Carbon Nanotubes In Epoxy Matrix Research Articles

Multiscale Composites of Kevlar Fibers and Carbon Nanotubes in Epoxy Matrix

Hybrid composites with high strength to weight ratio are very important in structural applications. An extensive research is being carried out to enhance the mechanical properties of composites by incorporating micro and nanoscale reinforcements. The nanoreinforcements provide unique strengthening mechanisms that result in an overall high mechanical performance of composites. In order to investigate the effect of nanoreinforcements on the mechanical properties of fiber reinforced composites a novel multiscale composites of Kevlar fibers and carbon nanotubes in epoxy matrix were prepared in this research. A combination of hand layup and vacuum bagging technique was used to manufacture multiscale composites. Nanotubes at three different concentrations, i.e. 0.33wt%, 0.66wt% and 0.99wt% were incorporated after their functionalization through ultraviolet ozone-treatment to improve their interfacial interaction with epoxy matrix. The microstructural and mechanical property characterization of multiscale composites was performed by optical and electron microscopy, and tensile, hardness and interlaminar shear testing. An increase of ~45% in tensile strength was noted by incorporating 0.99wt% of nanotubes while the improvements of ~60% in hardness and ~13% rise in interlaminar shear strength were observed. The improved mechanical performance owes to the uniform dispersion of nanotubes along with their adherence to nanotubes promoting anchoring effect between fibers and matrix.

Fracture toughness enhancement of fuzzy CNT-glass fiber reinforced composites with a combined reinforcing strategy

Low interlaminar mechanical properties is the foremost drawback of glass fiber reinforced composites (GFRPs). Hierarchical nanoparticles on fibers (e.g. carbon nanotubes (CNTs)) can improve interlaminar properties of composites with negligible weight increase because of excellent mechanical properties, and low density. Interlaminar properties of composites can be enhanced with the well-dispersed CNTs in polymer matrices as it facilitates load transfer from matrix to fibers. This paper investigates the mechanical properties of CNT-reinforced GFRPs. Two reinforcing strategies were studied as dispersion of CNTs in epoxy matrix and direct growth of CNTs onto glass fibers (GFs), simultaneously. The former is referred to as nanotube-reinforced composites (NRCs) while the latter is known as fuzzy architectures. Furthermore, the combination of NRCs and fuzzy glass fibers (F-GFs), also known as fuzzy nano-reinforced composites (F-NRCs), is used to fabricate composites and identify the reinforcing capabilities through both methods. Mechanical properties are investigated by Mode-I fracture toughness and unidirectional (UD) composite tensile tests. Even though NRCs and F-NRCs yield similar enhancements in the propagation fracture toughness as 113% and 119%, respectively, the tensile strength of F-NRCs is decreased by 24% due to heat treatment during the CNT synthesis.

Morphology and mechanical characterization of carbon nanotubes/epoxy based material filled with hollow glass microsphere

The hollow glass microsphere (HGM)/carbon nanotubes (CNTs)/epoxy composite foam are fabricated by solution casting of functionalized CNT and functionalized HGM-epoxy dispersion. Five weight ratio configurations (2, 4, 6, 8, and 10 wt%) of functionalized–HGMs were considered and compared with 0.1 wt% CNT/epoxy to investigate the effects of hollow micro sphere enrichment. This study investigate the effect of hollow glass microspheres (HGM) on the compressive strength and storage modulus of CNT modified epoxy resin. The results revealed that the incorporation of HGM improved the damping performance evidently and broadened damping temperature range. TEM image of the composite show a better dispersion of CNTs in epoxy matrix. SEM micrographs of composite foams are investigated to determine structure development and CNTs, HGM dispersion, with regard to experimental results, especially compression test.

An effective and green H2O2/H2O/O3 oxidation method for carbon nanotube to reinforce epoxy resin

Facile green oxidation methods are always desired to functionalize carbon nanotubes (CNTs) in the production of advanced CNT/epoxy composites. In the present work, an optimized H2O2/H2O/O3 oxidation method was developed, and performances of the H2O2/H2O/O3 oxidized CNT in epoxy matrix were tested and compared with that of the H2O/O3 oxidized CNT and the most commonly used concentrated HNO3 oxidized CNT. The physical and chemical characteristics of the obtained oxidized CNTs were systematically characterized via transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman. Mechanical performances of the obtained composites were explored by tensile tests, impact tests, dynamic mechanical analysis (DMA) and fracture toughness tests. It was found that the H2O2/H2O/O3 oxidized CNT exhibited all-around overwhelming advantages over the concentrated HNO3 oxidized CNT on reinforcing the epoxy matrix, while the H2O/O3 oxidized CNT only improved the material strength. Reinforcing mechanisms for the different methods oxidized CNTs were studied and compared. The optimized H2O2/H2O/O3 oxidation method makes scaled production possible, avoids environment pollutions, and holds great potentials to replace the most commonly used concentrated HNO3 oxidation method to oxidize CNT during the preparation of the advanced CNT/epoxy composite.

