Nanocomposite Shell Research Articles

Nonlinear axisymmetric dynamic buckling of functionally graded graphene reinforced porous nanocomposite spherical caps

Here, the axisymmetric dynamic snap-through buckling of graphene platelets (GPLs) reinforced porous nanocomposite spherical caps subjected to a suddenly applied external pressure load is focused using finite element approach and adopting shear deformation theory. Different types of porosity distributions and dispersion patterns of GPLs in the matrix of nanocomposite shell are treated in the thickness direction of shell. The effective material properties of porous nanocomposite with graphene reinforcement are determined introducing Halpin-Tsai micromechanics model and the rule of mixture. A three-noded axisymmetric field consistent shell element is proposed to solve the governing equations developed from Lagrange’s equation of motion. The geometric nonlinearity is accounted for following von-Karman’s strain displacement relationship. The critical buckling pressure is evaluated based on dynamic response analysis obtained using Newmark’s integration technique coupled with the modified Newton-Raphson iteration scheme. For validating the formulation and solution technique, the results are compared with the available solutions in literature for the cases of isotropic and nanocomposite shells wherever possible. A comprehensive parametric study is performed to understand the effect of weight fraction of GPLs, distribution pattern of porosity and GPL, GPL geometry, shell geometry parameter and boundary conditions on the dynamic buckling of spherical caps.

Thermoelastic vibration of doubly-curved nano-composite shells reinforced by graphene nanoplatelets

The thermo-mechanical vibration characteristics of doubly-curved nano-composite shells reinforced by graphene nanoplatelets are investigated by considering a uniform distribution of graphene and a first-order shear deformation theory. The mechanical properties of the nano-composite shells are estimated by using the modified Halpin–Tsai model. The governing equations are first derived by a variational formulation using Hamilton’s principle and are solved using the Galerkin technique. Numerical results are presented for various shell curvatures and compared with those available in the archival literature. Furthermore, parametric studies are offered to highlight the significant influence of graphene nanoplatelets’ weight fraction, dimensions of graphene nanoplatelets, and temperature variation, on the free vibration of the nano-composite shells.

Wave dispersion characteristics of porous graphene platelet-reinforced composite shells

Wave propagation analysis of a porous graphene platelet reinforced (GPLR) nanocomposite shell is investigated for the first time. The homogenization of the utilized material is procured by extending the Halpin-Tsai relations for the porous nanocomposite. Both symmetric and asymmetric porosity distributions are regarded in this analysis. The equations of the shell\'s motion are derived according to Hamilton\'s principle coupled with the kinematic relations of the first-order shear deformation theory of the shells. The obtained governing equations are considered to be solved via an analytical solution which includes two longitudinal and circumferential wave numbers. The accuracy of the presented formulations is examined by comparing the results of this method with those reported by former authors. The simulations reveal a stiffness decrease in the cases which porosity influences are regarded. Also, one must pay attention to the effects of longitudinal wave number on the wave dispersion curves of the nanocomposite structure.

Accurate nonlinear buckling analysis of functionally graded porous graphene platelet reinforced composite cylindrical shells

By considering the pre-buckling effect and in-plane constraint, an accurate nonlinear buckling analysis of a functionally graded porous graphene platelet reinforced composite cylindrical shells under axial compressive load is performed. The stability equation is established according to a unified shell theory including the classical thin shell theory and the high-order shear deformation theory. Three types of porosity distributions and graphene platelet reinforced patterns are considered, and the modified Halpin–Tsai model and rule of mixtures are employed to determine their effective material properties. Explicit expressions of buckling equations for clamped or simply supported boundary conditions are obtained by the Galerkin's method. Highly accurate critical buckling loads and analytical buckling mode shapes are obtained simultaneously. A comparison between theoretical prediction and experiment is presented to verify the present method and very good agreement is reported. The influences of material properties on the buckling behaviors are also extensively investigated. It is recommended that the symmetric dispersion pattern is the optimal material distributions for both graphene platelets and porous, and the largest possible weight fraction, specific surface area and average thickness of graphene platelets could induce a better anti-buckling performance for the nanocomposite shell.

