Mechanical Properties Of Multi-walled Carbon Nanotubes Research Articles

Interfacial, electrical, and mechanical properties of MWCNT in polyurethane nanocomposite coating via 2D electrical resistance mapping for aircraft topcoat

Interfacial, electrical, and mechanical properties of polyurethane (PU)-type aircraft topcoat layers for LSP (Lightning Strike Protection) was evaluated by 2-D electrical resistance (ER) mapping with different oxidation times. Multi-wall carbon nanotubes (MWCNT) were treated using hydrogen peroxide to improve dispersion. Mechanical property of MWCNT/PU topcoat was determined via thin film tensile test, and oxidation degree was determined using TGA and EDS. Static contact angle measurements were used to evaluate work of adhesion between MWCNT and PU coating layer. Interfacial adhesion between MWCNT and PU coating layer was obtained via pull-out test and both results were consistent with different MWCNT oxidation times. Electrical properties of MWCNT/PU topcoats were evaluated by surface ER. Surface ER was the lowest at 5 days oxidation times. Higher tensile strength of MWCNT/PU topcoat could contribute to higher interfacial adhesion. Visualization was used to determine MWCNT dispersion and verified successfully using the color variation of 2D ER mapping.

Enhancement of Impact Properties by Using Multiwall Carbon Nanotubes as Secondary Reinforcement in Glass/Epoxy Laminates

Abstract This study is focused on the drop weight low-velocity impact (LVI) response of glass woven polymer composite laminates reinforced with multiwall carbon nanotubes (MWCNTs). Symmetrical quasi-isotropic laminates with zero bending-extension coupling were fabricated. Six hundred-grams per square meter plain glass woven fabric was used as a primary reinforcing agent while MWCNTs were used as the secondary reinforcement. The exceptional mechanical properties of MWCNTs in the context of impact damage tolerance in fiber-reinforced polymer composite laminates were examined and the limitation of scattered data was overcome by doing a range analysis. MWCNT-doped glass fiber reinforced polymer (GFRP) laminates were fabricated in seven proportions (neat, 0.25, 0.5, 0.75, 1, 1.5, and 2 weight percentage of resins) by using the hand layup technique, followed by the vacuum bagging method at 1 atm. By mixing MWCNTs as a secondary reinforcement, the maximum enhancement of 32.6 % in energy absorption, 10.26 % in peak load capacity (at 3.0 m/s impact velocity), and 32.44 % reduction in the visual damage area was attained (at 3.5 m/s indentation). Experiment results (for neat GFRP) were also validated by using three-dimensional finite element analysis software LS-DYNA.

Microstructure and mechanical properties of MWCNT/Ti6Al4V composites consolidated by vacuum sintering

Ti6Al4V alloys with low weight, high corrosion resistance, high melting point, high biocompatibility and unique mechanical properties have been receiving great attention for wide applicability in many industry fields such as automobiles, aerospace and biomedical. However, Ti6Al4V tends to be easily oxidized at high temperature, exhibit low thermal conductivity, low hardness and low yield strength and thus have led to the limitation of applicability in many industries. In this study, we have fabricated Ti6Al4V matrix composites reinforced with multi-walled carbon nanotubes (MWCNT) to enhance the hardness and yield strength. Vacuum sintering technique has been used to prepare MWCNT/Ti6Al4V composites. Microstructural and phase studies indicated that the composite structure consists of two main phases including ?-Ti and ?-Ti and MWCNTs were uniformly dispersed in Ti6Al4V matrix. The relative density of composite decreases as the CNT content increases as resulted from the porous structure of the CNT, which limits the aggregation process of the composite. When the CNT content increased, the hardness and yield strength of the composite increased, reaching maximum values of 378 HV and 356 MPa with 2 vol.% MWCNTs, which are nearly 16 and 38% higher than those of Ti6Al4V alloy. The enhancement in hardness and compressive strength is attributed to the good mechanical properties of MWCNTs and load transfer effect from Ti6Al4V alloy matrix to reinforcement material.

