Carbon Nanotube Reinforced Polymer Composites Research Articles

Inspection of microwave self‐healing efficiency in carbon nanotube reinforced polymer composites for aerospace applications

AbstractThe aerospace industry is evolving very rapidly every day, and due to the low operational and maintenance costs, unmanned aerial vehicles (UAVs) are utilized for many duties, including imaging, patrol, surveillance, and delivery. Flying platforms prioritize effective load‐carrying capacity and light weight. To achieve this, lightweight materials with sufficient strength are utilized, and design optimizations are implemented. This study investigates material development for a UAV propeller, taking into account the possible consequences of a bird strike or hard landing such as micro damage occurrence. In this study, a twin‐screw extruder was used to produce hybrid composites by blending a thermoplastic, polyamide‐6 (PA6) with olefin block copolymers (OBC) and carbon nanotubes (CNT). After manufacturing test specimens by injection molding, tensile and Charpy impact tests were performed. OBC increased the elongation capacity and impact resistance of the PA6 through maleic anhydride (MAH) grafting while reducing the tensile strength. CNT incorporation compensated for this drop, but it rendered the composites more brittle. More importantly, due to the CNT's microwave (MW) absorption capacity, the hybrid composites have gained self‐healing properties. Extended MW exposure time and high MW powers may cause localized burning of the material, resulting in a decrease in its self‐healing efficiency. Following the failure of the examined composites, SEM microscopy revealed various toughening mechanisms in the composites. The use of a modified Halpin‐Tsai model to estimate the elastic characteristics of CNT‐reinforced composites revealed promising results, with minimal discrepancies when compared to experimental data.Highlights CNTs were found efficient for the self‐healing behavior which is critical for improving the lifetime and planning maintenance for UAV propellers. CNT content, MW power & exposure time all impact the self‐healing efficiency. Extended MW exposure time and high MW powers can cause localized burning of the material, resulting in a decrease in its self‐healing efficiency. CNTs created bridge effects, ultimately leading to an enhancement in the strength of the composites. The use of a modified Halpin‐Tsai model yielded good accuracy with experimental data.

Fractal Approach to Dielectric Properties of Single Walled Carbon Nanotubes Reinforced Polymer Composites

In this paper, the internal structure and dielectric properties of unsaturated polyester resin-based neat and single-walled carbon nanotube reinforced composites were comprehensively evaluated with the fractal analysis using the Fast Fourier Transform (FFT). The greyscale images, bitmap (BMP) images and 3D tomographic images were obtained by converting the scanning electron microscope images of the materials. It was observed that the distributions of components in the resin for both materials are irregular and their surfaces exhibit anisotropic behaviors. The surface coating rate (SCR) and fractal dimensionality (FD) of the materials were also calculated using the power spectrum. It has been observed that the fractal dimensionality of the composites can be changed by the doping process and the fractalization of the nanotube doped sample increases compared to the pure material due to nanotube agglomeration, spatial distribution and the orientation. The increase in fractalization as a result of this agglomeration and orientation in carbon nanotubes explains the high dielectric constant values observed at low frequencies by increasing the number and size of carbon nanotubes clusters that act as micro capacitors in certain regions of the matrix. It has been reported that the calculations for the surface coverage ratios for both samples also support these results.

Percolation in Carbon Nanotube-Reinforced Polymers for Strain-Sensing Applications: Computational Investigation on Carbon Nanotube Distribution, Curvature, and Aggregation.

The present article investigates the possibility of simulating the electrical conductivity of carbon nanotube-reinforced polymer composites by numerical methods. Periodic representative volume elements are generated by randomly distributing perfectly conductive reinforcements in an insulating matrix and are used to assemble an electrical network representative of the nanocomposite, where the nanotube-nanotube contacts are considered equivalent resistors modeled by means of Simmons' equation. A comparison of the results with experimental data from the literature supports the conclusion that a random distribution of reinforcements is not suitable for simulating this class of materials since percolation thresholds and conductivity trends are different, with experimental percolation taking place before the expectations. Including nanotube curvature does not solve the issue, since it hinders percolation even further. In agreement with experimental observations, the investigation suggests that a suitable approach requires the inclusion of aggregation during the volume element generation to reduce the volume fraction required to reach percolation. Some solutions available in the literature to generate properly representative volume elements are thus listed. Concerning strain sensing, the results suggest that representative volume elements generated with random distributions overestimate the strain sensitivity of the actual composites.

Interfacial shear strength of carbon nanotube reinforced polymer composites: A review

This study provides a review of the research on the interfacial shear strength (IFSS) of the carbon nanotube (CNT) reinforced polymer composites. The IFSS reflects the efficiency of transferring load between the reinforced fiber and its surrounding matrix, which plays a critical part in determining the characteristics of the composite. The review focuses on the experimental as well as theoretical/modeling studies of the CNT and the polymer matrix interface. The major techniques required for the measurement of the IFSS of the composites have been discussed. The methods to enhance the shear strength at the interface along with the functionalization of CNT and the advantages and disadvantages have been explained in detail. Moreover, the review presents some of the research opportunities associated with IFSS for the growth and enhancement of the mechanical properties of the CNT-reinforced polymer nanocomposites.

