Mechanical Properties Of Carbon Nanotubes Research Articles

Molecular dynamics simulation of mechanical properties of carbon nanotube reinforced cellulose.

Cellulose, hemicellulose, and lignin are the major chemical components in wood paper. Various types of wet and dry strength additives are used to enhance the optical and mechanical properties of recycled paper. One of the possible materials is the carbon nanotube. In order to explore the probability of the use of carbon nanotubes as reinforcing materials and to understand how carbon nanotubes affect the mechanical properties of paper, a single-walled carbon nanotube is inserted into a [Formula: see text] cellulose nanocrystal, and its mechanical properties are studied by using energy minimization and molecular dynamics (MD) simulations. During simulations, the crystals are stretched in the axial direction at a constant speed, and stress and strain are computed and recorded at the atomic level. Our results indicate that carbon nanotube can significantly enhance the mechanical properties of paper.

Effects of solid-state interfacial reaction on the mechanical properties of carbon nanotubes reinforced aluminum matrix composites with heterogeneous structure

To overcome strength-ductility trade-off in carbon nanotubes (CNTs) reinforced Al matrix composites, we developed a novel and controllable strategy via a combination of different length of CNTs and fine/coarse-grained matrices. Microstructure analysis showed that Al4C3 nanorods about 100 nm were distributed in the fine grain zone (FGZ), while CNTs of micron length were distributed in the coarse grain zone (CGZ). Different sizes of reinforcements play different strengthening roles, and the bimodal grains can effectively coordinate deformation, thereby achieving a good combination of strength and ductility. Heat treatment does not affect the microstructure of the FGZ, but significantly affect the CNT/Al interface bonding in the CGZ. Heat treatment at an appropriate temperature can further improve the strength of the composite by improving the interface bonding. When the heat treatment temperature is too high, the coarsening of Al4C3 in CGZ will deteriorate the mechanical properties of the composite.

Ensemble Machine Learning approach for evaluating the material characterization of carbon nanotube-reinforced cementitious composites

Time and cost-efficient techniques are essential to avoid extra conventional experimental studies with large data-set for material characterization of composite materials. This study is aimed at providing a correlation between the structural performance and mechanical properties of carbon nano-tubes reinforced cementitious composites through efficient predictive Machine Learning (ML) models. The Flexural (FS) and Compressive (CS) Strength of Carbon Nanotube (CNT)-reinforced composites were predicted based on the data-rich framework provided in the literature. Two different ensembled ML methods including Random Forest (RF) and Gradient Boosting Machine (GBM) were implemented on those data for predicting the CNT-reinforced cement-based composites. Data-set were utilized for training the proposed models through employing SciKit-Learn library in Python, followed by hyper-parameter tuning and k-fold cross-validation method for obtaining an optimum model to predict the target values. It was shown that the CS values predicted by the proposed models were more accurate than the FS counterparts and the developed model of GBM has less sensitivity to the alteration of test data than the proposed RF model. Finally, sensitivity analysis was conducted through Sobol algorithm and the parameters with highest contribution were identified.

(Invited) Cerebrospinal Fluid Leakage Detection with Carbon Nanotube-Based Field-Effect Transistors

Cerebrospinal fluid (CSF) leakage is a life-threatening medical condition that could result in significant morbidity and mortality if left untreated. However, the gold-standard test for confirming CSF leakage by detecting beta2-transferrin (β2-Tf) proteins using gel electrophoresis and Western blot is labor intensive and requires 3–6 hours. Carbon nanotube-based field-effect transistors (NTFET) are promising candidates for point-of-care diagnostic devices, owing to the outstanding electronic and mechanical properties of carbon nanotubes. The use of enriched semiconducting (sc) single-walled carbon nanotubes (SWCNT) significantly improves the performance of NTFET devices and enables label-free protein detection. To demonstrate that sensitive and specific detection of β2-Tf in biological fluids can be achieved by using NTFET biosensor platform, we have developed a three-step strategy for β2-Tf detection using NTFET devices. The three-step strategy for β2-Tf detection includes two steps of affinity chromatography to isolate β2-Tf and a rapid β2-Tf sensing step utilizing a high-purity sc-SWCNT FET device. Three different sensing configurations for the sc-SWCNT FET sensor were investigated for obtaining the optimal β2-Tf sensing results. Compared to current methods for CSF leak diagnosis, such as electrophoresis and imaging methods, our three-step strategy can offer high quality CSF leak detection with a short turnaround time (around 1 hour), easy instrument access and simple operations, which could potentially benefit medical treatment of traumatic brain injury (TBI) patients and other people in need. The versatility of our sensing platform could also open opportunities for point-of-care applications for other disease-related protein detection, as we have recently demonstrated by rapid detection of SARS-CoV-2 antigens for COVID-19 testing.

