The Addition of Carbon Nanotube on the Tensile Properties of Carbon Fiber-Reinforced PEEK Composites

The main objective of this paper is to develop high strength resistance carbon fiber-reinforced polyether ether ketone (PEEK) composites with the addition of multiwall carbon nanotubes (MWCNT). These compounds were well mixed in a Haake batch mixer, and compounded polymers were fabricated into sheets of known thickness by compression moulding. Samples were tested for tensile properties with respect to different concentration of fillers. The tensile properties of these samples depend on filler aspect ratio. The tensile fracture surface has been examined using a scanning electron microscope (SEM). Photomicrographs of the worn surfaces revealed the effect of the addition of carbon nanotubes. Also, better interfacial adhesion between carbon and vinyl ester in carbon reinforced vinyl ester composite was observed.     

Aminofunctionalization effect on the microtribological behavior of carbon nanotube/bismaleimide nanocomposites

Original multiwalled carbon nanotubes (O‐MWCNTs) and aminofunctionalized ethylenediamine‐treated multiwalled carbon nanotubes (MWCNTs‐EDA) were mixed with bismaleimide (BMI) resin to prepare O‐MWCNT/BMI and MWCNT‐EDA/BMI composites, respectively. Raman spectroscopy, thermogravimetric analysis, and infrared spectroscopy were used to investigate the influence of aminofunctionalization on the multiwalled carbon nanotube (MWCNT) framework. Dynamic mechanical analysis, scanning electron microscopy images of the fractured surface, and field emission scanning electron microscopy of the worn surface were used to determine the possible friction and wear mechanisms of the system. The MWCNT‐EDA/BMI composite exhibited a higher friction coefficient value and a lower wear loss rate value than the O‐MWCNT/BMI composite, which was attributed to the larger number of defects caused by the aminofunctionalization of the MWCNTs, the stronger interfacial adhesion formed between the MWCNTs‐EDA and the BMI resin, and the better dispersive state of the MWCNTs‐EDA in the BMI matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of carbon nanotube content on adhesion strength and wear and corrosion resistance of epoxy composite coatings on AA2024-T3

The effects of multiwalled carbon nanotube (MWCNT) content on the adhesion strength and wear and corrosion resistance of the epoxy composite coatings prepared on aluminum alloy (AA) 2024-T3 substrates were evaluated using atomic force microscopy (AFM), blister test, ball-on-disk micro-tribological test and electrochemical impedance spectroscopy (EIS). The adhesion strength of the epoxy composite coatings improved with increasing MWCNT content. Increased MWCNT content also decreased the friction coefficient and increased the wear resistance of the epoxy composite coatings due to improved solid lubricating and rolling effects of the MWCNTs and the improved load bearing capacity of the composite coatings. Finally, EIS indicated that increased MWCNT content increased the coating pore resistance due to a decreased porosity density, which resulted in an increase in the total impedance of the coated samples.     

Morphology and tensile properties of unreinforced and short carbon fibre reinforced Nylon 6/multiwalled carbon nanotube-composites

The morphology and the tensile properties of unreinforced and short carbon fibre (SCF) reinforced Nylon 6/multiwalled carbon nanotube (MWCNT)-composites are investigated. The morphology analysis shows that MWCNT and SCF are randomly oriented in the composites. Furthermore, the SCF fail due to fibre pull-out, while the MWCNT fail due to fracture. Young's modulus and tensile strength of SCF reinforced Nylon 6 and Nylon 6/MWCNT-composites increase with increasing total filler volume content. Replacing SCF by MWCNT further enhances Young's modulus and the tensile strength. An additive modelling approach leads to better results at low MWCNT-volume contents, while at higher MWCNT loadings a multiplicative modelling approach results in a better approximation of the experimental data. Thus the SCF reinforced Nylon 6/MWCNT-composites behave at low MWCNT-volume contents like a polymer composite containing two different types of fillers, while at higher MWCNT loadings a behaviour of a short fibre reinforced nanocomposite is observed.     