Mechanical Performance and Applications of CNTs Reinforced Polymer Composites-A Review.

Developments in the synthesis and scalable manufacturing of carbon nanomaterials like carbon nanotubes (CNTs) have been widely used in the polymer material industry over the last few decades, resulting in a series of fascinating multifunctional composites used in fields ranging from portable electronic devices, entertainment and sports to the military, aerospace, and automotive sectors. CNTs offer good thermal and electrical properties, as well as a low density and a high Young’s modulus, making them suitable nanofillers for polymer composites. As mechanical reinforcements for structural applications CNTs are unique due to their nano-dimensions and size, as well as their incredible strength. Although a large number of studies have been conducted on these novel materials, there have only been a few reviews published on their mechanical performance in polymer composites. As a result, in this review we have covered some of the key application factors as well as the mechanical properties of CNTs-reinforced polymer composites. Finally, the potential uses of CNTs hybridised with polymer composites reinforced with natural fibres such as kenaf fibre, oil palm empty fruit bunch (OPEFB) fibre, bamboo fibre, and sugar palm fibre have been highlighted.

Reliability evaluation based on modal parameters of carbon-nanotube-reinforced-polymer-composite material using multiscale finite element model

Nanocomposite materials exhibit a more extensive range of scatter in material properties than that of conventional materials. The objective of the present work is to develop a computational framework to perform a probabilistic analysis of Carbon-Nanotube-Reinforced-Polymer-Composite (CNRPC) material by using a 3D multiscale finite element model of the Representative Volume Element of the nanocomposite material to determine the dynamic reliability and dynamic hazard based on its modal parameters. The consideration of the frequency sweep of the excitation and the nearness to resonance of the material system is used as a basis for the evaluation of dynamic reliability and dynamic hazard. A computational model consisting of a polymer matrix, an imperfect Single-Walled-Carbon-Nanotube (SWCN) and an imperfect interface region has been constructed for this purpose. The polymer matrix is modeled with the Mooney-Rivlin strain energy, while the imperfect interface region is modeled via van der Waals links. The imperfect SWCN possesses structural vacancies, which are characterized by using the Monte Carlo simulation technique, and is modeled using the Morse potential. The challenge-capacity model and the Maximum Entropy Method are used to calculate the dynamic reliability and dynamic hazard of the CNRPC material for its natural frequencies associated with bending and axial modes.

Investigation on microscale hygrothermal behavior of carbon nanotube‐reinforced polymer composite

AbstractIn this article, a simple and effective formulation of microscale deformation using to simplify the analysis of deformation and stress of carbon nanotube‐reinforced polymer composite (CNTRPC) material structures at the microscale is established. Using a numerical computation and a numerical simulation analysis, the effect of stress and deformation of the carbon nanotubes (CNTs) and polymer matrix on different distribution mode of CNTs, temperature, or moisture is researched. The changing of the inside and outside surfaces' temperature of the material makes the deformation of polymer material unevenly. This work can provide some help to simplify the analysis of hygrothermal deformation and stress of CNTRPC material at both microscale and macroscale.

A brief review on the mechanical properties of Carbon nanotube reinforced polymer composites

Abstract Carbon nanotubes (CNTs) have been in use for a long time for preparation of polymer composites due their excellent mechanical, thermal, electrical, physical properties etc. Many industries including automobile, aerospace, sports and marine industries have been using CNTs as a multi-functional material for improving the overall properties of their prepared composites with a small amount of loading value. In this review, we list the mechanical properties of nanotube reinforced polymer composites with processes used in order to find the ideal approach to the recently used methods for exploiting maximum properties of CNTs

Noncovalent engineering of carbon nanotube surface by imidazolium ionic liquids: A promising strategy for enhancing thermal conductivity of epoxy composites

Carbon nanotubes reinforced polymer composites with high thermal conductivity show attractive prospects as multifunctional thermal management materials for high-power electronics applications. The contradictory relationship between homogenous filler dispersion with enhanced interfacial interaction and the intrinsic properties of embedded filler, usually leads to the uncertainty and low thermal conductivity improvement efficiency of resulting polymer composites. Herein, noncovalently functionalized multi-walled carbon nanotubes with imidazolium amine-terminated ionic liquids (AIL-MWCNTs) were facilely prepared through cation-π stacking interactions and acted as low-defect fillers for improving the thermal conductivity of epoxy. The mild chemical modification process has considerable advantages for reserving the inherent intact structures of MWCNTs. Hence, the thermal conductivity enhancement of EP/AIL-MWCNTs composite (∼211%) is much higher than that of epoxy composite filled with acidified MWCNTs (∼102%) at 8 wt% loading. The noncovalent functionalization approach is a promising strategy for scalable fabrication of MWCNTs-based polymer composite with simultaneously enhanced thermal conductivity and mechanical properties.

