جستجوی مقالات مرتبط با کلیدواژه « نانوکامپوزیت » در نشریات گروه « مکانیک »

In this research, the load-bearing capacities of epoxy-based nanocomposite specimens containing rounded-tip V-shaped notches made of epoxy resin LR 630 and nanographene oxide were studied both experimentally and theoretically under pure opening mode conditions. In order to fabricate the studied specimens, first, the tensile properties and fracture toughness of pure epoxy resin and nanocomposite materials were determined by uniaxial monotonic tension and three-point bending tests. Rectangular plates containing a central rhombic hole with four blunt V-shaped corners with a notch angle of 60° and radii of 1, 2, and 4 mm were utilized as the samples for fracture tests. Then, the samples were subjected to uniaxial tensile loading, and their load-carrying capacities (LCC) were measured. For theoretical predictions, due to the ductile behavior of the studied specimens, a combination of the equivalent material concept (EMC) with the well-known brittle fracture criterion, maximum tangential stress (MTS), was employed. Then, experimental and theoretical results were compared. The results of the experiment showed that by adding nanoparticles to the epoxy resin, its strength improved by about 8%, and it was found that the maximum discrepancy between the theoretical and experimental results was related to the groove with a radius of 4 mm, approximately 9.2%. Finally, it was observed that the new criterion (EMC-MTS) could predict the experimental results well without performing any time-consuming and complex elastic-plastic analysis.

In the present investigation a new severe plastic deformation method called accumulative channel-die compression bonding (ACCB) was adapted for fabrication of Al1050-carbon nanotube (CNT) composites. Microstructure and mechanical properties of Al1050 matrix material and synthesized composites were analyzed using SEM and tensile testing. The obtained results showed that the average grain size of matrix is reduced to 7 and 4 μm after one and two passes of ACCB respectively. Processed composites and Al1050 showed a limited homogeneous plastic deformation indicating the limited work hardening capacity due to the high dislocation densities developed during ACCB process. Also, the tensile strength of Al1050-CNT composites was increased with increase in deformation passes. It was demonstrated that different mechanisms are responsible for improved mechanical properties including the increase in dislocation density and reinforcement fraction and grain refinement by plastic deformation. Fractured surface were showed a combination of ductile and brittle failure during tensile deformation.

In recent years, additive manufacturing has gained significant importance in the field of production. Most of the additive manufacturing technologies for metals involve melting and solidification processes, leading to metallurgical challenges. The friction stir additive manufacturing process is a novel solid-state method that does not face the common metallurgical challenges associated with the traditional melting methods. This process can be used for the production of aluminum-silicon carbide nanocomposites that find many applications in industries such as military, aerospace, automotive, etc. The primary objective of this research is to experimentally analyze the effect of tool rotational speed, tool traverse speed, and number of passes in friction stir additive manufacturing on the microhardness and wear amount of aluminum-silicon carbide nanocomposite manufactured by this method. To this end, the response surface method and Minitab software were used for experimental design, statistical analysis, and optimization of the parameters. Multi-objective optimization settings were selected to increase microhardness and reduce wear. The combinations of optimal values of the parameters were determined to achieve the optimization goals, and the results were validated. The optimization result with 0.87 desirability is obtained with a tool rotational speed of 1000 rpm, a tool traverse speed of 50 mm/min, and one pass. The predicted optimal responses of 104 Vickers for microhardness and 0.013 gr for wear had a small percentage of error compared to the experimental results.

In this study, a nanocomposite based on polyvinyl chloride (PVC)/nitrile butadiene rubber (NBR)/Graphene nanoplates was prepared by melt mixing method. The response surface methodology (RSM) was employed to investigate the effect of weight percentages of NBR elastomer and graphene nanosheets on the mechanical properties (tensile strength and elongation at break) of the PVC/NBR/graphene nanocomposite. Mathematical relationships for the mechanical properties of the nanocomposite were presented using analysis of variance (ANOVA) table, and the degree of influence of each material parameter on the mechanical properties was studied. The comparison of mathematical relationships and experimental results showed low error. Additionally, the microstructure of the samples was examined using scanning electron microscope (SEM) to confirm the results. The results showed that by increasing the weight percentage of graphene nanosheets from 0 to 2% and decreasing NBR from 40 to 20% weight percentage in the nanocomposite, the tensile strength increases while the elongation at break decreases. By optimizing the mechanical properties to achieve maximum tensile strength (15.4 MPa) and maximum elongation at break (107.6%), the weight percentages of graphene nanosheets and NBR will be respectively 0.81 and 35.18%.

