Graphene Weight Fraction Research Articles

Vibration analysis of functionally graded epoxy/graphene composite plates using the Boundary Element Method and new micromechanical model

This paper studies the free vibration and harmonic response of Functionally Graded Graphene/Epoxy composite plates, considering the First Order Shear Deformation Plate Theory. The weight fraction of graphene variation along the thickness direction with graphene homogeneous dispersed in a polymer matrix. The effective Young Modulus of the plate is predicted by a new micro-mechanical model. The model includes the aspect ratio and weight fraction of nanoplatelets embedded into the matrix. The modal and harmonic of Graphene/Epoxy plates are obtained by the Boundary Element Method formulation for composite plates. The Young modulus calculated from the proposed micro-mechanical model highly agrees with those obtained from experimental results reported in the literature. Results demonstrate a high correlation of the micromechanical model with experimental results and other analytical models. Graphene weight fraction and ratio aspect increase the effective Young modulus of the composite. Boundary Element results show high agreement with Finite Element solutions. Numerical results for modal and harmonic analysis show concentrating graphene near the top and bottom surfaces of the plate is the most effective way to reinforce the plate for increased natural frequencies. The results demonstrate the BEM formulation and micromechanical model can be used as reliable engineering tools for the vibrational analysis of functionally grade graphene composite plates.

Fabrication and Characterization of Diaphragm Headphones Based on Graphene Nanocomposites.

The goal of this paper is to fabricate innovative diaphragm headphones using graphene oxide paper (GOP) and GOP/epoxy nanocomposites (GOPC). Initially, graphene oxide suspension is fabricated, and the vacuum filtration method is adopted to make GOP. Then, vacuum bag molding is used to fabricate GOPC from GOP. Hot pressing and associated molds are adopted to fabricate line-indented (GOPC-L) or curve-indented patterns (GOPC-C) on the GOPC. The performances of one kind of GOP and three kinds of GOPC diaphragm headphones are analyzed based on their sound pressure level (SPL) curves achieved by the Soundcheck measurement system. There are four important processing parameters that will influence the performance of the diaphragm, including material type GOP versus GOPC, indented pattern type, sonication time on suspension, and graphene weight fraction in suspension. Compliances of various diaphragms are measured by the Klippel LPM laser measurement system. The results indicate that effects of sonication time and graphene weight fraction on SPL of GOP and GOPC headphones are in reverse, and this is associated with their difference on compliance (modulus), mass, damping ratio, and microstructure uniformity. Either GOPC-L or GOPC-C seems to improve the microstructure of the GOPC, and leads to better SPL performance. The correlation between the previous four factors and SPLs of four kinds of diaphragm headphones is proposed by using scanning electron microscope (SEM) to examine the microstructure of these diaphragms.

Coupling effect between highly nonlinear solitary waves and functionally graded porous plates reinforced with graphene platelets

ABSTRACT Solitary waves possess extensive potential for application in non-destructive testing due to their role as efficient information carriers. This study investigates the coupling effect between highly nonlinear solitary waves and functionally graded porous plates reinforced with graphene platelets (FGP-GPLs). An improved Halpin–Tsai micromechanics model and an improved two-variable precision plate theory are employed to derive a differential equation system for the coupling of particle chains and FGP-GPLs. The system is solved using the fourth-order Runge–Kutta method to obtain velocity and displacement solutions of the particles. The time and amplitude of the rebound waves are analysed, and it is found that the pore distribution, graphene distribution, porosity coefficient, thickness ratio, and graphene weight fraction impact the solitary wave. The results of this study provide a theoretical basis for the non-destructive detection of FGP-GPLs by solitary waves, which enables rapid inspection and controllability studies of structures. Moreover, this technology expands the application fields of nonlinear solitary waves based on one-dimensional spherical particle chains.