Reinforcement of Bisphenol-A epoxy resin nanocomposites with noncovalent functionalized and physical adsorption modified CNTs

The depolymerization of carbon nanotubes (CNTs) and dispersion of CNTs in polymer matrix are key to study the application properties of CNTs. We described using the aniline trimer (AT) as a noncovalent dispersant agent and the polyoxyethylene octyl phenyl ether (Triton X-100) as a nonionic surfactant to treat CNTs. UV–vis spectra showed the successful combination of two dispersants and CNTs. Scanning electron microscopy (SEM) analysis showed the dispersion effect was best when the mass ratio of AT to Triton X-100 was 1:1. And we described the preparation of treated-CNTs loaded bisphenol-A epoxy (E44) nanocomposites. We analyzed the fracture surface of nanocomposites by SEM analysis and analyzed the dispersion of CNTs in epoxy matrix by transmission electron microscopy (TEM) analysis. The mechanical properties of neat epoxy resin, raw CNTs loaded epoxy nanocomposites and treated-CNTs loaded epoxy nanocomposites were assessed. The tribological properties and thermodynamic properties of neat epoxy resin and treated-CNTs loaded epoxy nanocomposites were evaluated. The mechanical properties and the tribological properties of the treated-CNTs loaded epoxy nanocomposites were all improved. DSC showed loading treated-CNTs increased the glass temperature. TGA and DTG showed that the thermal stability of nanocomposites was not influenced by loading treated-CNTs.

Creep performance of CNT-based nanocomposites: A parametric study

Epoxy materials have been widely applied in various applications ranging from nanoscale structures, such as microelectronic devices, to macroscale components in aerospace and building constructions. The structural stability under constant loadings is a major concern for polymeric materials during long-term service. The incorporation of carbon nanotubes (CNTs) into epoxy matrix has been considered to enhance creep resistance in recent decades. Substantial improvement of CNT-based nanocomposites largely relies on optimized design of material microstructures, and such manipulation requires comprehensive understanding of creep behavior in CNT-epoxy nanocomposites. In addition, effective arrangement of CNTs in epoxy matrix for enhancement in creep resistance needs a systematic study of related parametric effects. In this work, the effects of CNT length, CNT weight fraction and CNT dispersion state on the creep response of nanocomposites are investigated using molecular dynamics simulations. The creep deformation of nanocomposites including creep strain and system dynamics are found to decrease with the increasing length, weight fraction and good dispersion state, showing the contribution of the additional CNTs towards the resistance in time-dependent deformation. These results suggest that the CNT-epoxy nanocomposites with superior creep resistance can be achieved in the design by optimizing the CNT-associated parameters.

A physics investigation for influence of carbon nanotube agglomeration on thermal properties of composites

In the present study, a micromechanics model is developed to investigate the thermal properties of nanocomposites with agglomerated fibers. This paper mainly analyzes the influence of carbon nanotube (CNT) agglomeration on the thermal expansion coefficients and thermal conductivity of epoxy nanocomposites based on the micromechanical theory proposed. The agglomeration of CNTs in epoxy matrix is divided into two parts: the regions with high concentrations of CNTs; the regions with low concentrations of CNTs. The analytical expressions are derived according to the micromechanics method, and the two aggregation parameters are introduced to analyze the effect of CNTs agglomerated. The influences of high and low CNT agglomerations on the thermal expansion coefficients and thermal conductivity of composites are investigated, respectively. It is shown that the non-uniform dispersion of CNTs in matrix has a significant influence on the thermal expansion coefficients and thermal conductivity of nanocomposites.

