Effects Of Nanotube Volume Fraction Research Articles

Low-velocity impact response of sandwich cylindrical panels with nanotube-reinforced and metal face sheet in thermal environment

ABSTRACTEmploying an analytical method, non-linear low-velocity impact response of carbon nanotube (CNT)-reinforced sandwich cylindrical panels in thermal environments is analysed. Two types of core (i.e. homogenous and functionally graded) are considered for sandwich panels. The face sheets of sandwich panels are multi-layer which consist of CNT-reinforced composite (CNTRC) and metal layers. Micromechanical models are used to estimate the material properties of CNTRCs. A higher-order shear deformation theory with a von Kármán-type of kinematic non-linearity provides the equations of motion. Temperature-dependent material properties are used to include the thermal effects. The equations of motion are solved using a two-step perturbation technique. Existing numerical results in the literature are used to validate the present method. The effect of nanotube volume fraction, material property gradient, impactor initial velocity, geometrical parameters of cylindrical panel, temperature change and edge boundary condition on the impact response of cylindrical panel structures is discussed. The quantitative results and analytical formulations can be helpful in better designing of CNTRC structures subjected to low-velocity impact in thermal environments.

On the mechanical properties of functionally graded materials reinforced by carbon nanotubes

In this paper, the elastic properties of functionally graded materials reinforced by single-walled carbon nanotubes are studied. Three different matrices, including steel-silicon, iron-alumina and alumina-zirconia are considered. Besides, the effects of nanotube length, radius and volume fraction on the Young’s modulus of functionally graded matrices reinforced by single-walled carbon nanotubes are investigated. It is observed that short nanotubes not only cannot increase the longitudinal elastic modulus of the matrices, but sometimes decrease their elastic modulus. Of the three selected matrices, steel-silicon matrix would have the most enhancement. Investigation of the effect of nanotube volume fraction on the mechanical properties of nanocomposites shows that increasing the volume fraction of long single-walled carbon nanotube results in increasing the elastic modulus of the nanocomposites.

Dynamic extended high order sandwich panel theory for transient response of sandwich beams with carbon nanotube reinforced face sheets

The dynamic version of the Extended High Order Sandwich Panel Theory (EHSAPT) for a sandwich beam with soft core and carbon nanotube reinforced composite (CNTRC) face sheets is first formulated. Distribution of fibers through the thickness of the face sheets could be uniform or functionally graded (FG). The influences of boundary conditions on dynamic response of the sandwich panel are investigated. In each type of boundary condition the effects of nanotube volume fraction and their distribution pattern, core-to-face sheet thickness ratio, on many essential involved parameters of the sandwich beam with functionally graded carbon nanotube reinforced composite (FG-CNTRC) face sheets are studied in detail. The results for a transient displacement of sandwich beam with isotropic face sheets reveal that the EHSAPT is very accurate during the initial, transient phase of dynamic loading in comparison with conventional high order sandwich panel theory (HSAPT). Finally, it is concluded that the sandwich beam with V distribution figure of face sheets is the strongest and the smallest transverse displacement, followed by the X, UD, O and ∧-ones, respectively.

Free vibration analysis of sandwich beams with carbon nanotube reinforced face sheets based on extended high-order sandwich panel theory

Free vibration analysis of a sandwich beam with soft core and carbon nanotube reinforced composite face sheets, hitherto not reported in the literature, based on extended high-order sandwich panel theory is presented. Distribution of fibers through the thickness of the face sheets could be uniform or functionally graded. In this theory, the face sheets follow the first-order shear deformation theory. Besides, the two-dimensional elasticity is used for the core. The field equations are derived via the Ritz-based solution which is suitable for any essential boundary conditions. Chebyshev polynomials multiplying boundary R-functions are used as admissible functions and evidence of their good performance is given. A detailed parametric study is conducted to study the effects of nanotube volume fraction and their distribution pattern, core-to-face sheet thickness ratio, and boundary conditions on the natural frequencies and mode shapes of sandwich beams with functionally graded carbon nanotube reinforced composite face sheets and soft cores. Since the extended high-order sandwich panel theory can be used with any combinations of core and face sheets and not only the soft cores that the other theories demand, the results for the same beam with functionally graded carbon nanotube reinforced composite face sheets and stiff core are also provided for comparison. It is concluded that the sandwich beam with X and V distribution figures of face sheets, no matter what the boundary conditions, has higher vibration performance than the beam with UD-CNTRC face sheets.

Lignin as dispersant for water-based carbon nanotubes nanofluids: Impact on viscosity and thermal conductivity

The viscosity and thermal conductivity of water-based nanofluids containing carbon nanotubes, stabilized by lignin as surfactant, are measured. These experiments were performed at 20°C and we study the effect of nanotube volume fraction which ranges from 0.0055% to 0.55%. In comparison with SDBS, we show that lignin reduces viscosity and shear-thinning behavior of nanofluids at high volume fraction, without penalizing thermal conductivity enhancement. Viscosity enhancement at high shear rate with respect to nanoparticle content is well modeled by the Maron–Pierce equation, suggesting that lignin is better than SDBS at dispersing carbon nanotubes within water at high volume fraction. The impact of surfactant on base fluid thermal conductivity is also reported and thermal conductivity enhancement of nanofluids with nanoparticle volume fraction is finally compared with previous published models.

