been investigated. Experimental and modelling results showed that the Young’s modulus, the fracture toughness and the fracture energy increased in all composites by the addition of the silica nano-particles and also by increasing the silica weight percent. In addition, it was observed that the particle size had no considerable effect on the properties. Mixed use of particles with different sizes in a composite also showed a negligible synergy effect on the Young’s modulus and the fracture characteristics. The addition of these nano-particles did not have a significant effect on the yield strength of composites. Moreover, the best modelling approach is selected and optimized values resulted by Particle Swarm Optimization (PSO). The fracture surface was examined to understand the role of nanoparticles on toughening mechanisms by SEM.
A modelling of fracture toughness (KIC), fracture energy (GIC) and Young's modulus of styrene... more A modelling of fracture toughness (KIC), fracture energy (GIC) and Young's modulus of styrene acrylonitrile composites by two volume content of 24% and 34% acrylonitrile has been conducted. ZnO nanoparticles were added to composites up to 1 vt%. Volume percent of nanoparticles and acrylonitrile’s content has been used as input parameters for ANN, RSM and regression tree modelling. The results of modeling showed that the second order response surface method makes the best prediction. Additionally, the selected model optimized by binary GA. Based on this optimization, the best value for Fracture toughness is 2.283 MPa.m1/2 when the volume percent of styrene acrylonitrile is 34% and volume percent of ZnO is 0.1%. Also, the best value for fracture energy is equal to 1101 J/m2, when the volume percent of styrene acrylonitrile is 34% and the volume percent of ZnO is 0.33%. And finally, this method shows that the best value for Young's modulus is 4.281 GPa when the volume percent o...
One way to enhance the mechanical properties of nanocomposites has been to use different fillers.... more One way to enhance the mechanical properties of nanocomposites has been to use different fillers. In this study, ternary hybrid composites of graphene oxide/hydroxyapatite/epoxy resin were investig...
Journal of Molecular Graphics and Modelling
Computational Materials Science
Computational Materials Science
Journal of Molecular Graphics and Modelling
This study is focused on the role of hydroxyapatite (HA) nanoparticles and graphene oxide (GO) na... more This study is focused on the role of hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanoplates on the flexural and compression properties of epoxy-based hybrid nanocomposites. In the first step, epoxy-based hybrid nanocomposites were reinforced by different HA nanoparticles and GO nanoplates up to 7 wt% and 0.5 wt%, respectively. Filler's weight fractions that used as design parameters have been achieved by central composite design method in Minitab software. The experimental results showed different combinations of HA-and GO-enhanced mentioned mechanical properties in various states. In the second step, a statistical modeling has been done by response surface method (RSM), artificial neural network (ANN) and decision tree methods. Modeling results showed that ANN and decision tree methods have the best fitness. Finally, the mechanical properties are optimized by genetic algorithm. The optimum values are 21.54 MPa for flexural strength in 5.17 wt% HA and 0.38 wt% Go and 25.7 GPa for flexural modulus in 2.73 wt% HA and 0.195 wt% GO. Also, the optimum results for compression strength are 23.95 MPa in 7 wt% HA and 0.289 wt% GO, and also 690.5 MPa for compression modulus in 6.89 wt% HA and 0.007 wt% GO. Effective mechanisms of fillers have been analyzed by SEM and observed that debonding, crack path deflection, plastic void growth and pullout were dominant.
In this paper, the crashworthiness of steel thin-walled square columns was investigated. These st... more In this paper, the crashworthiness of steel thin-walled square columns was investigated. These structures were reinforced with three types of reinforcers. The first type was aluminum shells which were placed inside the steel columns based on a specific fractal geometry, and two other types were aluminum and polyurethane foams. All samples were placed under axial loading, and fractals were thinned out up to three stages. At each stage, the effectiveness of aluminum shells alone and also in the presence of polyurethane and aluminum foams has been investigated. Also, the effect of foams' location and in or out of fractal geometry, was studied. The results showed that the presence of reinforcers with different geometries and materials improved the energy absorption. As the fractal geometry of the reinforcers becomes smaller, the energy absorption capacity increases. The presence of the foams well compensated the load-displacement diagram drop after the initial peak and made the energy absorption behavior more ideal. On the other hand, polyurethane foam showed a significant effect on buckling control so that in one of the samples it prevented buckling. Comparison of the studied samples showed that the energy absorption was better when polyurethane foam prevailed. The effect of the second-stage fractal geometry was almost twice the fractal geometry of the first stage. The best choice among the discussed examples was an absorbent in the second stage with foam, in which the polyurethane foam predominated. Finally, some results were validated.
In this paper, Structures are investigated by collapse test and loading will be quasi-static. As ... more In this paper, Structures are investigated by collapse test and loading will be quasi-static. As is evident, doing an experiment always containing cost and time. So by designing the experiment can be spending the minimum cost and time،get the most information about the process. This structure was investigated by two parameters side's ratio and slot location. The results showed that the maximum value of energy absorption parameters were achieved in side's ratio 2 and perforation's diameter 0.5. The reported results are 1.47 KJ for absorbed energy, 19.61 KN for mean crushing load, 15.05 KJ/Kg for specific energy absorption and 37.5 KN for peak load.
In this paper, the energy absorption parameters of walls with rectangular cross section are inves... more In this paper, the energy absorption parameters of walls with rectangular cross section are investigated. The ratio of the sides and sides of the diameters are two main parameters for conducting the analysis. Analysis has been done by ABAQUS software and the obtained result indicates that the best values of the energy absorption parameters are 39.88 KN for peak load and sample D; 19.61 KN for mean load crushing and sample A; 1.47 KJ for energy absorption and sample A and 15.05 KJ/Kg for the specific absorbed energy and sample A reported. Also, according to the modeling results, the response surface method was choosing as the selected model. The results of optimization using the genetic algorithm showed an optimal amount of specific energy absorption was equal to 14.51 KJ/Kg, in the ratio of the sides 2 and side's diameter 0.67 was achieved.