Preparation of nanocomposites with epoxy resins and thiol-functionalized carbon nanotubes by thiol-ene click reaction

Carbon nanotubes (CNTs) have attracted increasingly interest in preparing CNTs/epoxy nanocomposites for improving thermal and mechanical properties. The well distribution of prime CNTs in epoxy matrix is still a challenge due to the strong interaction among nanotubes and property of self-aggregation. Here, we report a highly efficient approach to functionalize prime CNTs by a thiol-ene click reaction between double bonds of CNTs and thiol groups of mercaptans, and the resulted in thiol-functionalized CNTs with different chemical chains show well dispersion in ethyl acetate and epoxy. The thiol-functionalized CNTs show a positive effect on reinforcing and toughening diglycidyl ether of bisphenol-A (DGEBA). With an increase in the thiol-functionalized CNTs content, the mechanical and thermal properties of the CNTs/DGEBA nanocomposites, including tensile, flexural and impact strengths, and thermal conductivity, increase first and then decrease. The maximum improvements on the tensile, flexural, impact strengths and thermal conductive were 43.75%, 25.11%, 196.44% and 33.81%, respectively. These grafted mercaptans chains play a bridging action between CNTs and epoxy matrix to supply a strong interaction, substantiated by their good rheological property and ductile SEM micrographs. Both the simple method of thiol-functionalized CNTs and preparation of CNTs/DGEBA nanocomposites will supply dependable data for wide application of CNTs. • A highly efficient thiol-ene click reaction was used to functionalize prime CNTs. • Thiol-functionalized CNTs showed well dispersion in ethyl acetate and epoxy. • Thiol-functionalized CNTs could reinforce and toughen diglycidyl ether of bisphenol-A. • A strong interaction between CNTs and epoxy matrix was substantiated by rheological property and SEM.

Mechanical and electrical properties of hybrid honeycomb sandwich structure for spacecraft structural applications

Multiphase composite sheets containing carbon fiber and functionalized multiwall carbon nanotubes in epoxy matrix were manufactured through compression molding technique. The loading of f-MWCNTs was varied (0.0, 0.1, 0.25 and 0.5 wt.% of epoxy matrix), while the quantity of carbon fiber was kept constant, i.e. ∼60 wt.% of the final composite in all samples. Prepared multiphase composite sheets were subjected to flexural test and the sheet offering maximum flexural strength was selected for subsequent hybrid sandwich structure manufacturing. Hybrid sandwich structure was manufactured via vacuum bagging process by bonding composite face sheet to the aluminum honeycomb core through an adhesive. Mechanical performance of hybrid sandwich structure was evaluated by performing flexural and quasi-static indentation tests, while electrical performance of hybrid sandwich structure was investigated by performing electromagnetic interference shielding effective and electrostatic dissipation tests. Optical and scanning electron microscopy was carried out for microstructural investigations. Fractography was also performed on composite face sheet after flexural test to study the underlying high flexural strength mechanism. Neat sandwich structure without functionalized multiwall carbon nanotubes addition was also manufactured and tested for comparison. Results show that hybrid sandwich structure outperformed the neat sandwich structure in all tests.

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.

Improvement of modulus, strength and fracture toughness of CNT/Epoxy nanocomposites through the functionalization of carbon nanotubes

Abstract Carbon nanotubes (CNTs) are considered as high potential filler material to improve the mechanical properties of epoxy nanocomposites. The CNTs are functionalized by attaching melamine to improve the dispersibility in epoxy matrix and to enhance the interfacial bonding between CNTs and matrix. The tensile tests and single edge notch bending (SENB) tests were performed for CNT/Epoxy and M-CNT/Epoxy nanocomposites at various weight fraction of functionalized CNTs. The M-CNT/Epoxy nanocomposites with addition of 2wt% functionalized CNTs exhibited enhancements of Young's modulus by 64% and ultimate tensile strength by 22%. Furthermore, a significant increase of fracture toughness by 95% was observed for 2wt% M-CNT/Epoxy nanocomposite. The homogeneity of CNTs in epoxy matrix has been analyzed and related to the improvement of modulus and strength. The phenomena of crack propagation has been investigated and related to the improvement of fracture toughness.

Study on the effect of carbon nanotube on the properties of electrically conductive epoxy/polyaniline adhesives

Electrically conductive hybrid epoxy (EP) adhesives filled with p-toluenesulfonic acid (PTSA) doped polyaniline (PANI) and carbon nanotubes (CNT) were prepared and their electrical, thermal and morphological properties were investigated. The CNT was incorporated in EP/PANI (1, 3, 5, 7, 10 and 15 wt%) to obtain hybrid composites aiming to achieve better conductivity. Percolation threshold in EP/PANI and EP/CNT binary composites achieved was at around 5% of PANI and 0.2% CNT, respectively. It was observed that the addition of 0.1% CNT in EP/PANI (5%) composites improved the electrical conductivity of composites with a minimal effect on lap shear strength. Differential scanning calorimetry (DSC) studies revealed that while 0.1% CNT addition had an insignificant retardation effect on the curing of EP/PANI (5%), it increased the glass transition temperature (T g ) of cured sample significantly. Although, incorporation of PANI increased the thermal stability of epoxy significantly, addition of CNT further enhanced it marginally in the temperature range of 200–400 °C. FT-IR and XRD spectra of PANI/CNT hybrid fillers system showed molecular level interaction and good dispersing ability of CNT with PANI, respectively. Interestingly, morphological studies showed good dispersion of PANI and CNT in epoxy matrix in binary composites as well as in hybrid composites with no phase separation between PANI and CNT. Optical micrographs showed better dispersion of hybrid PANI/CNT filler system within epoxy matrix compared to PANI only.