Higher-order model with interlaminar stress continuity for multi-directional FG-GRC porous multilayer panels resting on elastic foundation

In this paper, the bending behaviors of multilayer panels composed of multi-directional functionally graded porous graphene reinforced composites (GRCs) resting on a two-parameter Winkler-Pasternak elastic foundation are investigated for the first time based on a higher-order layerwise model with interlaminar stress continuity. Since the material properties are discontinuously distributed through the thickness of specific multilayer structure and multi-directional graded in each layer of the panels caused by the distribution of both graphene and porosities, traditional higher-order plate theories have difficulty in predicting continuous stress fields efficiently. For this reason, the proposed model adopts higher-order interpolation functions and piecewise descriptions for transverse shear-stress fields to obtain accurate results satisfying continuity of interlaminar stresses, accounting for the distribution of material properties along the thickness direction and multilayer structure of the panel. Furthermore, to perform efficient numerical results for multi-directional functionally graded materials, the proposed higher-order layerwise model is combined with graded finite element method (GFEM) by sampling material properties directly at the Gaussian points within each element. Lastly, numerical examples are presented to verify the accuracy and efficiency of the proposed model, and the effects of porosity and graphene distribution patterns, graphene weight fraction, porosity coefficient, and elastic foundation parameters are investigated.

Bandgaps in functionally graded phononic crystals containing graphene origami-enabled metamaterials

This paper investigates the dispersion characteristics of elastic waves propagating along the thickness direction in functionally graded laminated phononic crystals (FGLPCs) containing novel auxetic metamaterials enabled by graphene origami that is created with the aid of hydrogenation. Both graphene weight fraction and hydrogen coverage which are the key parameters governing the auxetic property are nonuniformly distributed in unit cells of FGLPCs whose material properties are determined by genetic programming-assisted micromechanical models. The dispersion relations of elastic waves in the structure are obtained based on the state space approach and the method of reverberation-ray matrix. A comprehensive parametric study is conducted to discuss the effects of graphene origami weight fraction and hydrogen coverage on bulk waves in elastic solids made of the metamaterial and elastic waves in FGLPCs. It is found that introducing auxetic metamaterials into FGLPCs can effectively manipulate elastic waves. The graded distribution of weight fraction in FGLPCs can lead to bandgaps for both transverse and longitudinal waves, while a through-thickness graded pattern in hydrogen coverage can trigger broad bandgaps for longitudinal waves only with transverse waves nearly unchanged.

Hygrothermal Buckling of Smart Graphene/Piezoelectric Nanocomposite Circular Plates on an Elastic Substrate via DQM

This paper aims to study the hygrothermal buckling of smart graphene/piezoelectric circular nanoplates lying on an elastic medium and subjected to an external electric field. The circular nanoplates are made of piezoelectric polymer reinforced with graphene platelets that are uniformly distributed through the thickness of the nanoplate. The material properties of the nanocomposite plate are determined based on the modified Halpin-Tsai model. To capture the nanoscale effects, the nonlocal strain gradient theory is applied. Moreover, the principle of virtual work is employed to establish the nonlinear stability equations in the framework of classical theory. The differential quadrature method is utilized to solve the governing equations. Among the important aims of the paper is to study the influences of various parameters such as graphene weight fraction, elastic foundation parameters, external applied electric field, humid conditions, and boundary conditions on the thermal buckling of the smart nanocomposite circular nanoplates. It is found that the increase in graphene components and elastic foundation stiffness enhances the strength of the plates; therefore, the buckling temperature will increase.

Influence of graphene fillers on vibration characteristics of tapered hybrid GFRP composite beams under elevated temperature condition: Numerical and experimental study

In this study, numerically and experimentally the dynamic characteristics of graphene-reinforced glass fiber–reinforced polymer hybrid uniform and thickness tapered laminated composite beams were investigated. First, the graphene-epoxy nanocomposite solution without and with 0.25, 0.50, and 0.75 wt.% of graphene reinforcement is prepared by the heat shearing technique and then used for the fabrication of glass fiber–reinforced polymer hybrid uniform and thickness tapered composite beams using the hand lay-up method. The elastic properties of the hybrid beams were evaluated using the impulse excitation of vibration technique (ASTM E1876-15) under elevated temperature. Further, the numerical and experimental modal analysis of the hybrid beams with uniform and tapered configurations were conducted with variation in wt.% of graphene particles under fixed-fixed and fixed–free end supports. The results reveal that the natural frequencies of the glass fiber–reinforced polymer hybrid uniform and tapered configurations with 0.25 wt.% of graphene are greater than those of the glass fiber–reinforced polymer beams without graphene reinforcement and observed lesser for 0.5 and 0.75 wt.% of graphene under fixed-fixed and fixed-free end supports, respectively, due to unavoidable agglomeration effects. Furthermore, the parametric study was performed with the influence of weight fraction of graphene and temperature on the transverse response of the tapered composite beam. Hence, it can be concluded that the use of graphene filler in the glass fiber–reinforced polymer composites in the tapered composite beams improves the bending natural frequencies significantly when the weight fraction of the graphene is used lesser as agglomeration is unavoidable in practical condition. Therefore, the comprehensive numerical and experimental work presented in this study will be useful to the designers while using graphene fillers to improve the bending characteristics of the tapered composite beams.

