Weight Fraction Of Carbon Nanotubes Research Articles

Using ultra-thin interlaminar carbon nanotube sheets to enhance the mechanical and electrical properties of carbon fiber reinforced polymer composites

A major shortcoming of carbon fiber reinforced polymer composites (CFRP) is their interlaminar performance. This study provides an inexpensive and readily scalable solution to this problem by incorporating ultra-thin sheets of carbon nanotubes (CNT) between the plies (laminates) of CFRPs. To this end, dry carbon fiber fabrics are first sandwiched between CNT sheets. The fabrics are then stacked and infused with epoxy to form a CFRP with interlaminar CNT sheets. Contrary to the typical approach where microns-long CNTs are distributed randomly within a CFRP for reinforcement, this study uses ~100 nm thick CNT sheets consisting of aligned and ultra-long (0.3 mm) nanotubes. Despite their negligible weight fraction of only 0.016%, the interlaminar CNT sheets enhanced the CFRP's flexural strength by 49%, interlaminar shear strength by 30%, and mode I fracture toughness by 30%. X-ray micro-tomography revealed that samples with interlaminar CNTs are significantly resistant to delamination and crack propagation. Moreover, the in-plane electrical conductivity of these composites increased commensurate with the weight fraction of CNTs, providing a maximum enhancement of 278% over the reference sample for 0.048 wt% of CNT sheets. This study reveals that for almost no change in weight and thickness, interlaminar CNT sheets can enhance the electrical conductivity and interlaminar performance of CFRPs.

Molecular dynamics predictions of thermo-mechanical properties of carbon nanotube/polymeric composites

In this study, the mechanical and thermal properties of carbon nanotube-reinforced polymeric nano-composite have been predicted by simulating molecular dynamics (MD). The polymer matrix is of epoxy polymer type with EPON828 resin along with EpiCure Curing Agent-3234 hardener which is reinforced with a single-walled carbon nanotube (SWCNT). Mechanical and thermal properties such as density, elastic modulus, Poisson’s ratio, and coefficient of thermal expansion (CTE) for various states, including the cross-linking degree of resin and hardener molecules 10–65%, carbon nanotubes (CNTs) with different diameters, and weight fraction of carbon nanotubes of 0.5, 1 and 2% have been estimated. The cell’s stiffness matrix in all cases was extracted, and thermo-mechanical properties were obtained using it. The placement of carbon nanotubes in a representative cell is completely random which has a random orientation, and the cell is dynamically analyzed separately under constant temperature and constant pressure conditions at the specified time, and after equilibration, its properties are extracted. The results show an obvious increase in the elastic modulus by increasing cross-linking degrees and an increase in the elastic modulus, and a significant decrease in the nano-composite CTE when the weight fraction of CNTs has increased. The experimental studies and simulation of other researchers were examined to validate the simulation that, the results are in good agreement with each other.

Study on Plastic Strengthening Mechanisms of Aluminum Matrix Nano-Composites Reinforced by Nickel Coated CNTs

ABSTRACT The mechanical strength of pure aluminum matrix can be greatly enhanced by adding a small amount of nickel-coated carbon nanotubes (NiCNTs), where the nickel coating helps to the uniform dispersion of carbon nanotubes (CNTs) within the aluminum matrix through decreasing density difference and avoiding CNTs agglomeration. The yield strength of pure aluminum can be increased by 33.3% with 1% weight fraction of NiCNTs. This strengthening effect is caused by three mechanisms: Orowan looping, load bearing, and thermal expansion mismatch which are studied by both finite-element method and analytical method. A series of finite-element analyses using a representative volume element (RVE) method are conducted considering influences of CNTs aspect ratios, volume fraction of hardened zone, and the hardened plastic strain of hardened zone. The results show that the aspect ratio of CNTs is very important in the strengthening of CNT-reinforced composites, and the yield stress increases with increasing aspect ratio. A set of parameters for analytical solutions are optimized that can well describe and accurately predict the experimental data. Both the finite-element analysis and analytical solution are well correlated with the experimental results for Al/NiCNT composites with different weight fractions of CNTs.

