Graphene Oxide Nanofillers Research Articles

Pseudoboehmite or graphene oxide, what is the best additive for natural polymer pla—poly (l-lactic acid)?

In cases of severe injuries or burns, skin grafts (scaffold) are often necessary skin substitutes. To not harm the patient or the donor, research is necessary to search for heterografts, that are formed by biomaterials and are also biodegradable and bioabsorbable to the human body, as is the case with poly (L-lactic acid) - PLA. However, the natural polymers placed on the skin suffer great degradation in media with large amounts of carbon and water, have little durability due to their low ductility. For the proposal, the graphene oxide (GO) nanocharge and pseudoboehmite (PB) were obtained. It is believed that the nanofillers dispersed in the polymer matrix can improve mechanical properties regarding ductility and tenacity, without losing thermal properties. Subsequently, the hybrid nanocharge dispersion methods were employed to obtain in the poly (L-Lactic Acid) (PLA) matrix, forming the material for the desired scaffold. For this research, injectable specimens of pure PLA, PLA structured with GO nanoparticles, and PLA structured with PB nanoparticles, were manufactured. The microstructural and mechanical characterizations were performed on the specimens, to compare the effect generated by the nanocharges on the bulk material. The results showed that the increase in the concentrations of PB and GO nanofillers showed an increase in tenacity and ductility compared to pure PLA, a property that is desired in the scaffold structure.

Desalination by direct contact membrane distillation using mixed matrix electrospun nanofibrous membranes with carbon-based nanofillers: A strategic improvement

Robust hydrophobic and superhydrophobic mixed matrix electrospun nanofibrous membranes (MM-ENMs) have been prepared from low- and high- molecular weight polyvinylidene fluoride with either multi-walled carbon nanotubes or graphene oxide nanofillers (0.05–0.5 wt%). The polymer solutions' properties, including their electrical conductivity, viscosity, and surface tension, were determined and used to guide the design of single-, dual-, and triple-layered MM-ENMs combining layers with different hydrophobic character. All MM-ENMs were subsequently prepared and characterized in terms of their morphology, hydrophobicity, mechanical properties, and direct contact membrane distillation (DCMD) performance. A thinner hydrophobic layer with a thicker hydrophilic support layer in dual-layered MM-ENMs reduced water vapor transport resistance and improved DCMD performance relative to single-layer MM-ENMs. Conversely, placing an intermediate hydrophilic layer between two hydrophobic layers in triple-layered MM-ENMs promoted water condensation (water pocket formation) and thus reduced DCMD performance. Over 10 h DCMD, the best-performing dual-layered MM-ENM allowed ultra-high permeate fluxes of up to 74.7 kg/m2 h while maintaining a stable permeate electrical conductivity of around 7.63 μS/cm and a salt (NaCl) rejection factor of up to 99.995% when operated with a feed temperature of 80°C, a permeate temperature of 20°C, and a feed solution containing NaCl at a concentration of 30 g/L.

Nanocomposites based on biocompatible polymers and graphene oxide for antibacterial coatings

Recently, antibacterial coatings based on graphene oxide (GO) nanocomposites have attracted many studies around the world. The use of polymers as the matrices of GO nanofillers in the nanocomposites has been explored to produce efficient coatings against bacteria. One of the most prospective applications is the incorporation of GO into biocompatible polymers, which can produce antibacterial coatings. Here, recent progresses on the antibacterial coatings of nanocomposites based on biocompatible polymers and GO are reviewed. The effect of GO filler concentrations, biocide materials, and biocompatibility are discussed to find the most efficient antibacterial activity and biocompatibility of nanocomposites. Among biocompatible polymers, chitosan (Cs), poly vinyl alcohol (PVA), and poly lactic acid (PLA) are the most popular matrices used for the nanocomposites. This review also elaborates challenges in the use of other biocompatible polymers. Future works on biocompatible antibacterial coatings should be conducted by considering the concentration of GO nanofillers or adding other materials such as essential oils to suppress the toxicity toward functional cells.