Wave propagation characteristics of a cylindrical laminated composite nanoshell in thermal environment based on the nonlocal strain gradient theory

In this article, the wave propagation behavior of a size-dependent laminated composite cylindrical nanoshell in a thermal environment is presented. The small-scale effects are analyzed based on nonlocal strain gradient theory (NSGT). The governing equations of the cylindrical laminated composite nanoshell in a thermal environment were obtained using Hamilton’s principle and solved by the analytical method. The novelty of this study is considering the effects of the composite layers and NSGT in addition to considering the thermal environment of the cylindrical composite nanoshell. Finally, the investigation was performed on the influence of temperature difference, wave number, angular velocity and the different types of laminated composite on the phase velocity using the mentioned continuum mechanics theory. The results show that wave number, ply angle, shear correction factor and thermal environment play an important role on the phase velocity of the laminated composite nanostructure. Another significant result is that, in a specific temperature difference, there is an inverse relation between the number of layers in a laminate and the dynamic behavior of the nanostructure. The outcome of the present work can be used in a structural health monitoring and ultrasonic inspection techniques.

On modeling of wave propagation in a thermally affected GNP-reinforced imperfect nanocomposite shell

Due to rapid development of process manufacturing, composite materials with porosity have attracted commercial attention in promoting engineering applications. For this regard, in this research wave propagation-thermal characteristics of a size-dependent graphene nanoplatelet-reinforced composite (GNPRC) porous cylindrical nanoshell in thermal environment are investigated. The effects of small scale are analyzed based on nonlocal strain gradient theory (NSGT). The governing equations of the laminated composite cylindrical nanoshell in thermal environment have been evolved using Hamilton’s principle and solved with the assistance of the analytical method. For the first time, wave propagation-thermal behavior of a GNPRC porous cylindrical nanoshell in thermal environment based on NSGT is examined. The results show that by increasing the thickness, the effect of porosity on the phase velocity decreases. Another important result is that by increasing the value of the radius, the difference between the minimum and maximum values of the phase velocity increases. Finally, influence of temperature change, wave number, angular velocity and different types of porosity distribution on phase velocity are investigated using the mentioned continuum mechanics theory. As a useful suggestion, for designing of a GPLRC nanostructure should be attention to the GNP weight function and radius, simultaneously.

Controlled synthesis of metal-organic frameworks coated with noble metal nanoparticles and conducting polymer for enhanced catalysis

The combination of noble metal nanoparticles (NM NPs) and metal-organic frameworks (MOFs) for enhanced properties in catalysis is a rapidly developing interdisciplinary research field. Herein we report a facile one-step approach to the deposition of functional nanocomposite shell composed of NM NPs and conducting polymer on the surface of particulate UiO-66. Our approach is based on the recently developed double solvents method involving a hydrophobic solvent (n-hexane) and a hydrophilic solvent (water). Particularly, the n-hexane was used in a large amount to suspend the UiO-66 particles with hydrophilic inner pores and promoted the enrichment of the water containing the palladium chloride (PdCl2) inside the pores of UiO-66 particles, because these two solvents are immiscible and the volume of water is smaller than the pore volume of the UiO-66 particles. After the introduction of hydrophobic pyrrole into the n-hexane, the UiO-66 particles are successfully coated with a nanocomposite shell, composed of Pd NPs and polypyrrole (PPy) resulting from the interfacial polymerization of pyrrole on the external surface of UiO-66 particles initiated by PdCl2 presented within the UiO-66 particles. Significantly, in such a unique structure, the prepared hybrid particles noted as UiO-66/Pd@PPy nanocomposite particles are demonstrated to be an excellent catalyst with both high activity and stability in the reduction reaction of p-nitrophenol and sodium borohydride. Furthermore, this synthetic method not only effectively controls the mass loading of Pd NPs and PPy on the UiO-66 particles but also enables the deposition of Au@PPy and Ag@PPy nanocomposite shells onto the surface of the UiO-66 particles.