Experimental and Numerical Study on Free Vibration of Multiwall Carbon Nanotube Reinforced Composite Plates

The effects of different percentages of multiwall carbon nanotube (MWCNT) on natural frequencies of polymer composite plates of varying edge-to-thickness ratio, aspect ratio and boundary conditions at ambient temperature are investigated experimentally and numerically. Conventional hand lay-up technique is used to prepare the MWCNT polymer composite plates with different percentages of carbon nanotubes (CNTs) mixed to the polymer. The elastic properties are determined experimentally by conducting uniaxial tensile test in the universal testing machine INSTRON 8862 as per ASTM D-3039. A set of experiments were conducted for the natural frequencies of vibration of MWCNT composite plates using the Bruel and Kjaer Fast Fourier Transform (FFT) analyzer with pulse platform. Detailed parametric studies are carried out to determine the effect of weight fraction of CNTs, aspect ratios, edge-to-thickness ratios and boundary conditions on the natural frequency of composite plates. Numerical solutions were obtained by the commercial finite element method (FEM) package ABAQUS. A simulation model is developed using the same geometrical and material properties determined experimentally from which the frequency responses are obtained. The simulation results are found to be consistent with the experimental ones. The results obtained showed an increase in elastic properties and natural frequencies up to 0.3 wt.% of MWCNT and decrease thereafter for all cases due to agglomeration of CNT in the polymer matrix. The morphology and dispersion of the CNTs in composites at micro level are investigated by using scanning electron microscopy (SEM) to further corroborate the behavior of specimens.

Static bending analysis of functionally graded polymer composite curved beams reinforced with carbon nanotubes

This article deals with the static bending response of a functionally graded polymer composite (FG-PC) curved beam reinforced with carbon nanotubes (CNTs) subjected to sinusoidal and uniform loads. The effective material properties of beam are approximated according to modified rule of mixture. Four types of CNT distribution are also considered. Assuming Timoshenko beam theory and a higher-order strain gradient theory, size-dependent equilibrium equations are extracted. Using Navier solution procedure, nonlocal strain gradient governing equations are solved for simply-supported edges. Ultimately, numerical results are expanded to show the influence of weight fraction and distribution patterns of CNTs, small scale parameters, and opening angle on the static bending response of CNTs reinforced nanocomposite curved beam.

Prediction of tensile strength of polymer carbon nanotube composites using practical machine learning method

This paper is devoted to the development and construction of a practical Machine Learning (ML)-based model for the prediction of tensile strength of polymer carbon nanotube (CNTs) composites. To this end, a database was compiled from the available literature, composed of 11 input variables. The input variables for predicting tensile strength of nanocomposites were selected for the following main reasons: (i) type of polymer matrix, (ii) mechanical properties of polymer matrix, (iii) physical characteristics of CNTs, (iv) mechanical properties of CNTs and (v) incorporation parameters such as CNT weight fraction, CNT surface modification method and processing method. As the problem of prediction is highly dimensional (with 11 dimensions), the Gaussian Process Regression (GPR) model was selected and optimized by means of a parametric study. The correlation coefficient (R), Willmott’s index of agreement (IA), slope of regression, Mean Absolute Percentage Error (MAPE), Root Mean Squared Error (RMSE) and Mean Absolute Error (MAE) were employed as error measurement criteria when training the GPR model. The GPR model exhibited good performance for both training and testing parts (RMSE = 5.982 and 5.327 MPa, MAE = 3.447 and 3.539 MPa, respectively). In addition, uncertainty analysis was also applied to estimate the prediction confidence intervals. Finally, the prediction capability of the GPR model with different ranges of values of input variables was investigated and discussed. For practical application, a Graphical User Interface (GUI) was developed in Matlab for predicting the tensile strength of nanocomposites.

Homogeneity Permitted Robust Connection for Additive Manufacturing Stretchable Electronics.

