Weight Percentages Of Carbon Nanotubes Research Articles

Dynamic plastic impact behavior of CNTs/fiber/polymer multiscale laminated composite doubly curved shells

In the present paper, the dynamic elastoplastic response of carbon nanotube (CNT) fiber/polymer multiscale laminated composite (CNTFPC) doubly curved shell subjected to low-velocity impact of the projectile is investigated. For this purpose, the effective material properties of the multiphase composite are calculated by combining the Halpin-Tsai model and a micromechanical approach that strengths are estimated by an empirical equation and modified through a mixture rule. The elastoplastic constitutive equations are obtained incrementally using Hoffman’s criterion and isotropic hardening model. Also, the Green-Lagrange type of nonlinear kinematics is extracted in terms of displacement terms based on Reddy’s higher-order shear deformation theory for the CNTFPC shell. All incremental relations are regulated in the framework of the updated Lagrangian formulations to solve by an iterative finite element procedure through conforming isoparametric quadrilateral elements. Moreover, an elastoplastic Brake’s contact model is developed to determine truly the contact force between the CNTFPC plate and impactor. Temporal discretization is done by the Newmark’s average acceleration scheme. The results are validated with the data available in the literature to demonstrate the accuracy of the model. A parametric study was carried out to analysis stress and investigate the yield conditions and the effects of plastic deformation, weight percentage of CNTs, fiber volume fraction and curvature radius on the contact force history, indentation, permanent indentation depth, central deflection. Numerical results show that in the low velocity impact analysis, the stresses occurring in the shell for the areas further away from the contact area are also yielded.

Mechanical Pressure Characterization of CNT-Graphene Composite Material.

Carbon nanotubes (CNTs) and graphene are extensively studied materials in the field of sensing technology and other electronic devices due to their better functional and structural properties. Additionally, more attention is given to utilize these materials as a filler to reinforce the properties of other materials. However, the role of weight percentage of CNTs in the piezoresistive properties of these materials has not been reported yet. In this work, CNT-graphene composite-based piezoresistive pressure samples in the form of pellets with different weight percentages of CNTs were fabricated and characterized. All the samples exhibit a decrease in the direct current (DC) resistance with the increase in external uniaxial applied pressure from 0 to 74.8 kNm−2. However, under the same external uniaxial applied pressure, the DC resistance exhibit more decrease as the weight percentage of the CNTs increase in the composites.

Analytical approach to study the vibration of delaminated multi‐scale composite cylindrical shells

AbstractIn this study, the effect of carbon nano‐tubes (CNTs) and fiber carbons on vibration frequency of delaminated anti‐symmetric cross‐ply cylindrical shells is investigated. In this case, (CNTs) are added into polymer matrix of industrial composite. The mixture of rule and Halpin‐Tsai relation are used to obtain the effective materials of reinforced delaminated multi‐scale composite cylindrical shell. Based on Galerkine's method an approximate‐analytical solution is presented to predict the frequency vibration of delaminated multi‐scale composite shells. The results are used to assess the effect of various parameters including CNTs weight percentage, geometric parameters, delamination length and position across circumferential and thickness direction on frequency ratio for CNTs reinforced anti‐symmetric cross‐ply delaminated composite cylindrical shells.

Nonlinear vibration of thick multi-scale composite doubly curved shells

ABSTRACT: In this paper, the large amplitude vibration of moderately thick three-phase multi-scale composite doubly curved shells is investigated. The epoxy resin is enriched by carbon nanotubes (CNTs) and the E-glass fibers are embedded in the reinforcement matrix. The effective materials properties are predicted by combination of Halpin-Tsai relation and micromechanics approach. The von Kármán geometric nonlinearities terms and first-shear deformation theory are employed to obtain the governing equations. Galerkine’s method is used to reduce the coupled governing equations to an ordinary nonlinear differential equation. The first-order analytical approximate and periodic solution is derived by homotopy perturbation method (HPM). The results include the effect of CNTs weight percentage, CNTs aspect ratio and vibration amplitude on nonlinear frequency of multi-scale composite doubly curved shells.