Axial magnetic field effect on wave propagation in bi-layer FG graphene platelet-reinforced nanobeams

This paper aims to investigate the size-dependent wave propagation in functionally graded (FG) graphene platelet (GPL)-reinforced composite bi-layer nanobeams embedded in Pasternak elastic foundation and exposed to in-plane compressive mechanical load and in-plane magnetic field. The small-scale effects are taken into account by employing the nonlocal strain gradient theory that contains two different length scale parameters. The present two nanobeams are made of multi-composite layers. Each layer is composed of a polymer matrix reinforced by uniformly distributed and randomly oriented GPLs. The GPLs weight fraction is graded from layer to other according to a new piece-wise rule and then four distribution types will be established. Our technique depends on applying the four-variable shear and normal deformations theory to model the wave propagation problem. The equations of motion are obtained using Hamilton principle. These equations are then analytically solved to obtain the wave frequencies and phase velocities of the waves. The calculated results are compared with those published in the literature. The impacts of the length scale parameters, foundation stiffness, in-plane magnetic field, weight fraction of graphene, graphene platelets distribution type and beam geometry on the propagating waves in the FG GPLs nanobeams are discussed in details. It is found that the strength of the composite beams may be enhanced with increasing in the GPLs weight fraction and magnetic field leading to an increment in the phase velocity and wave frequency of the present system.

Fatigue analysis of graphene oxide papers fabricated under various processing parameters

AbstractThe effects of processing parameters on fatigue lives of graphene oxide papers (GOP) and reduced GOP (RGOP) are investigated. The fabrication method could be either vacuum filtration or pressure filtration, and the important processing parameters include graphene weight fraction in suspension, sonication time for suspension and pressure value for pressure filtration. Fatigue performance of the papers are studied by strain‐controlled fatigue test. Under vacuum filtration method, fatigue lives of both GOP and RGOP decrease with increasing graphene weight fraction. The longest fatigue life is 403 284 cycles for the GOP under highest power sonication time and lowest graphene weight fraction. Fatigue lives of most GOP increase with increasing sonication time up to medium level. Under pressure filtration method, all GOP have shorter fatigue lives than those by vacuum filtration. Scanning electron microscopy is employed to carefully analyse the failed papers in order to clarify the fatigue failure mechanism.

Differential quadrature method for magneto-hygrothermal bending of functionally graded graphene/Al sandwich-curved beams with honeycomb core via a new higher-order theory

Based on the differential quadrature method (DQM), the bending of sandwich-curved beams with graphene platelets/aluminum (GPLs/Al) nanocomposite face sheets and aluminum honeycomb core is investigated using a new shear and normal deformations curved beam theory. The present new model is resting on elastic foundation and subjected to a circumferential magnetic field, thermal load, and humid conditions. The face sheets are made of several bonded composite layers with randomly oriented and uniformly distributed graphene platelets in each layer. The mechanical and hygrothermal properties of the faces are assumed to be functionally graded (FG) using a piece-wise law by varying the weight fraction of the GPLs in the face thickness direction. Four governing differential equations are derived based on a novel four-variable curved beam theory taking into account the thickness stretching effect. The governing equations are solved for various boundary conditions on the basis of the DQM. The displacements presented by the DQM are compared with those obtained by Navier solution. Impacts of various parameters such as geometric shape parameters, magnetic parameter, temperature, moisture, elastic foundation parameters, core thickness, boundary conditions, and graphene weight fraction on the displacements and stresses of the functionally graded graphene/aluminum sandwich-curved beams are illustrated.

