Amount Of Graphene Nanoplatelets Research Articles

Phenol-formaldehyde resin enriched with graphene nanoplatelets as an electroconductive adhesive for wood composites

The study demonstrates that phenol-formaldehyde (PF) resin, commonly used for lignocellulosic composites, can become electroconductive when modified with graphene nanoplatelets (GNPs) while still serving as an effective adhesive for particleboard production. The PF resins enriched with various amounts of GNPs were tested for viscosity, gel time, and thermal stability, followed by electrical conductivity measurements for GNP-enriched resins applied to several lignocellulosic surfaces of varying wettability. These tests showed that the optimum weight percentages of GNP at which the resins maintain both the electrical conductivity and process parameters, enabling the formation of particleboard, amount to 18.5%. Consequently, a prototype of electroconductive particleboard was created and evaluated for bending strength (EN 310: 1993), modulus of elasticity (EN 310: 1993), tensile strength (EN 319: 1993), thickness swelling (EN 317: 1993), water adsorption (PN-76/D-04234) and formaldehyde emission (EN ISO 12460–5:2015). Impressively, the panels achieved a conductivity of 320 Ω m, indicating their potential use as resistive heaters and other applications in the Internet of Things (IoT) area. Simultaneously, the GNP-enriched panels showed formaldehyde emission well below the threshold set by the standards and exhibited mechanical properties that in most cases met the criteria for use in furniture and interior design.

Removal of toxic Cr(VI) from aqueous medium with effective magnetic carbon-based nanocomposites.

Cr(VI), which has toxic effects, is a heavy metal and it must be removed from the environment due to the various damages it causes. In this study, the removal of Cr(VI) pollutants from aqueous solutions with Fe3O4-based materials using a batch adsorption technique was investigated. Magnetically modified graphene nanoplatelet (GNP)-based nanocomposites were prepared and their structures were characterized by FTIR, XRD, SEM, BET, and TGA techniques. The effects of various physicochemical parameters such as adsorbent dose, contact time, initial Cr(VI) solution concentration, pH, and the presence of coexisting ions (NaCl) on the adsorption process were investigated. Accordingly, the optimum conditions for Cr(VI) removal were determined. Nonlinear Langmuir, Freundlich, and Temkin isotherm models and pseudo-first-order, pseudo-second-order, and Bangham kinetic models were used to investigate the adsorption mechanism. The experimental data relatively fit the second-order kinetic model and the Freundlich isotherm model. The maximum adsorption capacities for pure Fe3O4 (Fe:GNP 1:0), Fe:GNP (2:1), and Fe:GNP (1:1) nanocomposite materials at 298 K and pH of approximately 5 were obtained as 12.71 mg/g, 27.03 mg/g, and 62.27 mg/g, respectively. This result showed that Cr(VI) removal increased as the amount of GNP in the composite material increased. Generally, the results confirmed that magnetically modified GNP-based adsorbents are functional and promising materials that can be used for the removal of pollutants such as Cr(VI) from aqueous media.

EFFECT OF MACHINABILITY OF GNP–GFRP COMPOSITES ON TENSILE STRENGTH AND FATIGUE BEHAVIOR

The paper focuses on the cutting behavior of Glass Fiber Reinforced Polymer (GFRP) composites and GNP–GFRP composites that contain varying amounts of Graphene Nano Platelets (GNP). GFRP composites are increasingly being used in a variety of industrial applications due to their excellent mechanical properties, such as high strength, stiffness, and low weight. However, their machining and cutting behavior can be challenging due to the presence of the reinforcing fibers. Therefore, the study aims to investigate the machining behavior of GFRP composites and the effect of adding GNP on their cutting behavior. The effect of different parameters such as cutting speed, feed rate and reinforcement rate on cutting forces and delamination factor is investigated. In addition, the tensile strength and fatigue behavior of the composite materials with the best and worst delamination factors were also determined. Addition of up to 0.2 wt.% of GNP to GFRP composites resulted in an increase in cutting forces and delamination factor when drilling GFRP composites. While the cutting force and delamination factor decreased with the increase in cutting speed, the cutting force and delamination factor increased with the increase in the feed rate. Analysis of variance (ANOVA) was performed to determine the effects of drilling parameters and reinforcement ratio on cutting force and delamination factor according to full factorial experimental design. The most efficient factor on the cutting forces is found to be feed rate (84.97%), followed by the reinforced rate (6.48%) and cutting speed (6.13%). The most efficient factor on the delamination factor is determined to be feed rate for (44.49%), followed by the reinforced rate (29.20%) and cutting speed (21.73%).

