Coefficients of thermal expansion of carbon nanotube-reinforced polyimide nanocomposites: A micromechanical analysis

2016 ◽  
Vol 233 (2) ◽  
pp. 169-179 ◽  
Author(s):  
R Ansari ◽  
MK Hassanzadeh-Aghdam ◽  
A Darvizeh
Keyword(s):  
Thermal Expansion ◽  
Carbon Nanotube ◽  
Present Model ◽  
Volume Fraction ◽  
Critical Role ◽  
Micromechanical Model ◽  
Temperature Deviation ◽  
Two Phases ◽  
Polyimide Matrix ◽  
Good Agreement

In this work, a unit cell-based micromechanical model with a proper representative volume element is proposed to evaluate the coefficients of thermal expansion of carbon nanotube-reinforced polyimide nanocomposites. The model takes an interphase between carbon nanotube and polyimide matrix into account which characterizes the non-bonded van der Waals interaction between two phases. The effects of some important parameters on the coefficients of thermal expansion such as thickness and adhesion exponent of interphase, temperature deviation as well as volume fraction, diameter and waviness of carbon nanotubes are investigated in detail. It is found that the interphase plays a critical role in determining the coefficients of thermal expansion and should be incorporated into the modeling of nanocomposite. According to the obtained results, there exists a specific value for carbon nanotube diameter beyond which further increasing in carbon nanotube diameter does not affect the coefficients of thermal expansion of nanocomposite. Also, the results reveal that the carbon nanotube waviness has a significant influence on the coefficients of thermal expansion of the nanocomposite. The results of the present model are compared with those of finite element method and a very good agreement is pointed out.

Transformation Textures in Unstable Austenitic Steel

2002 ◽  
Vol 125 (1) ◽  
pp. 12-17 ◽  
Author(s):  
R. Kubler ◽  
M. Berveiller ◽  
M. Cherkaoui ◽  
K. Inal
Keyword(s):  
Martensitic Transformation ◽  
Volume Fraction ◽  
Micromechanical Model ◽  
Slip Rate ◽  
Transformation Strain ◽  
Dislocation Motion ◽  
Lattice Spin ◽  
Two Phases ◽  
The One ◽  
Elastic Plastic Materials

During the martensitic transformation in elastic-plastic materials, the local transformation strain as well as the plastic flow inside austenite are strongly related with the crystallographic orientation of the austenitic lattice. Two mechanisms involved in these materials, i.e., plasticity by dislocation motion and martensitic phase formation are coupled through kinematical constraints so that the lattice spin of the austenitic grains is different from the one due to classical slip. In this work, the lattice spin ω˙eA of the austenitic grains is related with the slip rate on the slip systems of the two phases, γ˙A and γ˙M, the evolution of the martensite volume fraction f˙ and the overall rotation rate Ω˙ of the grains. This new relation is integrated in a micromechanical model developed for unstable austenite in order to predict the evolution of the austenite texture during TRansformation Induced Plasticity (TRIP). Results for the evolution of the lattice orientation during martensitic transformation are compared with experimental data obtained by X-ray diffraction on a 304 AISI steel.

Interphase influences on the mechanical behavior of carbon nanotube–shape memory polymer nanocomposites: A micromechanical approach

2018 ◽  
Vol 30 (3) ◽  
pp. 463-478 ◽  
Author(s):  
MK Hassanzadeh-Aghdam ◽  
MJ Mahmoodi ◽  
R Ansari ◽  
A Darvizeh
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Shape Memory ◽  
Polymer Nanocomposites ◽  
Elastic Moduli ◽  
Volume Fraction ◽  
Shape Memory Polymer ◽  
Micromechanical Model ◽  
Elastic Behavior ◽  
Interphase Region

The effects of interphase characteristics on the elastic behavior of randomly dispersed carbon nanotube–reinforced shape memory polymer nanocomposites are investigated using a three-dimensional unit cell–based micromechanical method. The interphase region is formed due to non-bonded van der Waals interaction between a carbon nanotube and a shape memory polymer. The influences of temperature, diameter, volume fraction, and arrangement type of carbon nanotubes within the matrix as well as two interphase factors, including adhesion exponent and thickness on the carbon nanotube/shape memory polymer nanocomposite’s longitudinal and transverse elastic moduli, are explored extensively. Moreover, the results are presented for the shape memory polymer nanocomposites containing randomly oriented carbon nanotubes. The obtained results clearly demonstrate that the interphase region plays a crucial role in the modeling of the carbon nanotube/shape memory polymer nanocomposite’s elastic moduli. It is observed that the nanocomposite’s elastic moduli remarkably increase with increasing interphase thickness or decreasing adhesion exponent. It is found that when the interphase is considered in the micromechanical simulation, the shape memory polymer nanocomposite’s elastic moduli non-linearly increase as the carbon nanotube diameter decreases. The predictions of the present micromechanical model are compared with those of other analytical methods and available experiments.