Oligoaniline assisted dispersion of carbon nanotubes in epoxy matrix for achieving the nanocomposites with enhanced mechanical, thermal and tribological properties

A critical challenge for initiating many applications of the carbon nanotubes (CNTs) is their dispersion in organic solvent or in polymer melt. In the present study, we described a novel strategy for fabricating carbon nanotubes (CNTs)-reinforced epoxy nanocomposite by utilizing aniline trimer (AT) as the noncovalent dispersant. Tensile testing showed that the tensile modulus of the CNTs-reinforced epoxy composites was considerably improved by adding a small amount of AT functionalized CNTs. Additionally, the as-prepared CNTs-epoxy nanocomposites exhibited superior tribological properties with much lower frictional coefficients and wear rates compared to those of neat epoxy resin. The well dispersed AT-functionalized CNTs in epoxy matrix played an important role in enhancing the mechanical properties, as well as acting as a solid lubricant for improving the tribological performance of epoxy/CNTs nanocomposite.

A simple chemical treatment for easy dispersion of carbon nanotubes in epoxy matrix for improving mechanical properties

Carbon nanotubes have considerable potential for use as reinforcements in high-performance polymer composites, but their large-scale application has been hindered by their poor processability. Here, we report an extremely simple and scalable method for the chemical treatment of single-wall carbon nanotubes (SWNTs) to enable easy dispersion in an epoxy matrix. The treatment involves stirring SWNTs in a concentrated solution of sodium hydroxide in ethanol. The chemicals used can be recovered and re-used. The treated SWNTs show greater ease of exfoliation into organic solvents without the need for high-intensity ultrasonic probe treatment. Raman spectroscopy shows that the treatment does not create any noticeable defects or functional groups on the SWNT walls. As a result of the treatment, the SWNTs could be dispersed in epoxy with minimal, low-power ultrasonic treatment. The resulting composites showed increased fracture toughness and tensile strength at SWNT loadings as low as 0.5 weight percent, when compared with neat epoxy. The enhancement in properties of the composites does not decrease with increased SWNT loading, implying that the SWNTs do not re-aggregate.

Effective thermal conductivity of epoxy matrix filled with poly(ethyleneimine) functionalized carbon nanotubes

Abstract Considering that amine group can react with epoxy resin, poly(ethyleneimine) (PEI) functionalized carbon nanotubes (CNTs) have been used to fabricate CNT/epoxy matrix composite for the potential of thermal performance improvement. The functionalization of CNTs, the dispersion of CNTs in epoxy matrix, and the effective thermal conductivity of the composites have been characterized by thermal gravimetric analysis (TGA), scanning electron microscope (SEM), and thermal analyzer, respectively. The PEI functionalized CNTs show better dispersion in epoxy matrix and higher thermal conductivity under the same volume fraction, compared to the non-functionalized ones, which means that PEI molecule is a good bridge between CNTs and epoxy. And from a proper model, the calculated results confirm that PEI functionalization on CNTs can not only reduce the interface thermal resistance, but also improve the dispersion of CNTs in the epoxy, both of which would contribute to the enhancement of thermal conductivity. A 660% enhancement in thermal conductivity can be achieved in the CNT/epoxy matrix composite when the PEI functionalized CNTs’ loading is as high as 8 vol.%.

Electrical Conductivity and Hardness Property of CNTs/Epoxy Nanocomposites

This study investigates the effect of carbon nanotubes (CNTs) as conductive fillers and epoxy resin as matrix on the electrical conductivity and hardness property. The different CNTs weight percentage (0 ~ 10 wt.%) were added into the epoxy resin. The dispersion of CNTs in epoxy resin was conducted by high speed mixer through mechanical shearing mechanism. The mixture of CNTs/epoxy was poured into the mold and compression molding was conducted for fabrication of CNTs/epoxy nanocomposites. The electrical conductivity and hardness of CNTs/epoxy nanocomposites by several of CNTs loading concentration were measured by the four point probe and dynamic ultra micro hardness tester. Agglomeration of CNTs in epoxy matrix was observed on fractured surface by scanning electron microscopic. Non conductive epoxy polymer becomes conductor as addition of CNTs. Electrical conductivity of CNTs/epoxy nanocomposites were increased with increasing of CNTs loading concentration. Hardness property of CNTs/epoxy nanocomposites ware reached the highest value at 5 wt.%, and then it was decreased.

