Properties Of Carbon Nanotube Reinforced Composites Research Articles

Effect of nonlinear FG-CNT distribution on mechanical properties of functionally graded nano-composite beam

This work focused on the novel numerical tool for the bending responses of carbon nanotube reinforced composites (CNTRC) beams. The higher order shear deformation beam theory (HSDT) is used to determine strain-displacement relationships. A new exponential function was introduced into the carbon nanotube (CNT) volume fraction equation to show the effect of the CNT distribution on the CNTRC beams through displacements and stresses. To determine the mechanical properties of CNTRCs, the rule of the mixture was employed by assuming that the single-walled carbon nanotubes (SWCNTs)are aligned and distributed in the matrix. The governing equations were derived by Hamilton's principle, and the mathematical models presented in this work are numerically provided to verify the accuracy of the present theory. The effects of aspect ratio (l/d), CNT volume fraction (Vcnt), and the order of exponent (n) on the displacement and stresses are presented and discussed in detail. Based on the analytical results. It turns out that the increase of the exponent degree (n) makes the X-beam stiffer and the exponential CNTs distribution plays an indispensable role to improve the mechanical properties of the CNTRC beams.

Agglomeration and aspect ratio effects on the long-term creep of carbon nanotubes/fiber/polymer composite cylindrical shells

The present study is an attempt to trace the influences of agglomeration, uniform dispersion, and aspect ratio of carbon nanotubes on long-term creep strain and stress in carbon nanotubes/fiber/polymer composite cylindrical shells. The thin-walled cylindrical vessel is subjected to an internal pressure. For this purpose, the effect of the carbon nanotubes agglomeration and aspect ratio on the elastic properties of carbon nanotube-reinforced composites were investigated, by means of the Halpin–Tsai and Eshelby–Mori–Tanaka approaches. Classical-laminated plate theory and stress–strain relations were used to derive the governing equations for radial and circumferential creep strain. The Schapery single integral nonlinear viscoelasticity model was used for modeling the behavior of materials reliably. The present results indicated that the higher aspect ratio and uniform dispersion decreased creep strain, but agglomeration increased creep strain.

Effect of rare earth surface modification of carbon nanotubes on enhancement of interfacial bonding of carbon nanotubes reinforced epoxy matrix composites

Rare earth (RE) lanthanum chloride was used to modify carbon nanotubes (CNTs) to obtain rare earth modified carbon nanotubes (RECNTs). The modified CNTs were characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results show that RE has a significant effect on improving the surface activity of carbon nanotubes. Through the chemical function of RE, the CNTs were successfully grafted with functional groups such as amino groups and carboxyl groups. This method can be used to connect any oxygen- or nitrogen-containing functional groups to the CNTs according to actual needs. Then, the modified CNTs were incorporated into epoxy resin (EP) to prepare composite (REACNTs/EP). The mechanical properties of the composites were tested by Zwick/Roell Z100 and Zwick/Roell Z20 test machine, and the tensile fractural sections were analyzed by scanning electron microscopy, and compared to the composites prepared with untreated CNTs (CNTs/EP), acidified carbon nanotubes (ACNTs/EP), acidification and RE synergistic modification of carbon nanotubes (REACNTs/EP). The results show that the ultimate tensile strength and tensile modulus of RECNTs/EP were increased by 33.9%, 73.7%, respectively, compared with pure EP, while the properties of REACNTs/EP were increased by 50.7%, 90.9%, indicating that RE has excellent effect on improving the mechanical properties of carbon nanotube-reinforced composites.

Vibrational analysis of sandwich sectorial plates with functionally graded sheets reinforced by aggregated carbon nanotube

In the present work, by considering the agglomeration effect of single-walled carbon nanotubes, free vibration characteristics of functionally graded nanocomposite sandwich sectorial plates are presented. The volume fractions of randomly oriented agglomerated single-walled carbon nanotubes are assumed to be graded in the thickness direction. To determine the effect of carbon nanotube agglomeration on the elastic properties of carbon nanotube-reinforced composites, a two-parameter micromechanical model of agglomeration is employed. In this research work, an equivalent continuum model based on the Eshelby–Mori–Tanaka approach is considered to estimate the effective constitutive law of the elastic isotropic medium (matrix) with oriented straight carbon nanotubes. The two-dimensional generalized differential quadrature method as an efficient and accurate numerical tool is used to discretize the equations of motion and to implement the various boundary conditions. The proposed sectorial plates are simply supported at radial edges, while all possible combinations of free, simply supported, and clamped boundary conditions are applied to the other two circular edges. The benefit of using the considered power-law distribution is to illustrate and present useful results arising from symmetric and asymmetric profiles. The effects of agglomeration, geometrical, and material parameters together with the boundary conditions on the frequency parameters of the sandwich functionally graded nanocomposite plates are investigated. It is shown that the natural frequencies of structure are seriously affected by the influence of carbon nanotubes agglomeration. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analyze the sandwich sectorial plates.