Interface is the Achilles' heel in flexible electronics, where slipping, delamination, or cracking resulting from the intrinsic mechanical property mismatch of different materials might fail the device or cause degradation. Robust connections with strong interfacial strength and low interfacial impedance are highly desired in all kinds of flexible devices, especially when they require stretchability. Here, a new strategy of employing homogeneity is proposed to facilely achieve robust connection without introducing a third-party interlayer. The key to this strategy is implementing different functions in the same component materials, and in this work, this strategy is demonstrated by exploring the uniformity of carbon nanotube (CNT) in thermoplastic polyurethane (TPU) elastomer. Tuning the uniformity of CNT in TPU elastomer, two kinds of CNT-TPU composites (CTCs) are fabricated. They present contrasting properties of conductivity (281 folds), Young's modulus (7.1 folds), and strain sensitivity (15.7 folds) with the same weight fraction of CNT (15 wt %), and thus they can respectively act as strain sensor and interconnector in all-CNT-based stretchable strain monitoring electronics. The interlocking effect caused by spontaneous entanglement of surface polymer chains and the reconstruction of percolation network at the interface during drying confer the connection with robustness. The practical value of this strategy has been exemplified by the fabrication of a robust epidermis device via additive manufacturing. This epidermis device is patterned in a fractal motif for conformal contact and can sensitively monitor body motions and radial artery pulse.

Hygro-thermal buckling analysis of polymer–CNT–fiber-laminated nanocomposite disk under uniform lateral pressure with the aid of GDQM

In this research, we study the thermal buckling performance of multi-scale hybrid laminated nanocomposite (MHLC) disk (MHLCD) subjected hygro-mechanical loading. The matrix material is reinforced with carbon nanotubes (CNTs) or carbon fibers (CF) at the nano- or macro-scale, respectively. The disk is modeled based on higher order shear deformation theory. We present a modified Halpin–Tsai model to predict the effective properties of the MHLCD. The minimum total potential energy principle is employed to establish the governing equations of the system, which is finally solved by the generalized differential quadrature method. To validate the approach, numerical results are compared with available results from the literature. Subsequently, a comprehensive parameter study is carried out to quantify the influence of different parameters such as stiffness of the substrate, patterns of temperature increase, moisture coefficient, stacking sequence of the CFs, weight fraction and distribution patterns of CNTs, outer radius to inner radius ratio and inner radius to thickness ratio on the response of the plate. Some new results related to critical buckling of an MHLCD are also presented, which can serve as benchmark solutions for future investigations.

Experimental and theoretical studies of free vibration of a sandwich functionally graded nanocomposite beam under thermal condition

The free vibration analysis of a sandwich three-layer functionally graded beam is studied experimentally and theoretically based on Timoshenko beam theory. The beam consists of a pure epoxy in the mid-plane and two inhomogeneous multi walled carbon nanotube (MWCNT)/epoxy nanocomposite on the upper and lower layers. The effect of weight fraction of MWCNT on the first natural frequency are obtained theoretically and experimentally and then compared with each other in this study. The effect of distribution of MWCNT is studied through a semi-analytical approach. A detailed parametric study is conducted on functionally graded MWCNT/epoxy beams. The effects of geometrical parameters, boundary conditions, slenderness ratio and temperature change are also studied. The differential quadrature method is employed as a numerical method to solve the equations of motion. The main contribution of this work is to present comparable experimental and theoretical results for sandwich functionally graded beams. Comparison of the results revealed that the obtained non-dimensional frequencies from theoretical approach are in good agreement with experimental results, especially for lower weight fractions of carbon nanotubes.

Nonlinear vibrations of variable thickness curved panels made of multi-scale epoxy/fiberglass/CNT material using Jacobi elliptic functions

This article deals with nonlinear vibration study of variable thickness cylindrical panels made of multi-scale composite materials containing epoxy matrix, glass fibers, and carbon nanotubes (CNTs). The elastic properties of multi-scale material have been defined in the context of 3D Mori-Tanaka scheme considering unidirectional aligned macro-fibers and randomly oriented CNTs. It is considered that the panel thickness is varying in axial direction and may have linear and parabolic changes. The governing equations of variable thickness curved panel have been stablished using thin shell theory containing geometric nonlinearity. Then, Jacobi elliptic functions are proposed for solving the governing equations since they leads to exact frequency-amplitude curves of the curved panels. It is reported that frequency-amplitude curves are varying with the changes of CNT weight fraction, fiber orientation, fiber volume, variable thickness parameters, panel curvature radius, and length-to-radius ratio of CNTs.