In this study, the production of nanocomposite samples was investigated using digital light processing (DLP). First, the effect of the thickness of the printing layer in three values of 50, 75, and 100 micrometers on the tensile properties of neat and composite resin samples as well as the printing time was investigated. Next, by adding different amounts of aluminum oxide nanopowder with a particle size of 50 nm to the resin, the effect of different percentages of nanopowder on the mechanical properties of the samples, including tensile strength and wear resistance, was investigated. The results showed that samples with less layer thickness have better strength than samples with more layer thickness. By reducing the thickness of the layer from 100 to 75 and 50 micrometers, the tensile strength in neat samples increases by 4 and 8.55%, respectively. Also, with the increase of alumina up to 2% by weight, the tensile strength first decreases, and then with the continued increase in the number of reinforcing particles, the tensile strength improves, so that finally, with 8% by weight of alumina, the tensile strength shows an increase of nearly 16% compared to the neat resin sample. . In addition, with the increase in the weight percentage of alumina in the nanocomposite, the wear resistance first weakens and then improves, and finally (similar to the tensile strength) at 8 weight percent of reinforcing particles, the specific wear rate decreases by nearly 67% compared to the neat resin sample.

The aim of carrying out this research was to fabricate and characterize a nano–SiC scaffold with PEG in order to utilize in bone tissue engineering. For this purpose, nano–SiC powder was synthesized via ball milling method. Fabrication of scaffolds and their coating were carried out using polymeric sponge replication and dip – coating methods. Nano–SiC and scaffolds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), particle size distribution test (DLS), transmission electron microscopy (TEM), and Brunauer Emmet Teller (BET). In order to examine the physical and mechanical properties of the scaffolds, porosity percentage and compressive strength values were measured. Results showsd that nano–SiC powder were synthesized and characterized via ball milling method with success. Fabrication and characterization of nano–SiC–PEG scaffolds was conducted via polymeric sponge replication and dip coating methods with success. The porosity of the scaffolds was found to be around 65-80%. The compressive strength of the scaffolds was found to be around 0.72-2.32 MPa. Finally, the 30% by weight silicon carbide scaffold with polyethylene glycol coating and 30 seconds coating time was introduced as the optimal scaffold that can be used for bone tissue engineering applications (spongy bone).

This paper discusses the nonlinear dynamic behavior of nanocomposite microplates reinforced with carbon nanotubes in contact with static fluids. Equations of motion are derived using the first-order shear deformation theory of plates and considering the size effects and large deformations. Effective mechanical properties are determined by applying the law of mixtures. By use of the Galerkin method, the nonlinear equations governing motion are discretized and the numerical solution is obtained. The results have been verified and the effect of micro-plate geometrical characteristics, small size parameter, fluid height and weight fraction of the carbon nanotubes studied on natural linear and nonlinear frequencies and the dynamic response has been evaluated. The results indicate that the natural frequency of the system decreases with increasing fluid height. The reinforcement of microplates by carbon nanotubes also results in a softening of the stiffening behavior of the spring and a substantial bending of the response curve. Depending on the excitation frequency, this bending may result in jump instability. By examining the time response, phase, and Poincaré map of the system, periodic, quasi-periodic, and chaotic vibration behavior can be observed.

In this research, processing and 3D printing of PETG-ABS- Fe 3 O 4  nanocomposites reinforced with iron oxide nanoparticles in three different weight percentages of iron oxide nanoparticles with PETG70-ABS30 polymer matrix was done. This research was carried out with the aim of strengthening the shape memory properties, thermal properties, mechanical properties and adding the ability to indirectly stimulate the background matrix through the addition of iron oxide nanoparticles. SEM images confirmed that the mixture of PETG-ABS is immiscible and adding nanoparticles does not change the compatibility and miscibility of the base polymer, and this result is consistent with the DMTA analysis was also checked and confirmed. With increasing amount of iron oxide, the tensile strength and elongation decrease, and this decrease in mechanical properties is more pronounced in the sample of 20% by weight of iron oxide compared to the sample of 10% by weight. Nevertheless, the final strength of the samples is around 25 to 32 MPa, which indicates a suitable and acceptable distribution of nanoparticles up to 15% by weight in the polymer field. By increasing the amount of iron oxide nanoparticles, the amount of shape recovery increases and the nanocomposites containing 10, 15 and 20% by weight show shape recovery of 63.77%, 88.48 and 93.33%, respectively.

