scholarly journals Dynamic Stability Analysis in Hybrid Nanocomposite Polymer Beams Reinforced by Carbon Fibers and Carbon Nanotubes

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 106
Author(s):  
Behrooz Keshtegar ◽  
Reza Kolahchi ◽  
Arameh Eyvazian ◽  
Nguyen-Thoi Trung
Keyword(s):  
Carbon Nanotubes ◽  
Dynamic Stability ◽  
Carbon Fibers ◽  
Volume Fraction ◽  
Dynamic Instability ◽  
Excitation Frequency ◽  
Hybrid Nanocomposite ◽  
Governing Equations ◽  
Volume Percent ◽  
Nanocomposite Polymer

The objective of this innovative research is assessment of dynamic stability for a hybrid nanocomposite polymer beam. The considered beam formed by multiphase nanocomposite, including polymer–carbon nanotubes (CNTs)–carbon fibers (CFs). Hence, as to compute the effective material characteristics related to multiphase nanocomposite layers, the Halpin–Tsai model, as well as micromechanics equations are employed. To model the structure realistically, exponential shear deformation beam theory (ESDBT) is applied and using energy methods, governing equations are achieved. Moreover, differential quadrature method (DQM) as well as Bolotin procedures are used for solving the obtained governing equations and the dynamic instability region (DIR) relative to the beam is determined. To extend this novel research, various parameters pinpointing the influences of CNT volume fraction, CFs volume percent, boundary edges as well as the structure’s geometric variables on the dynamic behavior of the beam are presented. The results were validated with the theoretical and experimental results of other published papers. The outcomes reveal that increment of volume fraction of CNT is able to shift DIR to more amounts of frequency. Further, rise of carbon fibers volume percent leads to increase the excitation frequency of this structure.

Nonlinear high-order dynamic stability of AL-foam flexible cored sandwich beam with variable mechanical properties and carbon nanotubes-reinforced composite face sheets in thermal environment

2017 ◽  
Vol 22 (2) ◽  
pp. 248-302 ◽  
Author(s):  
Saeid Shahedi ◽  
Mehdi Mohammadimehr
Keyword(s):  
Dynamic Stability ◽  
Dynamic Instability ◽  
Differential Quadrature Method ◽  
Excitation Frequency ◽  
Sandwich Beam ◽  
High Order ◽  
Al Foam ◽  
Generalized Differential ◽  
Composite Face ◽  
Flexible Core

In this paper, the nonlinear dynamic stability analysis of sandwich beam including AL-foam flexible core and carbon nanotubes-reinforced composite face sheets subjected to axial periodic load are investigated by using generalized differential quadrature method. The flexible core of sandwich beam is made of Aluminum alloy foam with variable mechanical properties in the thickness direction. With considering the high-order geometrical nonlinearity in the core and face sheets, the high-order sandwich panel theory and modified couple stress theory are employed for AL-foam flexible core and face sheets, respectively. The governing nonlinear partial differential equations of dynamic stability are derived from the Hamilton’s principle and then discretized by using generalized differential quadrature method to convert them into a linear system of Mathieu–Hill equations. These formulations lead to nine partial differential equations which are coupled in axial and transverse deformations. The boundaries of the instability region are achieved by Bolotin’s method and are illustrated in the dimensionless nonlinear excitation frequency (Ω NL) and excitation frequency ratio (Ω NL/Ω L) to load amplitude plane. A parametric study is carried out to investigate the influence of some important parameters such as slenderness ratio, face sheet thickness, temperature rise, carbon nanotube volume fraction, static load factor, coefficients of Pasternak foundation, and end supports on the nonlinear dynamic instability characteristics of AL-foam core sandwich beam. The numerical results show that with temperature increasing, the nonlinear excitation frequency (Ω NL) and width of corresponding unstable zone decrease, but dynamic frequency ratio (Ω NL/Ω L) and associated unstable region increase. With an increase in the application of sandwich structures for compressible core in advanced industries such as spacecraft, high-speed aircraft, naval vessels, transportation, and automobiles, a further interest in the problem-involving dynamic instability of structures has resulted. Because of their applications, sandwich structures are frequently exposed to periodic axial compressive forces and so the dynamic instability has been a very important topic in structural dynamics and is of practical importance in different engineering industries.