GO based PVA nanocomposites: tailoring of optical and structural properties of PVA with low percentage of GO nanofillers

Graphene-based polymer composites are gaining interest as a modish class of substance that holds promising angles on diverse applications. In this work, Graphene Oxide (GO) based Polyvinyl Alcohol (PVA) nanocomposites (PVA-GO) have been prepared by employing a facile solution casting method. Low concentrations of GO nanofiller (0.25%, 0.50%, 0.75%, and 1.0%) were used and the result of the use of them over the distinct substantial characteristics of the nanocomposites was evaluated. The different features of the as-synthesized nanocomposites such as optical, structural, chemical, and thermal properties were identified by UV-Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), and Thermo-gravimetric analysis (TGA), respectively. From the structural analysis of the crystallinity of the nanocomposite it is evident that a reduction in crystallinity caused by the amalgamation of the GO nanofiller. FTIR study shows improved interaction between the GO nanofiller and PVA matrix. The incorporation of GO was found to reduce the optical band gap of the nanocomposite both for the direct and indirect transition. The Urbach energy of the nanocomposite increases with the increase of the GO concentration suggests the formation of localized states causing a reduction in the optical band gap. PVA-GO nanocomposites with improved and tunable physical properties synthesized from a simple and economic route may pave a new horizon for polymer-based optoelectronic devices.

Thin polymer films based on poly(vinyl alcohol) containing graphene oxide and reduced graphene oxide with functional properties

AbstractIn this article, the effect of the addition of graphene oxide (GO) and reduced graphene oxide (rGO) on the mechanical properties, thermal stability, and electrical conductivity of polyvinyl alcohol (PVA) has been investigated. Different weight percentages of nanofillers ranging from 0.5 to 5 wt% have been combined with PVA. The ultrasonic technique has been applied to disperse nanofillers in the PVA solution. The nanocomposite films have been prepared via solution casting technique and the dispersion of nanofillers into the PVA has been studied through optical microscopy. The microstructure, crystallization behavior, and interfacial interaction were characterized through X‐ray diffraction and Fourier transform infrared spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis have been applied to study the thermal properties of the prepared nanocomposites. The DSC results revealed that the crystallization temperature and melting temperature were enhanced in the presence of GO nanofiller. Besides, the tensile strength at break was improved along with the addition of GO; however, elongation at break for PVA/GO and PVA/rGO was diminished. Moreover, all specimens showed insulating behavior and the only sample was electrically conducting, which contain a high amount of rGO (5 wt%).

Fabrication of biodegradable polyurethane electrospun webs of fibers modified with biocompatible graphene oxide nanofiller

A successful optimization of the electrospinning parameters for obtainment of biodegradable polyester urethane (DP) webs of fibers, neat and graphene oxide (GO) modified, was performed. The effect of the processing parameters (distance between the needle tip and the collector, applied voltage, and flowing rate), solution type and polymer concentration, on the fiber-forming process and the obtained fibers’ morphology was examined. The best homogeneity of the fibers was achieved for 12 wt% DP dissolved in 80:20 wt% mixture of chloroform and ethanol, applying similar processing parameters for the neat and modified samples (0.5 ml/h pumping rate, 15 kV applied voltage, and 150 mm distance to the collector, for the neat sample, and 0.4 ml/h, 18 kV, and 110 mm, for the GO modified samples). The main novelty of this work is the modification of DP with low quantities (0.5, 1.0 and 2.0 wt%) of GO – the “next generation” nanomaterial for stem cell control. The morphological characterization revealed a fibrous microstructure consisting of randomly oriented fibers with a diameters ranging from hundreds nanometers to couple micrometers, representing a feasible imitation of the structure of extracellular matrix (ECM). The XRD studies showed high dispersion of GO in DP matrix and even exfoliation for the sample that contains 2 wt% GO. Raman studies neatly complemented the highest filler/matrix interactions and the superior levels of dispersion for this sample. TGA was used to analyze the thermo-oxidative degradation and also to determine the actual content of GO present in the samples.

Unveiling the Role of Graphene Oxide as an Interface Interlocking Ingredient in Polyvinylidene Fluoride‐Based Multilayered Thin‐Film Capacitors for High Energy Density and Ultrafast Discharge Applications

Rising energy storage demands have accelerated the research to develop highly efficient dielectrics, such as polymer nanocomposites for capacitor applications. Herein, high energy and power density in dielectric composites via incorporating a large number of hetero‐interfaces and microcapacitors driven by interfacial polarization for thin‐film‐based flexible polymer capacitors are demonstrated. The barium titanate (BT) nanoparticles (NPs) and graphene oxide (GO) nanosheets are selectively localizing in the outer and middle layers, respectively. The BT/polyvinylidene fluoride (PVDF) as a “hard layer” helps in blocking the propagation of the electrical tree. The strong interaction between GO and PVDF in the GO/PVDF layer improves the interfacial polarization through formation of microcapacitors. Also, the confinement of the conduction charges simultaneously enhances the dielectric constant and breakdown strength. Thus, the GO nanofillers to work as both “soft layer” and “hard layer” are designed, and the energy density is improved to 11.4 J cm−3 at 3617 kV cm−1, ≈650% higher than that of commercially available biaxially oriented polypropylene (BOPP). Also, an ultrafast discharge time of 0.37 μs as compared to 2.8 μs for BOPP is achieved. These attributes make NP‐BaTiO3/nano‐GO/PVDF trilayered capacitors a suitable and promising candidate for the next‐generation flexible thin‐film dielectric capacitors.