Wear analysis of CNT-AL Nanocomposites using surface response method

Carbon nanotube (CNT) reinforced aluminium (Al) nano-composites were produced using powder metallurgy route with different weight percent of CNT in to the Al matrix. The wear behaviour of CNT-Al nano-composite was studied using a pin-on-disc tribometer against AISI4340 steel disc. Experiments were conducted using different sliding velocities of 0.5, 0.65 and 0.8 m/s and a normal load of 5, 7.5 and 10 N. Design Expert (DOE) version 6.0.8 was used to optimize the process variable for wear and friction test of the developed CNT-Al nano-composite using face centered central composite design based on response surface methodology and confirmed that 1.5 wt% was the optimum CNT-Al nano-composite formulations. The result showed that higher hardness value of the material showed a lesser wear rate and better wear resistance. The result showed that the wear rate of the developed nano-composite decreased with the increasing of CNT content but up to 1.5 wt% CNT into the nano-composite. The wear rate values varied from 2-0.6 x10-3 mm3/m (2, 0.2, 0.17. 0.3 and 0.6 mm3/m x10-3 for 0 wt%, 1 wt%, 1.5 wt%, 2 wt% and 2.5 wt% CNT respectively). These results also showed that the rate of wear decreases with the increase in normal load and sliding speed. DOE confirm the accuracy of the experimental result for the evaluation of the developed CNT-Al nano-composite. Keywords: Wear testing, Sliding wear, Wear modelling, Metal-matrix composite and CNTAl nano-composite

Enhancing The Mechanical Properties o f Chopped Basalt Composites b y Incorporating o f Multiwall Carbon Nanotubes

This study aims to develop and determine mechanical properties chopped basalt fibre reinforced composites (CBFRP) modified with multiwall carbon nanotubes (CNT). Chopped basalt composite modified with CNT was fabricated using a combination of mechanical stirring and hand layup process. Three different weight percentages of CNT i.e. 0.5, 1, 1.5wt. % were filled into epoxy resin before mixing with chopped basalt fiber. The mechanical performance namely tensile properties and fracture toughness behaviour of the fabricated chopped basalt composites was assessed using Universal Testing Machine in accordance to ASTM standard D368 and D695, respectively. The results showed that the incorporation of CNT enhanced tensile and fracture toughness properties of the CBFRP composites. However, a higher amount of CNT (1.5wt%) incorporated into the CBFRP caused reduction in tensile strength, tensile modulus and Gic by 4.40%, 2.46% and 30.36 %, respectively, as compared to those of 1.0CNT-CBFRP.

Influence of carbon nanotubes on thermal expansion coefficient and thermal buckling of polymer composite plates: experimental and numerical investigations

The first aim of this article is to experimentally explore the effect of multi-walled carbon nanotubes (MWCNTs) on the coefficient of thermal expansion (CTE) of epoxy-based composites. Focusing on the obtained experimental data, two important conclusions can be drawn. (1) Though the CTE of carbon nanotubes (CNTs) is lower than that of neat epoxy, using more CNT does not necessarily decrease the CTE of epoxy polymer. (2) The optimum weight percentage of CNT is 0.3 which can reduce the CTE of epoxy up to 33%. As the second goal of the present research work, thermal buckling analysis of rectangular carbon-fiber-reinforced CNT/epoxy polymer (CFRCNTEP)-laminated composite plates is performed numerically. To this purpose, first, using the obtained experimental data and micro-mechanical models, the thermo-elastic properties of structure are calculated. Then, based on the first-order shear deformation theory (FSDT) and by means of generalized differential quadrature (GDQ) method, the influence of CNTs on the critical buckling temperature of CFRCNTEP composite plates is investigated. The numerical results reveal that MWCNTs can strongly affect thermal buckling behavior of composite plates. It is observed that by adding 0.3 wt. % CNTs into the matrix phase, the critical buckling temperature increases between 35 and 42%.