Dynamic stability analysis of microcomposite annular sandwich plate with carbon nanotube reinforced composite facesheets based on modified strain gradient theory

2018 ◽  
Vol 22 (4) ◽  
pp. 1199-1234 ◽  
Author(s):  
M Mohammadimehr ◽  
M Emdadi ◽  
B Rousta Navi
Keyword(s):  
Carbon Nanotubes ◽  
Dynamic Stability ◽  
Sandwich Plate ◽  
Scale Parameter ◽  
Volume Fraction ◽  
Strain Gradient Theory ◽  
Gradient Theory ◽  
Dimensionless Length ◽  
Modified Strain Gradient Theory ◽  
Reinforced Composite

In this article, dynamic stability of annular sandwich plate with carbon nanotubes reinforced composite facesheets and an isotropic homogeneous core are presented based on first-order shear deformation theory and modified strain gradient theory. The generalized rule of mixture is employed to predict mechanical properties of microcomposite sandwich plate. The equations of motion are derived from Hamilton’s principle and solved by differential quadrature method. The fast rate of convergence of the method is shown and the results are compared against existing results in the literature. The results indicate that volume fraction of carbon nanotubes in facesheets and dimensionless length scale parameter has significant effects on the dynamic stability region and the parametric resonance. Dynamic stability region increases with considering of dimensionless length scale parameter, increasing of volume fraction of carbon nanotubes, and static load factor. Also, the influence of inner-to-outer radius ratios, radius-to-thickness ratios, and core-to-facesheets ratios are considered. The results can be employed for design of materials science, in junction high pressure micropipe connections, solid-state physics, micro-electro-mechanical systems, and nano electromechanical systems such as microactuators and microsensor.

Dynamic Instability of Laminated-Composite and Sandwich Plates Using a New Inverse Trigonometric Zigzag Theory

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Rosalin Sahoo ◽  
B. N. Singh
Keyword(s):  
Stability Analysis ◽  
Boundary Conditions ◽  
Dynamic Stability ◽  
Dynamic Instability ◽  
Excitation Frequency ◽  
Laminated Composite ◽  
Sandwich Plates ◽  
Load Amplitude ◽  
Instability Regions ◽  
Zigzag Theory

A structure with periodic dynamic load may lead to dynamic instability due to parametric resonance. In the present work, the dynamic stability analysis of laminated composite and sandwich plate due to in-plane periodic loads is studied based on recently developed inverse trigonometric zigzag theory (ITZZT). Transverse shear stress continuity at layer interfaces along with traction-free boundary conditions on the plate surfaces is satisfied by the model obviating the need of shear correction factor. An efficient C0 continuous, eight noded isoparametric element with seven field variable is employed for the dynamic stability analysis of laminated composite and sandwich plates. The boundaries of instability regions are determined using Bolotin's approach and the first instability zone is presented either in the nondimensional load amplitude–excitation frequency plane or load amplitude–load frequency plane. The influences of various parameters such as degrees of orthotropy, span-thickness ratios, boundary conditions, static load factors, and thickness ratios on the dynamic instability regions (DIRs) are studied by solving a number of problems. The evaluated results are validated with the available results in the literature based on different deformation theories. The efficiency of the present model is ascertained by the improved accuracy of predicted results at the cost of less computational involvement.

Dynamic Stability of Rotating FG-CNTRC Cylindrical Shells under Combined Static and Periodic Axial Loads

2018 ◽  
Vol 18 (12) ◽  
pp. 1850151 ◽  
Author(s):  
Yasin Heydarpour ◽  
Parviz Malekzadeh
Keyword(s):  
Dynamic Stability ◽  
Volume Fraction ◽  
Dynamic Instability ◽  
Cylindrical Shells ◽  
Shear Deformation Theory ◽  
Mechanical Stresses ◽  
Functionally Graded ◽  
Coriolis Acceleration ◽  
Axial Forces ◽  
Instability Regions

The dynamic stability behavior of rotating functionally graded carbon nanotube reinforced composite (FG-CNTRC) cylindrical shells under combined static and periodic axial forces is investigated. The governing equations are derived based on the first-order shear deformation theory (FSDT) of shells. The initial mechanical stresses due to the steady state rotation of the shell are evaluated by solving the dynamic equilibrium equations. The equations of motion under different boundary conditions are discretized in the spatial domain and transformed into a system of Mathieu–Hill type equations using the differential quadrature method (DQM) together with the trigonometric series. The influences of both the initial mechanical stresses and Coriolis acceleration are considered. Then, the parametric resonance is analyzed and the dynamic instability regions are determined by employing the Bolotin’s first approximation. After validating the approach, the effects of rotational speed, Coriolis acceleration, carbon nanotubes (CNTs) distribution in the thickness direction, CNTs volume fraction, length and thickness-to-mean radius ratios on the principal dynamic instability regions are examined in detail.

