Carbon Nanotube-reinforced Epoxy Research Articles

Carbon nanotube-reinforced epoxy composites in seawater: effect of amino-functionalization and post-curing process‬

Carbon nanotube-reinforced epoxy composites in seawater: effect of amino-functionalization and post-curing process‬

The Effect of Thermal Cycling on the Tensile and Shear Behaviors of the Carbon Nanotube-Reinforced Epoxy

The aim of this research is to study the tensile and shear properties and mechanical behavior of carbon nanotube- (CNT-) reinforced epoxy after the resulting composites have been exposed to different thermal cycling environments. Single-walled carbon nanotubes (SWCNTs) are cylindrical molecules that consist of rolled-up sheet of single-layer carbon atoms (graphene) with a diameter of less than 1 nanometer (nm). Thermal cycling environments can exist in many conditions, such as in-earth orbit for satellites which rotate around the earth and pass through the sun illumination and earth’s shadow, and for airplanes which fly in different altitudes with different temperatures. Carbon nanotube-reinforced epoxy is one of the nanocomposite materials which have been broadly used in many applications such as aerospace, automotive, electronics, and other industries. The goal of this study is to fabricate this nanocomposite with different multiwall and single-wall CNT concentrations and expose it to different thermal cycle numbers and determine the changes in tensile and shear properties and failure characteristics. For this purpose, tension and short-beam tests have been used in this research. The addition of multiwall CNT produces better mechanical properties compared to the use of SWCNT reinforcement. However, unreinforced epoxy showed the highest mechanical properties.

Impedance Spectroscopy and Dielectric Properties of Carbon Nanotube-Reinforced Epoxy Polymer Composites

Abstract: The aim of this work is to investigate the electric properties of carbon nanotube-reinforced epoxy polymer composites, using impedance spectroscopy, in the frequency range from 1 to 10 and over the temperature range from 25 to 105 . The dielectric response was analyzed using the complex permittivity and the electrical modulus formalisms, depending on temperature and filler concentration in the polymer matrix. Furthermore, an equivalent circuit model is proposed to describe the impedance response of carbon nanotubes/epoxy composites. The impedance studies disclosed the appearance of grain and grain-boundary effects, as confirmed by the Nyquist plot. Keywords: Carbon nanotubes, Composites, Impedance spectroscopy, Equivalent circuit model, Grain effect, Grain-boundary effect.

The Influence of CNT Structural Parameters on the Properties of CNT and CNT-Reinforced Epoxy

The main objective of this research is to review and investigate the influence of carbon nanotube structure on the properties of carbon nanotube and carbon nanotube-reinforced epoxy. Carbon nanotube and carbon nanotube-reinforced epoxy are currently being frequently used in many applications such as aerospace, automotive, and electronics industries due to their excellent properties such as high tensile strength, high Young’s modulus, and electrical and thermal conductivity. In this study, the obstacles to apply carbon nanotubes as fibers within the matrix have been introduced and discussed. Additionally, the epoxy properties and application have been cited, and failure mechanisms of carbon nanotube-reinforced epoxy and geometries of carbon nanotubes have been reviewed. Furthermore, with using experimental data and applying an analytical method, the effect of carbon nanotube diameter on interlaminar shear stress within the carbon nanotube-reinforced epoxy interface has been evaluated. Additionally, the effect of temperature variation on the value of interlaminar shear stress within the single-walled carbon nanotube-reinforced epoxy interface has been discussed. Finally, the influence of the number of hexagons in the unit cell on the Young’s modulus of zigzag and armchair single-walled carbon nanotubes has been evaluated.