Effect of graphene additions on polishing of silicon carbide wafer with functional PU/silica particles in CMP slurry

In this paper, a functional ternary slurry consisting of polyurethane (PU) microspheres, graphene oxide (GO) nano platelets and silicon oxide (SiO2) abrasives was used to carry out the polishing process on Si face of 4H-SiC wafers. The processing parameters of the slurry include graphene weight fraction in slurry GO1–GO7 (0.1–0.7[Formula: see text]wt.%), pH value (3–5), and sonication time T5–T15 (5–15[Formula: see text]min). Polishing process is conducted with two kinds of polishing pads A and B, PU and PC (polycarbonate). Results show that material removal rate (MRR) increases with increasing GO weight fraction up to GO5; besides, MRR also increases with increasing sonication time up to T10, and with increasing pH value. Using PU pad, the GO5-T10-pH5-A slurry leads to highest MRR 102.220[Formula: see text]nm/h of the polished SiC wafer. On the other hand, surface roughness improvement rate (SRIR) increases with increasing GO weight fraction up to GO5, and increases with increasing sonication time up to T15. But SRIR is not affected by pH value. Regarding effect of pad type, on average the PU pad results in higher MRR and better SRIR compared with the PC pad. Using PC pad, GO5-T10-pH5-B leads to lower MRR of 87.627[Formula: see text]nm/h. The addition of GO as the ternary slurry demonstrates its better effect on polishing SiC wafers by comparing with the counterpart binary slurry without GO. For example, MRR by the counterpart slurry SiO212-pH5-A is 58.411[Formula: see text]nm/h, which is lower than 102.220[Formula: see text]nm/h by the ternary slurry GO5-T10-pH5-A. Both XPS and Raman spectra demonstrate that the wafer polished by the functional ternary slurry can effectively produce the softer SiO2 reactant layer on SiC wafer, and result in better polishing performance.

Highly filled multilayer thermoplastic/graphene conducting composite structures with high strength and thermal stability for electromagnetic interference shielding applications

ABSTRACTPolyvinyl chloride (PVC)/graphene and poly(methyl methacrylate) (PMMA)/graphene nanocomposites were made by solution casting technique with graphene weight fractions of 1, 5, 10, 15, and 20%. Multilayer structures of the composites were made by hot compression technique to study their electromagnetic interference shielding effectiveness (EMI SE). Tensile strength, hardness, and storage modulus of the nanocomposites were studied in relation with graphene weight fraction. There has been a substantial increase in the electrical conductivity and EMI SE of the composites with 15–20% filler loading. Differential thermal analysis of the composites shows improved thermal stability with an increase in graphene loading. PMMA/graphene composites have better thermal stability, whereas PVC/graphene composites have superior mechanical properties. About 2 mm thick multilayer structures of PMMA/graphene and PVC/graphene composites show a maximum EMI SE of 21 dB and 31 dB, respectively, in the X band at 20 wt % graphene loading. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47792.

Wire electrical discharge machinable SiC with GNPs and GO as the electrically conducting filler

SiC based composites filled with graphene nano-platelets (GNPs) or graphene oxide (GO) prepared by rapid hot-pressing exhibit sufficient electrical conductivity for their machinability by wire electro-discharge machining (WEDM). Composites microstructure anisotropy caused by graphene alignment as a consequence of rapid hot pressing was confirmed by measuring of electrical conductivity and thermal diffusivity. Electrical conductivity increased significantly with increased weight fraction of graphene in both measured directions. Highest value of 2031 S/m was obtained for composites with 15 wt. % of GNPs in parallel direction and only 1246 S/m in perpendicular direction to aligned GNPs. Thermal diffusivity is 63.3 mm2/s in parallel and only 23.3 mm2/s in perpendicular direction. The increase of the electrical conductivity has resulted in successful WEDM. The MRR was almost doubled when the filler concentration increased from 5 wt. % GNPs/GO to 15 wt. % GNPs. At the same time, the surface roughness decreased.

Advancing Dielectric and Ferroelectric Properties of Piezoelectric Polymers by Combining Graphene and Ferroelectric Ceramic Additives for Energy Storage Applications.