Size-dependent forced vibration response of embedded micro cylindrical shells reinforced with agglomerated CNTs using strain gradient theory

This article presents an analysis into the nonlinear forced vibration of a micro cylindrical shell reinforced by carbon nanotubes (CNTs) with considering agglomeration effects. The structure is subjected to magnetic field and transverse harmonic mechanical load. Mindlin theory is employed to model the structure and the strain gradient theory (SGT) is also used to capture the size effect. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite cylindrical shell and consider the CNTs agglomeration effect. The motion equations are derived using Hamilton\'s principle and the differential quadrature method (DQM) is employed to solve them for obtaining nonlinear frequency response of the cylindrical shells. The effect of different parameters including magnetic field, CNTs volume percent and agglomeration effect, boundary conditions, size effect and length to thickness ratio on the nonlinear forced vibrational characteristic of the of the system is studied. Numerical results indicate that by enhancing the CNTs volume percent, the amplitude of system decreases while considering the CNTs agglomeration effect has an inverse effect.

An analytical approach on nonlinear mechanical and thermal post-buckling of nanocomposite double-curved shallow shells reinforced by carbon nanotubes

This work presents the nonlinear mechanical and thermal post-buckling of nanocomposite double-curved shallow shells reinforced by single-walled carbon nanotubes resting on elastic foundations based on the higher order shear deformation theory with geometrical nonlinearity in von Karman–Donnell sense. The composite shells are made of various amorphous polymer matrices: poly(methyl methacrylate) (PMMA) and poly{(m-phenylenevinylene)-co-[(2,5-dioctoxy-p-phenylene) vinylene]} (PmPV). The governing equations are solved by the Galerkin method and Airy's stress function to achieve mechanical and thermal post-buckling behaviors of nanocomposite double-curved shallow shells. Various types of distributions of carbon nanotubes, both uniform distributions, and functionally graded distributions are examined. The material properties of nanocomposite double-curved shallow shells are assumed to be temperature dependent. Detailed parametric studies are carried out on the effect of various types of distribution and volume fractions of carbon nanotubes, temperature increments, elastic foundations, edge to radius and edge to thickness ratios on the nonlinear mechanical and thermal post-buckling of nanocomposite double-curved shallow shells reinforced by CNTs.

Mechanical buckling analysis of functionally graded power-based and carbon nanotubes-reinforced composite plates and curved panels

The main aim of this paper is to investigate the mechanical buckling behavior of functionally graded materials and carbon nanotubes-reinforced composite plates and curved panels. The governing equations are established using a double directors finite element shell model which induces a high-order distribution of the displacement field and takes into account the effect of transverse shear deformations. The effective material properties of functionally graded materials are estimated using a power law distribution and those of nanocomposites by an extended rule of mixture with some efficiency parameters. Uniform and four profiles of carbon nanotubes are considered to describe the distribution of these reinforcements through the thickness of the nanocomposite shell structure. A comparison study of the present results with those available in the literature is carried out for the isotropic case in order to prove the validity as well as the accuracy of the present model. Then, the results are extended to functionally graded materials and nanocomposites. The results reveal that the critical buckling load of plates and curved panels can be significantly increased as a result of a functionally graded reinforcement. They also show that the mechanical buckling behavior of such structures is significantly influenced by the plate aspect ratio, the length-to-thickness ratio, radius-to-thickness ratio, boundary conditions, power law index as well as the carbon nanotubes profiles and their volume fractions.