Molecular Dynamics Simulation of Carbon and Boron Nitride nanotubes: Tensile and Compressive Behavior

In this paper, the mechanical properties of Carbon nanotubes (CNTs) and Boron Nitride nanotubes (BNNTs) are studied systematically by using molecular dynamics simulations. CNTs are considered semi-metallic, whereas the BNNTs, of the large band gap, are considered to be insulators, regarding the difference in the electrical properties of CNTs and BNNTs; comparing the mechanical properties of both nanotubes offers great scientific significance for their prospective applications. The simulations were carried out with the help of a Large-scale atomic/molecular massively parallel simulator (LAMMPS) and were based on the Airebo and Tersoffs force fields for C-C interaction in CNTs and B-N interaction in BNNTs, respectively. Failure behavior of armchair and zigzag CNTs and BNNTs under tensile and compressive loading has been predicted and observed that for both the nanotubes the armchair nanotubes showed higher tensile and compressive strength as compared to zigzag nanotubes. The maximum tensile and compressive strength for CNTs is 205 GPa and 35.62 GPa respectively and for BNNTs are 159 GPa and 24.81 GPa respectively. CNTs are identified as axially stronger and stiffer than BNNTs for the same diameter under identical loading conditions.

Influence of defects on the static and dynamic buckling behavior of single-wall carbon nanotubes via molecular dynamics method

Carbon nanotubes (CNTs) exhibit often various defects during the preparation process. Thus, a detailed understanding of the impact of defects on the mechanical properties of CNTs is essential for the design of both CNTs devices and composites. Along these lines, in this work, the effects of two common defects (vacancy and Stone-Wales) on static buckling and dynamic vibration properties of single-walled carbon nanotubes (SWCNTs) are investigated. Firstly, the formation energies of single vacancy defects and Stone-Wales (S-W) defects are studied by molecular dynamics (MD), while the impact of these two defects on the compression performance and natural frequency properties of SWCNTs are explored. Secondly, the axial vibration properties of SWCNTs are studied by using the nonlocal elastic theory and the influence of defects on the dynamic axial displacement of SWCNTs under different aspect ratio is also studied. Moreover, through the change of axial displacement, the change trend of SWCNTs natural frequency with the change of aspect ratio is predicted. The results show that SWCNTs with larger aspect ratios are more prone to defects and its natural frequency will decreases. The study also found that the existence of defects will reduce the buckling properties and vibration characteristics of SWCNTs, and the impact of the S-W defect on the axial mechanical properties of SWCNTs are greater than that of the vacancy defect.

Atomic Scale Investigation on the Structural and Mechanical Properties of Carbon Nanotubes Reinforced Polylactic acid Composites

AbstractMolecular characterization of nanocomposites is of great significance for the design, prediction, and understanding of the structure and properties of nanocomposites. Herein, a molecular dynamics simulation method is employed to investigate the structures, thermodynamical, and mechanical properties of carbon nanotubes (CNTs) reinforced polylactic acid (PLA) composites, as well as the effects and mechanisms of CNTs on the structure and mechanical properties of PLA matrices. The concentration profile result suggests that the type of CNTs has a significant influence on the distribution of PLA molecular chains, with relative concentration profiles around CNTs in the order of PLA/CNTs‐COOH > PLA/CNTs‐OH > PLA/CNTs‐NH2 > PLA/CNTs. Incorporating CNTs into the PLA matrix decreases the FFV and mobility of the polymer, where the trend is PLA > PLA/CNTs > PLA/CNTs‐NH2 > PLA/CNTs‐OH > PLA/CNTs‐COOH. Meanwhile, the tensile properties of the PLA matrix increase with the incorporation of CNTs, and the trend agrees with the results of fractional free volume (FFV) and relative concentration distribution. Finally, the analysis results of interaction illustrate that hydrogen bond interactions between PLA molecular chains and the functional groups on CNTs surface are involved in the adsorption of the polymers on the CNTs surface, thus affecting their interfacial interaction, structure, and properties.