To address the limitations of piezoelectric polymers which have a low dielectric constant andto improve their dielectric and ferroelectric efficiency for energy storage applications, we designed and characterized a new hybrid composite that contains polyvinylidene fluoride as a dielectric polymer matrix combined with graphene platelets as a conductive and barium titanite as ceramic ferroelectric fillers. Different graphene/barium titanate/polyvinylidene fluoride nanocomposite films were synthesized by changing the concentration of graphene and barium titanate to explore the impact of each component and their potential synergetic effect on dielectric and ferroelectric properties of the composite. Results showed that with an increase in the barium titanate fraction, dielectric efficiency ofthe nanocomposite was improved. Among all synthesized nanocomposite films, graphene/barium titanate/polyvinylidene fluoride nanocomposite in the weight ratio of 0.15:0.5:1 exhibited thehighest dielectric constant of 199 at 40 Hz, i.e., 15 fold greater than that of neat polyvinylidene fluoride film at the same frequency, and possessed a low loss tangent of 0.6. However, AC conductivity and ferroelectric properties of graphene/barium titanate/polyvinylidene fluoride nanocomposite films were enhanced with an increase in the graphene weight fraction. Graphene/barium titanate/polyvinylidene fluoride nanocomposite films with a weight ratio of 0.2:0.1:1 possessed a high AC conductivity of 1.2 × 10−4 S/m at 40 Hz. While remanent polarization, coercive field, and loop area of the same sample were 0.9 μC/cm2, 9.78 kV/cm, and 24.5 μC/cm2·V, respectively. Our results showed that a combination of graphene and ferroelectric ceramic additives are an excellent approach to significantly advance the performance of dielectric and ferroelectric properties of piezoelectric polymers for broad applications including energy storage.

Investigation on Mechanical Properties of Graphene Oxide reinforced GFRP

Graphene and E-glass fibres individually find a very wide field of applications because of their various mechanical and chemical properties. Recently graphene has attracted both academic and industrial interest because it can produce a dramatic improvement in properties at very low filler content. The primary interest of this venture is to investigate on Graphene reinforced polymer matrix nanocomposites and finding the mechanical properties. The composites were fabricated by Hand Lay Process and have been evaluated by the addition of Graphene with 1, 1.5, 2, 2.5 and 3 by weight% as reinforcement in composites. The theoretical and experimental results validate the increase in properties such as tensile strength, hardness and flexural strength with increase in weight proportions from 1% to 3% of graphene powder. It was observed that the composite material with 2.5% weight fraction of graphene yielded superior properties over other weight percentages. Graphene reinforced polymer matrix nanocomposites finds its major applications in the manufacture of aircraft bodies, ballistic missiles, sporting equipment, marine applications and extraterrestrial ventures.

Characterization of graphene reinforced Al-Sn nanocomposite produced by mechanical alloying and vacuum hot pressing

In the present work, graphene (Gr) reinforced Al-Sn matrix nanocomposites were prepared by ball milling and vacuum hot pressing. The powder morphologies of Al-Sn and graphene during different intervals (2, 4, 8 & 12 hours) of time were studied using Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS). Further the 12 hours ball milled nanocomposite powders were subjected to vacuum hot pressing at a temperature and pressure of 540°C and 40 MPa respectively. The size of Al-Sn/Gr powders decreased with the increasing in milling time due to fracturing of big particles. The graphene was seen on the surface at the initial hours of ball milling but found to disappear in the Al-Sn powders at end of 12 hours of ball milling. The presence of high weight fraction of graphene in Al-Sn matrix grain boundaries made sintering process difficult leading slight drop in experimental density values when compared to that of theoretical density. However, the addition of 1 and 2 wt% graphene to Al-Sn showed about 27 and 48% increase in the microhardness values respectively.

