Graphene Nanoplatelets Loading Research Articles

Incorporating Graphene Nanoplatelets and Carbon Nanotubes in Biobased Poly(ethylene 2,5-furandicarboxylate): Fillers' Effect on the Matrix's Structure and Lifetime.

Poly(ethylene 2,5-furandicarboxylate) (PEF) nanocomposites reinforced with Graphene nanoplatelets (GNPs) and Carbon nanotubes (CNTs) were in situ synthesized in this work. PEF is a biobased polyester with physical properties and is the sustainable counterpart of Polyethylene Terephthalate (PET). Its low crystallizability affects the processing of the material, limiting its use to packaging, films, and textile applications. The crystallization promotion and the reinforcement of PEF can lead to broadening its potential applications. Therefore, PEF nanocomposites reinforced with various loadings of GNPs, CNTs, and hybrids containing both fillers were prepared, and the effect of each filler on their structural characteristics was investigated by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), and X-Ray Photoelectron Spectroscopy (XPS). The morphology and structural properties of a hybrid PEF nanocomposite were evaluated by Transmission Electron Microscopy (TEM). The thermo-oxidative degradation, as well as lifetime predictions of PEF nanocomposites, in an ambient atmosphere, were studied using Thermogravimetric Analysis (TGA). Results showed that the fillers' incorporation in the PEF matrix induced changes in the lamellar thickness and increased crystallinity up to 27%. TEM analysis indicated the formation of large CNTs aggregates in the case of the hybrid PEF nanocomposite as a result of the ultrasonication process. Finally, the presence of CNTs caused the retardation of PEF's carbonization process. This led to a slightly longer lifetime under isothermal conditions at higher temperatures, while at ambient temperature the PEF nanocomposites' lifetime is shorter, compared to neat PEF.

Dielectric and electromagnetic interference shielding properties of nano‐silicon carbide/montmorillonite and graphene nanoplatelets filled polyvinylidene fluoride/poly(3,4‐ethylenedioxythiophene)‐block‐poly(ethylene glycol) blend nanocomposites

AbstractHerein, hybrid polymer nanocomposite films comprising polyvinylidene fluoride (PVDF) and poly(3,4‐ethylenedioxythiophene)‐block‐poly(ethylene glycol) (PEDOT‐block‐PEG) as matrices and silicon carbide nanoparticles (SiC NPs), montmorillonite (MMT) nanoclay, and graphene nanoplatelets (GNPs) as nanofillers were fabricated by solution casting. The structural, morphological, and thermal characteristics of the nanocomposite films were assessed using Fourier transform infrared spectroscopy (FTIR), x‐ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analyzer (TGA), and differential scanning calorimetry (DSC). The SEM results show the homogeneous distribution of nanofillers within the polymer matrix. The dielectric behavior and electromagnetic interference shielding efficiency (EMI SE) of the nanocomposites were also analyzed. The maximum dielectric constant (ε) and dielectric loss (tan δ) obtained are 47.77 and 12.08, respectively, at lower frequency (50 Hz, 150°C). The maximum EMI SE was observed to be 16.8 dB in the Ku‐band region (12–18 GHz) for the nanocomposites with 20 wt% SiC, 8 wt% MMT, and 2 wt% GNPs loading. The EMI shielding was found to be absorption dominant and originated from the formation of a conductive network between hybrid nanofillers within the PVDF/PEDOT‐block‐PEG blend thereby improving the EMI SE values. These results suggest that PVDF/PEDOT‐block‐PEG/SiC/MMT/GNPs nanocomposites can be used as an efficient EMI shielding material.

Thermal Properties of Graphene Nanoplatelets Reinforced Crosslinked and Short Chain Branched Polyethylenes for Geothermal Pipe Applications

AbstractTwo types of polyethylenes, the crosslinked high‐density polyethylene (PEX) and the short‐chain branched medium‐density polyethylene (polyethylene of raised temperature resistance [PE‐RT]), are selected as matrices for graphene nanoplatelets (GNPs) nanocomposites preparation (PEX/GNPs, PE‐RT/GNPs). The melt‐mixing technique is used to synthesize the nanocomposites containing various loadings of GNPs. Differential scanning calorimetry (DSC) is employed to study the effect of the GNPs on the melting and crystallization behavior of the prepared materials. The thermal stability of the nanocomposites was evaluated by thermogravimetric analysis (TGA). Laser flash analysis (LFA) is used to estimate the thermal conductivity of both PEX and PE‐RT/GNPs nanocomposites. TGA measurements reveal that PEX nanocomposites present decreased thermal stability with increasing filler content. The DSC results show that the crystallinity of both matrices increases with increasing filler content. PEX/GNPs nanocomposites show more significant thermal conductivity augmentation compared to the corresponding PE‐RT nanocomposites.