Complex electrical impedance and dielectric spectroscopy of Na+-conducting PEO/PVP/NaIO4 solid polymer electrolyte with incorporated nano-sized Graphene Oxide

Being of significant interest as electrolytic materials for mini-mobile energy storage devices, we have studied solid-state polymer-based electrolytic systems – nanocomposites, in particular, NaIO4 salt-complexed poly(ethylene oxide) (PEO)/polyvinyl pyrrolidone (PVP) polymer blends doped with nano-sized Graphene Oxide (GO). The GO monolayer average size and thickness were 5 μm and 2 nm, respectively. In the PEO/PVP polymer blend, the PEO:PVP ratio was 70:30 weight percent (wt.%), the concentration of the salt sodium metaperiodate NaIO4 was 10 wt.%. The nano-sized GO was dispersed with concentration of 0.2; 0.4 and 0.6 wt.%. Thin films (150 μm) of GO/PEO/PVP/NaIO4 Na+ ion-conducting nanocomposites were produced by solution casting technique. They were studied by complex electrical impedance and dielectric spectroscopy in the frequency range 0.1 Hz – 1 MHz of the applied electric field. The room-temperature ion conductivity, the complex dielectric function, dielectric loss and AC conductivity of GO/PEO/PVP/NaIO4 at various concentration of GO were obtained, and the effect from the GO nanofillers was estimated.

Synthesizing a novel fluorinated reduced graphene oxide-CeO2 hybrid nanofiller to achieve highly corrosion protection for waterborne epoxy coatings

Although fluorinated graphene (FG) inherits the physical barrier characteristic from graphene, its limited dispersibility seriously impedes its application in corrosion resistance. Here, this study aims to present a facile strategy to effectively eliminate this undesired feature of FG. We developed a well-dispersed cerium oxide grafting fluorinated reduced graphene oxide (FrGO@CeO2) nanofiller to enhance the anti-corrosion properties of epoxy coating on Q235 mild steel surfaces. The in situ F-doping and hydrothermal techniques were employed to synthesize FrGO@CeO2 nanofillers and functionalize them with waterborne epoxy coating. Combining the electrochemical results and the corrosion morphologies, the resultant nanofillers were found to significantly reinforce the protection properties of epoxy coatings due to the physical barrier effect derived from FrGO. In addition to impermeability, FrGO presented the insulating nature and endowed composite coatings to combat galvanic corrosion. Local electrochemical impedance spectroscopy (LEIS) indicated that cerium oxide adsorbed on mild steel surface could form a passive layer and thus further resisted the metal corrosion process. The related corrosion protection mechanism of FrGO@CeO2/EP coating was proposed in detail, which could provide broader platforms for designing new corrosion protection materials.

A third order shear deformable model and its applications for nonlinear dynamic response of graphene oxides reinforced curved beams resting on visco-elastic foundation and subjected to moving loads

In present work, a nonlinear functionally graded curved beam model including the von Karman geometric nonlinearity is developed on the basis of the third-order shear deformation theory. Due to incorporating the trapezoidal shape factor in the proposed model, the errors caused by geometric curvatures are eliminated. The governing equations of motions related to the dynamics of curved beams are derived by Lagrange method and solved using a standard Newmark time iteration procedure in conjunction with Newton–Raphson technique. Some comparisons are performed and indicate that the results from our model coincide favorably with semi-analytical solutions. Afterwards, utilizing the proposed model, the present investigation focuses on the nonlinear transient response of functionally graded multilayer curved beams reinforced by graphene oxide nano-fillers subjected to moving loads. A modified Halpin–Tsai micromechanical model is implemented to determine the effective modulus of graphene oxide/polymer nanocomposite, and the rule of mixture is used to calculate the mass density and Poisson’s ratio. The curved beams are assumed to rest on a visco-Pasternak foundation. The effects GO nano-fillers, including their weight fractions, distribution patterns and size on the nonlinear dynamic responses of the nanocomposite curved beams subjected to moving loads are studied. Moreover, the effects of radius-to-span ratios and visco-Pasternak foundation on the nonlinear dynamic response of curved beams are also discussed as subtopics.