Increased sensitivity of multiwalled carbon nanotube network by PMMA functionalization to vapors with affine polarity

Multiwalled carbon nanotube network (MWCNT‐N)/poly(methyl methacrylate) (PMMA ) composite is prepared by solution radical polymerization. The entangled multiwall carbon nanotube network (MWCNT‐N) is obtained by vacuum filtration and functionalized by allyl isocyanate to form polymerizable vinyl groups on a nanotube surface. The solution polymerization binds PMMA covalently to these groups and yields MWCNT‐N/PMMA composite manifesting electrical conduction and selective chemical vapor sensing. The latter property is evaluated in terms of affinity of organic solvent vapor and PMMA polarities. It is found that the affinity of acetone polarity with polarity of PMMA improves significantly the sensitivity of the composite to this solvent while the sensitivity to methanol is the same and to iso‐pentane even decreased in comparison with the corresponding property of MWCNT‐N. The composite selective response is favorable for a possible composite use as a sensing element and/or vapor switch. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of temperature on fatigue strength of poly(ether-imide)/multiwalled carbon nanotube/carbon fibers composites for aeronautical application

This work concerns the fatigue behavior at three different temperature conditions (−40, 20, and 80°C) and the addition of multiwalled carbon nanotube (MWCNT) into a carbon-fiber reinforced poly(ether-imide) composite. The incorporation of MWCNT into the composite increased the tensile strength and Young's modulus by up 5 and 2%, respectively. At low temperature, the incorporation of the nanoparticles improved the fatigue strength of the laminates by 15%. The shear strength results obtained by interlaminar shear strength and compression shear test tests have shown an increase of about 16 and 58%, respectively, by the introduction of nanotubes into the laminates. Fractographic observations revealed that the surface of carbon nanotube laminate (PEI/MWCNT/CF) presented a ductile behavior, and differences in the fracture aspects of the material compared to the traditional PEI/CF laminate have been observed.     

Solution spinning of cellulose carbon nanotube composites using room temperature ionic liquids

Multiwall carbon nanotube (MWCNT)/cellulose composite fibers were processed from solutions in ethyl methylimidazolium acetate (EMIAc). Rheological percolation in MWCNT/Cellulose/EMIAc solution was observed above 0.01 mass fraction of MWCNT, while electrical percolation in oriented fibers was observed above 0.05 mass fraction of MWCNTs with respect to the weight of the cellulose. Cellulose orientation and crystal size were significantly higher in the composite than in the control cellulose fiber. In addition, in the composite fiber, carbon nanotube orientation was higher than cellulose orientation. At 0.05 mass fraction MWCNT, fiber tensile strength increased by about 25%, strain to failure increased by 100%, and modulus essentially remained unchanged. The composite fibers showed lower thermal shrinkage than the control cellulose fiber. The axial electrical conductivity at 0.1 mass fraction MWCNTs in these oriented fibers was more than 3000 S/m.     

Mechanical properties and electrical conductivity in a carbon nanotube reinforced silicon nitride composite

The influence of carbon nanotubes (CNTs) addition on basic mechanical, thermal and electrical properties of the multiwall carbon nanotube (MWCNT) reinforced silicon nitride composites has been investigated. Silicon nitride based composites with different amounts (1 or 3 wt%) of carbon nanotubes have been prepared by hot isostatic pressing. The fracture toughness was measured by indentation fracture and indentation strength methods and the thermal shock resistance by indentation method. The hardness values decreased from 16.2 to 10.1 GPa and the fracture toughness slightly decreased by CNTs addition from 6.3 to 5.9 MPa m^1/2. The addition of 1 wt% CNTs enhanced the thermal shock resistance of the composite, however by the increased CNTs addition to 3 wt% the thermal shock resistance decreased. The electrical conductivity was significantly improved by CNTs addition (2 S/m in 3% Si₃N₄/CNT nanocomposite).     