Free and forced vibration analysis of a sandwich beam considering porous core and SMA hybrid composite face layers on Vlasov’s foundation

This paper aims to investigate the free and forced vibration behavior of a sandwich beam with functionally graded porous core and composite face layers embedded with shape memory alloy (SMA). Three different porosity patterns are assumed through the thickness direction of the core, and composite face layers are reinforced with carbon nanotubes (CNT). The sandwich beam is resting on an elastic foundation which is simulated by Vlasov’s model. By using Hamilton’s principle and first-order shear deformation theory, the governing equations of motion are derived. The analytical solution is presented to solve the equations of motion using Navier’s solution. Results are verified with corresponding literatures. Finally, the effects of important parameters such as temperature, volume fraction of SMA, porosity distribution, weight fraction of CNT, and geometric parameters are explored in detail.

Analysis of nonlinear vibrations of CNT- /fiberglass-reinforced multi-scale truncated conical shell segments

The truncated conical shell segments made from multi-scale epoxy/carbon nanotube/fiberglass material are studied in this research in the view of evaluating nonlinear free vibration behavior. Incorporating random dispersion of carbon nanotubes (CNTs) and parallel alignment of glass fibers, a three-dimensional (3D) Mori–Tanaka micro-mechanic method has been utilized for defining the hybrid material properties. For defining the configuration of truncated conical shell segments, a semi-vertex angle and also an open angle are used in the thin shell formulation. With the usage of Jacobi elliptic functions, exact values of nonlinear vibration frequencies have been derived which are more accurate compared to familiar approximate solutions. A specific attention is drawn to the impacts of fiber volume, fiber directions, semi-vertex angle, CNT weight fraction, and CNT aspect ratio on nonlinear free vibrations of multi-scale truncated conical shell segments. Communicated by Jie Yang

Dynamic and buckling analysis of polymer hybrid composite beam with variable thickness

This work deals with a study of the dynamic and buckling analysis of polymer hybrid composite (PHC) beam. The beam has variable thickness and is reinforced by carbon nanotubes (CNTs) and nanoclay (NC) simultaneously. The governing equations are derived based on the first shear deformation theory (FSDT). A three-phase Halpin-Tsai approach is used to predict the mechanical properties of the PHC. We focus our attention on the effect of the simultaneous addition of NC and CNT on the vibration and buckling analysis of the PHC beam with variable thickness. Also a comparison study is done on the sensation of three impressive parameters including CNT, NC weight fractions, and the shape factor of fillers on the mechanical properties of PHC beams, as well as fundamental frequencies of free vibrations and critical buckling load. The results show that the increase of shape factor value, NC, and CNT weight fractions leads to considerable reinforcement in mechanical properties as well as increase of the dimensionless fundamental frequency and buckling load. The variation of CNT weight fraction on elastic modulus is more sensitive rather than shear modulus but the effect of NC weight fraction on elastic and shear moduli is fairly the same. The shape factor values more than the medium level do not affect the mechanical properties.

Frequency Characteristics of Multiscale Hybrid Nanocomposite Annular Plate Based on a Halpin–Tsai Homogenization Model with the Aid of GDQM

In this article, we study the vibration performance of multiscale hybrid nanocomposite (MHC) annular plates (MHCAP) resting on Winkler–Pasternak substrates exposed to nonlinear temperature gradients. The matrix material is reinforced with carbon nanotubes (CNTs) or carbon fibers (CF) at the nano- or macroscale, respectively. The annular plate is modeled based on higher-order shear deformation theory (HSDT). We present a modified Halpin–Tsai model to predict the effective properties of the MHCAP. Hamilton’s principle was employed to establish the governing equations of motion, which is finally solved by the generalized differential quadrature method (GDQM). In order to validate the approach, numerical results were compared with available results from the literature. Subsequently, a comprehensive parameter study was carried out to quantify the influence of different parameters such as stiffness of the substrate, patterns of temperature increase, outer temperature, volume fraction and orientation angle of the CFs, weight fraction and distribution patterns of CNTs, outer radius to inner radius ratio, and inner radius to thickness ratio on the response of the plate. The results show that applying a sinusoidal temperature rise and locating more CNTs in the vicinity of the bottom surface yielded the highest natural frequency.