Mechanical and thermal properties of graphene nanoplatelets-reinforced recycled polycarbonate composites

Nanocomposites have received significant interest in recent years, as they offer improved properties compared to conventional materials for various applications. Among many available nanofillers, graphene nanoplatelets (GNP) have shown promising results for polymer-based nanocomposite applications. This paper investigates the mechanical and thermal properties of GNP-reinforced virgin and recycled polycarbonate (PC) nanocomposites blended via a twin-screw extruder. Effects of various key processing parameters such as filler concentration, processing speed, barrel/die set temperature, and PC type (virgin and recycled) on the reinforced composites were examined. Mechanical properties were characterised by tensile testing, while thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to characterise the thermal properties. The results show that the processing speed and barrel/die set temperature have a slight influence, while the filler concentration significantly affects the properties of PC/GNPs composites. The Young's modulus and yield strength were enhanced with increasing GNP loading, where the maximum enhancement of Young's modulus was obtained as ∼33% for virgin-PC/GNP and ∼39.5% for recycled-PC/GNP composites at 10 wt.-% GNP loading. However, the failure strain was reduced with the increased GNP loading for both virgin and recycled PC/GNP composites. Embedding GNP into the PC matrix only slightly influenced the thermal stability and glassy transition temperature (Tg). The highest thermal stability for virgin PC/GNP composites was observed with 1 wt.-% (2.74% increase with respect to virgin PC), while for recycled PC/GNP, it was observed with 10 wt.-% (2.42% increase with respect to recycled PC) GNP loading. Under the same GNP loading, recycled PC-based composites showed lower thermal stability than virgin PC-based composites. The Tg evaluated from DSC showed a rise under 1 wt.-% GNP for virgin PC/GNP and decrease afterwards with higher filler loading, while an irregular variation for recycled PC/GNP was observed.

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.

Graphene-Based Thermoplastic Composites as Extremely Broadband and Frequency-Dependent EMI Absorbers for Multifunctional Applications

Multifunctional materials are the future of modern electronics. The reduction of weight and no interfacial mismatches perfectly fit the requirements of those industry sectors which require miniaturization, low weight, and high functionality, like aerospace or wearable electronics. Here, we show multifunctional thermoplastic polymer composites based on acrylonitrile–butadiene–styrene (ABS) with graphene nanoplatelet (GNP) inclusions at different weight loadings of GNPs, from the pure polymer up to 10 wt %. The multifunctionality is expressed via efficient electromagnetic interference (EMI) shielding in an extensive frequency range, from microwave to terahertz, and good electrical conductivity and heat management. The highest measured total shielding efficiency reached over 80 dB per 1 mm-thick sample in the terahertz range for the 5 wt % GNP concentration. Composites with the highest GNP loading show high thermal conductivity of 1.8 W/mK and an electrical conductivity of 188 S/m. All composites exhibited absorption as the primary shielding mechanism. These are some of the highest EMI shielding efficiency and thermal conductivity values reported in the literature. Our results suggest that the ABS/GNP composites reported here are suitable for multifunctional EMI absorber/heat management applications.

Dioctyl Phthalate-Modified Graphene Nanoplatelets: An Effective Additive for Enhanced Mechanical Properties of Natural Rubber.

Graphene has been extensively considered an ideal additive to improve the mechanical properties of many composite materials, including rubbers, because of its novel strength, high surface area, and remarkable thermal and electron conductivity. However, the pristine graphene shows low dispersibility in the rubber matrix resulting in only slightly enhanced mechanical properties of the rubber composite. In this work, graphene nanoplatelets (GNPs) were modified with dioctyl phthalate (DOP) to improve the dispersibility of the graphene in the natural rubber (NR). The distribution of the DOP-modified GNPs in the NR matrix was investigated using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The effect of the modified GNPs’ contents on the mechanical properties of the GNPs/NR composite was studied in detail. The results showed that the abrasion resistance of the graphene-reinforced rubber composite significantly improved by 10 times compared to that of the rubber without graphene (from 0.3 to 0.03 g/cycle without and with addition of the 0.3 phr modified GNPs). The addition of the modified GNPs also improved the shear and tensile strength of the rubber composite. The tensile strength and shear strength of the NR/GNPs composite with a GNPs loading of 0.3 phr were determined to be 23.63 MPa and 42.69 N/mm, respectively. Even the presence of the graphene reduced the other mechanical properties such as Shore hardness, elongation at break, and residual elongation; however, these reductions were negligible, which still makes the modified GNPs significant as an effective additive for the natural rubber in applications requiring high abrasion resistance.