Preparation and properties of multi-walled carbon nanotube/carbon/polystyrene composites

Multi-walled carbon nanotube (MWCNT)/C/polystyrene (PS) composite materials were prepared by in situ polymerization of monomer in preformed MWCNT/C foams. MWCNT/C foams were preformed using polyurethane foam as template. The preformed MWCNT/C foams had a more continuous conductive structure than the carbon nanotube networks formed by free assembly in composites. The structure of the MWCNT/C foam network was characterized with scanning electron microscopy. The MWCNT/C/PS composites have an electric conductivity higher than 0.01 S/cm for a filler loading of 1 wt.%. Enhancement of thermal conductivity and mechanical properties by the preformed MWCNT/C foam were also observed.     

Indentation and scratch behavior of functionalized MWCNT–PMMA composites at the micro/nanoscale

Polymethylmethacrylate (PMMA) and functionalized multiwalled carbon nanotube (F‐MWCNT) based composite films were prepared using solution casting method. Nanoindentation and scratch measurements were carried out to study the influence of F‐MWCNT as the reinforcement on the mechanical properties of the composite at the sub‐micron scale. The composites were prepared with varying weight percentages of F‐MWCNT in the PMMA matrix. The composites containing an adequate amount (0.25 wt%) of F‐MWCNT was found to demonstrate the maximum nanomechanical properties, viz. hardness, elastic modulus, recovery index. Scratch resistance measured in terms of coefficient of friction, also showed maximum value for the PMMA composite reinforced with 0.25 wt% of F‐MWCNT. POLYM. COMPOS., 35:948–955, 2014. © 2013 Society of Plastics Engineers     

The effect of carbon nanotube orientation on erosive wear resistance of CNT-epoxy based composites

Aligned carbon nanotube (CNT) polymer composites are envisioned as the next-generation composite materials for a wide range of applications. In this work, we investigate the erosive wear behavior of epoxy matrix composites reinforced with both randomly dispersed and aligned carbon nanotube (CNT) arrays. The aligned CNT composites are prepared in two different configurations, where the sidewalls and ends of nanotubes are exposed to the composite surface. Results have shown that the composite with vertically aligned CNT-arrays exhibits superior erosive wear resistance compared to any of the other types of composites, and the erosion rate reaches a similar performance level to that of carbon steel at 20° impingement angle. The erosive wear mechanism of this type of composite, at various impingement angles, is studied by Scanning Electron Microscopy (SEM). We report that the erosive wear performance shows strong dependence on the alignment geometries of CNTs within the epoxy matrix under identical nanotube loading fractions. Correlations between the eroded surface roughness and the erosion rates of the CNT composites are studied by surface profilometry. This work demonstrates methods to fabricate CNT based polymer composites with high loading fractions of the filler, alignment control of nanotubes and optimized erosive wear properties.     

Functionalization of multi-wall carbon nanotubes to reduce the coefficient of the friction and improve the wear resistance of multi-wall carbon nanotube/epoxy composites

Functionalization of multi-wall carbon nanotubes (MWCNTs) was achieved by grafting carboxyl groups and amino groups. Fourier transform infrared spectroscopy was used to detect the changes produced by functional groups on the surface of the MWCNTs. Three different MWCNTs were incorporated into epoxy resin and the friction and wear behavior of MWCNT/epoxy composites was investigated using a M-2000 wear testing machine at different sliding speeds under different applied loads. Scanning electron microscopy was used to observe the worn surfaces of the samples. The results indicated that the functional groups had been grafted on the surface of MWCNTs. Compared with neat epoxy, the composites with MWCNTs showed a lower friction coefficient and wear rate, and the wear rate decreased with the increase of MWCNT loading. Combining epoxy resin with MWCNTs is an efficient method to improve the wear resistance and decrease the coefficient of friction.     