Thermal, mechanical, thermo‐mechanical and morphological properties of graphene nanoplatelets reinforced green epoxy nanocomposites

AbstractThe efficient inclusion of GNPs (graphene nanoplatelets) as an effective nano‐fillers for green polymer matrices produced with 28% of carbon originating from biomass tends to significantly improve mechanical and thermal properties. In the present work, green epoxy nanocomposites with low loading of (0.1, 0.25, and 0.5) wt% of the GNPs were made using a solution blending technique using acetone as the solvent. In mechanical stirring, the ultrasonic bath was used to ensure the efficient dispersion of GNPs within green epoxy. The resulting nanocomposites were comprehensively characterized and compared to unfilled green epoxy. Different tools were used to appraise morphological, thermal, thermo‐mechanical, and mechanical behavior. The results confirmed through FE‐SEM showed an optimal dispersion of GNPs with nanocomposites. The thermal degradation temperature (Td) of GNPs curve with 0.25 wt% loading was shifted toward higher temperature (from 336°C to 342°C) due to low percentage of loading of GNPs which showed an enhance thermal stability of polymer matrix with 0.25 wt% loading. The mechanical results were also in lined with previously published literature, in the tensile test 6.45% and hardness 13.3% increment was achieved. Overall, the results underscored significant improvements in green nanocomposite performance with low wt% of GNPs.Highlights The study focuses on development and characterization of green epoxy nanocomposites, which utilize environmentally friendly materials as a matrix, highlighting the significance of sustainability. The study explores effects of low loading of GNPs in green epoxy nanocomposites. The results demonstrate significant improvements in mechanical and thermal properties with optimized presence of GNPs. This investigation provides insights into optimal amount of GNPs required to achieve improved properties. Research evaluates multifaceted analysis provides a holistic understanding of performance enhancements achieved through inclusion of GNPs.

The synergistic effects of micro-and nano-fillers on the properties of polyamide 11/poly (lactic acid) blend

This study focused on investigating the effects of micro-scale carbon fibers (CF) and nano-scale graphene nanoplatelets (GNP) on the morphological, rheological, mechanical, thermo-mechanical and thermal properties of polyamide 11/poly (lactic acid) (PA11/PLA) blend. A twin-screw extruder and an injection molding machine were utilized to produce the samples. The amount of GNPs was varied up to 5 wt% for a fixed CF fraction of 20 wt%, and the composites were characterized. SEM micrographs of hybrid composites revealed stronger interfacial interactions between the matrix and CF and improved dispersion of GNPs. The pseudo solid-like behavior transition and high modulus detected in the rheological study with the addition of GNP confirmed the strong matrix-filler interactions in hybrid composites. The synergistic effects of multi-scale fillers have been observed in mechanical and thermo-mechanical properties. In comparison to 20CF, hybrid composites’ tensile strength and modulus increased by 8%–4.8% and 4.5%–17%, respectively, by adding 0.5–5 wt% GNP. Dynamic mechanical analysis revealed that the tan δ peak shifted to higher temperatures in low GNP containing hybrid composites, indicating an increase in Tg. Also, differential scanning calorimetry confirmed the Tg increment and synergistic effect of fillers on crystallization. The thermogravimetric analysis demonstrated that hybrid composites exhibited enhanced thermal stability. As a consequence, these hybrid composites offer an inventive viewpoint for environmentally friendly composites in the automobile industry thanks to their enhanced mechanical and thermal characteristics.