Fabrication and mechanical properties of MWCNTs and graphene synergetically reinforced Cu–graphite matrix composites

ABSTRACT Multi-walled carbon nanotubes (MWCNTs) and graphene synergetically reinforced Cu–graphite matrix composites with alloying elements and the rare earth element lanthanum were fabricated by powder metallurgy, and their mechanical properties were evaluated. An innovative solution for dispersing the solution into the MWCNTs and graphene was adopted by surface modification with gallic acid solution or rutin solution, instead of strong acid and base solutions, respectively. The interfacial bonding between MWCNTs or graphene and the copper matrix, and the particle distribution uniformity, were enhanced by mechanical alloying and freeze-drying. Nearly complete densification of the MWCNTs and graphene synergetically reinforced Cu–graphite matrix composites was achieved by hot-pressing and hot isostatic pressing sintering. The microstructure and mechanical properties of the composites indicated that the interfaces between the reinforcing phases and matrix were tightly bonded, confirming that the interface bonding between the MWCNTs, graphene, and copper matrix was mainly established as mechanical locks. The dominant strengthening mechanisms in the composites were the fine grain strengthening, load transferring, and solution strengthening, followed by dislocation strengthening.

Effect of loading rate on inter laminar shear strength (ILSS) of highly doped MWCNTs carbon/epoxy laminates

The present experiment investigates the sensitivity of strain rate on mechanical properties of MWCNTs (multi-walled carbon nanotubes) reinforced carbon woven composites. The SBS (short beam strength) tests were done to evaluate the dependence of strain rate on ILSS (inter laminar shear strength) of prestine neat and 1, 2, 3 and 4 wt. % MWCNTs doped CFRP (carbon fiber reinforced polymer). The symmetrical bi-directional carbon fiber laminate comprising of eight layers with 0.5 mm thickness each and ply orientation of [(0, 90) / (+45,-45) / (+45,-45) / (0, 90)]S was designed. The laminates were prepared by hand lay-up method assisted by vacuum bagging technique. The prepared laminates were cut using the diamond cutter and the obtained samples were tested on H50KS, the UTM (universal testing machine) as per ASTM D2344. Three different loading rates of 1, 110 and 220 mm/min were used to see the mechanical performance of CFRP with no doping and with doping of higher percentage by weight of MWCNTs. The results revealed strain rate dependency of carbon/epoxy laminates on its mechanical performance. In the test, 3 wt. % MWCNTs doped CFRP showed maximum shear strength at the strain rate of 110 mm/min. Also, FEA (finite element analysis) using ANSYS were done and the results were found to be in good agreement with the experimental data.

Tunable mechanical properties of MWCNT–glass fiber fabric reinforced epoxy composites by controlling MWCNTs dispersing conditions

A novel, simple and cost-effective method, which is capable of easily tailoring the dispersion of multi-walled carbon nanotubes (MWCNTs), was developed here to fabricate the MWCNT–glass fiber fabric (MWCNT–GFf) multiscale composites with tunable mechanical properties. MWCNTs were dispersed into the commercial GFfs through the combined effect of the ultrasound and amino silane (AS) firstly, followed by a resin infusion process. By tuning the ultrasonic power and AS concentration, it is possible to control the MWCNTs dispersion level and subsequently mechanical properties of resultant composite. Making use of optimal dispersion conditions, which involves the optimal combination of ultrasonic power and AS concentration, the interlaminar shear strength of MWCNT–GFf reinforced composites was dramatically increased by 40.5%, and the storage modulus in the glassy region and rubbery region was improved by 27.7% and 125.0%, respectively. The work demonstrates the great promise of this novel method toward practical, industrial application in manufacturing fiber-reinforced composites with superior mechanical properties.

Superior mechanical and electrical properties of multiwall carbon nanotube reinforced acrylonitrile butadiene styrene high performance composites

In-house synthesized multiwall carbon nanotubes (MWCNTs) have been dispersed in acrylonitrile butadiene styrene (ABS) using a micro twin-screw extruder with back flow channel. The electrical and mechanical properties of MWCNTs in ABS with different wt% have been studied. Incorporation of only 3 wt. % MWCNTs in ABS leads to significant enhancement in the tensile strength (up to 69.4 MPa) which was equivalent to 29% increase over pure ABS. The effect of MWCNTs on the structural behaviour of ABS under tensile loading showed a ductile to brittle transition with increase concentration of MWCNTs. The results of enhanced mechanical properties were well supported by micro Raman spectroscopic and scanning electron microscopic studies. In addition to the mechanical properties, electrical conductivity of these composites increased from 10−12 to 10−5 Scm−1 showing an improvement of ∼7 orders of magnitude. Due to significant improvement in the electrical conductivity, EMI shielding effectiveness of the composites is achieved up to −39 dB for 10 wt. % loaded MWCNTs/ABS indicating the usefulness of this material for EMI shielding in the Ku-band. The mechanism of improvement in EMI shielding effectiveness is discussed by resolving their contribution in absorption and reflection loss. This material can be used as high-strength EMI shielding material.