Synergistic toughening of epoxy with carbon nanotubes and graphene oxide for improved long-term performance

Epoxy based nanocomposites using graphene oxide (GO) sheets dispersed multi-walled carbon nanotubes (CNTs) as combination fillers were prepared using an in situ polymerization technique. A remarkable synergetic effect was observed between CNTs and GO sheets which improved the mechanical properties of the epoxy. It was confirmed by optical and field-emission scanning electron microscopy (FESEM) images that the dispersion of CNTs in epoxy matrix can be significantly improved by adding GO sheets. The overall mechanical properties of CNT–GO/epoxy composites were greatly enhanced with only adding 0.04 wt% (percent by weight) CNTs and 0.2 wt% GO sheets. Moreover, the fatigue and creep rupture lives of pure epoxy was also significantly increased by the addition of GO dispersed CNTs. Approximately a 950% improvement in fatigue life, and 400% improvement in creep rupture life were observed at the applied stress levels tested.

EPOXY COMPOSITES WITH CARBON NANOTUBES

In the work viscosity, curing process of epoxy resins, electrical conductivity and mechanical strength of epoxy composites with carbon nanotubes were investigated. As a component was used Epidian 6 epoxy resin cured with 1-buthylimidazole by anionic polymerization. Compositions with nanofillers were prepared by sonification of multiwall carbon nanotubes (BAYTUBES 150 P and BAYTUBES 150 HP) in epoxy resin without any solvent. The morphology of prepared nanocomposites was examined by using SEM. Scanning electron microscopy confirms good dispersion of CNTs, but the presence of agglomerates is also identified. Viscosity of compositions with two kind of carbon nanotubes was established by means of ARES rheometer. Curing process with ARES rheometer and DSC was investigated. Bending strengths and electrical conductivity were performed on composites made of an epoxy resin loaded with 0.1, 0.2, 0.5, 1 and 2 wt.% both types of MWNTs. The incorporation of MWCNT to epoxy resin results in a sharp insulator-to- conductor transition with a percolation threshold (φc) as low as 0.5 wt.% for Baytubes 150 HP and 1.0 wt.% for Baytubes 150 P. An electrical conductivity of 10 -4 S/cm was achieved for 0.5 wt. % of MWCNT 150 HP. The low percolation threshold for each MWCNTs and relatively high electrical conductivity are attributed to the high aspect ratio, large surface area and uniform dispersion of the carbon nanotubes in epoxy matrix.

Electrical conductivity improvement of aeronautical carbon fiber reinforced polyepoxy composites by insertion of carbon nanotubes

An increase and homogenization of electrical conductivity is essential in epoxy carbon fiber laminar aeronautical composites. Dynamic conductivity measurements have shown a very poor transversal conductivity. Double wall carbon nanotubes have been introduced into the epoxy matrix to increase the electrical conductivity. The conductivity and the degree of dispersion of carbon nanotubes in epoxy matrix were evaluated. The epoxy matrix was filled with 0.4wt.% of CNTs to establish the percolation threshold. A very low value of carbon nanotubes is crucial to maintain the mechanical properties and avoid an overload of the composite weight. The final carbon fiber aeronautical composite realized with the carbon nanotubes epoxy filled was studied. The conductivity measurements have shown a large increase of the transversal electrical conductivity. The percolative network has been established and scanning electron microscopy images confirm the presence of the carbon nanotube conductive pathway in the carbon fiber ply. The transversal bulk conductivity has been homogenized and improved to 10−1S·m−1 for a carbon nanotubes loading near 0.12wt.%.

Thermal and mechanical interfacial properties of epoxy composites based on functionalized carbon nanotubes

Abstract Carbon nanotubes (CNTs) were treated by a mixture of acid and functionalized subsequently by amine treatment to improve interfacial interactions and dispersion of CNTs in epoxy matrix. The thermal stabilities and mechanical interfacial properties of epoxy/CNT composites were investigated using several techniques. The dispersion state of CNTs in the epoxy matrix was observed by scanning electron microscope (SEM) and transmission electron microscopy (TEM). As a result, the glass transition temperature of epoxy/CNT composites increased by about 11 °C compared to neat epoxy resins. The mechanical interfacial property of the composites was significantly increased by the addition of amine treated CNTs. The SEM and TEM results showed that the separation and uniform dispersion of CNTs in the epoxy matrix.