scholarly journals PARAMETRIC RESONANCE CHARACTERISTICS OF ANGLE-PLY TWISTED CURVED PANELS

2008 ◽  
Vol 08 (01) ◽  
pp. 61-76 ◽  
Author(s):  
S. K. SAHU ◽  
A. V. ASHA
Keyword(s):  
Shear Deformation ◽  
Dynamic Stability ◽  
Dynamic Instability ◽  
Excitation Frequency ◽  
Shear Deformation Theory ◽  
Laminated Composite ◽  
First Order ◽  
Cylindrical Panels ◽  
Instability Regions ◽  
Curved Panels

The present study deals with the dynamic stability of laminated composite pre-twisted cantilever panels. The effects of various parameters on the principal instability regions are studied using Bolotin's approach and finite element method. The first-order shear deformation theory is used to model the twisted curved panels, considering the effects of transverse shear deformation and rotary inertia. The results on the dynamic stability studies of the laminated composite pre-twisted panels suggest that the onset of instability occurs earlier and the width of dynamic instability regions increase with introduction of twist in the panel. The instability occurs later for square than rectangular twisted panels. The onset of instability occurs later for pre-twisted cylindrical panels than the flat panels due to addition of curvature. However, the spherical pre-twisted panels show small increase of nondimensional excitation frequency.

Endoscopy Analysis for the Peristaltic Flow of Nanofluids Containing Carbon Nanotubes with Heat Transfer

2015 ◽  
Vol 70 (9) ◽  
pp. 745-755 ◽  
Author(s):  
Noreen Sher Akbar
Keyword(s):  
Carbon Nanotubes ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Peristaltic Flow ◽  
Governing Equations ◽  
Long Wavelength ◽  
Flow Parameters ◽  
Proposed Model ◽  
Frictional Forces ◽  
Temperature And Pressure

AbstractCu–water nanofluid with carbon nanotubes is considered for the peristaltic flow in an endoscope. The peristaltic flow for nanofluid is modelled considering that the peristaltic rush wave is a sinusoidal wave that propagates along the walls of the tube. The governing equations for the proposed model are simplified by using the assumptions of long-wavelength and low Reynolds number. Exact solutions have been evaluated for velocity, temperature, and pressure gradient. Graphical results for the numerical values of the flow parameters, i.e. Hartmann number M, the solid volume fraction ϕ of the nanoparticles, Grashof number Gr, heat absorption parameter β, and radius of the inner tube ε, have been presented for the pressure difference, frictional forces, velocity profile, and temperature profile, and trapping phenomena have been discussed at the end of the article.

Analysis of Dynamic Stability for Composite Laminated Beam with Delamination

2012 ◽  
Vol 204-208 ◽  
pp. 3074-3077 ◽  
Author(s):  
Jin Hua Yang ◽  
De Liang Chen ◽  
Ming Zhe Ning
Keyword(s):  
Dynamic Stability ◽  
Dynamic Instability ◽  
Ritz Method ◽  
Step Function ◽  
Total Potential Energy ◽  
Governing Equations ◽  
Heaviside Step Function ◽  
Laminated Beam ◽  
Total Potential ◽  
Delamination Length

Abstract. By introducing the Heaviside step function into assumed displacement components and using the Rayleigh-Ritz method for minimizing the total potential energy, a set of dynamic governing equations for the delaminated beam is derived. Then, the dynamic governing equations are written as the Mathieu-type equations to describe the parametric vibrating behavior of the beam, and these equations are solved by employing the Bolotin’s method. Numerical results in dynamic stability of laminated beam with delamination are presented, and the effects of static loading, delamination length and material property on the principal dynamic instability region of the laminated beam are discussed. Present results are compared with available data.

DYNAMIC STABILITY CHARACTERISTICS OF FUNCTIONALLY GRADED PLATES UNDER ARBITRARY PERIODIC LOADS

2013 ◽  
Vol 13 (06) ◽  
pp. 1350026 ◽  
Author(s):  
CHUN-SHENG CHEN ◽  
CHIH-WEN CHEN ◽  
WEI-REN CHEN
Keyword(s):  
Layer Thickness ◽  
Dynamic Load ◽  
Volume Fraction ◽  
Dynamic Instability ◽  
Plate Thickness ◽  
Excitation Frequency ◽  
Frequency Instability ◽  
Functionally Graded ◽  
Functionally Graded Plates ◽  
Periodic Load

The dynamic instability of functionally graded material (FGM) plates under an arbitrary periodic load is studied. The properties of the functionally graded plates (FGPs) are assumed to vary continuously across the plate thickness according to a simple power law. With the derived Mathieu equations, the dynamic instability regions of the FGPs are determined by using the Bolotin's method. The in-plane periodic load is taken to be a combination of periodic axial and bending stress in the example problems. The influences of the volume fraction index, layer thickness ratio, static and dynamic load on the dynamic instability of ceramic-FGM-metal plates are discussed. The results reveal that the excitation frequency, instability region and dynamic instability index of these plates are significantly affected by the static load, dynamic load, volume fraction index and layer thickness.