Analysis of CNT reinforced polymer nanocomposite plate in the presence of discontinuities using XFEM

In the present study, the effect of holes and inclusions on the stress intensity factor (SIF) in a Carbon NanoTube (CNT) modified polymer nanocomposite (PNC) has been investigated using extended finite element method (XFEM). In order to perform the failure analysis of CNT reinforced nanocomposite two-step procedure is adopted. In the first step, the equivalent properties of the nanocomposites (elastic modulus, fracture energy and fracture toughness) are computed by changing the percentage of weight content of CNTs inside the polymer matrix. Halpin-Tsai equation has been employed to compute the elastic modulus of the material. Whereas, the fracture toughness and fracture energy have been evaluated considering CNT debonding and CNT pull-out as the main toughness criterion. For this purpose, a modified Cottrell-Kelly-Tyson scheme has been chosen in order to account the hollowness of CNTs. In the second step, a thin finite size plate containing an edge crack with multiple holes and inclusions has been taken into consideration. Then, XFEM approach is implemented to perform the failure analysis of cracked nanocomposite plate. The interaction integral approach has been employed to compute the SIF value at the crack tip. The numerical integration has been done using higher order Gaussian quadrature. Few numerical problems have been solved in the presence of discontinuities. It was found that the elastic modulus, fracture toughness and fracture energy improved with increase in weight percent of CNT. The effect of holes was found to be more pronounced than the effect of inclusion on the SIF.

Nonlinear aeroelastic stability analysis of three-phase nano-composite plates

The main aim of this study is to investigate the geometrical nonlinear flutter of three-phase nano-composite plates reinforced with carbon nano-tubes (CNTs). The effective material properties are obtained using Halpin-Tsai relation and rule of mixture. The classical plate theory and von Karman geometrical nonlinearities assumptions are employed to obtain the governing equation of the system. The homotopy perturbation method (HPM) is utilized to conduct a numerical investigation to study the aeroelastic behavior of multiscale composite plates. The effects of different parameters such as CNTs weight percentage, aspect ratio, and elastic modulus ratio on flutter pressure of nano-composite plates are considered.Communicated by S. Velinsky.

Compressive Strength Enhancement of Carbon Nanotube Reinforced 13-93B1 Bioactive Glass Scaffolds.

45S5 Bioglass® has been used quite extensively in the form of particulate as synthetic bone graft. However, 45S5 glass has certain limitations such as difficulty in sintering and slow and partial conversion to hydroxy carbonated apatite. In pursuit of overcoming these limitations, bioactive glasses (13-93B1) containing increased amount of B₂O₃ by partial replacement of SiO₂ have been prepared using sol-gel technique in this study. Since bioactive glasses are brittle in nature, therefore, they are unsuitable for load bearing sites. Consequently, 3D porous scaffolds by reinforcement with varying weight percent of carbon nanotubes (CNTs) have been fabricated in this work by physical mixing and polymer foam replication technique. Compared with pure 13-93B1 bioactive glasses, addition of 0.2 weight percent of CNT resulted in maximum increase in compressive strength from 1.80 MPa to 5.84 MPa (a 224% increase) and elastic modulus from 102 MPa to 269.4 MPa (a 164% increase), respectively. Bioactivity of these scaffolds was confirmed in vitro using simulated body fluid test for 28 days. The compressive strength post-SBF studies were within the range of compressive strength of trabecular bone. These results show potential of fabricating a 3D porous scaffold with sufficient strength and biocompatibility using CNT-1393B1 bioactive glasses.

Damage sensing in multi-functional hybrid natural fiber composites under shear loading