An investigation into the impact of graphene nanoplatelets reinforced with glass fiber reinforced polymer composite on the hole quality using abrasive water jet drilling

AbstractGlass fiber reinforced polymer (GFRP) composites are being increasingly used in various industries owing to their low cost, lightweight, and impressive mechanical properties. For the present study, composites were fabricated with various weight percentages of graphene nanoplatelets (GNPs), i.e., 0, 0.125, 0.25, 0.375, and 0.5 wt%, which were mixed with epoxy resin of GFRP. Characteristics such as flexural strength, interlaminar shear strength (ILSS), and tensile strength of the prepared composites were tested, which established that reinforcement of 0.25 wt% of GNPs ensures optimum properties in the composite. The GNPs, loaded with 0.375 and 0.5 wt% agglomerated, on the other hand, showed interface‐governed failure. The influence of machining factors, such as wt% of GNPs, jet pressure, and traverse rate, were also studied to assess the hole quality of the composite samples, machined by abrasive water jet (AWJ). Subsequently, machining characteristics of the GNPs loaded GFRP composites are explored in detail using AWJ drilling in terms of surface roughness (Ra), kerf angle (KA), and entry and exit delamination factor (DF). The AWJ machining outcomes demonstrated that the incorporation of GNPs significantly influences the machining response of the composites. The Ra, KA, entry, and exit DF of composite laminates reduce with advancement in GNPs loadings. In addition, the surface of the drilled holes was characterized using FESEM analysis.

Degradation and Breakdown of Polymer/Graphene Composites under Strong Electric Field

In this work, we study the effect of strong electric fields on a polymer/graphene composite and the resulting morphology upon its dielectric breakdown. Our model system was produced by compounding up to 0.25 wt % graphene nanoplatelets (GNP) into poly(ethylene-co-vinyl acetate) (EVA), which is a soft polymer with low melt viscosity. A strong electric field of up to 400 Vrms/mm was applied to the EVA/GNP composite in the melt. The sample’s resistance over the electric field application was simultaneously measured. Despite the low GNP loading, which was below the theoretical percolation threshold, the electric conductivity of the composite during electric field application dramatically increased to >10−6 S/cm over 5 min of electric field application before reaching the current limit of the experimental apparatus. Conductivity growth follows the same scaling relationship of the theoretical model that predicts the rotation and translation time of GNPs in a polymer melt as a function of electric field strength. Since no significant GNP alignment in the composite was observed under transmission electron microscopy (TEM), we hypothesized that the increase in electrical conductivity was due to local electrical treeing of the polymer matrix, which eventually leads to dielectric breakdown of the composite. Electrical treeing is likely initiated by local GNP agglomerates and propagated through conductive channels formed during progressive dielectric breakdown.

Influence of graphene nanoplatelets geometrical characteristics on the properties of polylactic acid composites

The influence of graphene nanoplatelets (GNP) surface area and size on the dispersion, electrical percolation behavior, electrical conductivity, thermal conductivity, electromagnetic interference (EMI) attenuation, and EMI attenuation mechanisms of GNP/polylactic acid (PLA) were investigated. The GNP/PLA composite's electrical percolation threshold decreased with the increase in GNP surface area and decrease in GNP size. The higher number of GNP particles associated with the decrease in GNP size and increase in GNP surface area facilitated the creation of a conductive network at a lower GNP content. However, at a GNP loading of 30 wt%, the GNP/PLA composites' electrical, EMI SE, and thermal conductivity decreased with the increase in GNP surface area and decrease in GNP size. At high nanofiller loading, the contact resistance between the nanofiller particles is more important than the nanofiller aspect ratio or size. The smaller filler size means more particles and more filler/filler resistance points. The most exciting finding is the dependence of EMI attenuation mechanisms on the GNP surface area. EMI attenuation by absorption was found to increase with the increase in GNP surface area.