Influence of Multiwall Carbon Nanotube on mechanical and wear properties of Copper – Iron composite

2020 ◽  
Vol 17 (1) ◽  
pp. 7570-7576 ◽  
Author(s):  
H. Sh. Hammood ◽  
S. S. Irhayyim ◽  
A. Y. Awad ◽  
H. A. Abdulhadi
Keyword(s):  
Carbon Nanotubes ◽  
Volume Fraction ◽  
Hybrid Composites ◽  
Hydraulic Press ◽  
Dry Sliding Wear ◽  
Multiwall Carbon Nanotube ◽  
Wear Properties ◽  
Sem Images ◽  
Wear Rates ◽  
Multiwall Carbon

Multiwall Carbon nanotubes (MWCNTs) are frequently attractive due to their novel physical and chemical characteristics, as well as their larger aspect ratio and higher conductivity. Therefore, MWCNTs can allow tremendous possibilities for the improvement of the necessarily unique composite materials system. The present work deals with the fabrication of Cu-Fe/CNTs hybrid composites manufactured by powder metallurgy techniques. Copper powder with 10 vol. % of iron powder and different volume fractions of Multi-Wall Carbon Nanotubes (MWCNTs) were mixed to get hybrid composites. The hybrid composites were fabricated by adding 0.3, 0.6, 0.9, and 1.2 vol.% of MWCNTs to Cu- 10% Fe mixture using a mechanical mixer. The samples were compressed under a load of 700 MPa using a hydraulic press to compact the samples. Sintering was done at 900°C for 2 h at 5ºC/min heating rate. The microscopic structure was studied using a Scanning Electron Microscope (SEM). The effect of CNTs on the mechanical and wear properties, such as micro-hardness, dry sliding wear, density, and porosity were studied in detail. The wear tests were carried out at a fixed time of 20 minutes while the applied loads were varied (5, 10, 15, and 20 N). SEM images revealed that CNTs were uniformly distributed with relative agglomeration within the Cu/Fe matrix. The results showed that the hardness, density, and wear rates decreased while the percentage of porosity increased with increasing the CNT volume fraction. Furthermore, the wear rate for all the CNTs contents increased with the applied load.

Ciliary Flow of Casson Nanofluid with the Influence of MHD having Carbon Nanotubes

2020 ◽  
Vol 16 ◽  
Author(s):  
Adel Alblawi ◽  
Saba Keyani ◽  
S. Nadeem ◽  
Alibek Issakhov ◽  
Ibrahim M. Alarifi
Keyword(s):  
Carbon Nanotubes ◽  
Velocity Profile ◽  
Pressure Gradient ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Pressure Rise ◽  
Shear Stresses ◽  
Left Wall ◽  
Coupled Equations ◽  
The Right

Objective: In this paper, we consider a model that describes the ciliary beating in the form of metachronal waves along with the effects of Magnetohydrodynamic fluid over a curved channel with slip effects. This work aims at evaluating the effect of Magnetohydrodynamic (MHD) on the steady two dimensional (2-D) mixed convection flow induced in carbon nanotubes. The work is done for both the single wall nanotube and multiple wall nanotube. The right wall and the left wall possess a metachronal wave that is travelling along the outer boundary of the channel. Methods: The wavelength is considered as very large for cilia induced MHD flow. The governing linear coupled equations are simplified by considering the approximations of long wavelength and small Reynolds number. Exact solutions are obtained for temperature and velocity profile. The analytical expressions for the pressure gradient and wall shear stresses are obtained. Term for pressure rise is obtained by applying Numerical integration method. Results: Numerical results of velocity profile are mentioned in a table form, for various values of solid volume fraction, curvature, Hartmann number [M] and Casson fluid parameter [ζ]. Final section of this paper is devoted to discussing the graphical results of temperature, pressure gradient, pressure rise, shear stresses and stream functions. Conclusion: Velocity profile near the right wall of the channel decreases when we add nanoparticles into our base fluid, whereas an opposite behaviour is depicted near the left wall due to ciliated tips whereas the temperature is an increasing function of B and ߛ and decreasing function of ߶.

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