A comprehensive experimental study is performed to investigate the electro-mechanical response of jute/epoxy composites for in situ damage detection under in-plane shear loading conditions. By embedding carbon nanotubes (CNTs) in epoxy matrix and also reinforcing carbon fibers (CFs) using electro-flocking process between the jute laminates, a three-dimensional sensory network is generated inside the composites. A parametric study is conducted to examine the effect of two different weight percentages of CNTs (0.025% and 0.1%), two different CFs lengths (150 and 350 μm), four different CF flock densities (500, 1000, 1500, and 2000 fibers mm−2), and two different laminate orientations ((0-0-0-0)T and (0-90-0-90)T) on the generation of electrical conductive network and its role on damage detection. The electrical resistance values are measured using four circumferential ring probes measurement system. Results indicated that (0-0-0-0)T orientation showed 400% improvement in interlaminar shear strength compared to (0-90-0-90)T composites. CF flocking between the laminates experienced maximum increase of 50% in shear strength compared to non-flocked composites. For all composite types, there is no change in resistance during the elastic deformation of shear loading. Beyond elastic deformation, the increase in CF length and its density showed similar electrical response. The increase in CNTs concentration and laminate orientations did not show significant change in electrical response under shear loading conditions.

Electrical response of novel carbon nanotubes embedded and carbon fiber Z‐axis reinforced jute/epoxy laminated composites

Novel conductive jute/epoxy laminated composites were fabricated by embedding carbon nanotubes (CNTs) in the matrix and flocking short carbon fibers between the laminates. A three‐dimensional electrical conductive network was generated inside the composites and the electrical resistivity values were measured using a four circumferential probe measurement system. A parametric study was performed to investigate the effect of three different weight percentages of CNTs (0%, 0.025% and 0.1%), two different carbon fiber lengths (150µm and 350µm), four different carbon fiber flock densities (500, 1000, 1500 and 2000 fibers/mm2) and two different laminates' orientations ((0‐0‐0‐0)T and (0‐90‐0‐90)T) on the resistivity values of the composites. Composites with the lowest resistivity value of 0.019 Ohms‐m was achieved for 0.1 wt.% of CNTs and 350µm with flock density of 2000 fibers/mm2 for ((0‐0‐0‐0)T laminate orientation. The increase in flock length from 150µm to 350µm significantly decreased the resistivity by several orders because 350µm generated better conductive network with neighbouring carbon fibers as well as with CNTs. The flock density of carbon fibers has a dominant effect on 150µm long fibers compared to 350µm when the flock density increased from 1000 fibers/mm2 to 1500 fibers/mm2. Variation of both CNTs weight percentage and laminate orientation did not have significant effect on change in resistivity. The electrical measurement investigation of these novel conductive natural fiber composites will have applications in in‐situ damage sensing and structural health monitoring. POLYM. COMPOS., 40:E1189–E1198, 2019. © 2018 Society of Plastics Engineers

Smart control and vibration of viscoelastic actuator-multiphase nanocomposite conical shells-sensor considering hygrothermal load based on layerwise theory

Smart control and vibration analysis of laminated sandwich truncated conical shells with piezoelectric layers as sensor and actuator are presented in this paper. The core of the sandwich structure is reinforced by carbon fibers and carbon nanotubes (CNTs) where the effective material properties are obtained by Halpin–Tsai model. The actuator layer is subjected to external voltage and a Proportional-Derivative (PD) controller is used for sensor output control. Based on Kelvin–Voigt model, the structural damping effects are assumed. The formulation of the problem is based on the layerwise first order shear deformation theory (FSDT). Considering the continuity of the displacements and the internal stress fields at the interfaces of the layers, the motion equations are derived utilizing Hamilton's principle. The solution of the problem is carried out by differential quadrature method (DQM) for calculating the frequency of the smart sandwich structure. The effects of different parameters such as structural damping, weight percent of CNTs, boundary conditions, geometrical parameters of the structure, semi vertex angle of the cone, external voltage, temperature and moisture changes are examined on the vibration response of the smart sandwich structure. Numerical results indicate that using a PD controller can increase the frequency of the structure. In addition, the hygrothermal load decreases the vibration frequency of the system.