Thermal buckling and vibration analysis of rotating porous FG GNPs-reinforced Reddy microplates

Thermal buckling and free vibration analysis of rotating functionally graded (FG) graphene nanoplatelets (GNPs) reinforced nanocomposite porous metal-matrix microplates subjected to a linear thermal gradient are presented in this paper. The third-order shear deformation theory (TSDT) of Reddy and the Lagrange's equation of the second kind are adopted to derive the governing equations of motion via the modified couple stress theory (MCST). Different patterns of porosity distribution and GNPs dispersion are considered. The effective material properties of the microplate are determined by employing the Halpin-Tsai micromechanical model and rule of mixture. Galerkin method is chosen as a numerical technique, in which the comparison functions for displacements are approximately described as the boundary functions multiplied by Chebyshev polynomials, to solve the governing equations for various boundary conditions. The accuracy and effectiveness of the present results are validated by comparing with the previous literature. The effects of GNPs dispersion pattern, geometry and weight fraction as well as porosity coefficient, porosity distribution, angular velocity and material length scale parameter on the critical buckling temperature rise and fundamental frequency are studied. It is contrary to expectations that either increasing the amount of GNPs or increasing the porosity coefficient improves the thermal buckling behavior. Results also show that the GNPs' performances are affected not only by their geometry, but also by the centrifugally stiffening and small-scale effects. Rotating motion weakens the enhancement of GNPs on the thermal buckling behavior. More clamped boundaries enhance the critical buckling temperature rise and fundamental frequency. The outcomes of this work can be used as the reference for future applications in various fields of industry and technology.

Effect of graphene coating on modified and pristine carbon fibers on the tribological response of carbon fiber epoxy composites

Addition of graphene nanoplatelets (GNP) as nanofillers in carbon fiber reinforced polymer composites improves a range of mechanical properties e.g. flexural, tensile and fatigue. Multiple studies have reported that this occurs through the formation of a carbon-enriched interphase with intermediate properties between the epoxy, graphene and carbon fiber. However, even though GNPs act as a solid lubricant and have exceptional strength and thermal conductivity, the wear performance and failure mechanism of GNP-incorporated composites are still not understood. The current study aims to investigate the effect of GNP-coated-pristine as well as GNP-coated-oxidized carbon fibers on the wear performance of carbon fiber reinforced epoxy composites manufactured through vacuum-assisted resin transfer molding technique (VARTM). It has been found that specific wear rate and coefficient of friction were lower for GNPs added composites compared to pristine laminates and it was the least in the case of composites in which an optimum amount of GNPs was coated on oxidized carbon fibers. Moreover, smaller temperature within the specimens has been found during the wear test in the case of GNP-added laminates owing to the higher thermal conductivity of the GNPs. Worn surface morphology has shown formation of thin epoxy layers at lower number of cycles for all the laminates. Fiber breakage, debonding resulting in clean fibers and a large amount of wear debris has been seen on worn surfaces of pristine laminates. However, GNP-added laminates have shown less wear debris and enhanced fiber-epoxy bonding. The wear response has been correlated with the size of the interphase formed between the fiber and the epoxy.

Enhanced mechanical and thermal properties of graphene nanoplatelets‐reinforced polyamide11/poly(lactic acid) nanocomposites

AbstractThe present paper aims to obtain a sustainable nanocomposite by using bio‐based polyamide 11 and biodegradable poly (lactic acid) blend as matrix and graphene nanoplatelets (GNP) as nanofiller. GNP was incorporated in the PA11/PLA blend matrix in the ratio of 0.5‐1‐3‐5‐10 wt% through the twin‐screw extruder. The crystallinity of PA11 in the blend, which was 12.9%, increased with the inclusion of GNP, and the highest crystallinity value was observed at 20% for the 1GNP sample. The crystallinity of PLA in the blend, which was 2.3%, increased to 4.6% with 5 wt% GNP addition. The inclusion of GNP to PA11/PLA improved the thermal degradation temperatures and increase the char residue. Also, increments were observed for storage modulus, loss modulus, and glass transition temperature of the matrix with the inclusion of GNP. The addition of GNP caused the tensile strength of the matrix to increase first and then decrease at higher amounts due to the agglomerations. 0.5–1 wt% GNP increased tensile strength by 10% and 5%, respectively. Increasing the amount of GNP to 10 wt% led to a sharp decrease in tensile strength by 24%. Overall, GNP is a suitable nanofiller to enhance the thermal and mechanical features of the PA11/PLA blend.