Tribological application of carbon nanotubes in a metal-based composite coating and composites

Ni-P-carbon nanotube (CNT) composite coating and carbon nanotube/copper matrix composites were prepared by electroless plating and powder metallurgy techniques, respectively. The effects of CNTs on the tribological properties of these composites were evaluated. The results demonstrated that the Ni-P-CNT electroless composite coating exhibited higher wear resistance and lower friction coefficient than Ni-P-SiC and Ni-P-graphite composite coatings. After annealing at 673 K for 2 h, the wear resistance of the Ni-P-CNT composite coating was improved. Carbon nanotube/copper matrix composites revealed a lower wear rate and friction coefficient compared with pure copper, and their wear rates and friction coefficients showed a decreasing trend with increasing volume fraction of CNTs within the range from 0 to 12 vol.% due to the effects of the reinforcement and reduced friction of CNTs. The favorable effects of CNTs on the tribological properties are attributed to improved mechanical properties and unique topological structure of the hollow nanotubes.     

Tribological behavior of carbon nanotube and polytetrafluoroethylene filled polyimide composites under different lubricated conditions

The friction and wear behavior of polyimide (PI) composites reinforced with carbon nanotube (CNT) and polytetrafluoroethylene (PTFE) were comparatively evaluated under dry sliding, water‐, oil‐ or alkali‐lubricated condition. The wear mechanisms of the composites were also discussed. Results indicate that, when comparison with the dry friction situation, PI‐based composites results lower friction coefficients and wear rates under oil‐ or alkali‐lubricated condition. The lowest wear rate of the CNT/PTFE/PI composite is recorded as 1.2 × 10⁻⁶ mm³/Nm during the composite sliding in alkali, which is only about 40% of the value sliding under dry friction condition. The worn surface of neat PI under dry sliding is characterized by severe adhesive wear, whereas abrasive wear is the main character for CNT/PTFE/PI composites. The worn surfaces of CNT/PTFE/PI composites sliding in oil or alkali lubricated condition are smoother than those under dry or water condition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The fracture behaviors of carbon nanotube and nanoscroll reinforced silicon matrix composites

Fracture properties of both carbon nanotube (CNT) and carbon nanoscroll (CNS) reinforced silicon (Si) matrix composites under tension are investigated by molecular dynamics simulations. It is found that either a single-wall CNT or a multi-wall one (MWCNT) will be pulled out if the length of the CNT is short, while brittle fracture of CNT will happen for a relatively long one. It is interesting to find that the “sword-in-sheath” fracture mode observed experimentally in a long MWCNT reinforced alumina matrix composite is verified well by our simulations. Furthermore, comparing to a CNT reinforced Si matrix composite, fracture toughness of a CNS reinforced one can be significantly enhanced by both the length and the layer of the CNS. Crack in CNS propagates along its circumference and moves inward layer by layer so that large parts of the fracture energy are dissipated. The results provide a direct understanding of the fracture strength observed experimentally and an insight for improving the fracture toughness of some novel composites.     

Cyclic tension and compression piezoresistivity of carbon nanotube/vinyl ester composites in the elastic and plastic regimes

The piezoresistive behavior of multi-walled carbon nanotube/vinyl ester composites tested under a low number of cycles and different levels of applied strain is investigated for specimens loaded in axial tension and compression. Since the vinyl ester thermosetting matrix is brittle in tension but ductile in compression, the piezoresistive behavior of the composite material is linear and reversible in tension for all levels of applied strain, but it is nonlinear and non-monotonic in compression. In compression, the reversibility of the electrical resistance upon unloading depends on the level of strain attained during loading, and the permanent changes of electrical resistance which occur after matrix yielding are correlated to matrix irreversible damage.     