Studies on structural, optical and mechanical properties of MWCNTs and ZnO nanoparticles doped PVA nanocomposites

AbstractThis paper presents a novel class of multiwalled carbon nanotubes (MWCNTs) and zinc oxide (ZnO) doped polyvinyl alcohol (PVA) nanocomposites prepared using coagulation and solvent casting method. The dopant, ZnO nanoparticles, was prepared using precipitation method, and another dopant, MWCNTs, was treated with H2SO4and HNO3taken in 3:1volume ratio to create carboxylated MWCNTs. Furthermore, prepared ZnO and treated MWCNTs were doped into PVA matrix to prepare PVA nanocomposites by solvent casting technique. The Fourier transform infrared (FTIR) spectra detect the irregular shift in the bands of doped PVA nanocomposites indicating the presence of intra/intermolecular hydrogen bonding creating the interaction between the nanoparticles and neighboring OH group of PVA. Crystallinity of the prepared nanocomposites films was investigated using XRD technique, which explores the average particle size of the embedded nanoparticles and explains the complex formation and variation in crystallinity of the nanocomposites due to interaction of dopants. The decrease in optical energy band gap of nanocomposite films and the information of Urbach energy (Eu) were assessed by UV/vis spectroscopy. By using a universal testing machine, the mechanical properties of doped polymer films found escalation for doping percentage concentrationx=7.5 wt%. The phase homogeneity, film morphology, and chemical configuration of the nanocomposites were inspected using atomic force microscope, scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively.

BCN nanotubes as highly sensitive torsional electromechanical transducers.

Owing to their mechanically tunable electronic properties, carbon nanotubes (CNTs) have been widely studied as potential components for nanoelectromechanical systems (NEMS); however, the mechanical properties of multiwall CNTs are often limited by the weak shear interactions between the graphitic layers. Boron nitride nanotubes (BNNTs) exhibit a strong interlayer mechanical coupling, but their high electrical resistance limits their use as electromechanical transducers. Can the outstanding mechanical properties of BNNTs be combined with the electromechanical properties of CNTs in one hybrid structure? Here, we report the first experimental study of boron carbonitride nanotube (BCNNT) mechanics and electromechanics. We found that the hybrid BCNNTs are up to five times torsionally stiffer and stronger than CNTs, thereby retaining to a large extent the ultrahigh torsional stiffness of BNNTs. At the same time, we show that the electrical response of BCNNTs to torsion is 1 to 2 orders of magnitude higher than that of CNTs. These results demonstrate that BCNNTs could be especially attractive building blocks for NEMS.

Synthesis and characterization of carbon nanotube–polyethylene oxide composites

We have investigated the structural, electrical and mechanical properties of multi-walledcarbon nanotube (MWNT)–polyethylene oxide (PEO) composites. Composites withdifferent wt% (between 0 and 50 wt% of MWNTs) were prepared and characterized by thescanning electron microscopic technique. Enhanced electrical conductivity and mechanicalstrength were observed for the MWNT–PEO composites. The conductivity measurementson the MWNT–PEO composite films with highest concentration of MWNTs(∼50 wt%) showed anincrease of eight orders (∼7.5 × 10−8 to 6.52 S cm−1)of magnitude in conductivity from bare PEO film. The temperature dependence of the conductivity forMWNT (∼50 wt%)–PEO composite showed predominantly semiconductingbehaviour. The elastic modulus and tensile strength of an MWNT(∼50 wt%)–PEO film were increased by about five- and tenfold respectively, as compared to thecorresponding values for a PEO film.

Radial compression of carbon nanotubes: deformation and damage, super-elasticity andsuper-hardness

Molecular dynamics (MD) simulations of nanoindentation of multiwalled carbon nanotubes(MWCNTs) are carried out to study the deformation mechanism and the mechanicalproperties of MWCNTs in the radial direction. The MWCNT is found to be soft in itsradial direction, with nanohardness rising slowly from about 6 to 15 GPa. The soft phasepersists until all spaces between adjacent layers of the MWCNT are compressedbeyond a critical value of about 1.9 Å. Beyond the critical stage the formation ofnew bonds between different layers starts to increase, producing a super-hardamorphous phase with a hardness of up to 94 GPa. Though locally compressedto a large radial strain of about 63%, the amorphous phase with a mixture ofsp3 andsp2 bondsis completely reversible upon unloading, showing super-elasticity. Further indentation afterwards leads topermanent sp3 and even sp rehybridization, the MWCNT is badly damaged and the hardness fluctuateswith a maximum of about 124 GPa which is comparable to the microhardness of diamond.