Effect of the Particle Size and Layer Thickness of GNP Fillers on the Dielectric Properties and Actuated Strain of GNP-PDMS Composites.

Dielectric elastomer actuators (DEAs), a type of electroactive polymers (EAPs), are smart materials that are used in various fields such as artificial muscles and biomimetic robots. In this study, graphene nanoplatelets (GNPs), which are conductive carbon fillers, were added to a widely used DEA, namely, polydimethylsiloxane (PDMS), to improve its low actuated strain. Four grades of GNPs were used: H5, H25, M5, and M25 (here, the number following the letter indicates the average particle size of the GNPs in μm). The average layer thickness of the H grade is 13–14 nm and that of the M grade is 5–7 nm. PDMS composites were prepared by adding 0.5, 1, 2, and 3 wt% of each GNP, following which the mechanical properties, dielectric properties, and actuated strain of the composites were measured. The mechanical properties were found to increase as the particle size increased. Regarding the dielectric characteristics, it was found that the higher the aspect ratio of the filler, the easier the formation of a micro-capacitor network in the composite—this led to an increase in the dielectric constant. In addition, the higher amounts of GNPs in the composites also led to an increase in the dielectric constant. For the actuated strain analysis, the electromechanical sensitivity was calculated using the ratio of the dielectric constant to the Young’s modulus, which is proportional to the strain. However, it was found that when the loss tangent was high, the performance of the actuated strain decreased owing to the conversion of electric energy into thermal energy and leakage current loss. As a result, the highest actuated strain was exhibited by the M25 composite, with an actuated strain value of 3.01% measured at a low electric field (<4 kV/mm). In conclusion, we proved that the GNP–PDMS composites with a thin layer and large particle size exhibited high deformation.

A study on graphene reinforced carbon fiber epoxy composites: Investigation of electrical, flexural, and dynamic mechanical properties

AbstractIn this study, graphene nanoplatelets (GNPs) added to epoxy matrix composite reinforced by aeronautical grade carbon fibers (CFs) were fabricated by the vacuum infusion method, and the effect of different GNPs contents (0.05, 0.25, and 1.25 wt%) on electrical conductivity, flexural properties, and dynamic mechanical properties were investigated. The results revealed an 8‐ and 73‐times improvement in conductivity values across the thickness with the addition of 0.05 and 0.25 wt% GNPs, respectively, compared to the neat composite. Flexural test results showed that with the addition of 0.05 GNP, only 6% increase in flexural strength was obtained, while with the addition of 0.25 wt% GNP flexural strength remained almost the same as for the neat composite. On the contrary, the addition of GNPs (1.25% by weight) causes a reduction in the flexural strength with respect to the neat composite. This was confirmed by the fractured surfaces examined by scanning electron microscope which reveals that considerable amount of fiber‐matrix debonding was observed with 1.25 GNPs loading. Dynamic mechanical analysis (DMA) revealed that the storage modulus of the neat composite increased by 12.6% with the addition of only a small amount of GNP (0.05% wt) compared to the neat composite. Composite with 1.25 GNP shows upward bending, affecting the shape of the cole–cole plot obtained from DMA results, indicating inappropriate interactions of GNPs in both the matrix and CF in the composite.

Effect of Temperature and Humidity on the Water and Dioxygen Transport Properties of Polybutylene Succinate/Graphene Nanoplatelets Nanocomposite Films.