Viscoelastic material damping characteristics of carbon nanotubes based functionally graded composite shell structures

This work deals with the study of viscoelastic modeling and vibration analysis of functionally graded nanocomposite shell panels where carbon nanotubes are reinforced in the polymer matrix based on the functionally graded distributions of carbon nanotubes. Five types of grading of carbon nanotubes (such as UD, FGX, FGV, FGO, and FGΛ) in the thickness directions have been considered in order to investigate the vibration damping performance of such composite shell panels. A detailed mathematical formulation for the determination viscoelastic properties is presented. The Mori–Tanaka micromechanics in conjunction with weak interface theory has been developed for the mathematical formulations of the viscoelastic modeling of carbon nanotubes based polymer matrix phase. An eight-noded shell element with five degrees-of-freedom per node has been formulated to study the vibration damping characteristics of various panels made by such functionally graded nanocomposite materials. The shell finite element formulation is based on the transverse shear effects as per the Mindlin’s hypothesis, and stress resultant-type Koiter’s shell theory. Impulse and frequency responses of such structures have been performed to study the effects of various important parameters (such as volume fraction of carbon nanotubes, interfacial condition, agglomeration, temperature, geometries of shell panel) on the dynamic responses. Obtained results demonstrate that quick vibration mitigation may be possible using such carbon nanotubes based proposed composite materials.

Temperature-Responsive Hydrogel-Coated Gold Nanoshells.

Gold nanoshells (~160 nm in diameter) were encapsulated within a shell of temperature-responsive poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AA)) using a surface-bound rationally-designed free radical initiator in water for the development of a photothermally-induced drug-delivery system. The morphologies of the resultant hydrogel-coated nanoshells were analyzed by scanning electron microscopy (SEM), while the temperature-responsive behavior of the nanoparticles was characterized by dynamic light scattering (DLS). The diameter of the P(NIPAM-co-AA) encapsulated nanoshells decreased as the solution temperature was increased, indicating a collapse of the hydrogel layer with increasing temperatures. In addition, the optical properties of the composite nanoshells were studied by UV-visible spectroscopy. The surface plasmon resonance (SPR) peak of the hydrogel-coated nanoshells appeared at ~800 nm, which lies within the tissue-transparent range that is important for biomedical applications. Furthermore, the periphery of the particles was conjugated with the model protein avidin to modify the hydrogel-coated nanoshells with a fluorescent-tagged biotin, biotin-4-fluorescein (biotin-4-FITC), for colorimetric imaging/monitoring.

Vibration analysis of functionally graded graphene platelet reinforced cylindrical shells with different porosity distributions

ABSTRACTThis paper studies free vibrational behavior of porous nanocomposite shells reinforced with graphene platelets (GPLs). GPLs are uniformly and nonuniformly distributed thorough the thickness direction. Different porosity distributions called uniform, symmetric, and asymmetric are considered. The elastic properties of the nanocomposite are obtained by employing Halpin–Tsai micromechanics model. The GPL-reinforced shell is modeled via first order shear deformation theory and Galerkin's method is implemented to obtain vibration frequencies. New results show the importance of porosity coefficient, porosity distribution, GPL distribution, GPL weight fraction, and geometrical and foundation parameters on vibration behavior of porous nanocomposite shells.

Li[sbnd]Si[sbnd]C anode material with amorphous core – nanocomposite shell structure

Li-rich LiSi alloy-type anodes with high tap density, specific capacity and cycling stability are highly demanded for pairing Li-free cathodes to develop high energy Li ion batteries (LIBs). Here we fabricated for the first time a type of micron-scale composite of Li21Si5 and carbon with outstanding electrochemical performance, which has unique amorphous core-nanocomposite shell structure (denoted as a-Li21Si5@C). The thin graphene stacks in the nanocomposite shell have multiple functions of constraining effectively the volume change during cycling, providing numerous pathways for rapid charge transport and inhibiting side reactions at particle surface. Benefit from the special configuration, the a-Li21Si5@C composite has a reversible specific capacity of 870 mAh g−1 (2479 mAh g−1 evaluated from Si composition). Moreover, the a-Li21Si5@C composite retains a specific capacity of 582 mAh g−1 after 100 cycles, which exhibits a remarkably increased stability as compared with the previous micron-scale LiSi alloys. The energy density of the full cell constructed by the present composite and sulfur is evaluated as 2.6 times high as that of the commercial LIBs. The studies pave the way for developing micron-scale Li-rich composites as high-performance anode candidates for advanced LIBs.