Analyzing the effect of chirality and defects on mechanical properties of carbon nanotube reinforced polycarbonate composites using molecular dynamics

This study is mainly focused on predicting the impact of change in chirality and defects in carbon nanotubes (CNTs) on the mechanical properties of CNT reinforced polycarbonate (PC) composites using molecular dynamics (MD) simulations. The effect of single-walled carbon nanotube (SWCNT) reinforcement with different chirality, [three armchair {(5,5), (6,6), (7,7)}, three zigzag {(9,0), (10,0), (12,0)}, and three chiral {(6,4), (7,5), (8,6)}] in PC has been studied using MD simulation. Also, the effect of vacancy and Stone–Wales (SW) defects in CNTs on the mechanical properties of SWCNT-PC composites has also been predicted. It was concluded that for a constant CNT volume fraction (3%), the longitudinal Young’s modulus of armchair SWCNT-PC composites decreases with an increase in (n, n) value by 35.65%. For zigzag and chiral SWCNT-PC composites, the decrease in Young’s modulus was 53.12% and 36% respectively. Vacancy defected SWCNT-PC composites exhibited greater reduction in Young’s modulus in comparison to the SW defected composites. Chiral SWCNT-PC composites showed the highest reduction in Young’s modulus with an increase in the number of defects.

Mechanical characterization of reinforced vertically-aligned carbon nanotube array synthesized by shock-induced partial phase transition: insight from molecular dynamics simulations

Despite intriguing mechanical properties of carbon nanotubes (CNTs), vertically-aligned carbon nanotube (VACNT) array does not possess a high strength against compression along the CNT axis and also the loadings perpendicular to the CNT axis. Here in this study, shock compression is introduced as a means for partial phase transition (PPT) in the VACNT array to reinforce the structure against the mentioned loadings. Molecular dynamics simulations are exploited to investigate the synthesis of a novel nanostructure from a VACNT array with 10 nm long (5, 5) CNTs. Employing Hugoniostat method, shockwave pressures of 6.6 GPa and 55 GPa are extracted from Hugoniot curves as the instability limit and the PPT point, respectively. Coordination analysis reveals the nucleation of carbon atoms in sp3 hybridization while preserving the dominant nature of CNT due to the high percent of sp2 hybridization. Recovery of the shocked samples yields the final structure to be tested for mechanical characteristics. Tensile and compression tests on the samples reveal that for the shockwave pressures below the PPT point, an increase of the shock strength leads to higher compliance in the VACNT array. However, beyond the PPT point the novel nanostructure shows an extraordinary strong behavior against loading along all directions.

Thermal stress analysis of perforated unsymmetric FG-CNTRC plate using a general analytical solution

In this study, based on the development of the complex variable method, a general solution is presented to calculate thermal stresses in unsymmetric functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates weakened by a hole under uniform heat flux. The extracted equations can also be used for thermal analysis of perforated FGM plates and unsymmetric composites laminates. Due to the fact that size and temperature affect the mechanical properties of carbon nanotubes (CNT), the material properties of the unsymmetric FG-CNTRC plates are approximated based on gradual changes in the direction of thickness and extended rule of the mixture. The present analysis considers the effect of important parameters such as CNT volume fraction, CNT angle, hole aspect ratio, hole orientation, and heat flux angle on the distribution of thermal stresses and moments around elliptical and circular holes. The present comprehensive parametric study shows that the aforementioned variables have a significant effect on the thermal stresses in perforated FG-CNTRC plates. Therefore, by properly selecting their values in the design of such plates, thermal stresses can be significantly reduced.

Nano-interface effect of graphene on carbon nanotube reinforced carbon/carbon composites

In order to further improve the mechanical properties of carbon nanotube (CNT)-reinforced carbon/carbon (C/C) composites, graphene nanosheet (GN), as a nano-interface, is seamlessly grown on CNT with a radial distribution morphology to improve the efficiency of stress transfer between the pyrocarbon (PyC) matrix and CNT. The growth of GN is controlled to ensure that the CNT substrate is not excessively etched and to maintain the strength of CNT and its contribution to the mechanical properties of the composite. After GN grafting, the PyC matrix of the C/C composites is further refined with an improved stress distribution and an efficiently stiffened CNT/PyC interface. Thus, a 72.7% improvement in the interlaminar shearing strength was obtained for CNT-reinforced C/C. Our work provides an alternative approach to fully explore the potential of CNT-based nanocomposites and hierarchical composites.