Microchannel insulating foams comprising a multifunctional epoxy/graphene‐nanoplatelet nanocomposite

AbstractGraphene nanomaterials have demonstrated simultaneous enhancement of both the thermal and mechanical properties of many base polymer systems, but for application as a reinforcement in multifunctional thermally insulating polymer foam the graphene additive must not significantly increase the macroscopic thermal conductivity. In an effort to study and decouple these mechanical and thermal properties, low loadings of reduced graphene oxide nanoplatelets have been added into epoxy formulations to comprise the matrix structure of hollow microchannel nanocomposite foams. Substantial improvements of 226% were achieved in the microchannel foam specific flexural modulus at only 0.15% graphene nanoplatelet loading without compromising the foam flexural strength and while also maintaining the low thermal conductivity of the baseline epoxy foam material. These results support the use of these nanocomposite foams as mechanically reinforced thermal insulation, with the addition of the graphene nanoplatelets potentially providing additional multifunctional improvements to the foam such as reduced UV‐radiation transmittance, improved electrical surface conductivity for diminished static charge buildup, and/or lowering of the coefficient of thermal expansion for enhanced structural stability in extreme environments. This particular combination of multifunctional properties makes these materials well suited as high‐performance structural thermal insulation materials in support of next generation space system applications.

Graphene/Nanohydroxyapatite hybrid reinforced polylactic acid nanocomposite for load-bearing applications

ABSTRACT We studied polylactic acid (PLA) nanocomposite reinforced with graphene nanoplatelets (GNP)/Nanohydroxyapatite (NHA) hybrid prepared using the melt-mixing technique. Before mixing with the GNP, NHA was surface modified using 3-aminopropyl triethoxysilane (APTES). The surface-modified NHA (mNHA) loading was constant at 5wt% while varying the GNP loading from 0.01–0.1wt%. Results show with 0.01 wt% GNP, the impact strength of the PLA/mNHA/GNP nanocomposite increased, tensile strength decreased, thermal stability, and viscoelastic properties improved significantly compared to neat PLA and PLA/mNHA. The FESEM images show the agglomeration of mNHA/GNP hybrid at higher loading (>0.05 wt%), leading to the deterioration of PLA/mNHA/GNP nanocomposite properties.

Synergistic effects of nano-enhanced phase change material (NePCM) and fin shape on heat storage performance of a finned shell-and-tube unit: An experimental study

Adding a fin or using a nano-enhanced phase change material (NePCM) can both improve the performance of shell-and-tube thermal energy storage (TES) units, but the combination of them may not be simple to achieve synergistic effect. In this paper, an experimental study was conducted to reveal the combined effects of fin shape and nano-additive loading on the heat storage performance of a finned shell-and-tube TES unit filled with NePCM, with nine cross-portfolio experimental configurations, i.e., three loadings of the nano-additive, graphene nanoplatelets (GNP) in this work, and three fin shapes including annular, helical and longitudinal fins. It was shown that the changes of GNP loading and fin shape could have either enhancement or deterioration effect on the various mechanisms of heat transfer during melting, such as conduction, convection, and close-contact melting mode, and that their combined effects on the heat transfer and heat storage rates of the TES unit are very complicated. The fin with a given shape should be combined with a suitable GNP loading to achieve synergistic effect for different application scenarios. For example, in pursuit of higher heat transfer rate (fast charging and discharging), the configuration of a certain GNP loading combined with the annular fin can be adopted. Considering the manufacturing cost, the annular fin with a gap between the fin and the shell wall can also be used to achieve the same heat transfer enhancement effect as that of the helical fin. In case of the longitudinal fin, the GNP loading has a great negative impact on the overall melting rate and the instantaneous heat storage rate, so it should be used in combination with pure PCM without adding any nano-additives.

Effect of graphene nanoplatelet addition on the electrical conductivity of poly(hydroxybutyrate-co-hydroxyvalerate) biocomposites

Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) is one of the most promising biodegradable polymers used in many applications due to its biodegradability and non-toxicity. However, the usage of PHBV in electronic, biomedical, and biosensor applications has been limited due to its poor electrical properties. This study shows a simple method of producing and enhancing the electrical conductivity of PHBV-based biocomposites by adding graphene nanoplatelet (GNP) as a conductive filler. The biocomposite films were prepared using the solvent casting method, consist of five GNP loading (0-5 wt. %). The prepared PHBV/GNP biocomposites show enhanced electrical conductivity compared to neat PHBV. PHBV/GNP biocomposite with 5 wt. % filler loading exhibits the highest electrical conductivity at 3.83 × 10−3 S/cm. Higher crystalline regions in the PHBV/GNP biocomposites have facilitated the transfer of electrons between PHBV, resulting in the formation of conductive biocomposites, as evident from X-ray diffraction (XRD) characterization.