Simulation-based verification of homogenization approach in predicting effective thermal conductivities of wavy orthotropic fiber composite

2019 ◽  
Vol 08 (04) ◽  
pp. 1950015
Author(s):  
C. Mahesh ◽  
K. Govindarajulu ◽  
V. Balakrishna Murthy
Keyword(s):  
Volume Fraction ◽  
Fiber Composite ◽  
Micromechanical Model ◽  
Two Stage ◽  
Micromechanics Models ◽  
Simulation Based ◽  
Homogenization Approach ◽  
Homogenized Model ◽  
Good Agreement ◽  
Thermal Conductivities

In this work, applicability of homogenization approach is verified with the micromechanics approach by considering wavy orthotropic fiber composite. Thermal conductivities of [Formula: see text]-300 orthotropic wavy fiber composite are determined for micromechanical model and compared with the results obtained by two stage homogenized model over volume fraction ranging from 0.1 to 0.6. Also, a methodology is suggested for reducing percentage deviation between homogenization and micromechanical approaches. Effect of debond on the thermal conductivities of wavy orthotrophic fiber composite is studied and compared with perfectly aligned fiber composite for different volume fraction. It is observed that results obtained by the homogenization approach are in good agreement with the results obtained through micromechanics approach. Maximum percentage deviation between homogenized and micromechanics models is 2.13%.

Analyzing the effects of interphase on the effective damping properties of aligned carbon nanotube-reinforced epoxy nanocomposites using a micromechanical approach

2020 ◽  
Vol 234 (7) ◽  
pp. 910-923
Author(s):  
M Pakseresht ◽  
R Ansari ◽  
MK Hassanzadeh-Aghdam
Keyword(s):  
Carbon Nanotube ◽  
Polymer Nanocomposites ◽  
Volume Fraction ◽  
Contact Region ◽  
Damping Capacity ◽  
Damping Properties ◽  
Epoxy Nanocomposites ◽  
Damping Coefficients ◽  
Micromechanical Approach ◽  
Good Agreement

In this work, a micromechanical approach consisting of high-fidelity generalized method of cells (HFGMC) and Mori-Tanaka (M-T) model is proposed to calculate the damping properties of aligned carbon nanotube-epoxy nanocomposites. To determine the resultant directional specific damping coefficients, these models, by applying strain energy approach in the global system utilize each constituent’s specific damping coefficients and mechanical properties. The effects of interphase created in the contact region of the two initial phases—carbon nanotube and polymer matrix—are extensively investigated. Comparative studies show that the micromechanical results are in good agreement with experimental data. One major finding is the thickness and mechanical and damping properties of interphase significantly affect the overall specific damping coefficients of the carbon nanotube-polymer nanocomposites. It is found that by increasing the elastic modulus of the interphase, the longitudinal specific damping property continuously increases, while other components of damping, initially increase and then asymptotically decrease. The damping properties of polymer nanocomposites can be increased by increasing the interphase damping capacity. However, the rise of interphase thickness leads to a reduction of nanocomposite damping properties. Also, the influences of carbon nanotube volume fraction and radius are examined on the damping response of polymer nanocomposites.

Free Vibration and Buckling Analysis of Sandwich Beams with Functionally Graded Carbon Nanotube-Reinforced Composite Face Sheets

2015 ◽  
Vol 15 (07) ◽  
pp. 1540011 ◽  
Author(s):  
Helong Wu ◽  
Sritawat Kitipornchai ◽  
Jie Yang
Keyword(s):  
Carbon Nanotube ◽  
Free Vibration ◽  
Volume Fraction ◽  
Slenderness Ratio ◽  
Micromechanical Model ◽  
Sandwich Beam ◽  
Sheet Thickness ◽  
Functionally Graded ◽  
Sandwich Beams ◽  
Reinforced Composite

This paper investigates the free vibration and elastic buckling of sandwich beams with a stiff core and functionally graded carbon nanotube reinforced composite (FG-CNTRC) face sheets within the framework of Timoshenko beam theory. The material properties of FG-CNTRCs are assumed to vary in the thickness direction, and are estimated through a micromechanical model. The governing equations and boundary conditions are derived by using Hamilton's principle and discretized by employing the differential quadrature (DQ) method to obtain the natural frequency and critical buckling load of the sandwich beam. A detailed parametric study is conducted to study the effects of carbon nanotube volume fraction, core-to-face sheet thickness ratio, slenderness ratio, and end supports on the free vibration characteristics and buckling behavior of sandwich beams with FG-CNTRC face sheets. The vibration behavior of the sandwich beam under an initial axial force is also discussed. Numerical results for sandwich beams with uniformly distributed carbon nanotube-reinforced composite (UD-CNTRC) face sheets are also provided for comparison.

Effect of aluminum carbide interphase on the thermomechanical behavior of carbon nanotube/aluminum nanocomposites

2018 ◽  
Vol 233 (9) ◽  
pp. 1843-1853 ◽  
Author(s):  
Xiaolong Shi ◽  
Mohammad Kazem Hassanzadeh Aghdam ◽  
Reza Ansari
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Thermal Expansion ◽  
Carbon Nanotube ◽  
Volume Fraction ◽  
Chemical Interaction ◽  
Coefficient Of Thermal Expansion ◽  
Aluminum Matrix ◽  
Aluminum Carbide ◽  
Element Method

The objective of this work is to investigate the coefficient of thermal expansion of carbon nanotube reinforced aluminum matrix nanocomposites in which aluminum carbide (Al4C3) interphase formed due to chemical interaction between the carbon nanotube and aluminum matrix is included. To this end, the micromechanical finite element method along with a representative volume element, which incorporates, carbon nanotube, interphase, and aluminum matrix is employed. The emphasis is mainly placed on the effect of Al4C3 interphase on the coefficient of thermal expansion of aluminum nanocomposites with random microstructures. The effects of interphase thickness, carbon nanotube diameter, and volume fraction on the thermomechanical response of aluminum nanocomposite are discussed. The results reveal that the effect of Al4C3 interphase on the coefficient of thermal expansion of the aluminum nanocomposites becomes more significant with (i) increasing the coefficient of thermal expansion volume fraction, (ii) decreasing the coefficient of thermal expansion diameter, and (iii) increasing the interphase thickness. It is clearly observed that the coefficient of thermal expansion varies nonlinearly with the carbon nanotube diameter; however, it decreases linearly as the carbon nanotube volume fraction increases. Furthermore, the axial and transverse coefficient of thermal expansions of aligned continuous and discontinuous carbon nanotube-reinforced aluminum nanocomposites with Al4C3 interphase are predicted. Also, the presented finite element method results are compared with the available experiment in the literature, rule of mixture, and concentric cylinder model results.

scholarly journals Coefficient of Thermal Expansion of Single-Wall Carbon Nanotube Reinforced Nanocomposites

2021 ◽  
Vol 5 (1) ◽  
pp. 26
Author(s):  
Chensong Dong
Keyword(s):  
Experimental Data ◽  
Thermal Expansion ◽  
Carbon Nanotube ◽  
Interfacial Adhesion ◽  
Coefficient Of Thermal Expansion ◽  
Single Wall Carbon Nanotube ◽  
Single Wall Carbon ◽  
The Matrix ◽  
Adhesion Factor ◽  
Good Agreement

A study on the coefficient of thermal expansion (CTE) of single-wall carbon nanotube (SWCNT)-reinforced nanocomposites is presented in this paper. An interfacial adhesion factor (IAF) is introduced for the purpose of modelling the adhesion between SWCNTs and the matrix. The effective CTE and modulus of SWCNTs are derived using the IAF, and the effective CTE of the nanocomposite is derived by the Mori–Tanaka method. The developed model is validated against experimental data and good agreement is found.