Stability analysis of thin-walled spinning reinforced pipes conveying fluid in thermal environment

Abstract The divergence and flutter instabilities of the thin-walled spinning pipes reinforced by single-walled carbon nanotubes in thermal environment are investigated. The material properties of carbon nanotube-reinforced composites are assumed to be uniform distribution as well as two types of functionally graded distribution patterns. The thermal effects are also considered and the material properties of carbon nanotube-reinforced composites are assumed to be temperature-dependent. The cantilever pipe conveying fluid is spinning along its longitudinal axis and subjected to an axial force at the free end. Based on the thin-walled Timoshenko beam theory, the governing equations of motion are derived using the extended Hamilton's principle and discretized via the Galerkin method. The resulting thermal-structural-fluid eigenvalue problem is solved and the frequency and the critical fluid velocities are calculated. The effects of carbon nanotubes distributions, volume fraction of carbon nanotubes, compressive axial force, spinning speed, gravity and fluid mass ratio on the critical divergence and flutter velocities of the thin-walled spinning pipe conveying fluid are studied.

Micromechanical Constitutive Equations for the Effective Thermoelastic Properties of Carbon Nanotube-Reinforced Composites

Predicting thermomechanical properties of composites containing carbon nanotubes (CNTs) is significantly depending on the assumed microstructural parameters (MSPs) of CNTs and CNT/matrix morphology. These MSPs include geometry, dispersion and orientation. On the other hand, CNT/matrix morphology refers to two microstructural observations. The first is whether or not an interphase exists between CNTs and matrix, whereas the second is whether or not voids exist due to, for example, debonding of CNTs. In this work, the aim is to propose micromechanical constitutive equations, which are based on the micromechanics principles of Eshelby and Mori-Tanaka models, for considering all of these MSPs altogether in addition to the other well-known MSPs. Accordingly, these equations can be used for modeling realistic nanocomposites to predict their effective thermomechanical properties in different directions. The obtained computational results are compared with other results of both experimental and theoretical investigations found in the literature, and good agreement is obtained.

Dependence of equivalent thermal conductivity coefficients of single-wall carbon nanotubes on their chirality

Composite materials (composites) composed of a matrix and reinforcing components are currently widely used as structural materials for various engineering devices designed to operate under extreme thermal and mechanical loads. By modifying a composite with structure-sensitive inclusions such as single-wall carbon nanotubes, one can significantly improve the thermomechanical properties of the resulting material. The paper presents relationships obtained for the equivalent thermal conductivity coefficients of single-wall carbon nanotubes versus their chirality using a simulation model developed to simulate the heat transfer process through thermal conductivity in a transversely isotropic environment. With these coefficients, one can conventionally substitute a single-wall carbon nanotube with a continuous anisotropic fiber, thus allowing one to estimate the thermal properties of composites reinforced with objects of this sort by using the well-known models developed for fibered composites. The results presented here can be used to estimate the thermal properties of carbon nanotube-reinforced composites.

Stochastic nonlinear bending response of elastically supported nanotube-reinforced composite beam in thermal environment

This paper presents the second-order statistics of the nonlinear bending response of elastically supported single-wall carbon nanotube reinforced composite (CNTRC) beam composed of uniformly distributed (UD) and functionally graded (FG) reinforcements in thermal environments with uncertain system properties. The uncertain system properties such as material properties of matrix and SWCNTs, foundation parameters, thermal expansion coefficients are be modeled as uncorrelated Gaussian random variables. The material properties of FG-CNTRCs are assumed to be graded in the beam thickness direction and are evaluated through a micromechanical model. The higher order shear deformation theories (HSDT) with von-Karman nonlinear strain kinematics are used for the mathematical formulation of CNTRCs beam. The thermal effects are also included in the material properties of CNTRCs which are assumed to be temperature dependent and independent. The second-order perturbation technique (SOPT) and Monte Carlo simulation (MCS) via [Formula: see text] nonlinear finite element method (FEM) through Newton–Raphason method are proposed to examine the mean, COV and probability density function (PDF) of transverse deflection of the beam. Typical numerical results are presented for the different volume fraction of carbon nanotube, slenderness ratios, boundary conditions, foundation parameters, load parameters, CNTRC distribution, temperature dependent and independent material properties with random system properties. The present outlined approach is validated with the results available in the literature and by employing MCS.

Free vibration of functionally graded carbon nanotube-reinforced conical panels integrated with piezoelectric layers subjected to elastically restrained boundary conditions

This article presents the free vibration of piezoelectric functionally graded carbon nanotube-reinforced composite conical panels with elastically restrained boundary conditions. The material properties of carbon nanotube-reinforced composites are assumed to be temperature-dependent and are obtained using the extended rule of mixture. First-order shear deformation theory is adopted to obtain the kinematics of the hybrid panels, and the boundary spring technique is used to implement arbitrary boundary conditions. Meanwhile, two types of electrical boundary conditions, closed circuit and open circuit, are considered for the free surfaces of the piezoelectric layers. The complete sets of electro-mechanically coupled governing equations are obtained using the Rayleigh–Ritz procedure with the Chebyshev polynomial basis functions. The resultant eigenvalue problem is solved to obtain natural frequencies and mode shapes of the hybrid panels. Convergence and comparison studies have been conducted to verify the stability and accuracy of the proposed method. Several numerical examples are examined to reveal the influences of the carbon nanotube volume fractions, carbon nanotube distribution types, boundary conditions, geometrical parameters, and temperatures on the natural frequencies of the hybrid panel. Moreover, the mode shapes of the hybrid panels under various boundary conditions are also presented.