Mechanical performance and thermal stability of modified epoxy nanocomposite with low loading of graphene platelets

AbstractIn this study, graphene nanoplatelets (GNP) of 0.2%–1.0% by weight were introduced to the rubber toughened epoxy matrix with via a direct method. The effect of GNP loadings on the mechanical (tensile and impact properties) and thermal properties of the rubber toughened epoxy/GNP nanocomposites were evaluated. The results showed that the incorporation of GNP had optimally improved the tensile strength and tensile modulus by 70% and 74%, respectively, at 0.6 wt% filler loading. Thermogravimetric analysis (TGA) and Tg increment result proved the barrier effect via delaying decomposition process which induced by the layered structure of GNP and thus significantly enhanced the thermal stability of epoxy‐based resin, irrespective of GNP loadings (insignificant difference in the decomposition temperature). The fractured surfaces of these nanocomposites showed the good interfacial interaction between the matrix and the GNP nanofiller. X‐ray diffraction (XRD) analysis demonstrated the exfoliation and intercalation states of GNP dispersion in epoxy/LENR.

Ternary Nanocomposite System Composing of Graphene Nanoplatelet, Cellulose Nanofiber and Jatropha Oil Based Waterborne Polyurethane: Characterizations, Mechanical, Thermal Properties and Conductivity.

This work aims to evaluate the performance of graphene nanoplatelet (GNP) as conductive filler with the presence of 0.5 wt.% cellulose nanofiber (CNF) on the physical, mechanical, conductivity and thermal properties of jatropha oil based waterborne polyurethane. Polyurethane was made from crude jatropha oil using an epoxidation and ring-opening process. 0.5, 1.0, 1.5, 2.0 wt.% GNP and 0.5 wt.% CNF were incorporated using casting method to enhance film performance. Mechanical properties were studied following standard method as stated in ASTM D638-03 Type V. Thermal stability of the nanocomposite system was studied using thermal gravimetric analysis (TGA). Filler interaction and chemical crosslinking was monitored using Fourier-transform infrared spectroscopy (FTIR) and film morphology were observed with field emission scanning electron microscopy (FESEM). Water uptake analysis, water contact angle and conductivity tests are also carried out. The results showed that when the GNP was incorporated at fixed CNF content, it was found to enhance the nanocomposite film, its mechanical, thermal and water behavior properties as supported by morphology and water uptake. Nanocomposite film with 0.5 wt.% GNP shows the highest improvement in term of tensile strength, Young’s modulus, thermal degradation and water behavior. As the GNP loading increases, water uptake of the nanocomposite film was found relatively small (<1%). Contact angle test also indicates that the film is hydrophobic with addition of GNP. The conductivity properties of the nanocomposite film were not enhanced due to electrostatic repulsion force between GNP sheet and hard segment of WBPU. Overall, with addition of GNP, mechanical and thermal properties was greatly enhanced. However, conductivity value was not enhanced as expected due to electrostatic repulsion force. Therefore, ternary nanocomposite system is a suitable candidate for coating application.

Tribological characteristics of mahua oil with graphene nanoplatelets as anti-wear and extreme pressure additive

The tribological investigation was performed to seek the role of graphene nanoplatelets (GNPs) in enhancing the physico-tribological properties of mahua oil. The flashpoint, fire point, viscosity, wear preventive characteristics (WPC) and extreme pressure characteristics (EPC) were conducted following the governing standards. A substantial decrement of 17% in the coefficient of friction, 15.15% in wear scar diameter was observed upon blending the 0.25 wt.% GNPs with mahua oil. The WPC morphology on the steel balls portrayed the micro tracks. The EPC investigation presented 1 wt.% GNPs blended mahua oil with the augmented outcome of 7.7% and this was portrayed to be the best GNPs loading in weld load perspective. However, at 0.1 wt.% of GNPs loading was identified as the best loading with a wear point of view. The morphology of EPC revealed severe abrasion and steel balls were exposed to very high temperatures and have undergone metal squeeze out from the contact surface. This article also discusses the different wear regimes and corresponding wear phenomena in four-ball tribology testing with the aid of micrographs.