Analyzing the effects of interphase on the effective damping properties of aligned carbon nanotube-reinforced epoxy nanocomposites using a micromechanical approach

In this work, a micromechanical approach consisting of high-fidelity generalized method of cells (HFGMC) and Mori-Tanaka (M-T) model is proposed to calculate the damping properties of aligned carbon nanotube-epoxy nanocomposites. To determine the resultant directional specific damping coefficients, these models, by applying strain energy approach in the global system utilize each constituent’s specific damping coefficients and mechanical properties. The effects of interphase created in the contact region of the two initial phases—carbon nanotube and polymer matrix—are extensively investigated. Comparative studies show that the micromechanical results are in good agreement with experimental data. One major finding is the thickness and mechanical and damping properties of interphase significantly affect the overall specific damping coefficients of the carbon nanotube-polymer nanocomposites. It is found that by increasing the elastic modulus of the interphase, the longitudinal specific damping property continuously increases, while other components of damping, initially increase and then asymptotically decrease. The damping properties of polymer nanocomposites can be increased by increasing the interphase damping capacity. However, the rise of interphase thickness leads to a reduction of nanocomposite damping properties. Also, the influences of carbon nanotube volume fraction and radius are examined on the damping response of polymer nanocomposites.

Polythiophene-coated multi-walled carbon nanotube-reinforced epoxy nanocomposites for enhanced mechanical, electrical and thermal properties

In this paper, epoxy nanocomposites were developed via polythiophene–carbon nanotube with different loadings of 0–1.0 wt%. Polythiophene–carbon nanotube (PTh–CNT) hybrids produced using in situ chemical polymerization method and the microstructures, morphology and properties of the PTh–CNT hybrids and epoxy nanocomposites were studied using Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), transition electron microscopy (TEM), mechanical (tensile and flexural properties), electrical, dynamic mechanical thermal analysis (DMTA) and thermogravimetric techniques (TGA). Mechanical analysis demonstrated that nanocomposites containing 0.5% PTh–CNT hybrids exhibited the highest properties among all nanocomposites and showed 78% and 51% increment of Young’s modulus and strength. The fracture analysis of samples and extent of fillers dispersion were visualized by SEM and demonstrated that dispersion of hybrids within epoxy matrix related to the hybrid nature (PTh–CNT ratio) and its concentration that are the key factors affected final properties of nanocomposites. DMA thermograms represented higher modulus for all epoxy/PTh–CNT nanocomposites systems as compared to epoxy/CNT and the pristine epoxy. Electrical conductivity measurements showed that conductivity of epoxy filled nanocomposites increased up 10−1 S cm−1 for epoxy/PTh–CNT nanocomposites. In addition, epoxy/PTh–CNT nanocomposites were also compared to pure epoxy and epoxy/CNT nanocomposites and showed higher thermal stability. The PTh–CNT particles enhanced electrical, thermal and fracture toughness of nanocomposites, confirming the synergistic effect of PTh–CNT as multifunctional filler.

MWCNT/epoxy strip-like sensors for buckling detection in beam-like structures

Buckling of slender structures constitutes a hazardous failure mechanism that can yield partial or total collapses. Nonetheless, given that buckling failure is characterized by a highly non-linear and sudden loss of stability, most off-the-shelf monitoring systems fail to detect buckling and very few research works in the literature can be found in this regard. Recent advances in the field of Nanotechnology have fostered the development of innovative composite materials with multifunctional properties, offering vast possibilities in the field of Structural Health Monitoring. Along these lines, the present work proposes a novel concept of smart beams for buckling detection applications. This consists of the deployment of carbon nanotube-reinforced epoxy strip-like sensors on the upper and bottom faces of a beam-like structure. Carbon nanotube-reinforced composites exhibit strain self-sensing capabilities, that is to say, these composites provide measurable variations in their electrical properties under the action of mechanical strains. In this way, the proposed sensing strips not only act as mechanical reinforcements, but also confer self-diagnostic properties to the system. The failure detection principle of the proposed smart beams consists of the assessment of the bending-induced variations of the normal strains during buckling. To do so, the electrical resistance of the sensing strips is continuously monitored through a two-probe resistivity measurement scheme. The present research furnishes detailed numerical parametric analyses to investigate the effectiveness of the proposed smart beams to detect buckling under uniaxially compression, as well as to evaluate the influence of design parameters such as filler volume fraction, boundary conditions and electrodes layouts. The macroscopic behaviour of the smart beams is simulated by a micromechanics-based piezoresistivity model and a multiphysics finite element code. The numerical results demonstrate that the buckling failure can be tracked through sudden disturbances in the electrical output of the smart strips.