An integrated numerical–experimental study on the optimum utilization of carbon nanotubes in laminated composites

In this paper, a set of numerical and experimental studies are performed to improve mechanical and vibrational properties of carbon nanotubes-reinforced composites. First, at a design concept level, linear distribution patterns of multi-walled carbon nanotubes through the thickness of a typical beam is adopted to investigate its fundamental natural frequency for a given weight percent of multi-walled carbon nanotubes. Both Timoshenko and Euler-Bernoulli beam theories are used in the derivation of the governing equations. The finite element method is employed to obtain a numerical approximation of the motion equation. Next, based on the introduced distribution patterns, laminated multi-walled carbon nanotubes-reinforced polystyrene-amine composite beams are fabricated. Static and experimental modal tests are performed to measure the effective stiffness and fundamental natural frequencies of the fabricated composite beams. Also, in order to generate realistic model to investigate the material properties of fabricated composite beams, the actual tensile specimens of multi-walled carbon nanotubes/polystyrene-amine composites are successfully fabricated and the tensile behaviors of both pure matrix and composites are investigated. To better interfacial bonding between carbon nanotubes and polymer, a chemical treatment is performed on carbon nanotubes. It is seen that the addition of a few wt. % of multi-walled carbon nanotubes make considerable increase in the Young's modulus and the tensile strength of the composite. It is observed from the free vibration tests that the uniform distribution of multi-walled carbon nanotubes results in an increase of 9.5% in the fundamental natural frequency of the polymer cantilever beam, whereas using the symmetric multi-walled carbon nanotube distribution increased its fundamental natural frequency by 17.32%.

Semi-analytical solutions to buckling and free vibration analysis of carbon nanotube-reinforced composite thin plates

The multi-term Kantorovich–Galerkin method is proposed to investigate buckling and free vibration behavior of thin carbon nanotube-reinforced composite (CNTRC) plates with the classical plate theory. The properties of CNTRC are determined with the extended rule of mixture. The transverse displacement is expressed in a sum of products of characteristic beam functions in one direction and unknown functions in the other. By applying the Galerkin technique, the governing partial differential equation is reduced to the ordinary differential equations which are then solved through the state-space approach. Non-dimensional buckling loads and frequencies of CNTRC plates with different boundary conditions are obtained, and the effects of number of approximation terms, CNT distribution, CNT volume fraction, aspect ratio, and thickness-to-width ratio are examined. It is shown that the exact solutions can be found using the present method for the CNTRC plates with two opposite sides both simply-supported, as well as the semi-analytical solutions for the ones with two opposite sides both clamped and one clamped the other simply supported.

Vibration characteristics of nanocomposite plates under thermal conditions including nonlinear effects

Thermo-mechanical dynamic characteristics of SWCNT-Reinforced Composite Plates are studied in this paper. The material properties of SWCNTs are assumed to be temperature-dependent and are obtained from molecular dynamics simulations. The material properties of carbon nanotube-reinforced composites (CNTRCs) are assumed to be uniform in the thickness direction, and are estimated through a micromechanical model. Based on the multi-scale approach, numerical illustrations are carried out for CNTRC plates and uniformly distributed CNTRC plates under different values of the nanotube volume fractions. The natural frequencies are obtained for nonlinear problem. Numerical results reveal that the natural frequencies as well as the nonlinear to linear frequency ratios are increased by increasing the CNT volume fraction. The results also show that the natural frequencies are reduced but the nonlinear to linear frequency ratios are increased by increasing the temperature rise.

Vibrations of carbon nanotube-reinforced composites

This work deals with a study of the vibrational properties of carbon nanotube-reinforced composites by employing an equivalent continuum model based on the Eshelby–Mori–Tanaka approach. The theory allows the calculation of the effective constitutive law of the elastic isotropic medium (matrix) with dispersed elastic inhomogeneities (carbon nanotubes). The devised computational approach is shown to yield predictions in good agreement with the experimentally obtained elastic moduli of composites reinforced with uniformly aligned single-walled carbon nanotubes (CNTs). The primary contribution of the present work deals with the global elastic modal properties of nano-structured composite plates. The investigated composite plates are made of a purely isotropic elastic hosting matrix of three different types (epoxy, rubber, and concrete) with embedded single-walled CNTs. The computations are carried out via a finite element (FE) discretization of the composite plates. The effects of the CNT alignment and volume fraction are studied in depth to assess how the modal properties are influenced both globally and locally. As a major outcome, the lowest natural frequencies of CNT-reinforced rubber composites are shown to increase up to 500 percent.