In the present research, classic micromechanical methods and their application as constitutive models in conjugation with incremental theory were developed. Using the modified Eshelby model, the Eigen strain concept in polymeric composite, and a modified form of self-consistent model the elastic properties of nanocomposites were predicted. Also, the stress-strain behavior of elastomer nanocomposites was calculated and validated by the experimentally determined ones. The results showed that the new model can predict the stress-strain behavior of elastomer nanocomposite at different particle volume fractions.

Trapezoidal plates are referred to as simple models for aircraft wings. These wings can be produced from different materials, each of which has its own advantages. One of the materials that has attracted the attention of researchers in recent years is nanocomposites, which with their high strength and low weight can be a good option for making aircraft wings. In fact, when nanocomposites are produced, they are not without weaknesses and have weaknesses that reduce their mechanical properties. One of these weaknesses is the agglomeration of nanotubes. In the present paper, a trapezoidal nanocomposite plate will be modeled and its behavior in the presence or absence of nanotubes agglomeration will be compared. The data extracted from the relations are for bending of trapezoidal plates. For this purpose, the three-dimensional theory of elasticity will be used as the most accurate theory for modeling of thin and thick plates. A review of the research conducted so far concludes that this is the first time that the effect of nanotubes agglomeration on the flexural behavior of trapezoidal plates has been studied.  It is worth mentioning that in the studied cases, it was observed that the agglomeration of nanotubes has no significant effect on the final results and can be neglected by engineering approximation.

A three-dimensional analytical micromechanical model based on the unit cell is extended to extract the elastic properties of GNP-reinforced polymer nanocomposites. GNP/matrix interphase region changing gradually and is considered elastic with isotropic behavior. In order to simulate the random distribution of GNPs, the geometry of the representative volume element of the nanocomposite is divided into a three-dimensional cubic with N_α×N_β×N_γ subcells. First, the obtained results are compared with the available researches. Then, the effect of parameters such as the volume fraction and aspect ratio of GNPs, the effect of agglomeration as well as the random distribution of GNPs in the epoxy resin, and the thickness of the interphase on the response of the nanocomposite are investigated. It is shown that the agglomeration of GNP depends on its volume fraction. The results show that the elastic properties obtained from the present micromechanical model with taking into account the random distribution and the agglomeration of nanoparticles and also interphase are close to the experimental data. According to the obtained results, adding even a small volume fraction of GNPs has a significant effect on improving the properties of the nanocomposite. In addition, the modeling of the interphase region also has a great impact on the properties of the nanocomposite. Therefore, in order to realistically predict the behavior of nanocomposites, it is important considering to the interphase.

A nanoparticle or an infinitesimal particle is usually defined as a particle of matter that has a diameter between 1 and 100 nanometers (nm). The properties of nanoparticles often differ significantly from larger particles of matter. Nanoparticles show different dislocation mechanics, which together with their unique surface structure, lead to different mechanical properties from bulk materials. Nowadays, by adding nanoparticles, the mechanical properties of composites are improved. Due to their small size, nanoparticles increase the surface area between the base material and the reinforcement and therefore improve the mechanical properties. The type of nanoparticle used, dimensions, weight percentage and the way of nanoparticle distribution are determining factors in improving mechanical properties. In the present study, while presenting the concepts related to nanocomposite, the effect of five different nanoparticles on the common mechanical properties considered by structural designers is investigated. The results show that the addition of nanoparticles up to a certain weight percentage improves the properties, and more than that amount sometimes has the opposite effect, one of the reasons for which is the clumping of nanoparticles.