Mechanical and fracture properties of hyperbranched polymer covalent functionalized multiwalled carbon nanotube-reinforced epoxy composites

Using a covalent functionalization strategy, hyperbranched poly (trimellitic anhydride-diethylene glycol) ester epoxy resin (HTDE) was grafted on multiwalled carbon nanotubes (MWCNTs). Then the HTDE grafted MWCNTs (HTDE-g-MWCNTs) were used as toughener to prepare epoxy composites (HTDE-g-MWCNT/EP). The results show that the HTDE-g-MWCNTs are homogeneously dispersed in the epoxy matrix and the tensile strength and fracture toughness of HTDE-g-MWCNT/EP composites are enhanced. The property improvements are due to the enhanced interfacial shear stress and relieved internal residual stress. The main toughening mechanisms are pull-out, breakage of HTDE-g-MWCNTs, and their bridging effect to crack, and shear failure of epoxy matrix around HTDE-g-MWCNTs.

Effect of Temperature on Creep Behavior in Carbon Nanotube-Reinforced Epoxy Bonded Interface — An Atomistic Investigation

ABSTRACTEpoxy is widely used as structural adhesive for bonded material systems in aerospace, construction, microelectronics and other industrial applications. In order to achieve better performance, carbon nanotubes are often applied as reinforced additives due to the extraordinary mechanical properties. The resulting carbon nanotube-reinforced epoxy has presented enhancement in the bonding strength and durability during long-term sustained loading. However, the bonded material systems in reality usually suffer from different ambient environments, especially varying temperature conditions. The evaluation of temperature effect on creep responses at the interface between epoxy adhesive and substrate becomes an essential issue. The investigation is conducted using molecular dynamics simulations to study the interfacial creep behavior in the bilayer system containing carbon nanotube-reinforced epoxy and silica substrate. The simulation results show the atomistic movement at the interface region under constant loading at various temperature levels, and indicate the improved properties with the addition of carbon nanotubes in epoxy matrix. The study enriches the understanding of temperature effect on the interfacial creep behavior at the atomic level, and provides promising predictions and guidelines for the design of composite materials in long-term applications.

Glass transition temperature of amino groups grafted carbon nanotubes reinforced epoxy resin composites: Role of strong interphase

In order to verify roles of interphase played in glass transition temperatures (Tgs) of carbon nanotubes reinforced epoxy resin (CNT/epoxy) composites, three types of interphase were produced between the CNTs and the cured epoxy. It was achieved by selection of pristine CNTs (p‐CNTs), amino groups grafted CNTs (NH2‐CNTs) and hydroxyl groups grafted CNTs (OH‐CNTs) as the reinforcement, respectively. Both dynamic mechanical analysis (DMA) and molecular dynamics (MDs) simulation were conducted to study Tg of the CNT/epoxy composites. The DMA tests showed that Tg of NH2‐CNT/epoxy composites increased, while Tg of OH‐CNT/epoxy composites decreased, compared with p‐CNT/epoxy composites. The MD simulation of the CNT/epoxy composites models explained effects of interphases on Tgs of the CNT/epoxy composites. Tg of the NH2‐CNT/epoxy composites increased with the formation of covalent bonds between the NH2‐CNTs and the cured epoxy. Although Tg of the OH‐CNT/epoxy composites decreased due to the weak interphase, where no such covalent bonds were formed. It can be inferred that the covalent bonds between the CNTs and the polymer matrix is beneficial to increase Tg of the CNT/polymer composites. POLYM. COMPOS., 39:E1129–E1138, 2018. © 2017 Society of Plastics Engineers

Determination of nonlinear behavior of multi-walled carbon nanotube reinforced polymer: Experimental, numerical, and micromechanical