Nonlinear thermal torsional post-buckling of carbon nanotube-reinforced composite cylindrical shell with piezoelectric actuator layers surrounded by elastic medium

The paper focuses on thermal torsional post buckling of functionally graded carbon nanotube reinforced composite cylindrical shells with sur-bonding piezoelectric layers and embedded in an elastic medium. The distribution of reinforcements through the thickness of the shells is considered to be uniform and functionally graded. The basic equations using geometrically nonlinearity in von Karman-Donnell sense within the classical thin shell theory are established. The torsional post-buckling behavior of the piezoelectric functionally graded carbon nanotubes reinforced composite (FG-CNTRC) shells is analyzed with using the Airy's stress function and the Galerkin's method, in which a three-term approximate solution of the deflection of the shell is assumed. Effects of thermal environment, CNT volume fraction, piezoelectric layers (the thickness and the constant voltage), distribution type of the reinforcement, dimensional parameters and Winkler and Pasternak foundation are investigated in this paper. Numerical and graphical results show that the carbon nanotube volume fraction and the piezoelectric layers as well as the elastic foundation and the thermal loads have significantly influenced on the torsional postbuckling behavior of nanocomposite shells.

Nonlocal strain gradient shell model for axial buckling and postbuckling analysis of magneto-electro-elastic composite nanoshells

Abstract The present study deals with the size-dependent nonlinear buckling and postbuckling characteristics of magneto-electro-elastic cylindrical composite nanoshells incorporating simultaneously the both of hardening-stiffness and softening-stiffness size effects. To accomplish this purpose, the nonlocal strain gradient elasticity theory is applied to the classical shell theory. Via the virtual work's principle, the size-dependent governing differential equations are constructed including the coupling terms between the axial mechanical compressive load, external magnetic potential and external electrical potential. The nonlinear prebuckling deformations and the large postbuckling deflections are taken into consideration based upon the boundary layer theory of shell buckling. Finally, an improved perturbation technique is employed to achieve explicit analytical expressions for nonlocal strain gradient stability curves of magneto-electro-elastic nanoshells under various surface electric and magnetic voltages. It is seen that a positive electric potential and a negative magnetic potential cause to increase both of the nonlocality and strain gradient size dependencies in the nonlinear instability behavior of axially loaded magneto-electro-elastic composite nanoshells, while a negative electric potential and a positive magnetic potential play an opposite role.

Modeling aerothermoelastic properties and active flutter control of nanocomposite cylindrical shells in supersonic airflow under thermal environments

We examine the aeroelastic behavior of a cylindrical nanocomposite (i.e. CNT-reinforced composite) shell in a supersonic airflow under thermal environments. Meanwhile, using piezoelectric materials, active flutter control of the cylindrical nanocomposite shell is conducted. Reddy’s high-order shear deformation theory is applied in the structural modeling, and the displacement fields of piezoelectric patches are derived according to the geometrical deformation relationship. The partial differential equation of motion is formulated by way of Hamilton’s principle and then is discretized by the assumed mode method. The active controller is designed by the displacement feedback and linear quadratic regular (LQR) methods. The aerothermoelastic properties of the cylindrical shell are analyzed using the frequency-domain method. The flutter bounds of the cylindrical shell are computed using the third-order shear deformation theory (TSDT), and the first-order shear deformation theory (FSDT) is compared in order to verify the necessity of the high-order shear deformation theory in the vibration analysis of thick nanocomposite structures. The influences of temperature change, CNT distribution and CNT volume fraction on the aeroelastic stability of the nanocomposite cylindrical shell are investigated. The active flutter control effects of different control methods are performed. The influence of thickness of the cylindrical shell on the flutter control effects is examined.