High-performing multi-walled carbon nanotubes/silica nanocomposites for elastomer application

Elastomer composites with high comprehensive performance have been the focus of the studies in the rubber industry. Especially, the multicomponent nanocomposites as fillers in the rubber matrix have attracted global attention. In the present work, silica nanoparticles (SiO2) were assembled with multi-walled carbon nanotubes (CNTs), and the resulting CNTs/SiO2 nanocomposites were incorporated into solution-polymerized styrene butadiene rubber/butadiene rubber (SSBR/BR) to fabricate CNTs/SiO2-SSBR/BR elastomer composites. The morphologies and structures of CNTs/SiO2 and CNTs/SiO2-SSBR/BR were characterized, and the performances of CNTs/SiO2-SSBR/BR composites were measured. The results showed that the SiO2 with small particle size (10–15 nm) could be tightly anchored on the surface of CNTs through covalent bonds, and the resulting CNTs/SiO2 nanocomposites were highly compounded with SSBR/BR in a uniformly dispersed status. With the increasing weight percentage of CNTs in CNTs/SiO2 nanocomposites, both the tensile strength and elongation at break of CNTs/SiO2-SSBR/BR is increased to 23.6 MPa and 603.9%, respectively. These results clearly illustrate the high reinforcement effect of CNTs/SiO2 nanocomposites to SSBR/BR. Meanwhile, compared with that of commercial Zeosil 1165MP highly-dispersed nano-SiO2 (Zeosil 1165MP)-SSBR/BR, the tan δ of the 2% CNTs/SiO2-SSBR/BR (2 wt% CNTs in CNTs/SiO2) is 17.1% higher at 0 °C and 17.3% lower at 60 °C, indicating the endowed high wet skid resistance and low rolling resistance of CNTs/SiO2-SSBR/BR. Also, the heat build-up and wear resistance exhibit significantly decline at the low weight percentages of CNTs. The enhanced comprehensive performances demonstrate the utilizability of CNTs/SiO2 as a reinforcing filler for the application of high performance green tire.

Cross-Sectional Design and Analysis of Multiscale Carbon Nanotubes-Reinforced Composite Beams and Blades

The present work addresses with the cross-sectional design and analysis of fiber-reinforced multiscale composite beams of general cross-sectional shape and arbitrary anisotropic material properties and investigates the effect of carbon nanotubes (CNTs) on their stiffness properties. The three-dimensional strain field was formulated in terms of one-dimensional strains and a three-dimensional warping displacement. The bulk material properties of the multiscale composite were predicted using Halpin–Tsai equations and fiber micromechanics. The carbon nanotubes were assumed to be uniformly distributed and randomly oriented throughout the polymer matrix. The variational asymptotic beam section (VABS) was used to numerically evaluate the stiffness and mass matrices of four test cases: strip, circular pipe, box beam and airfoil. The influence of CNTs weight percentage and volume fraction of fibers was investigated through a detailed parametric study. The numerical results indicate that the inclusion of a small weight percentage of carbon nanotubes in the polymer matrix is sufficient to induce a significant improvement in stiffness properties.

Mechanical and piezoresistive properties of self-sensing smart concretes reinforced by carbon nanotubes

ABSTRACTConcrete structures such as bridges, towers, and roads are constantly prone to damage due to development of cracks, stresses, and other defects. The present study is focused on manufacturing of self-sensing smart concretes and investigates their mechanical and piezoresistive behavior for health monitoring of concrete structures. To this end, concrete is combined with multi-walled carbon nanotubes (MWNTs) to produce an internal electrical network. Using the high piezoresistive properties of the carbon nanotubes, the concrete is able to indicate the mechanical stresses. Carbon nanotubes are also capable of reinforcing concretes and increasing mechanical strength. To this end, the concrete nanocomposite was prepared in three general cases including cement paste and concretes of grade 400 and 350 for water-cement ratios of 0.45 and 0.6. Then, the effect of different weight percentages of carbon nanotubes on the electrical and mechanical properties of the nanocomposite was experimentally investigated. In the next stage, the piezoresistive property of concrete was investigated when subject to static and dynamic loads. The results indicate that concrete nanocomposites are sensitive to the amount of applied compressive stresses so that application of compressive stresses up to 6 MPa leads to changes of up to 8 percent in the electrical resistance of concrete in the case of using cement paste nanocomposite reinforced with 1 wt.% of carbon nanotubes.