Active packaging systems for food have more benefits and performance than conventional packaging which are designed only as a barrier to protect food against the external environment. Most active packages contain antimicrobial compounds. Since these particles may be swallowed with food when using active packaging, the food safety aspects should be considered and the migration of nanoparticles from packaging to food surfaces should be controlled. In addition, these particles can also cause respiratory and skin problems due to their ability to be released into the environment. Most active packaging systems contain antimicrobial compounds that are released at the food surface as microorganisms grow and multiply, therefore prevent the growth of germs and spoilage of food. The severity of this effect depends on the nature of the antimicrobial agent. Among these, nanocomposite systems have been designed with antibacterial properties which include antimicrobial agents at the nanoscale. They are able to expand the level involved in the reaction between food and antimicrobial components due to increasing surface to volume ratio. Therefore, these systems play a more effective role in increasing the shelf life of food compared to similar compounds.

In this paper, multiscale modeling of Epoxy-based hybrid nanocomposites was performed. Single-walled carbon nanotube and carbon nanoparticle (diamond) were used as reinforcements and the elastic behavior of hybrid nanocomposite was investigated. In the multiscale modeling, at the nanoscale and pico-second time range, molecular dynamics method was used to make an accurate model of the interaction between the nano-scale reinforcements and the polymer matrix to predict the interface behavior more realistically. At the micro and macro scales, micromechanical models were used to predict the elastic properties of the nanocomposites, incorporating the effects of interface behavior. Finite element method was also used to check the accuracy of the results obtained at the macro scale. First, pure thermoset polymer with 75% crosslinking ratio was simulated using molecular dynamics method. Then two nanocomposites, one consisting of a single-walled carbon nanotube and another one containing a carbon nanoparticle (diamond) were simulated to obtain equivalent fiber mechanical properties. Next, a micromechanical model was developed for hybrid nanocomposite using the equivalent fiber and pure thermoset polymer mechanical properties. In addition, the results obtained from the molecular dynamics simulations, along with a correction coefficient were employed in the micromechanical models and finite element simulations. Finally, micromechanical multiscale modeling results were compared with finite element multiscale modeling results and a good agreement was observed. Results suggest that the use of two types of nano-reinforcement together, hybrid nanocomposite, improves nanocomposite mechanical properties.

In this paper, the design, fabrication and testing of a single L-shaped adhesive bond between a composite sheet and an aluminum piece under tensile loading has been performed experimentally. In this experimental study, nanographene sheets with different weight percentages have been used to strengthen the composite and structural adhesive (compatible with the composite phase phase resin) to improve the mechanical properties of the joint. The effect of changing the base length of the aluminum L-shaped piece on the bond strength has also been investigated. 12 bonding modes with a combination of weight percentages of 1.0 and 0.3 for multilayer and weight percentages of 0.1, 0.3 and 0.5 for adhesive were made and examined by considering 5 repetitions of the test. has taken. By comparing and examining the tensile test results of the samples and photographs taken by scanning electron microscopy (SEM) of the separation of the multilayer and the L-shaped piece at the separation site, it was found that the bonding combined with zero weight percentage for multilayer and The weight percentage of 0.3 for the adhesive has the highest tensile strength. This means that the addition of nano-graphene without surface-modifying agent to the multilayer reduces the tensile strength and adding it to epoxy resin epr 1080 as a homogeneous adhesive with the composite improves the tensile strength of the joint. Finally, the effect of increasing the length of the overlap area of ​​the two adhesive pieces was investigated.

Magnesium-based nanocomposites are widely used in the aerospace, automotive, and medical industries. Due to the special properties of boron nitride nanotubes, these nanotubes play an important role in strengthening nanocomposites. In this research, magnesium nanocomposites are reinforced by boron nitride nanotubes and the mechanical properties of these nanocomposites under uniaxial tensile loading in the axial direction of the nanotubes have been investigated by the molecular dynamics method by Lammps software. Also, the coefficients of the atomic potential function of magnesium atoms have been calculated using the law of composition and the data extracted by Gaussian software. The results of molecular dynamics simulations show the improvement of mechanical properties of magnesium-based metal nanocomposites due to the addition of boron nitride nanotubes. The presence of boron nitride (0,12), (0,14), (0,16) and (0,18) nanotube reinforcers as magnesium field reinforcers increased the elastic modulus by 13, 14.9, 16.2 and 17 percent. Other results of this study indicate that the elastic behavior of nanocomposites is independent of strain rate changes. Also, by performing this simulation over a wide range of temperatures, obvious changes in the mechanical properties of the nanocomposite at different temperatures have been obtained.

The present study evaluated the effect of simultaneous change of the material of tube bundle fins and air gap between rows of fins in consecutive tube bundles on the performance of A.C.C in order to improve their performance. Changing this air gap as well as the fin material can affect the heat transfer coefficient, air pressure drop, and weight of the tube bundle. In this paper, the suitable material for fin was first determined in different air gap, and then the effect of the velocity of inlet air on tube bundle as well as ambient temperature conditions on the thermo-hydraulic performance of airflow on the selected tube bundle side was studied. According to the results, among the 54 simulated tube bundles, the use of the selected fin material and 1-mm air gap on the tube bundle airside exhibited improved thermohydraulic performance. Using the selected tube bundle, the Nusselt number and the performance evaluation criteria increased by 57.2% and 64.4%, and the friction factor and the overall weight of the tube bundle decreased by 7.9% and 10.8%, respectively, compared to the current bundle.

In the present paper, the effect of addition of a functionalized graphene oxide (FGO) on the mechanical properties of an epoxy adhesive was investigated. GO was first prepared by oxidation of graphite using Modified Hummers’ method. Then silane coupling agents 3-aminopropyltriethoxysilane (APTES) was used for surface modification of GO. The solution mixing method is used for dispersing 0.1 wt%, 0.2 wt% and 0.3 wt% amine-modified graphene oxide (GO-NH2) in the epoxy adhesive to investigate the tensile and shear properties of the nano-composite. The tensile and shear properties of the neat and GO-NH2 reinforced epoxy adhesives were determined using the bulk and the thick adherend shear test (TAST) specimens, respectively. Significant improvements in the mechanical properties have been observed by the addition of nano-fillers in epoxy adhesive. The highest improvement in strength was obtained by 0.1 wt% loading of GO-NH2. So that, the addition of 0.1 wt% of FGO increases the Young’s modulus, tensile strength, toughness and shear modulus by 35% , 44%, 53% and 34%, respectively.

Abrasion in many industrial machines increases the clearance between moving parts, reduces accuracy, causes vibration, fatigue, and can ultimately cause complete machine failure and impose high costs on the industry. In this paper, the dry sliding behavior of metal on the surface of epoxy-based nanocomposites and their mechanical properties have been studied. Neat epoxy, carbon nanotube/ epoxy, nanoclay/ epoxy and carbon nanotube/ nanoclay/ epoxy are the samples. To investigate the sliding behavior, the samples were made in the form of a disc and according to the standard. The abrasive metal pin moved a distance of 1000 m in a circular path on the surface of the sample. Different axial loads were applied to the steel pin. The coefficient of friction between the metal and the samples, and the weight loss of the samples were measured. Also the mechanical properties of samples were determined by simple tensile test. The results showed that the addition of nanostructured reinforcements in all three nanocomposite samples made the sample more resistant to abrasion compared to the pure epoxy sample. At the maximum axial load, the coefficient of friction between the metal pin and the epoxy was measured to be 0.27, which indicated a reduction of 40% after adding 1.5% by weight of nanoclay to the epoxy.

In this research article, the effect of zeolite nanoparticles on the tribological properties of high molecular weight polyethylene, which are widely used in orthopedic implants, has been studied. Improving the tribological properties of this polymer is one of the medical industry challenges which has an important effect on the life-time of orthopedic implants. Nanocomposites based on ultra-high molecular weight polyethylene (UHMWPE) blend, containing 2 to 6 phr of nano-zeolite, were prepared via melt compounding followed by injection molding. The morphology was studied using scanning electron microscopy. The wear and temperature of specimens as well as friction coefficient were characterized by employing a pin on disk test under 50 N and sliding velocity of 0.5 m/s. The wear rates, temperature and friction coefficient of nanocomposite containing 4 phr of nano-zeolite, were 56, 32 and 26%, respectively, lower than those of neat UHMWPE. In contrast, the application of 6 phr of of nano-zeolite, led to agglomeration and increased wear, temperature and coefficient of friction compared to nanocomposite samples. In addition, the morphology of nanocomposite samples, after testing, revealed a smoother surface with the mild abrasion marks than that of of pure UHMWPE sample.