Mechanical Properties of Carbon Nanotubes (CNTs): A Review

Mechanical Properties of Carbon Nanotubes (CNTs): A Review

Study on dynamic mechanical properties of carbon nanotubes reinforced concrete subjected to freeze–thaw cycles

AbstractAs a nanometer material, carbon nanotubes can inhibit the expansion of microcracks and is of great significance to improve the mechanical properties and durability of concrete. In order to explore the mechanism of dynamic mechanical properties enhancement of carbon nanotube reinforced concrete under impact load after freeze–thaw cycles, the dynamic compression test of carbon nanotube reinforced concrete samples was carried out by using the control variable method with freeze–thaw cycles and impact air pressure as variables. The results showed that under the same impact pressure, the peak stress of carbon nanotube reinforced concrete sample decreased gradually with the increase of freeze–thaw cycles. The corresponding strain increased slightly, and the stress–strain curve moved to the right and down as a whole. Under the same freeze–thaw cycle, the peak stress of carbon nanotube reinforced concrete sample increased with the increase of strain rate, and the dynamic strength growth factor DIF also increased, showing an obvious strain rate strengthening effect. In addition, under the same freeze–thaw cycles and external impact load, the dynamic strength of carbon nanotube concrete is 41.97 and 54.21 MPa, respectively, which is 22.27 and 25.81% higher than that of ordinary plain concrete. The results show that carbon nanotube reinforced concrete samples have higher dynamic mechanical properties and freeze–thaw cycle resistance than ordinary plain concrete samples.

Remarkable improvement of mechanical properties of layered CNTs/Al composites with Cu decorated on CNTs

Interfacial bond and structure as key points significant restrict the mechanical properties of carbon nanotubes (CNTs) reinforced aluminum matrix composites (CNTs/Al composites). In order to further enhance the interfacial bond of CNTs/Al composites, this paper proposed a novel fabrication process of CNTs/Al composites with Cu nanoparticles decorated CNTs, which results in the remarkable improvement of strength and ductility of CNTs/Al composites. The in-depth study results from microstructure of layered CNTs/Al composites show that: Cu nanoparticles can repair CNTs structural defects, and passivate the reaction activity of the defect points, which successfully inhibit producing big Al4C3 phase. On the other hand, Cu nanoparticles as a bridge connecting Al and CNTs, can improve the interface wettability, and produce an “Al-Cu-CNT” interlocking effect. Due to the improvement of the interfacial bond and structure between CNTs and Al matrix, the strengthening and toughening effect of CNTs is effectively exerted in the Al matrix composites. Additionally, this work avoids the traditional mismatch relationship between strength and ductility in CNTs/Al composites.

Improving the mechanical properties of carbon nanotubes reinforced aluminum matrix composites by heterogeneous structural design

A novel aluminum matrix composites with different lengths of CNTs and heterogeneous structural were prepared in this paper. The synergistic effect of reinforcements with different lengths improves the mechanical properties of composites. Meanwhile, the heterogeneous structure design introduced fiber-like reinforcement to enhance the strength and toughness of composite.

Production and characterization of carbon nanotubes by methane decomposition over Ni–Fe/Al2O3 catalyst and its application as nanofillers in polypropylene matrix

This paper studies the influence of metal precursors in the CVD´s catalyst synthesis of carbon nanotubes (CNTs) used as fillers in a polypropylene (PP) matrix (∼0.3 wt%). Two catalytic schemes, Fe/Al2O3 (50:50) and Ni–Fe/Al2O3 (40:10:50), were prepared to determine the influence of the reduction temperature over the characteristics and mechanical properties of CNT as PP fillers. The conversion temperature was varied to see the dependance of the CNT structure to this variable (700 °C–750 °C–800 °C). CNTs products were characterized by SEM and Raman spectroscopy. The SEM micrographs showed a sharper fiber type CNTs for the bimetallic catalyst and the Raman confirmed that better crystallites are obtain over the Fe catalyst. The Fe–PP composite presented enhanced mechanical properties when compare with Fe–Ni–PP, with tensile strength, hardness, and impact properties are higher in 16%, 9%, and 9% respectively. Other carbonaceous materials, as CNF, with less crystallinity presented poorer mechanical properties. Finally, can be stated that for the use of CNF as fillers in PP composites a Fe/Al2O3 catalyst, and a reaction temperature 700 °C–750 °C will produce a CNF with 60 nm mean diameter, is better than the use of Fe-Ni based catalysts.