Mechanical Properties and the Characterization of Polyacrylonitrile/Carbon Nanotube Composite Nanofiber

This work describes the fabrication of the composite nanofibers containing polyacrylonitrile polymer (PAN) and different weight percentage of carbon nanotubes (CNTs) using electrospinning technique which is simplest and highly versatile method to enhance the mechanical properties by removing the surface defects of the composite nanofibers. The tensile test, X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy measurements are used to find the mechanical properties and the characterization of PAN/CNT composite nanofibers. The result demonstrated that adding CNTs to the polymer enhances the mechanical properties like tensile strengths and Young’s modulus with an average 55 and 60 %, respectively at only 0.1 wt% of CNTs.

Synthesis of Cu-CNTs nanocomposites via double pressing double sintering method

In this research, copper (Cu)-carbon nanotubes (CNTs) nanocomposites were synthesized with different weight percentages of CNTs by double pressing double sintering (DPDS) method as well as conventional sintering method. A planetary ball mill was used to disperse CNTs in Cu matrix. The milled powders were first cold pressed to 450 MPa in a uniaxial stainless-steel die with cylindrical compacts (diameter: 12 mm and height: 5 mm). The effect of CNTs content and the DPDS method on the properties of the nanocomposites were investigated. The microstructure and phase analysis of Cu-CNTs nanocomposite samples were studied by FESEM and X-Ray Diffraction. The electrical conductivity of nanocomposites was measured and compared to both sintering methods. Mechanical properties of Cu-CNTs nanocomposites were characterized using bending strength and micro-hardness measurements. Enhancements of about 32% in bending strength, 31.6% in hardness and 19.5% in electrical conductivity of Cu-1 wt.% CNTs nanocomposite synthesized by DPDS method were observed as compared to Cu-1 wt.% CNTs nanocomposites fabricated under the similar condition by a conventional sintering process.

Synthesis and cryogenic mechanical properties of CO2-blown carbon-reinforced polyurethane foam

In the present study, carbon-nanotube-polyurethane foams were synthesized by adding (0.02, 0.1, and 0.3 wt%) carbon nanotubes during the polymerization reaction between polyol and isocyanate liquids. After the synthesis process, the microstructural cell morphology of the carbon-nanotube-polyurethane foams, based on the amount of carbon nanotubes, was observed using field emission scanning electron microscopy. To evaluate the mechanical characteristics of the carbon-nanotube-polyurethane foams, temperature-dependent (20°C, −90°C, and −163°C) compressive tests were performed, and the results were compared to those of the pure polyurethane foam to verify the effectiveness of the developed carbon-nanotube-polyurethane foams. Specifically, the effects of the weight percent of carbon nanotubes, density, and temperature on the overall behavior of the carbon-nanotube-polyurethane foams were considered. Finally, the permanent deformation ratio and material failure characteristics were investigated. The results showed that the cell morphology and compressive strength of the carbon-nanotube-polyurethane foam with 0.02 wt% carbon nanotubes were superior to those of pure polyurethane foam, and these properties showed a significant dependence on the weight percent of carbon nanotubes, test temperatures, and the density.

A comparison study on mechanical properties of polymer composites reinforced by carbon nanotubes and graphene sheet

To compare enhancements of mechanical properties of polymer composites reinforced by carbon nanotubes and graphene sheet, molecular models of polymer matrix reinforced by the same weight percentage of carbon nanotubes and graphene sheet are developed. Pull-out process and strain constant method are applied to find mechanical properties of the nano-composites by examining the interfacial interactions between nano-reinforcements and polymer matrices. The results show that about 18% higher in Young's modulus, 8.7% higher in tensile strength, and 5% higher in surface crack energy are obtained for the composites by incorporation of graphene sheet than those by incorporation of carbon nanotubes. Graphene sheet is found to play a better role in delaying the propagations of cracks. To explore the mechanisms on the enhanced tensile and fracture properties, the interfacial interaction energy and shear forces between the nano-reinforcements and polymer matrices, and total van der Waals energy of the polymer composites are examined and interpreted accordingly.