Nanocomposite films of polybutylene succinate (PBS)/graphene nanoplatelets (GnP) with a GnP content ranging from 0 to 1.35 wt.% were prepared by melt processing. The morphology of both the neat PBS and PBS/GnP nanocomposites were investigated and revealed no significant impact of GnP on the crystalline microstructure. Moisture sorption at 10 °C, 25 °C, and 40 °C were analyzed and modeled using the Guggenheim, Andersen, and De Boer (GAB) equation and Zimm-Lundberg theory, allowing for a phenomenological analysis at the molecular scale. An understanding of the transport sorption properties was proposed by the determination of the molar heat of sorption (ΔHs), and the activation energy of the diffusion (Ed) of water in the matrix since both solubility and diffusion are thermo-activable properties. Both ΔHs and Ed showed a good correlation with the water clustering theory at high water activity. Water and dioxygen permeabilities ( and ) were determined as a function of temperature and water activity. and decreased with the addition of a small amount of GnP, regardless of the studied temperature. Moreover, the evolution of as a function of water activity was driven by the solubility process, whereas at a given water activity, was driven by the diffusion process. Activation energies of the permeability (Ep) of water and dioxygen showed a dependency on the nature of the permeant molecule. Finally, from the ΔHs, Ed, and Ep obtained values, the reduction in water permeability with the addition of a low content of GnP was attributed mainly to a tortuosity effect without diffusive interfaces rather than a significant change in the transport property mechanism.

Hybrid reinforcement of styrene‐butadiene rubber nanocomposites with carbon black, silica, and graphene

AbstractThe complex structure of tyres makes them hard to recycle economically; hence, it is crucial to minimize the generation of tyre waste. Nano‐reinforcement, such as graphene, has the potential to increase the abrasion resistance of rubber and thus their lifespan as well. In this research, hybrid styrene‐butadiene rubber‐based (SBR) nanocomposites reinforced with carbon black, silica and various amounts of graphene nanoplatelets are investigated with great emphasis on their combined effects on the mechanical properties of the rubber samples. Sixty‐five phr of precipitated silica can holistically improve the properties of SBR. However, further addition of carbon black and graphene nanoplatelets to silica‐containing samples do not benefit the properties of the samples. Further studies on the compatibilization of silica with carbon‐based reinforcement are necessary. On the other hand, graphene and carbon black constitute an effective hybrid reinforcement system. The tensile strength and elongation at break of SBR are improved by almost 100% with 10 phr of graphene nanoplatelets in combination with 10 phr of carbon black. However, the abrasion resistance of samples was negatively influenced by the addition of graphene nanoplatelets whenever it was added in combination with other fillers. Silica was particularly effective in increasing the abrasion resistance of rubber.

Graphene Based Wideband Electromagnetic Absorbing Textiles at Microwave Bands

The design and realization of graphene based wideband electromagnetic (EM) absorbing textiles are becoming of primary interest. Hence, the development of new conductive coatings to be cast onto commercial textiles is crucial. In this article, we propose new graphene based absorbing textiles that conjugate outstanding EM absorbing properties at radiofrequency with low-weight, flexibility, cost-effectiveness, and washability. With this purpose, an innovative production process of polyvinylidene fluoride (PVDF) coatings filled with graphene nanoplatelets (GNPs) is developed for the production of radar-absorbing coated textiles, which are fully characterized in terms of morphological, electrical, and EM absorbing properties. In particular, the complex dielectric permittivity of the coated textiles including different amounts of GNPs is assessed through the measurement of the complex permittivity of a benchmark sample, the consequent estimation of the average GNP size and the prediction by simulations of the effective complex permittivity of graphene based coatings loaded with different GNP amounts. Such predicted data are crucial to design radar absorbing textiles with minimum bandwidths at −10 dB of 5 GHz and reflection coefficients below −5 dB over all the frequency range from 8 up to 18 GHz. These textiles are then produced and characterized in terms of reflection coefficient in free space against a plane wave with normal incidence. The obtained results demonstrate the full satisfaction of the design requirements. In fact, the produced samples show a reflection coefficient with a bandwidth at −10 dB up to 77% of the resonant frequency.

Thermal Percolation Behavior in Thermal Conductivity of Polymer Nanocomposite with Lateral Size of Graphene Nanoplatelet.