The Nail Penetration Behaviour of Carbon Nanotube Composite Electrodes for Energy Storage

The high surface area, electrical and mechanical properties of carbon nanotube (CNT) composites has rendered them promising candidates for structural power composites. Nevertheless, it is important to understand their mechanical behaviour before they are applied in energy storage devices amid the safety concerns. This work explores the nail penetration behaviours of supercapacitor specimens consisting of CNT electrodes and pseudocapacitor specimens with carbon nanotube-polyaniline (CNT/PANI) electrodes. Specimens with and without electrolyte were tested. The dry cells without electrolyte follow a power law behaviour, while the wet cells with the electrolyte exhibit a piece-wise nonlinear relationship. The force, voltage and temperature of the supercapacitor were recorded during the nail penetration test. No temperature change or overheating was observed after short-circuit. Moreover, electrochemical testing is performed before and after the specimen penetration. The cyclic voltammetry shows the dramatic loss of capacitance, changing the cell behaviour from capacitor to resistor-like manner. Johnson-Cook model was used to predict the nail penetration behaviour. The coefficients of Johnson-Cook model are calibrated from the experimental load-displacement curves. The finite element model predictions are in a good agreement with the experimental results.

Aggregation of nanoparticles and their effect on mechanical properties of carbon nanotube networks

Nanoparticles (NPs) are widely used to tune the mechanical and physical properties of carbon nanotube (CNT) networks in many practical applications. However, the distribution of NPs in CNT networks and their effects on microstructural evolutions and mechanical properties remain elusive. We employed the coarse-grained molecular dynamics (CGMD) simulations to systematically investigate these issues. First, we found that compared to ambient temperature and the frequency of cyclic loads, the relative cohesion energy of NPs and strain amplitude of cyclic loads are more important factors for controlling the aggregation of NPs; it was also revealed that NPs with larger relative cohesion energy and in larger-strain cyclic loads would aggregate more severely in CNT networks. Second, we observed that the Young's modulus and the tensile strength of the material can be increased by up to ∼3.2 and ∼2.0 times, respectively, at the critical volume fraction of NPs (∼21.6%). Finally, the underlying mechanisms by which NPs strengthen the inter-tube joints and constrain the bundling of CNTs are unveiled. These results should be useful for the optimal design of CNT-based advanced materials.

Effect of Mechanical Properties on Carbon Nanotubes, Nanoclays Reinforced Epoxy Carbon Fabric Composite Pipes

Generally, the nanofillers increase the mechanical and impact behaviors of fiber reinforced polymer based composites. However, the effects of the hybridization of nanofillers and their reasons over the nano scale damage mechanisms have not been adequately studied for fabric reinforced composites. The low velocity impact responses and mechanical properties of carbon nanotubes, nanoclays particles reinforced epoxy carbon fabric composite pipes have been evaluated in this study. Carbon fabric composite pipes have been prepared with 1 ,and 3 wt % of carbon nanotube and 1,and 3 wt% of nanoclay particles and unfilled nanofillers, using hand lay-up technique. Mechanical properties of low velocity impact for carbon nanotubes (MWCNT), nanoclays particles reinforced epoxy carbon fabric composite pipes have been obtained as a function of content of nanofillers particles. The low-velocity impact tests applied on composite pipes for energy levels 5 J,10 J, and 15 J according to in accordance with ASTM D7136 / D7136 M-12 standards. It was observed that carbon nanotubes (MWCNT) and nanoclay nanofillers addition to Carbon Fabric/Epoxy for 5J, 10 J and 15 J showed maximum force, absorbed energy and the lowest displacements and rebound energy. MWCNTs and nanoclays nano-hybrid addition to Carbon Fabric/Epoxy improved higher low velocity impact responses than none nanofillers addition. The specimens of unfilled nanofillers Carbon Fabric/Epoxy composites showed the lowest maximum force , highest displacements and rebound energy. The results show that the mechanical properties are found to increase substantially with increasing carbon nanotube (MWCNT) and nanoclays particles with Carbon Fabric/Epoxy composite pipes.

Temperature and size-dependent modeling for predicting mechanical properties of carbon nanotubes

In this paper, a temperature and size-dependent molecular model is proposed to calculate the mechanical properties of carbon nanotubes. The cross section of carbon nanotubes is regarded as a hexagonal ring structure, and the covalent bond between carbon atoms is regarded as a beam of nonlinear spring structure, that is, the molecular structure system is regarded as a "beam-helical spring" structure. For considering the wall thickness of carbon nanotube, the influence of force constant on the molecular structure model is analyzed. On this basis, according to the principle of molecular mechanics, the expressions of calculating surface Young's modulus, Poisson's ratio, shear modulus and bulk modulus are obtained. It is found that due to the wall thickness, the Young's modulus, shear modulus, and bulk modulus of carbon nanotubes decrease with the increase of radius size.