Enhancing performance of phosphorus containing vanillin-based epoxy resins by P–N non-covalently functionalized graphene oxide nanofillers

In this study, non-covalently functionalized graphene oxide (FGO) containing phosphorus and nitrogen was synthesized using dibenzyl N,N′-diethyl phosphoramidite (DDP) via a single step process. Meanwhile, novel bio-based phosphorus containing vanillin epoxy resin (VPE) was made via a two-step process and used as a flame-retardant adhesive. Subsequently, FGO was dispersed in the epoxy resin matrix at different weight ratios as reinforcement for improving mechanical, thermal and flame-retardant properties of the resultant composite systems. Curing behavior of the VPE and FGO mixtures with 4,4′-diaminodiphenylsulfone (DDS) as the crosslinker was investigated using a Differential Scanning Calorimeter (DSC). Thermal and flame-retardant properties of the cured VPE/FGO nanocomposites were systematically investigated by Thermogravimetric Analysis (TGA), Gas Chromatography – Mass Spectrometry (GC-MS), Limited Oxygen Index (LOI), vertical burning test (UL-94), and cone calorimeter test. Results indicated that all VPE/FGO nanocomposites exhibited excellent thermal and flame-retardant properties. In particular, VPE with 9 wt% of FGO achieved the highest LOI value (29.1%) and passed the V-0 rating in the UL-94 test. Furthermore, cone calorimetry test showed that flame retardancy performance of the VPE and VPE/FGO composites significantly improved compared to vanillin epoxy control resin without phosphorus. The gaseous and high boiling pyrolysis products of VPE cured by DDS were collected and characterized by GC/MS to reveal their formation mechanisms. The char layers of the cued VPE showed a high oxidation resistance with intumescent structures. The combined barrier and quenching effects of the char layer imparted VPE with excellent flame retardancy. This study illustrated a promising approach for synthesizing mechanically strong, thermally-stable and environmentally-friendly flame-retardant bio-based composite resins.

Electromagnetic Interference Shielding Properties of BaCo2Fe16O27 Nanoplatelets and RGO Reinforced PVDF Polymer Composite Flexible Films

AbstractThe electromagnetic Interference (EMI) shielding effectiveness of W‐Type barium hexaferrite (BaCo2Fe16O27) and reduced graphene oxide (RGO) nanofillers reinforced poly(vinylidenefluoride) (PVDF) polymer composite films are reported. Two different amounts of BaCo2Fe16O27 (10 wt% and 30 wt%) nanofillers and fixed amount of RGO (10 wt%) are loaded in PVDF matrix by solvent casting in order to fabricate the multifunctional PVDF/RGO/BaCo2Fe16O27 composite films. The synthesized samples are investigated using various instruments including X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), Raman spectroscopy, high resolution scanning electron microscopy (HRSEM), energy dispersive X‐ray spectroscopy (EDX), X‐ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) analysis. The microwave properties of PVDF/RGO/BaCo2Fe16O27 composites are tested with vector network analyser (VNA) in 8–12 GHz frequency (X‐Band). The possible mechanism of EMI shielding is investigated from the analysis of complex permittivity and permeability.The resultant flexible films exhibit desirable EMI SE of 35.94 dB at 11.8 GHz for the 10 wt% of BaCo2Fe16O27 addition in PVDF composite for a very small thickness of 0.2 mm. The combination of high dielectric loss ( tanδε = 1.63) and magnetic loss (tanδμ = 0.26) contributes to high absorption of 29.85 dB (>99% attenuation) dominated over reflection. Thus, the simple and cost‐effective fabrication of ultrathin and flexible PVDF/RGO/BaCo2Fe16O27 composite film with low filler content has a great potential as suppresser in electromagnetic fields.