In this study, the thermal percolation behavior for the thermal conductivity of nanocomposites according to the lateral size of graphene nanoplatelets (GNPs) was studied. When the amount of GNPs reached the critical concentration, a rapid increase in thermal conductivity and thermal percolation behavior of the nanocomposites were induced by the GNP network. Interestingly, as the size of GNPs increased, higher thermal conductivity and a lower percolation threshold were observed. The in-plane thermal conductivity of the nanocomposite containing 30 wt.% M25 GNP (the largest size) was 8.094 W/m·K, and it was improved by 1518.8% compared to the polymer matrix. These experimentally obtained thermal conductivity results for below and above the critical content were theoretically explained by applying Nan’s model and the percolation model, respectively, in relation to the GNP size. The thermal percolation behavior according to the GNP size identified in this study can provide insight into the design of nanocomposite materials with excellent heat dissipation properties.

A novel approach on production of carbon steels using graphene via powder metallurgy

ABSTRACT Powder metallurgy (P/M) allows producing net or near net-shaped ferrous parts at lower temperatures compared to conventional casting. Carbon steels have a wide range of applications due to their comparatively low cost. So far, iron powders have been compacted and sintered with graphite to produce carbon steels via P/M. However, many studies have been published on the usage of graphene nanoplatelets (GNPs) in metal matrix composites, in recent years. To the best of our knowledge, there is no study on the investigation of the effect of GNPs on microstructural, mechanical, and tribological properties of ferrous materials. For this purpose, carbon steels containing different amounts of GNPs (0.25, 0.50, 0.75 wt.%) were fabricated via P/M. To better understand its effect, graphite was also used at the same contents. Results show that graphene reinforced samples had nearly 11%, 25%, 10% higher tensile strength, hardness, and wear resistance, respectively than graphite-reinforced samples at 0.25 wt.% reinforcement ratio. However, the graphene with a reinforcement ratio of more than 0.5 wt.% showed lower tensile properties nearly 15% compared to graphite-reinforced steels due to its agglomeration.

Positive Temperature Coefficient and Electrical Conductivity Investigation of Hybrid Nanocomposites Based on High‐Density Polyethylene/Graphene Nanoplatelets/Carbon Black

Hybrid nanocomposites of high‐density polyethylene have been prepared via the melt‐mixing method in the presence of different amounts of graphene nanoplatelets (GNPs) and conductive carbon black (CB). The electrical conductivity, positive temperature coefficient (PTC), and the correlation between crystallinity and electrical conductivity of hybrid nanocomposites are investigated to study the effect of crystallinity on electrical conductivity. The samples are characterized using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X‐ray diffraction (XRD), and electrical resistivity. SEM micrographs reveal good distribution of CB and GNPs in nanocomposites. According to DSC and XRD results, the crystallinity of samples decreases by the addition of CB and GNP. The electrical conductivity of all the samples increases, whereas in the sample 16% of CB and 1% of GNP electrical conductivity decrease due to GNP acting as a heterogeneous nucleating agent and the numerous incomplete and small crystals formation. The highest electrical conductivity (1.46×10−4 S cm−1) is obtained in the sample high‐density polyethylene (HDPE)/CB18/GNP1, which shows high increment in the PTC curve in the range of 105−120 °C. Also, repeatability and reversibility of PTC in this sample show good potential for use in different applications such as thermistors, temperature sensors, and self‐regulating heaters.

Waterproof Graphene-PVDF Wearable Strain Sensors for Movement Detection in Smart Gloves.

In this work, new highly sensitive graphene-based flexible strain sensors are produced. In particular, polyvinylidene fluoride (PVDF) nanocomposite films filled with different amounts of graphene nanoplatelets (GNPs) are produced and their application as wearable sensors for strain and movement detection is assessed. The produced nanocomposite films are morphologically characterized and their waterproofness, electrical and mechanical properties are measured. Furthermore, their electromechanical features are investigated, under both stationary and dynamic conditions. In particular, the strain sensors show a consistent and reproducible response to the applied deformation and a Gauge factor around 30 is measured for the 1% wt loaded PVDF/GNP nanocomposite film when a deformation of 1.5% is applied. The produced specimens are then integrated in commercial gloves, in order to realize sensorized gloves able to detect even small proximal interphalangeal joint movements of the index finger.