Enhancing flutter stability in nanocomposite thin panels by harnessing CNT/polymer dissipation

Numerical and analytical investigations into the aeroelastic response of thin nanocomposite panels are discussed. The mechanical data of the nanocomposite plates with different weight fractions of randomly oriented carbon nanotubes (CNT) are obtained via an extensive experimental campaign based on dynamic mechanical analysis (DMA). Panel flutter induced by high supersonic flows is studied through both linear and nonlinear dynamic analyses aimed to investigate the effect of the CNT weight fraction onto the flutter and post-flutter condition. To this end, multiple scales perturbation analysis is carried out to characterize the flutter boundaries and the type of Hopf bifurcation at flutter. It is shown that a few percent CNT weight fraction, while entailing negligible weight penalty, can considerably increase the flutter speed as well as reduce the limit cycle oscillations amplitude.

Experimental characterization of the quasi-static and dynamic piezoresistive behavior of multi-walled carbon nanotubes/elastomer composites

Multi-walled carbon nanotube (MWCNT)/elastomer composites exhibit a piezoresistive behavior, i.e. their resistivity changes when they are subjected to mechanical loading. Thus, these materials can be used as strain or pressure sensors. In this paper, the effect of carbon nanotube weight fraction on the sensitivity and repeatability of the electrical response of multi-walled carbon nanotube/ethylene–propylene–diene monomer composites is investigated, under quasi-static and dynamic compression (using split Hopkinson pressure bars). It was found that multi-walled carbon nanotube weight fraction and the strain rate have a major influence on the piezoresistivity of such composites. Although all samples exhibited a good repeatability of their electrical response under quasi-static cyclic compression, those with a lower multi-walled carbon nanotube weight fraction had a higher sensitivity to strain. An increase in the electrical resistance during compression was observed under both quasi-static and dynamic compression. Reversible movements of multi-walled carbon nanotube in the transverse direction of compression increased the average inter-multi-walled carbon nanotube distance under quasi-static compression, leading to higher values of resistance. After the dynamic tests, the Young’s modulus of the composites decreased by about 45% and the electrical resistance increased a hundredfold, indicating damage induced by dynamic loading.

Energy dissipation characteristics of additively manufactured CNT/ABS nanocomposites

PurposeThis study aims to discuss the effect of carbon nanotubes (CNTs) on the mechanical properties of acrylonitrile–butadiene–styrene (ABS) composites fabricated by additive manufacturing (AM). Insight into the energy-dissipation mechanisms introduced and/or enhanced by the addition of CNTs is presented in this study.Design/methodology/approachABS/CNT filaments were fabricated with different concentrations of CNTs. Using a fused deposition modeling approach, unidirectional specimens were printed using a MakerBot Replicator 2X (MakerBot Industries, Brooklyn, NY, USA). Specimens were tested under static and dynamic conditions, with the loading coinciding with the printing direction, to determine elastic modulus, strength and viscoelastic properties.FindingsA CNT reinforcing effect is evident in a 37 per cent increase in elastic modulus. Likewise, the strength of the composite increases by up to 30 per cent with an increase in weight fraction of CNTs. At low dynamic strain amplitudes (0.05 per cent), a correlation between dissipated strain energy of the butadiene phase and strength of the composite is found such that less dissipation, from constraint of the butadiene particles by the CNTs, leads to higher strength of the composite. At higher dynamic strains, the presence of a high concentration of CNT leads to increased energy dissipation, with a maximum measured value of 24 per cent higher loss factor compared to baseline specimens. Because the trend of the composite behavior is similar (with a higher absolute value) to that of neat ABS, this study’s results indicate that well-established polymer/CNT dissipation mechanisms (such as stick-slip) are not significant, but that the CNTs amplify the dissipation of the ABS matrix by formation of crazes through stress concentrations.Originality/valueThis study provides knowledge of the dissipation behavior in additively manufactured ABS/CNT composites and provides insight into the expansion to new printable materials for dynamics applications.