Natural rubber/multiwalled carbon nanotube composites developed with a combined self-assembly and latex compounding technique

Carbon nanotubes (CNTs), with their high aspect ratio and exceptionally high mechanical properties, are excellent fillers for composite reinforcement if they are uniformly dispersed without aggregation. Combining the latex compounding and self-assembly techniques, we prepared a novel natural rubber (NR)/multiwalled carbon nanotube (MWCNT) composite. Before self-assembly, the MWCNTs were treated with mixed acid to ensure that the MWCNTs were negatively charged under an alkaline environment. The structure of the MWCNTs was tested with Fourier transform infrared spectroscopy. The properties of composites with different MWCNT loadings were characterized with transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, and tensile testing. The results indicate that the MWCNTs were homogeneously distributed throughout the NR matrix as single tubes and had good interfacial adhesion with the NR phase when the MWCNT loading was less than 3 wt %. In particular, the addition of the MWCNT led to a remarkable reinforcement in the tensile strength, with a peak value of 31.4 MPa for an MWCNT content of 2 wt %, compared to the pure prevulcanized NR (tensile strength = 21.9 MPa). The nanocomposites reinforced with MWCNTs should have wide applications because of the notable improvement in these important properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Tribological testing of peroxide cured HNBR with different MWCNT and silica contents under dry sliding and rolling conditions against steel

The sliding, and rolling friction and wear behaviors of peroxide cured hydrogenated nitrile rubber (HNBR) with 10 and 30 parts per hundred rubber (phr) multiwall carbon nanotube (MWCNT) and silica, respectively, were investigated. Mechanical properties (hardness, tensile modulus, ultimate tensile strength and strain, tear strength) of the rubbers were determined. Dynamic-mechanical thermal analysis was also performed and the apparent crosslink density estimated. Tribological properties were investigated in pin (steel)-on-plate (rubber), with roller (steel)-on-plate (rubber), with oscillating steel cylinder on rubber plate (Fretting) and with rolling ball (steel)-on-plate (rubber) (RBOP) test configurations. Coefficient of friction and specific wear rate (Ws) of the HNBR systems were determined. It was established that the resistance to wear increases with increasing filler content, and the incorporation of MWCNT was more advantageous than silica from the viewpoint of dry sliding and rolling performance. The friction and wear characteristics strongly depended on the test configurations. The worn surface of the HNBR systems was inspected in scanning electron microscope to conclude the typical wear mechanisms which were discussed accordingly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Friction and wear mechanisms of PA66/PPS blend reinforced with carbon fiber

The mechanical and tribological properties of carbon fiber (CF) reinforced polyamide 66 (PA66)/polyphenylene sulfide (PPS) blend composite were studied in this article. It was found that CF reinforcement greatly increases the mechanical properties of PA66/PPS blend. The friction coefficient of the sample decreases with the increase of CF content. When CF content is lower (below 30%), the wear resistance is deteriorated by the addition of CF. However, the loading of higher than 30% CF significantly improves the tribological properties of the blend. The lowest friction coefficient (0.31) and the wear volume (1.05 mm³) were obtained with the PA66/PPS blend containing 30% CF. The transfer film and the worn surface formed by sample during sliding were examined by scanning electron microscopy. The observations revealed that the friction coefficient of PA66/PPS/CF composite depends on the formation and development of a transfer film on the counterface. The abrasive wear caused by ruptured CFs (for lower CF content) and the load bearing ability of CFs (for higher CF content) are the major factors affecting the wear volume. In addition, the improvements of mechanical properties, thermal conductivity, and self‐lubrication of bulk CFs are also contributed to the wear behavior of PA66/PPS/CF composite. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Surface modification of carbon fiber and its effects on the mechanical and tribological properties of the polyurethane composites

To improve the friction and wear behavior of the polyurethane composites, carbon fibers were modified with 2, 4‐diisocyanatotoluene. The mechanical and tribological properties of the reinforced polyurethane composites were studied. Tensile strength of the composites increased with the addition of carbon fibers. The friction and wear experiments were tested on a MRH‐3 model ring‐on‐block test rig at different sliding speeds and loads under dry sliding. Experimental results revealed that carbon fibers with chemical treatment contributed to largely improve the tribological properties of the polyurethane composites. Scanning electron microscopic (SEM) investigations showed that the worn surface of the modified polyurethane composite was smoother than pure polyurethane under given load and sliding speed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers