Carbon Nanotube-reinforced Nanocomposites Research Articles

DETERMINATION OF PHYSICAL AND MECHANICAL PROPERTIES OF POLYETHYLENE AND POLYMER NANOCOMPOSITES USING THE METHODS OF MOLECULAR DYNAMICS

Today, molecular dynamics (MD) simulation become an effective method for investigating and predicting the physical and mechanical properties (PMP) of materials at the atomic scale. In this work, initial configurations of molecular systems of pure polyethylene (PE) and carbon nanotube-reinforced nanocomposites (PE-CNT) are created and described by the united atom model and Dreiding force field. Equilibration of the initial configurations of molecular models carried out using NVT and NPT ensembles in LAMMPS. Simulated complex of PMP of PE and PE-CNT includes elastic modulus, Poisson's ratio, bulk modulus, shear modulus, yield strength, mass isobaric heat capacity, and coefficient of linear thermal expansion (CLTE). The results verification of the PE molecular model showed the obtained MD simulation data either coincide with available literature data or are close to them. The results justify the use of the same algorithms to obtaine reliable data on the PMP of PE-CNT. Comparing the complex PMP of molecular models of pure PE and PE-CNT, it was established the elastic modulus of PE-CNT α=1.4 % increases by 10.4% at 300 K and by 29.3% at 320 K. The yield strength of PE-CNT α=1.4 % also increases by 33.2 % at a strain rate of 109 s−1 and a temperature of 300 K compared to PE. Meanwhile, mass isobaric heat capacity and CLTE decrease with increasing temperature: mass isobaric heat capacity decreases by 1.3 % at 300 K and by 4.4 % at 320 K; CLTE decreases by 20.2 % at 300 K and by 22.6 % at 320 K. Nonlinear two-parameter dependencies of the PMP of PE-CNT obtained in the temperature range (280–320) K and the volume fraction of fillers (0–1.5) %. These results allow to develop of new composite materials without conducting sufficiently complex and time-consuming numerical experiments based on MD simulation. The obtained data on the complex PMP are necessary for modeling the thermo-elastic-plastic state of products made of PE-CNT under operational conditions in a continuum approximation.

Thermal buckling characterization of nanocomposite beams activated by PZT with temperature-dependent characteristics considering the pyroelectricity

Employing piezoelectrically activated beam-like structures is extending in numerous applications for instance energy harvesters and sensors. On the other hand, advanced materials such as carbon nanotube-reinforced nanocomposites are widely implemented in making passive structures with the aim of using their advantages. For the first time, a study is established on the critical temperature of a piezoelectric sandwich aggregated CNTRC beam regarding the pyroelectricity. The stabilization contribution of pyroelectricity against the thermal buckling incidence of sandwich beams has been demonstrated specifically. It is found that the pyroelectricity develops the critical point for the temperature of a clamped-clamped piezoelectric sandwich non-reinforced beam.

The effect of carbon nanotube amount in machining of ZA-27 matrix carbon nanotube reinforced nano composite

In recent years, the usage area of nano material reinforced composites has been increasing gradually. Accordingly, machining of metal matrix and nano material reinforced composite materials becomes important. In this study, the effect of carbon nanotube (CNT) on the machining of CNT-reinforced ZA-27 (zinc-aluminum) nano composite was investigated. For this purpose, 0.5%, 1.0%, 1.5%, 3.0% CNTreinforced ZA-27 based composites were produced by powder metallurgy method. Firstly, SEM images of composites were taken. Then, hardness measurements were made and pore amounts were determined. At the last stage, the machinability tests of nano composites have been carried out. Machinability tests were carried out by turning method to determine the cutting forces and surface roughness amounts. The tests were carried out with cemented carbide cutting tools under dry cutting conditions. Cutting speeds of 75, 125, 175, 225 m/min, feed values of 0.05, 0.10, 0.20 mm/rev and constant cutting depth of 1.0 mm were chosen as test parameters. The data obtained as a result of the tests were interpreted together with microstructure, porosity and hardness values. Hardness values decreased and the pore amounts increased with the increase in the CNT-reinforcement ratio within the composite structure.Cutting forces and the surface roughness amounts increased with the increase in feed value. Cutting forces and surface roughness amounts decreased together with increase in cutting speed. CNT-reinforcement material in the composite structure caused a decrease in cutting forces. However, surface roughness values showed an increase with the increase of CNTreinforcement ratio. It has been determined that CNT-reinforcement material facilitates machining by lubricating effect in dry machining conditions. Built-up edge (BUE) was observed on all cutting tool bits used in machining tests. BUE amounts increased in itself with the increase in CNT ratios and feed rates.

Analytical solutions for nonlinear magneto-electro-elastic vibration of smart sandwich plate with carbon nanotube reinforced nanocomposite core in hygrothermal environment

This paper presents an analytical approach on the nonlinear magneto-electro-elastic vibration of smart sandwich plate. The sandwich plate consists of a carbon nanotube reinforced nanocomposite (CNTRC) core integrated with two magneto-electro-elastic face sheets. For core layer, three types of carbon nanotube (CNT) distribution such as FG-O, FG-V, FG-X are considered while the volume fraction of BaTiO3 − CoFe2O4 in each face sheet is chosen to be 0.5. It is assumed that the smart sandwich plate is rested on Pasternak-type elastic foundations and subjected to the combination of external pressure, thermal, electric and magnetic loads. The coupled constitutive relations are derived based on the Hamilton's principle in which the kinematic nonlinearity is defined using Reddy's higher order shear deformation theory. The analytical solutions which satisfy the boundary conditions are assumed to have the trigonometric form. The Galerkin method is used to obtain the closed form expressions of natural frequency, the relation between the frequency ratio and dimensionless amplitude and the dynamic response of the sandwich plate. The numerical results are conducted to illustrate the effect of geometrical parameters, CNT volume fraction, temperature and moisture increment, electric and magnetic potentials on the nonlinear vibration of smart sandwich plate. The reliability of present results is evaluated by comparing with the previous results based on different approach.

Partially unzipping carbon nanotubes: A route to synchronously improve fracture strength and toughness of nanocomposites inspired by pinning effect of screw

Carbon nanotube (CNT) reinforced nanocomposites (CNTRNs) have been regarded as the most promising substitutes for traditional carbon fiber reinforced composites, due to their excellent multi-functional properties. However, the weak CNT-matrix interface which impairs the mechanical properties of CNTRNs is always an issue, limiting their practical applications. Here, inspired by strong pinning effect of screws, we partially unzipped the CNTs into graphene nanoribbons (GNRs) and a screw-like CNT/GNR hybrid (CGH) nanostructure was proposed to reinforce the nanocomposites. It was found that the fracture strength, Young’s modulus and fracture toughness of CGH reinfroced nanocomposites can be boosted by 155 %, 89 % and 117 %, respectively, comparing to those of CNTRNs. The molecular dynamic simulation on pullout of CGHs from matrix revealed that the CNT-GNR junction can lead to a mechanical interlocking, which can not only hinder the pullout of CGH, but also cause remarkable matrix shear deformation, contributing to energy dissipation to a large extent. In addition, the morphology of CGHs can be tuned by changing structural chirality of CNTs, by which the interfacial properties can be further improved. This work opens a new route to engineer high-performance nanocomposites, and provides an in-depth understanding on the mechanical enhancement of CNT-based nanocomposites.

Modeling the Effects of Filler Network and Interfacial Shear Strength on the Mechanical Properties of Carbon Nanotube-Reinforced Nanocomposites

This modeling paper describes the roles of filler network and imperfect interfacial adhesion between polymer matrix and nanoparticles in the tensile modulus and yield strength of polymer/carbon nanotube (CNT) nanocomposites (PCNT). The percolation threshold ( $$ \phi_{\text{p}} $$ ) is assumed by the aspect ratio of the CNT; also, both the critical length of the nanotubes. Crucial for effective stress transfer from matrix to filler (Lc). and the interfacial shear strength (τ) reflect the incomplete interfacial adhesion. Two known micromechanics models are used to examine the influences of these parameters on the tensile modulus and yield strength of PCNT. The lowest ranges of $$ \phi_{\text{p}} $$ and Lc produce the highest levels of mechanical properties, while τ cannot affect the mechanical performance. The main reasons for these occurrences are explained in order to clarify the roles of the filler network and interfacial adhesion in the modulus and strength of PCNT.

FEM analysis of the elastic behavior of composites and nanocomposites with arbitrarily oriented reinforcements

This work is aimed at studying the effect of different morphological features on the stiffness of discontinuous fiber reinforced composites and nanocomposites by means of FEM analysis. The morphological features include not only volume fraction and aspect ratio of reinforcement, but also its orientation. The FEM approach, based on continuum mechanics, required the definition of a proper representative volume element, in which reinforcement is randomly dispersed in the simulation domain. The developed model has been used in order to calculate the stiffness matrix of unidirectional discontinuous glass fiber reinforced composite (DGFRC) as well as carbon nanotubes reinforced nanocomposites (CNTRNC). Comparison with closed form analytical models showed that the Halpin-Tsai (HT) model is able to predict the evolution of the elastic constants over a wide range of volume fractions and aspect ratio. The Tandon-Weng (TW) model, in contrast, shows a poor agreement with the simulation results.On the other hand, the developed FEM model also allowed accounting for reinforcement orientation. The calculated elastic properties are in excellent good agreement with the corresponding values calculated according to the classical lamination theory, indicating the accuracy of the developed FEM model for estimation of stiffness of composites and nanocomposites, also accounting for reinforcement orientation.

Development of Expanded Takayanagi Model for Tensile Modulus of Carbon Nanotubes Reinforced Nanocomposites Assuming Interphase Regions Surrounding the Dispersed and Networked Nanoparticles.

In this paper, we consider the interphase regions surrounding the dispersed and networked carbon nanotubes (CNT) to develop and simplify the expanded Takayanagi model for tensile modulus of polymer CNT nanocomposites (PCNT). The moduli and volume fractions of dispersed and networked CNT and the surrounding interphase regions are considered. Since the modulus of interphase region around the dispersed CNT insignificantly changes the modulus of nanocomposites, this parameter is removed from the developed model. The developed model shows acceptable agreement with the experimental results of several samples. “ER” as nanocomposite modulus per the modulus of neat matrix changes from 1.4 to 7.7 at dissimilar levels of “f” (CNT fraction in the network) and network modulus. Moreover, the lowest relative modulus of 2.2 is observed at the smallest levels of interphase volume fraction ( < 0.017), while the highest “” as 0.07 obtains the highest relative modulus of 11.8. Also, the variation of CNT size (radius and length) significantly changes the relative modulus from 2 to 20.

Transient heat transfer analysis of functionally graded CNT reinforced cylinders with various boundary conditions

In this work, transient heat transfer analysis of functionally graded (FG) carbon nanotube reinforced nanocomposite (CNTRC) cylinders with various essential and natural boundary conditions is investigated by a mesh-free method. The cylinders are subjected to thermal flux, convection environments and constant temperature faces. The material properties of the nanocomposite are estimated by an extended micro mechanical model in volume fraction form. The distribution of carbon nanotube (CNT) has a linear variation along the radial direction of axisymmetric cylinder. In the mesh-free analysis, moving least squares shape functions are used for approximation of temperature field in the weak form of heat transform equation and the transformation method is used for the imposition of essential boundary conditions. Newmark method is applied for solution time depended problem. The effects of CNT distribution pattern and volume fraction, cylinder thickness and boundary conditions are investigated on the transient temperature field of the nanocomposite cylinders.

A bridging law and its application to the analysis of toughness of carbon nanotube-reinforced composites and pull-out of fibres grafted with nanotubes

Bridging laws are essential in predicting the mechanical behaviour of conventional short-fibre-reinforced composites and the emerging nanofibre-reinforced composites. In this paper, we first review some studies on the toughness of carbon nanotube-reinforced composites that is induced by the pull-out of the nanotubes from the matrix, and on the development of the corresponding bridging laws. A close examination of the available bridging laws for carbon nanotubes reveals that some fundamental issues need to be further addressed. We propose a simple nonlinear and smooth bridging law to describe the pull-out force–displacement behaviour of carbon nanotubes from a matrix. This law contains only two material parameters, reflects the basic features of the pull-out experiments, and is easy to use. We then use this bridging law to calculate the fracture toughness of carbon nanotube-reinforced nanocomposites and predict the pull-out force–displacement response of conventional short fibres that are grafted with carbon nanotubes. Some parametric studies are conducted to reveal the influence of various parameters at the nano- and micro-scale on these properties.

Mechanical, Rheological, and Electrical Properties of Multiwalled Carbon Nanotube Reinforced Nanocomposites of 50/50 Acrylonitrile–Styrene–Acrylate/Zn+2 poly(ethylene-co-methacrylic acid) Ionomer Blend

The effect of variable amount of multiwalled carbon nanotubes on mechanical, rheological, and electrical properties of acrylonitrile–styrene–acrylate/Zn+2-poly(ethylene-co-methacrylic acid) ionomer blend system has been evaluated. Optical micrographs as well as alternating current conductivity data shows the formation of nanotube percolation network at 1 wt% nanotube content. The polymer/nanotube interaction increased the rate of tensile modulus to 55 GPa at low nanotube content. The polymer chain relaxation time was increased upto 1 wt% of nanotube content, but higher nanotube loading reduced the time. The zero-shear viscosity was function of nanotube content whereas the infinite-shear viscosity was independent of nanotube content.

Effects of carbon nanotubes’ dispersion on effective mechanical properties of nanocomposites: A finite element study

Effects of volume fraction and random dispersion of carbon nanotubes on effective mechanical properties of carbon nanotube-reinforced nanocomposites are studied at continuum level using finite element methods. Utilizing a continuum model of tubes with specific pairing of elastic properties and wall thickness for describing carbon nanotubes, representative volume elements with non-uniform distribution of uniaxial nanotubes within a base matrix are generated. Furthermore, a dispersion quantification technique is employed to quantify nanotubes’ dispersion degree. Finite element simulations are carried out in six independent loading conditions, while applying periodic boundary conditions to the models. Homogenizing the models and using the formulations of linear elasticity, equivalent mechanical properties of the models are computed and the effects of the aforementioned influential parameters as well as the modeling volume size are investigated. The results demonstrate that in volume fractions higher than 5%, the effects of carbon nanotubes’ dispersion become more significant and if increasing the volume fraction leads to bigger agglomerations and subsequently worse dispersion, the effective properties of the composite as a whole will decrease. Moreover, the pre- and post-processing procedures implemented are verified by analyzing previously studied models available in the literature and comparing the corresponding results.

A STUDY ON MECHANICAL BEHAVIOR OF FUNCTIONALLY-GRADED CARBON NANOTUBE-REINFORCED NANOCOMPOSITES

In this study, we are focusing on the investigation of the effects of gradient patterns on mechanical behavior of functionally-graded carbon nanotube-reinforced nanocomposites and considering typical beams made of such nanocomposites. Both analytic and finite element-based numerical models were developed. Analytic model was developed based on the first-order shear deformation and Timoshenko beam theories meanwhile finite element models were developed using Abaqus in conjunction with user-defined subroutines for defining the continuously gradient material properties for different gradient patterns. Position-dependent elastic modulus equations for four continuously graded patterns were studied. A nongraded pattern was used for benchmarking with the same geometry and total carbon nanotube (CNT) contents. For validation and verification, the results on both deflection and stress of these nanocomposite beams were analyzed, which clearly showed high influence from gradient patterns on these mechanical behaviors of such beams.

Preparation and properties of polyamide/epoxy/multi-walled carbon nanotube nanocomposite

Nanocomposite composed of amine-terminated polyamide (an aramid)/bisphenol A diglycidyl ether epoxy matrix and functionalized and non-functionalized multi-walled carbon nanotube have been fabricated. Polyamide/bisphenol A diglycidyl ether/multi-walled carbon nanotube nanocomposite was cured at 120℃ with different filler content. In order to investigate the influence of functional filler on nanocomposite properties, morphological, mechanical and thermal profile of polyamide/bisphenol A diglycidyl ether nanocomposite with varying multi-walled carbon nanotube content were studied. Functional multi-walled carbon nanotube-reinforced nanocomposite showed greater strengthening at all weight percent as they actively control the failure mechanism; 5 wt% functional multi-walled carbon nanotube-based sample showed 62% improvement in toughness i.e. area under the stress–strain curve (35.6 J/m3) relative to non-functional (13.7 J/m3) nanocomposite. The ultimate tensile strength also improved from 39.2 to 59.7 MPa. The multi-walled carbon nanotube ratio was an interesting feature significantly influencing the properties of polyamide/bisphenol A diglycidyl ether/multi-walled carbon nanotube due to the contribution of hydrogen bonding and π-π staking between the matrix and filler. Thermal stability consistently increased with amalgamation of functional multi-walled carbon nanotube in the polyamide/bisphenol A diglycidyl ether matrix ( T0 523–565℃; Tg 247–253℃) over polyamide/bisphenol A diglycidyl ether /non-functional multi-walled carbon nanotube ( T0 499℃; Tg 246℃). Novelty of the research lies in exclusive architecture, exceptional heat stability and mechanical properties of aramid/epoxy-based nanocomposite.