In this investigation, nonlinear behavior of Multi Walled Carbon Nanotube reinforced epoxy resin is determined using experimental, numerical and micromechanical methods. Standard nanocomposite samples containing various weight fractions of MWCNTs were prepared and were tested. Experimental results show significant improvement in tensile and compressive mechanical properties of epoxy resin as a result of CNT addition. Compressive modulus of elasticity initially increased with nanotube content up to 0.45wt.%. At higher CNT weight fractions, compressive modulus decreased slightly. In addition, Field Emission Scanning Electron Microscope was used to obtain images of the samples' fracture surface. These images suggested a good CNT dispersion in the matrix. Numerical simulations are conducted to evaluate the nanocomposite elastic moduli using two different interface models. Numerical results suggest that the connector model predicts values lower than the thin shell interface model. Also, the elastic-plastic behavior of nanocomposites was estimated using a combination of micromechanical and numerical methods. To achieve this goal, micromechanical methods based on Mori–Tanaka and Halpin–Tsai models were used to predict the tensile stress-strain curves for the nanocomposites. In addition, nanocomposite compressive behavior was predicted using a combination of numerical and micromechanical methods. Finally, the numerical and micromechanical results showed good agreement with experimental measurements.

The loading rate effect on Mode II fracture toughness of composites interleaved with CNT

The loading rate effect on Mode II interlaminar fracture toughness (ILFT) is examined in this study with interleaved epoxy/carbon fabric laminates tested under dynamic conditions. Specifically, an SP1 protein-treated carbon nanotube-reinforced epoxy leaf is inserted at the midplane of the laminates, and the fracture properties are measured by the crack lap shear method at two different loading rates. Whereas our preliminary study performed under quasi-static conditions showed that this specific interleaving generated an ~85% improvement in the Mode II ILFT, the current work shows that the occurrence and magnitude of the improvement depend on the loading rate and crack velocity, with different effects on the initiation and the instable/stable propagation stages. Improvements in Mode II ILFT for both the crack initiation and propagation phases can reach up to ~145% for certain dynamic loading conditions.

142 配向カーボンナノチューブ/エポキシ複合材料の熱膨張特性評価とその応用に関する研究

142 配向カーボンナノチューブ/エポキシ複合材料の熱膨張特性評価とその応用に関する研究

Improvements in fatigue life of amine-functionalized multi-walled carbon nanotube-reinforced epoxy composites: Effect of functionalization degree and microwave-assisted precuring

In this study, the effects of functionalization degree and precuring process were studied on the fatigue life of amine-functionalized multi-walled carbon nanotube-reinforced epoxy composites. The multi-walled carbon nanotubes were highly functionalized by ethylenediamine through a microwave-assisted method. The grafted amine moieties on the multi-walled carbon nanotubes could react with the epoxy chains of the matrix and consequently form covalent bonds between the multi-walled carbon nanotubes and the epoxy matrix. It has been found that higher functionalization degrees can lead to considerable enhancement on fatigue life of reinforced composites by increasing the dispersibility of multi-walled carbon nanotubes in the epoxy matrix and also improving the interfacial interactions between the reinforcing phase and the matrix. In the next step, the precuring process was performed by three apparatuses: oven, stirrer and microwave. While the precuring process with all three apparatuses resulted in higher mechanical properties of reinforced composites, the microwave-assisted precuring was more successful than the other two apparatuses. The reinforced composites prepared by microwave-assisted precuring experienced more than 19% improvement in the tensile strength in comparison to the non-precured composite; such improvements in the mechanical properties of reinforced composites were attributed to higher reactivity of amine moieties with the epoxy chains due to sufficient activation energy provided by microwave radiations. Observations with scanning electron microscopy indicated that highly functionalized multi-walled carbon nanotubes were uniformly distributed in the epoxy matrix; this can lead to uniform distribution of applied stress in the composites and consequently improve mechanical properties of the reinforced composites.

Improvements in mechanical properties of multi-walled carbon nanotube-reinforced epoxy composites through novel magnetic-assisted method for alignment of carbon nanotubes

A novel magnetic-assisted method has been proposed for alignment of multi-walled carbon nanotubes (MWCNTs) in a bulk epoxy matrix. In principle, MWCNTs was aligned by a drag force created inside the matrix. This drag force was imposed by the movement of magnetic particles under applied magnetic field in the direction of field lines. This method can be performed by low strength magnetic fields and magnetic particles can be removed from the final composite. The alignment of MWCNTs in the epoxy matrix has been studied by scanning electron microscopy observations. Considerable improvements have been observed in mechanical properties of aligned MWCNT-reinforced composites compared to non-aligned ones.