Influence of graphene oxide filler content on the dentin bond integrity, degree of conversion and bond strength of experimental adhesive. A SEM, micro-Raman, FTIR and microtensile study

The study aimed to evaluate the effect of graphene oxide (GO) nano-filler content in experimental dental adhesive on its degree of conversion (DC), microtensile bond strength (μTBS) and structural reliability, using Fourier transform infrared spectroscopy (FTIR), Micro-Raman spectroscopy and Scanning electron microscopy (SEM). A resin adhesive was fabricated (control adhesive - CA) and fabricated GO nano-particles were added at 0.5% and 2.0% (m/m) to produce adhesives GOA1 and GOA2 respectively. One hundred and two teeth (specimens) were prepared for dentin exposure and conditioned with 36% phosphoric acid. Specimens in each group (n = 34) were treated with formulated adhesives (CA, GOA1 & GOA2) and photo-polymerized for 20 s followed by composite build up. Sixty specimens were used for μTBS testing in the adhesive groups (CA, GOA1 & GOA2), with half exposed to thermocycling (TC) whereas the remaining half (n = 10) stored in distilled water. Seven specimens each were assessed using SEM and Micro-Raman spectroscopy, in each adhesive group (n = 7). DC for the adhesives was assessed using FTIR. The means of μTBS and DC were analyzed using ANOVA and post hoc Tukey multiple comparisons test. GO nano-filler content showed significant influence on the adhesive μTBS in comparison to controls (p < 0.01). Ageing (TC) revealed significant reduction in the μTBS, except in GOA2 specimens, which showed comparable outcomes among TC and non-TC specimens (p > 0.05). DC was significantly higher in control adhesive [46.8 (3.6)%] compared to GOA2 [37.7 (4.2)%] specimens, however DC was comparable among GOA1 [42.3 (2.9)%] and GOA2 [37.7 (4.2)%] specimens (p > 0.05) respectively. GO exhibited interaction within adhesive and tooth dentin comparable to control adhesive. Increasing GO content showed increase in μTBS of adhesive to dentin, but a decrease in degree of conversion. Under ideal conditions, experimental adhesive with 2% GO content showed acceptable bond strength and DC; and should be further assessed under dynamic conditions to recommend clinical use.

New insights into the impact of graphene oxide incorporation on molecular ordering and photophysical properties of PTB7:C70 blends

Nano-fillers have been successfully incorporated in the active layer to enhance the performance of bulk heterojunction (BHJ)-based organic solar cells (OSCs). However, only little information is available on their impact on the molecular ordering of polymers in the BHJ blends. Here, we comprehensively analyze the absorption, photoluminescence (PL), and Raman spectra to understand the effect of incorporation of the graphene oxide (GO) nano-filler in PTB7:C70 blends on the molecular ordering of PTB7 polymer. Absorption spectroscopy unveils how the interplay between interchain and intrachain coupling modifies the molecular order and backbone characteristic of PTB7. The addition of C70 weakens both intrachain and interchain interaction of PTB7. Whereas, intrachain interaction gradually rises with increasing the GO concentration. PTB7 films show weakly interacting J-aggregate behavior; nevertheless, the interaction strength gradually improves with the increasing GO content. The PL analysis indicates well-segregated phase domains and enhanced molecular ordering for composite films with 1 wt% GO. The Raman spectra of PTB7:C70:GO composite films suggests the formation of highly ordered PTB7 aggregates. An in-depth understanding of how these properties of polymer blends change with the GO concentration has significant implications on exploiting them towards the development of electronic devices.

Molecular simulation of different structure dopamine-modified graphene oxide and its effects on thermal and mechanical properties of the epoxy resin system

Molecular dynamics (MD) simulations were carried out to explore the ideal structure design of graphene oxide (GO) modified by poly (dopamine) (PDA) which is more conducive to performances improvement of epoxy resin composites. The epoxy resin matrix was compounded with PDA-modified GO (PDA-GO) particles with different structures including the surface modification and the interlayer inserted modification. The interaction energy (Einter), molecular mobility (MSD), packing density (RDF), thermal and mechanical properties of different structure of PDA-GO/epoxy composites were calculated. Interestingly, it was found that the increased layer number of GO weakened the interfacial binding between GO particles and the epoxy matrix, and prevented the compact stacking of epoxy molecular chains, but the PDA-GO with inserted-modification structure displayed a desirable interfacial binding with epoxy resin and dramatically improved thermal and mechanical performances of the resulting composites. In addition, the surface-modification of single layer GO using PDA had negative effects on micro and macro performances of epoxy matrix composites. This work provided special revelation for rationally designing the structure of GO nanofillers and better exerting its excellent properties in epoxy matrix composites.