On the Multi-Functional Behavior of Graphene-Based Nano-Reinforced Polymers.

The objective of the present study is the assessment of the impact performance and the concluded thermal conductivity of epoxy resin reinforced by layered Graphene Nano-Platelets (GNPs). The two types of used GNPs have different average thicknesses, <4 nm for Type 1 and 9–12 nm for Type 2. Graphene-based polymers containing different GNP loading contents (0.5, 1, 5, 10, 15 wt.%) were developed by using the three-roll mill technique. Thermo-mechanical (Tg), impact tests and thermal conductivity measurements were performed to evaluate the effect of GNPs content and type on the final properties of nano-reinforced polymers. According to the results, thinner GNPs were proven to be more promising in all studied properties when compared to thicker GNPs of the same weight content. More specifically, the glass transition temperature of nano-reinforced polymers remained almost unaffected by the GNPs inclusion. Regarding the impact tests, it was found that the impact resistance of the doped materials increased up to 50% when 0.5 wt.% Type 1 GNPs were incorporated within the polymer. Finally, the thermal conductivity of doped polymers with 15 wt.% GNPs showed a 130% enhancement over the reference material.

Optimization of graphene nanoplatelets dispersion and nano-filler loading in bio-based polymer nanocomposites based on tensile and thermogravimetry analysis

The incorporation of graphene nanoplatelets (GNPs) has attracted massive attention in polymer nanocomposite production. In this work, GNPs reinforced nanocomposites of liquid natural rubber (LNR) toughened poly (lactic acid) (PLA)/poly (aniline) (PANi) were fabricated through melt-mixing using internal mixer. The effects of ultrasonic treatment period, mixing rotor speed and GNPs loadings in PLA-LNR/PANi was investigated. A premix ultrasonication of LNR/PANi with GNPs for 1 h was found to be the most effective period as compared to the longer sonication time. The best melt-mixing of the materials was achieved at 100 rpm, in accordance to the tensile properties as well as homogeneous dispersion and distribution of nano-filler as shown in thermogravimetry analysis. Results revealed that the optimum loading was found at 0.4 wt.% of GNPs with excellent enhancement in tensile strength (25 MPa), tensile modulus (1188.9 MPa) and thermal stability of the nanocomposite, as proven by ANOVA statistical analysis.

Mode II Fracture Analysis of GNP/Epoxy Nanocomposite Film on a Substrate.

Epoxy resin with excellent mechanical properties, chemical stability, and corrosion resistance has been widely used in automotive and aerospace industries. A thin film of epoxy deposited on a substrate has great application in adhesive bonding and protective coating. However, the intrinsic brittleness of epoxy with a relatively low fracture toughness limits its applications. In this work, graphene nanoplatelets (GNP) were added to the epoxy resin to enhance its toughness, hardness, and elastic modulus. A series of nanocomposites with different loadings of GNP were fabricated. Ultrasonic sonication in combination with surfactant Triton X-100 were employed to disperse GNP in the epoxy matrix. A nanocomposite film with a thickness of 0.3 mm was deposited on an Al substrate using a spinning coating technology. The hardness and elastic modulus of the nanocomposite film on the Al substrate were experimentally measured by a nanoindentation test. Analytical expression of the mode II interfacial fracture toughness for the nanocomposite film on an Al substrate with an interfacial edge crack was derived utilizing the linear elastic fracture mechanics and Euler’s beam theory. End-notched flexure (ENF) tests were conducted to evaluate the mode II fracture toughness. It was found that the hardness, elastic modulus, and mode II fracture toughness of the nanocomposite film reinforced with 1 wt % of GNP were improved by 71.8%, 63.2%, and 44.4%, respectively, compared with the pure epoxy. The presence of much stiff GNP in the soft epoxy matrix prompts toughening mechanisms such as crack deflection and crack pinning, resulting in the improvements of the fracture toughness, hardness, and elastic modulus. Microscopic observation for the nanocomposite was examined by scanning electron microscopy (SEM) to investigate the dispersion of GNPs in the epoxy matrix. The performance of a nanocomposite film deposited on a substrate was rarely studied, in particular, for the interfacial fracture toughness of the film/substrate composite structure. Utilizing the theoretical model in conjunction with the ENF experimental test presented in this study, an accurate determination of the mode II interfacial fracture toughness of film/substrate composite structure is made possible.