Characterisation of multi-walled carbon nanotube reinforced epoxy resin composites

The main theme of this paper is to describe the mechanical properties of multi-walled carbon nanotube (MWCNT)/epoxy resin composites with the variation of MWCNT fillers. The work tried to achieve a uniform distribution of MWCNT filler in the epoxy matrix by modifying the hardener and mixing conditions. The MWCNT fillers were used to fabricate the MWCNT/epoxy resin composites with the variation of weight percentage of 0⋅5, 1, 2 and 3%. The dispersion of MWCNT in epoxy resin was carried out with the help of three ball rolling mill process. A significant improvement in tensile strength, compressive strength and elastic modulus was observed due to the excellent dispersion of the MWCNT filler in the epoxy resin that give higher values of tensile strength, compressive strength and elastic modulus at 3% MWCNT.

Improved Mode II delamination fracture toughness of composite materials by selective placement of protein-surface treated CNT

Abstract The recently invented SP1 protein treated CNT are utilized in this study together with the concept of selective application of nanoreinforcement to critical sections in composite structures – studied here for Mode II interlaminar fracture toughness and interlaminar shear strength of woven carbon fiber/epoxy laminates. Specifically, a treated carbon nanotube-reinforced epoxy leaf is inserted at the midplane of the laminates and the fracture properties are measured by end-notched-flexure and 3-point bend tests. It is shown that addition of a small amount of treated carbon nanotubes at the midplane of the composite results in an 85% improvement in the interlaminar fracture toughness, without deteriorating the interlaminar shear strength. This is taken as a strong indication of the unique properties of the protein-treated CNT and as strong support for the concept of selective placement of nanoreinforcement in critical sections with high stress concentrations instead of their wasteful dispersion throughout the structure. The study reveals that the unique contribution of the SP1 protein stems from its ability to bind simultaneously to the CNT and carbon fibers and to the epoxy matrix.

Mechanical properties of carbon nanotube reinforced Epoxy Resin composites

Overlapped have been prepared from epoxy resin material added to carbon Nanotube and percentages weight (0.1, 0.05, 0.01) % Studied the mechanical properties of the composite (bending, tensile an d hardness) has been found that the Flexural and tensile modulus of the composites were higher than the pure epoxy resin this may be due to the high mechanical strength of carbon nano tube (CNT). The hardness of the epoxy carbon Nanotube composites increased and the reason is due to increased overlap and stacking between the additives and material basis, which reduces the movement of polymer molecules leading to increased resistance to scratching material and cutting, will become more resistance to plastic deformation.

Mechanical properties of carbon nanotube reinforced Epoxy Resin composites

Overlapped have been prepared from epoxy resin material added to carbon Nanotube and percentages weight (0.1, 0.05, 0.01) % Studied the mechanical properties of the composite (bending, tensile an d hardness) has been found that the Flexural and tensile modulus of the composites were higher than the pure epoxy resin this may be due to the high mechanical strength of carbon nano tube (CNT). The hardness of the epoxy carbon Nanotube composites increased and the reason is due to increased overlap and stacking between the additives and material basis, which reduces the movement of polymer molecules leading to increased resistance to scratching material and cutting, will become more resistance to plastic deformation.

Fatigue of Nanotube-Reinforced Carbon Fiber Epoxy Composites

In the present investigation, resin transfer molding has been used to produce high quality carbon fiber epoxy composites and nanotube-reinforced carbon fiber epoxy composites. To study the influence of carbon nanotubes (CNTs) on improving the mechanical properties and fatigue life, the tension-tension fatigue test has been carried out on those two kinds of material in the fiber direction. The damage mechanism in the fiber directions was analyzed by X-ray radiography and electron microscopy. The results show that CNTs pulled out, rapture and bridged cracks during the test, the results also show that CNTs possess an obvious potential on improving the property of carbon fiber epoxy composite, especially for properties that dominated by matrix.