Factor analysis of key parameters on cutting force in micromachining of graphene-reinforced magnesium matrix nanocomposites based on FE simulation

Recently, graphene has become an attractive reinforcement to metal matrix nanocomposites owing to its excellent mechanical and physical properties. In this paper, a micro-finite element (FE) model of micromachining of graphene-reinforced metal matrix nanocomposites (Gr-MMNCs) is first established to investigate the machinability of the new nanocomposites. Compared with most previous FE models of MMNCs, the new model can realize the random distributions of both position and orientation of graphene nanoplatelets (GNPs) by developing a random algorithm in Abaqus. After indirect experimental validation of the micromechanical FE model, the effects of various machining technological and material design parameters on the average cutting force are studied by simulation, respectively. Then, the influences of these main parameters on cutting force are analyzed by the multi-factor analysis for quantitative comparison. It was found that the most significant parameters in the micromachining process of Gr-MMNCs are depth of cut, and the average size and weight fraction of graphene are the next significant ones. Finally, a practical model of the cutting force versus these key parameters was also proposed based on the factorial analysis results for graphene-reinforced MMNCs already applied in practice.

Processing and Characterization of Al 6061 – Graphene Nanocomposites

As one of the most important engineering materials, Aluminum alloys and its composites have been widely used in Aerospace and automobile industriesdue to its potential properties like low density and good structural rigidity. However, the important criteria in enhancing the mechanical properties without compromising the ductility is always challenging in Aluminum and its alloys based composites. In the recent years, enormous research has been carried on ceramic based and Carbon based reinforcement materials used in Aluminum metal matrix composites. But Graphene, being one of the allotropes of carbon; although with the limited studies, shows it can be considered as nanofiller and perfect reinforcement for conventional structural materials. The current research work is carried out to process, synthesize and perform the characterization of Al 6061 matrix nanocomposites. Graphene with different filling content (0.25, 0.5, 0.75, 1.0 weight%) is used use as reinforcement in the Aluminum matrix. The uniform dispersion of Graphene in the matrix is carried out by ultrasonic liquid processing method and the mixtures were consolidated by powder metallurgy (PM) approach followed by SEM and XRD analysis. Thus prepared compacts are sintered at various temperature and mechanical properties like microhardness, density are investigated as a function of sintering temperature and Graphene weight fraction. Diametrical expansions and relevant strengthening mechanism involved in the Al6061 – Graphene composites in comparison with monolithic Al 6061 alloy are discussed.

Diamond Lapping of Sapphire Wafer with Addition of Graphene in Slurry

In this paper, a novel method with addition of graphene in diamond slurry is proposed to conduct CMP lapping of sapphire wafer. Two kinds of graphenes are added including graphene oxide (GO), reduced graphene oxide (RGO). Effect of three important processing parameters on material removal rate (MRR) and surface roughness is investigated, including graphene type, graphene weight fraction, and ultrasonication time. Weight fractions of various graphenes versus diamond slurry are controlled in the range from 0.5 to 2.0 wt%. Results indicate that addition of graphene in diamond slurry can significantly increase MRR of sapphire wafer. MRR of sapphire wafer is proportional to graphene weight fraction. At higher weight fraction, GO/diamond slurry leads to higher MRR than RGO/diamond slurry does. MRR by the pure diamond is 285.80 nm/min, while MRR by the diamond/GO(2.0wt%) with 48-hour ultrasonication is 832.1 nm/min. Surface roughness is inversely proportional to graphene weight fraction and proportional to graphene particle size. Ultrasonication is able to efficiently reduce graphene particle size. RGO/diamond slurry can result in lower surface roughness than GO/diamond slurry.

Effect of graphene addition on flexural properties of al 6061 nanocomposites

Aluminium and its composites established themselves for various industrial applications due to its potential properties like low density and good structural rigidity. In the recent years, Graphene is being one of the allotropes of carbon; although with the limited studies shows it can be considered as nanofiller and perfect reinforcement for conventional structural materials. The current research work is carried out to prepare and perform characterization of Al 6061 matrix nanocomposites reinforced by Graphene with different filling content (0.2, 0.4, 0.6, 0.8 weight%). The uniform dispersion of Graphene in the matrix is done by ultrasonic liquid processer followed by ball milling and the mixtures were consolidated by powder metallurgy (PM) approach. The SEM and EDX analysis were done on prepared nanocomposites. The mechanical properties like microhardness, density and flexural strengths are investigated as a function of Graphene weight fraction. A three point flexural test is performed on the composites in a uniaxial loading system. A maximum enhancement in strength and relevant strengthening mechanism involved in the Al6061 – Graphene composites in comparison with monolithic Al 6061 alloy are discussed.