Effects of carbon nanotube weight fraction on the fracture toughness of spark plasma sintered nickel aluminide-NiAl3

Nickel aluminides have captured the attention of researchers for a few years now owing to their lightweight and high strength. They possess a huge potential for high temperature applications primarily due to their structural integrity at elevated temperatures. However the major limiting factor of these promising intermetallics is their room temperature fracture toughness, which is too low to satisfy service requirements. Although there are majorly three groups of nickel aluminides NiAl, Ni3Al and NiAl3, only the NiAl and Ni3Al groups have been intensely researched while documented literature on NiAl3 is rare, despite being the lightest intermetallic in the group. In this work, carbon nanotubes were incorporated into NiAl3 and consolidated using the spark plasma sintering (SPS) technique. The effect of carbon nanotube (CNTs) reinforcement on the fracture toughness of NiAl3 was studied. It was observed that the addition of the carbon nanotubes improved the fracture toughness of the reinforced composites over the un-reinforced sample initially, but the fracture toughness reduced with increase in carbon nanotube weight fraction.

Quantification of carbon nanotube dispersion and its correlation with mechanical and thermal properties of epoxy nanocomposites

ABSTRACTAn experimental study is carried out to quantitatively assess the dispersion quality of carbon nanotubes (CNTs) in epoxy matrix as a function of CNT variant and weight fraction. To this end, two weight fractions (0.05% and 0.25%) of as‐grown, oxidized, and functionalized CNTs are used to process CNT/epoxy nanocomposites. Scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared analysis of different variants of CNTs are used to establish the efficiency of purification route. While the relative change in mechanical properties is investigated through tensile and micro‐hardness testing, thermal conductivity of different nanocomposites is measured to characterize the effect of CNT addition on the average thermal properties of epoxy. Later on, a quantitative analysis is carried out to establish the relationship between the observed improvements in average composite properties with the dispersion quality of CNTs in epoxy. It is shown that carboxylic (‐COOH) functionalization reduces the average CNT agglomerate size and thus ensures better dispersion of CNTs in epoxy even at higher CNT weight fraction. The improved dispersion leads to enhanced interfacial interaction at the CNT/epoxy interface and hence provides higher relative improvement in nanocomposite properties compared to the samples prepared using as‐grown and oxidized CNTs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48879.

Effective reinforcements for thermoplastics based on carbon nanotubes of oil fly ash

Carbon nanotubes (CNTs) are widely investigated for preparing polymer nanocomposites, owing to their unique mechanical properties. However, dispersing CNTs uniformly in a polymer matrix and controlling their entanglement/agglomeration are still big technical challenges to be overcome. The costs of their raw materials and production are also still high. In this work, we propose the use of CNTs grown on oil fly ash to solve these issues. The CNTs of oil fly ash were evaluated as reinforcing materials for some common thermoplastics. High-density polyethylene (HDPE) was mainly reinforced with various weight fractions of CNTs. Xylene was used as a solvent to dissolve HDPE and to uniformly disperse the CNTs. Significantly enhanced mechanical properties of HDPE reinforced at a low weight fraction of these CNTs (1–2 wt.%), mainly the tensile strength, Young’s modulus, stiffness, and hardness, were observed. The tensile strength and Young’s modulus were enhanced by ~20 and 38%, respectively. Moreover, the nanoindentation results were found to be in support to these findings. Polycarbonate, polypropylene, and polystyrene were also preliminarily evaluated after reinforcement with 1 wt.% CNTs. The tensile strength and Young’s Modulus were increased after reinforcement with CNTs. These results demonstrate that the CNTs of the solid waste, oil fly ash, might serve as an appropriate reinforcing material for different thermoplastics polymers.