Pull-out simulations of a capped carbon nanotube in carbon nanotube-reinforced nanocomposites

Systematic atomic simulations based on molecular mechanics were conducted to investigate the pull-out behavior of a capped carbon nanotube (CNT) in CNT-reinforced nanocomposites. Two common cases were studied: the pull-out of a complete CNT from a polymer matrix in a CNT/polymer nanocomposite and the pull-out of the broken outer walls of a CNT from the intact inner walls (i.e., the sword-in-sheath mode) in a CNT/alumina nanocomposite. By analyzing the obtained relationship between the energy increment (i.e., the difference in the potential energy between two consecutive pull-out steps) and the pull-out displacement, a set of simple empirical formulas based on the nanotube diameter was developed to predict the corresponding pull-out force. The predictions from these formulas are quite consistent with the experimental results. Moreover, the much higher pull-out force for a capped CNT than that of the corresponding open-ended CNT implies a significant contribution from the CNT cap to the interfacial properties of the CNT-reinforced nanocomposites. This finding provides a valuable insight for designing nanocomposites with desirable mechanical properties.

Electrophoretic Deposition of Microwave Combustion Synthesized Hydroxyapatite and Its Carbon Nanotube Reinforced Nanocomposite on 316L Stainless Steel

Nanohydroxyapatite-carbon nanotube Nanocomposite (HA-CNT) coatings were deposited via electrophoretic deposition (EPD). Hydroxyapatite was synthesized via microwave combustion method using calcium nitrate and glycing as starting materials. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that pure hydroxyapatite nanoparticles have been synthesized. AISI 316L stainless steel and ethanol were used as substrate and dispersing medium, respectively. 5%wt carbon nanotube (CNT) was used as reinforcing phase. Uniform and macrocrack-free coatings were obtained both for HA and HA-5%wt CNT coatings. Scanning electron microscopy (SEM) showed that most of microcracks in HA coating has eliminated after introducing CNT as reinforcing phase. The variation of deposit weight by time and voltage is measured both for HA and HA-5%wt CNT coatings. Thickness measurements indicated that for both coatings, the thickness increases with deposition voltage. X-ray diffraction patterns indicated that HA has not decomposed after sintering at 850 ˚C for 2 hr in argon atmosphere.

Predictive model for carbon nanotube–reinforced nanocomposite modulus driven by micromechanical modeling and physical experiments

This article proposes an improved surrogate model for the prediction of the elastic modulus of carbon nanotube–reinforced-nanocomposites. By statistically combining micromechanical modeling results with limited amounts of experimental data, a better predictive surrogate model is constructed using a two-stage sequential modeling approach. A set of data for multi-walled carbon nanotube–bismaleimide nanocomposites is used in a case study to demonstrate the effectiveness of the proposed surrogate modeling procedure. In the case study, the theoretical composite modulus is computed with micromechanical models, and the experimental modulus is measured through tensile tests. Both theoretical and experimental composite moduli are integrated by using a statistical adjustment method to construct the surrogate model. The results demonstrate an improved predictive ability compared to the original micromechanical model.

Simulation and Experimental Studies and Applications of Carbon Nanotubes and Graphenes in Engineering and Medicine

Simulation and Experimental Studies and Applications of Carbon Nanotubes and Graphenes in Engineering and Medicine

Electrical Response of Carbon Nanotube Reinforced Nanocomposites Under Static and Dynamic Loading

An experimental investigation was conducted to study the effect of quasi-static and dynamic compressive loading on the electrical response of multi-wall carbon nanotube (MWCNT) reinforced epoxy nanocomposites. An in-situ polymerization process using both a shear mixer and an ultrasonic processor were employed to fabricate the nanocomposite material. The fabrication process parameters and the optimum weight fraction of MWCNTs for generating a well-dispersed percolation network were first determined. Absolute resistance values were measured with a high-resolution four-point probe method for both quasi-static and dynamic loading. In addition to measuring the percentage change in electrical resistance, real-time damage was captured using high-speed photography. The real-time damage was correlated to both load and percentage change in resistance profiles. The experimental findings indicate that the bulk electrical resistance of the nanocomposites under both quasi-static and dynamic loading conditions initially decreased between 40%–60% during compression and then increased as damage initiated and propagated.

Multi-scale Modeling of Nonlinear Tensile Behavior in Single-walled Carbon Nanotube Reinforced Nanocomposites

Multi-scale Modeling of Nonlinear Tensile Behavior in Single-walled Carbon Nanotube Reinforced Nanocomposites