The Effect of the Addition of Graphene Nanoplatelets on the Selected Properties of Cementitious Composites

The aim of the current study is to investigate the properties of graphene nanoplatelets-cementitious composites in a consistent sense. The influence of the addition of 2D graphene nanoplatelets (GNPs) on the workability, setting time, flowability, strengths and piezoresistive properties were studied. The dosage of the GNPs is 0 0.05, 0.1, 0.3, 0.5, 0.7, and 1.0 wt% of the binder material. PVP type surfactant was used to disperse GNPs. The experimental results showed that the addition of GNPs increases the water requirement for normal consistency and decreases the flowability. A small amount of GNPs (0.05 wt%) can facilitate the setting. When the dosage of GNPs is above 0.1 wt%, it leads to the delay of the setting time. In terms of the strengths, the addition of GNPs can considerably promote the flexural strength, while the compressive strength is slightly decreased until 28 days. A pre-treatment procedure consisting of drying specimens at 105°C for 1 day can be regarded as a proper way to enhance the piezoresistive properties of the GNPs-mortar. Piezoresistive properties under two different cyclical loading schemes were measured using the GNPs-mortar with 1 wt% GNPs. It has been shown that the average resistance change rate increases with the amplitude increasing and a reduction is observed for the sustained cyclical loading condition. In the end, the influence of the microcracks on the piezoresistive properties was investigated. This study will contribute to future developments of cementitious composites incorporating GNPs for a variety of applications.

Free vibration and dynamic transient response of functionally graded composite beams reinforced with graphene nanoplatelets (GPLs) resting on elastic foundation in thermal environment

In this article, free vibration and dynamic transient response of a multilayer polymer nanocomposite beam resting on elastic foundation reinforced by graphene platelets (GPLs) non-uniformly distributed through the thickness direction in thermal environment is investigated. Theoretical formulations are derived based on Hamilton’s principle, Timoshenko beam theory relationships. The effective Young’s modulus of the GPL/polymer composite is estimated by Halpin–Tsai micromechanics model to account for the effects of GPL geometry and dimensions. The vibration frequencies of the beam are obtained numerically by generalized differential quadrature method (GDQM). The influences of the distribution pattern, weight fraction, the number of layers, thermal environment, slenderness ratio of the beam, boundary conditions, and types of elastic foundations on the free vibration behavior and transient response are presented. The results show that adding a very small amount of GPLs into polymer matrix as reinforcements together with the elastic foundation, significantly increases the natural frequencies of the beam. Placing more GPLs near the top and bottom surfaces of the beam are the most effective ways to strengthen the beam stiffness and increase the natural frequencies. Besides, with the increasing of foundation’s stiffness, the displacement amplitude of the functionally graded composite beam reinforced by GPLs subjected to impulsive load decreases.

Novel Plasma Functionalized Graphene Nanoplatelets (GNPs) incorporated in forward osmosis substrate with improved performance and tensile strength

In this study, a novel thin-film nanocomposite forward osmosis (FO) membrane incorporated with plasma functionalized graphene nanoplatelets (GNPs) was developed. The well distributed GNPs in the polyethersulfone (PES) support increased the substrate porosity by 8%, and significantly improved the substrate tensile modulus even at a higher loading of GNPs. Unlike graphene oxide (GO), the linear increase in tensile strength with increasing the GNPs loading is due to the good dispersion properties of GNPs. The results indicated that in terms of water flux improvement, the optimal amount of GNPs incorporation is 0.3 wt%, while in terms of tensile strength, adding higher amounts of GNPs does not decrease the membrane stiffness even at 1 wt% of loading. The GNPs addition also significantly reduced the membrane structural parameter from 1323 µm with 0 wt% to 449 µm with 0.5 wt% loadings. Under the FO mode, water flux of 28.1 LMH was obtained for the membrane with the 0.5 wt% GNPs loading using 2 M NaCl as draw solution and DI water as feed. Overall, this study recommends that applying GNPs for the FO membrane development may be promising considering all types of FO applications where different membranes with different properties are required.