Improved mechanical properties of aligned multi-walled carbon nanotube/thermoplastic polyimide composites by hot stretching

2018 ◽  
Vol 53 (9) ◽  
pp. 1241-1253 ◽  
Author(s):  
Tran H Nam ◽  
Ken Goto ◽  
Toshiki Kamei ◽  
Yoshinobu Shimamura ◽  
Yoku Inoue ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotube ◽  
Volume Fraction ◽  
High Heat ◽  
Melt Processing ◽  
Multi Walled Carbon Nanotube ◽  
Vertically Aligned ◽  
Polyimide Composites ◽  
Polyimide Matrix ◽  
Surface Morphologies

High heat resistance composites based on thermoplastic polyimide resin and aligned multi-walled carbon nanotube sheets have been developed using hot-melt processing method with a vacuum-assisted system. The horizontally aligned carbon nanotube sheets were produced from vertically aligned carbon nanotube arrays using drawing and press-winding techniques. Effects of processing conditions, carbon nanotube contents, and hot stretching on the mechanical properties of the composites were examined. The aligned carbon nanotube/thermoplastic polyimide composites were fabricated successfully at a temperature of 410℃ under 2 MPa pressure. The surface morphologies of the composites showed high alignment and dense packing of carbon nanotubes, and a good impregnation of the thermoplastic polyimide matrix into the aligned carbon nanotube sheets. The best mechanical properties of the aligned carbon nanotube/thermoplastic polyimide composites were achieved at the carbon nanotube volume fraction of about 50% in this study. Hot stretching of the aligned carbon nanotube/thermoplastic polyimide composites at the temperatures above the glass transition temperature and below the melting temperature improved the mechanical properties of the composites considerably.

Modeling on mass loss and nose blunting of high-speed penetrator into concrete target

2018 ◽  
Vol 10 (1) ◽  
pp. 3-25
Author(s):  
Ouyang Hao ◽  
Xiaowei Chen
Keyword(s):  
Mass Loss ◽  
High Speed ◽  
Present Model ◽  
Volume Fraction ◽  
Depth Of Penetration ◽  
Calculation Results ◽  
Nose Shape ◽  
Good Agreement ◽  
Key Parameter ◽  
Concrete Target

Mass loss and nose blunting of the projectile are often observed in high-speed penetration into concrete target. A new theoretical model is established to present the process of mass abrasion of projectile during penetration and to predict the mass loss and nose shape of the residual projectile after penetration. In order to better describe the effect of aggregate on the mass abrasion of penetrator, both the aggregate volume fraction and its shear strength are introduced into the present model. In the present model, the caliber-radius-head value of projectile nose is a key parameter and the mass loss and nose shape of projectile can be obtained easily only by solving a differential equation for the caliber-radius-head value and the penetrating velocity v, which is much more convenient than the incremental calculation and all other methods of mass receding of projectile outer surface. The calculation results show a good agreement with experimental results. According to the present model of mass abrasion, the depth of penetration of projectile and its acceleration curve during penetration are further calculated by considering the effects of mass loss and nose blunting of projectile.

Thermomechanical nonlinear buckling of pressure-loaded carbon nanotube reinforced composite toroidal shell segment surrounded by an elastic medium with tangentially restrained edges

2018 ◽  
Vol 233 (9) ◽  
pp. 3193-3207 ◽  
Author(s):  
Pham Thanh Hieu ◽  
Hoang Van Tung
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Elastic Medium ◽  
Volume Fraction ◽  
Effective Properties ◽  
Micromechanical Model ◽  
Toroidal Shell ◽  
Nonlinear Buckling ◽  
Nonlinear Load ◽  
Reinforced Composite

Buckling and postbuckling behaviors of toroidal shell segment reinforced by single-walled carbon nanotubes, surrounded by an elastic medium, exposed to a thermal environment and subjected to uniform external pressure are investigated in this paper. Carbon nanotubes are reinforced into matrix phase by uniform distribution or functionally graded distribution along the thickness direction. Material properties of constituents are assumed to be temperature dependent, and the effective properties of carbon nanotube reinforced composite are estimated by extended mixture rule through a micromechanical model. Governing equations for toroidal shell segments are based on the classical thin shell theory taking into account geometrical nonlinearity, surrounding elastic medium, and varying degree of tangential constraints of edges. Three-term solution of deflection and stress function are assumed to satisfy simply supported boundary condition, and Galerkin method is applied to derive nonlinear load–deflection relation from which buckling loads and postbuckling equilibrium paths are determined. Analysis shows that tangential edge restraints have significant effects on nonlinear buckling of carbon nanotube reinforced composite toroidal shell segments. In addition, the effects of carbon nanotube volume fraction, distribution types, geometrical ratios, elastic foundation, and thermal environments on the buckling and postbuckling behaviors of carbon nanotube reinforced composite toroidal shell segments are analyzed and discussed.

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