Optical and electrical properties of poly (N-vinylcarbazole)/graphene oxide nanocomposites for organic semiconductor devices

In this work, organic semiconductor devices (OSD) incorporating both poly(N-vinylcarbazole) (PVK) and graphene oxide (GO) were fabricated. The stable solutions of PVK/GO were prepared in chloroform by a simple sonication method, which enabled the successful dispersion of GO with the polymer matrix. These nanomaterials have been used in the fabrication of OSD with configuration ITO/PVK:GO/Ag. The electrical and optical properties were investigated using several techniques. The electrical measurements show that the electrical behavior of PVK polymer enhanced with increasing GO nanofillers concentration. The observed electrical improvement in the nanocomposites can be attributed to the charge transfer interaction between carbazole electron donor and the functional groups onto the surface of GO. UV–Vis absorption and photoluminescence studies elucidated the energy transfer and the interaction between polymer chains and the graphene nanosheets which exhibit a strong blue-green luminescence.

Sulfonated poly(ether ether ketone)/amine-functionalized graphene oxide hybrid membrane with various chain lengths for vanadium redox flow battery: A comparative study

In this paper, a series of sulfonated poly(ether ether ketone) (SPEEK) hybrid membranes containing aliphatic amine-functionalized graphene oxide nanofillers as the interface modifiers, reacted with primary amine (NH2-GO), ethylenediamine (EDA-GO) and 1,6-hexanediamine (HMD-GO), respectively, have been fabricated via a simple solution-casting method. Three hybrid membranes (S/NH2-GO, S/EDA-GO, and S/HMD-GO) demonstrate much higher physicochemical property than that of pristine SPEEK and Nafion 117, which is originated from the varied interfacial interaction and the surface architecture behavior. A superior ion selectivity of S/EDA-GO-1 (24.8 × 103 S min cm−3), S/HMD-GO-2 (24.6 × 103 S min cm−3) and S/NH2-GO-2 (20.4 × 103 S min cm−3) to pristine SPEEK (4.3 × 103 S min cm−3) and Nafion 117 membrane (4.0 × 103 S min cm−3) is shown. At the current density of 50 mA cm−2, S/EDA-GO-1 hybrid membrane gives the highest energy efficiency than that of S/NH2-GO-2 and S/HMD-GO-2, endowing an excellent charge capacity retention during 100 cycles. The varied interfacial structure state originated from the introduced EDA-GO and HMD-GO nanofillers provide the different proton conductivity and vanadium ion permeability. This present work provides a guidance for developing high-performance PEMs through the regulated interfacial structure via the moderate chain length.

Elastomer based nanocomposites with reduced graphene oxide nanofillers allow for enhanced tensile and electrical properties

Elastomer based nanocomposites with reduced graphene oxide nanofillers allow for enhanced tensile and electrical properties

Extrusion of Polymer Nanocomposites with Graphene and Graphene Derivative Nanofillers: An Overview of Recent Developments

This review is focused on the recent developments of nanocomposite materials that combine a thermoplastic matrix with different forms of graphene or graphene oxide nanofillers. In all cases, the manufacturing method of the composite materials has been melt-processing, in particular, twin-screw extrusion, which can then be followed by injection molding. The advantages of this processing route with respect to other alternative methods will be highlighted. The results point to an increasing interest in biodegradable matrices such as polylactic acid (PLA) and graphene oxide or reduced graphene oxide, rather than graphene. The reasons for this will also be discussed.

Nonlinear static behaviors of functionally graded polymer-based circular microarches reinforced by graphene oxide nanofillers

This work investigates the nonlinear static behaviors of polymer-based nanocomposite circular microarches reinforced by a low content of graphene oxide (GO) and with inclusions of von Kármán nonlinearity. The weight fractions of the GO nanofillers are assumed to gradually vary along the thickness directions of the arches according to a given law. The GO nanofillers are considered to be circular reinforcements dispersed within a polymer matrix, and a modified Halpin–Tsai model is used to determine the effective modulus of the elasticity of the nanocomposite. In the present work, a modified couple stress-based model for analyzing the nonlinear behaviors of circular arches is developed based on the exponential shear deformation theory (ESDT). In this model, the trapezoidal shape factor is properly incorporated to receive more accurate stress-resultants along the thickness direction, making the present model capable of dealing with the mechanical behaviors of thick arches. The polynomial Ritz method is implemented to simulate the classical immovable end restraints of arches. Three kinds of external transverse loads are taken as external forces that act upon microarches. The governing equations of the considered problem are derived using the minimum energy procedures and are solved via the Newton-Raphson iteration technique. Comparisons are carried out to verify the results and accuracy of the proposed model. Some numerical illustrations are provided to show the effects of the load types, small scales, GO distribution patterns, and sizes of the GO nanofillers on the nonlinear response of nanocomposite arches reinforced by graphene oxide.