Effective mechanical properties of nanocomposites reinforced with wavy carbon nanotubes

Carbon nanotubes (CNTs) possess exceptional mechanical properties and are therefore suitable reinforcements for composite materials. Nanotube efficiency in reinforcing the matrix depends on the CNT alignment, volume fraction and configuration, as well as matrix properties. In this investigation, finite element method (FEM) is used to investigate the effects of nanotube waviness ratio, volume fraction, and matrix modulus on properties of CNT based polymer nanocomposites. Nanocomposite mechanical properties are evaluated using a 3D nanoscale representative volume element. Models consisting of CNTs with different waviness ratios are created to investigate the effects of nanotube configuration on nanocomposite mechanical properties. Next, the effect of nanotube volume fraction on nanocomposite moduli of elasticity is investigated. Finally, the effects of matrix modulus are investigated by analysing models consisting of matrices with different moduli. The results of this investigation are compared with those found in the literature and good agreement is observed.

Parametric numerical evaluation of the effective elastic properties of carbon nanotube-reinforced polymers

In this paper, the effective elastic properties of carbon nanotube-reinforced polymers have been evaluated as functions of material and geometrical parameters using a homogenized RVE. The RVE consists of the polymer matrix, a multi-walled carbon nanotube (MWCNT) embedded into the matrix and the interface between them. The parameters considered are the nanotube aspect ratio, the nanotube volume fraction as well as the interface stiffness and thickness. For the MWCNT, both isotropic and orthotropic material properties have been considered. Analyses have been performed by means of a 3D FE model of the RVE. The results indicate a significant effect of nanotube volume fraction. The effect of nanotube aspect ratio appears mainly at low values and diminishes after the value of 20. The interface mostly affects the effective elastic properties at the transverse direction. Having evaluated the effective elastic properties of the MWCNT–polymer at the micro-scale, the RVE has been used to predict the tensile modulus of a polystyrene specimen reinforced by randomly aligned MWCNTs for which experimental data exist in the literature. A very good agreement is obtained between the predicted and experimental tensile moduli of the specimen. The effect of nanotube alignment on the specimen’s tensile modulus has been also examined and found to be significant since as misalignment increases the effective tensile modulus decreases radically. The proposed model can be used for the virtual design and optimization of CNT–polymer composites since it has proven capable of assessing the effects of different material and geometrical parameters on the elastic properties of the composite and predicting the tensile modulus of CNT-reinforced polymer specimens.

Nonlinear vibration and bending of sandwich plates with nanotube-reinforced composite face sheets

This paper studied the large amplitude vibration and the nonlinear bending of a sandwich plate with carbon nanotube-reinforced composite (CNTRC) face sheets resting on an elastic foundation in thermal environments. The material properties of CNTRC face sheets are assumed to be graded in the thickness direction, and are estimated through a micromechanical model. The governing equation of the plate that includes plate-foundation interaction is solved by a two-step perturbation technique. The thermal effects are also included and the material properties of both CNTRC face sheets and homogeneous core layer are assumed to be temperature-dependent. A detailed parametric study is conducted to study the effects of nanotube volume fraction, core-to-face sheet thickness ratio, temperature change, foundation stiffness and in-plane boundary conditions on the nonlinear vibration characteristics and nonlinear bending behaviors of sandwich plates with functionally graded CNTRC face sheets. The results for the same plate with uniformly distributed CNTRC face sheets are also provided for comparison.

Nonlinear free vibration of functionally graded carbon nanotube-reinforced composite beams

This paper investigates the nonlinear free vibration of functionally graded nanocomposite beams reinforced by single-walled carbon nanotubes (SWCNTs) based on Timoshenko beam theory and von Karman geometric nonlinearity. The material properties of functionally graded carbon nanotube-reinforced composites (FG-CNTRCs) are assumed to be graded in the thickness direction and estimated though the rule of mixture. The Ritz method is employed to derive the governing eigenvalue equation which is then solved by a direct iterative method to obtain the nonlinear vibration frequencies of FG-CNTRC beams with different end supports. A detailed parametric study is conducted to study the influences of nanotube volume fraction, vibration amplitude, slenderness ratio and end supports on the nonlinear free vibration characteristics of FG-CNTRC beams. The results for uniformly distributed carbon nanotube-reinforced composite (UD-CNTRC) beams are also provided for comparison. Numerical results are presented in both tabular and graphical forms to investigate the effects of nanotube volume fraction, vibration amplitude, slenderness ratio, end supports and CNT distribution on the nonlinear free vibration characteristics of FG-CNTRC beams.