Size-dependent static stability of magneto-electro-elastic CNT/MT-based composite nanoshells under external electric and magnetic fields

In this paper, a modified shell model is developed for the buckling behavior of smart composite nanotubes under magneto-electro-mechanical loads. The hybrid nanotube consists of a carbon nanotube (CNT) and a microtubule (MT) which are integrated with a magneto-electro-elastic (MEE) layer by polymer matrix. In order to take into account size effects, nonlocal continuum mechanics is used. Explicit formulas are presented for the van der Waals (vdW) interaction between CNTs and MTs. Using Pasternak model, the effect of coupling polymer matrix is simulated. The nonlocal governing differential equations of the system are derived based on the principle of virtual work. Closed-form solutions are presented for the buckling load, voltage and magnetic potential of the composite nanoshell. It is observed that the buckling behavior of MEE CNT–MT nanotubes is greatly affected by nonlocal parameter. Moreover, the buckling properties of composite nanotubes can be tuned by the external electric voltage, applied magnetic potential and radius of CNTs.

Nonlinear size-dependent dynamic buckling analysis of embedded micro cylindrical shells reinforced with agglomerated CNTs using strain gradient theory

This article presents an analysis on the nonlinear dynamic buckling of a micro cylindrical shell reinforced by carbon nanotubes (CNTs) with considering agglomeration effects. The structure is surrounded by an elastic medium and is subjected to magnetic field and harmonic mechanical load. Mindlin theory is employed to model the structure and the modified strain gradient theory (SGT) is also used to capture the size effect. Mori–Tanaka approach is used to estimate the equivalent material properties of the nanocomposite cylindrical shell and consider the CNTs agglomeration effect. The motion equations are derived using Hamilton’s principle and the differential quadrature method (DQM) along with Bolotin method is employed to solve them for obtaining the dynamic stability region. The effect of different parameters including magnetic field, CNTs volume percent and agglomeration effect, boundary conditions, elastic medium, size effect and length to thickness ratio on the dynamic buckling behavior of the system is studied. The results indicate that considering elastic medium, magnetic field and size effects, increases the stiffness of the structure and so, the dynamic instability region occurs at higher frequency while considering the CNTs agglomeration effect has inverse effect. Also, by increasing the CNTs volume percent and considering the clamped–clamped boundary condition, the dynamic behavior of the system improves.

Synthesis, characterization and cellular cytotoxicity evaluation of a new magnetic nanoparticle carrier co-functionalized with amine and folic acid

In the present work, for the first time, co-functionalizing the surface of a core-shell Fe3O4@nSiO2 nanoparticle was performed for transporting doxorubicin anticancer drug (DOX). This core-shell nanoparticle (NP) is composed of superparamagnetic iron oxide core synthesized by solvothermal method and a nonporous silica (nSiO2) layer shell. The nanocomposite shell was co-functionalized with amine group (NH) and folic acid (FA). The characterization results confirmed the super-paramagnetic property of Fe3O4@nSiO2 nanoparticle with the average particle size of 75 nm. In addition, the successful co-functionalizing the surface of NPs was confirmed with FTIR analysis. Dox loading on the nanocomposite was performed at the optimum adsorption condition with the entrapment efficiency of 81.5%. In vitro release study showed a very slow release at pH = 7.4 while a relative rapid release within 10 h and a sustained release until 144 h was observed at pH = 5.5. Finally, the in vitro cytotoxicity assay showed that cellular cytotoxicity of DOX-loaded Fe3O4@nSiO2-NHFA on the breast cancer cell lines (MDA-MB-231) is increased considerably in comparison to free DOX. This confirms the improvement of the synthesized nanocomposite structure. All results confirmed that this new synthesized nanoparticle with an appropriate size and cellular cytotoxicity is a suitable candida for drug-delivery vehicles.