Prediction of interface stiffness of single-walled carbon nanotube-reinforced polymer composites by shear-lag model

Interfacial stress transfer of single-walled carbon nanotube-reinforced polymer composites subjected to uniaxial tension was investigated by a newly developed shear-lag model integrated with a spring layer model. A linear relationship between the tangential relative displacement and the interfacial shear stress was assumed for the interface which is determined by van der Waals forces. The interface stiffness parameter was determined through comparing the stress distribution of the shear-lag model with multiscale simulation results. The effect of the interface stiffness and the nanotube’s aspect ratios on the distribution of stress in CNT-reinforced composites was studied.

Dual-phase-lag heat conduction in FG carbon nanotube reinforced polymer composites

The numerical simulation of non-Fourier, dual-phase-lag (DPL) heat conduction in carbon nanotube (CNT) reinforced composites has been performed by developing the differential quadrature method (DQM) application. Although using the non-Fourier heat conduction has become popular, most of the simulations are conducted over simple geometries due to numerical restrictions. DQM copes with this problem easily even with complicated boundary conditions. The proposed method discretizes the time domain in the form of blocks. Each block contains several time levels, and each block needs to solve separately by using the output of one block as an initial condition of the next block. The effect of volume fraction of CNT on the temperature and heat flux profile is investigated, and all parameters are considered temperature dependent. To show the influence of time lag parameters, the Fourier, hyperbolic heat conduction and DPL heat conduction models were compared. Furthermore, various types of dynamic thermal loading have been examined to obtain the transient temperature distributions. We show the presence of heat wave in DPL heat conduction by considering the time lag parameter in the microstructural interactions of fast transient heat conduction. It is found that considering the mechanical properties of the CNTs dependent to the temperature is crucial to obtain accurate results.

A modulus gradient model for an axially loaded inhomogeneous elastic rod

A new gradient elasticity formulation is proposed for a one-dimensional linear elastic inhomogeneous rod. In the new formulation, similar to the differential relation between the local strain and the gradient enhanced strain in the classical models of gradient elasticity, a differential relation is proposed for the Young’s modulus. Analytical and finite element solutions of the proposed formulation are derived. Results of the proposed model are compared with a classical model of gradient elasticity for a model problem of carbon nanotube reinforced polymer composite.

A molecular dynamics study on Young's modulus and tribology of carbon nanotube reinforced styrene-butadiene rubber.

Styrene-butadiene rubber is a copolymer widely used in making car tires and has excellent abrasion resistance. The Young's modulus and tribology of pure styrene butadiene rubber (SBR) polymer and carbon nanotube reinforced polymer composites have been investigated using molecular dynamics simulations. The mechanism of enhanced tribology properties using carbon nanotube has been studied and discussed. The obtained Young's modulus shows the enhancement in mechanical properties of SBR polymer when carbon nanotubes are used as reinforcement. The concentration, temperature and velocity profiles, radial distribution function, frictional stresses, and cohesive energy density are calculated and analyzed in detail. The Young's modulus of SBR matrix increases about 29.16% in the presence of the 5% CNT. The atom movement velocity and average cohesive energy density in the friction area of pure SBR matrix was found to be more than that of the CNT/SBR composite. Graphical abstract Initial and final conditions of (a) pure SBR matrix and (b) CNT/SBR matrix subjected toshear loading and frictional stresses of top Fe layers of both pure SBR and CNT/SBR composite.

Carbon nanotube-reinforced smart composites for sensing freezing temperature and deicing by self-heating

Carbon nanotube-reinforced polymer composites were fabricated by high shear mixing. The microstructure and the electrical properties of the carbon nanotube–polymer composites were investigated by scanning electron microscopy and electrical resistance measurement. We found that the carbon nanotube composites showed high electrical conductivity (1.5 S m−1) at 7.0 wt% of carbon nanotubes, and the increase in thickness enhanced the electrical conductivity of the composites. The multifunctional properties of the carbon nanotube composites were also investigated for use in sensing the freezing temperature and also in deicing by self-heating. The results showed that the carbon nanotube–polymer composites had high temperature sensitivity in the freezing temperature range from −5 to 5 C and an excellent heating performance due to the Joule heating effect. The carbon nanotube composites are promising to be used as smart coating materials for deicing by self-heating as well as by detection of the freezing temperature.

Engineered carbon nanotubes reinforced polymer composites for enhanced thermoelectric performance

Thermoelectric materials have attracted great attention from researchers because of their unique ability to convert thermal energy to electrical energy and vice versa. Based on the coupled theory of transport between heat and electricity in metals, we have carried out finite element simulations on carbon nanotube (CNT)/polyaniline (PANI) composites to compute effective Seebeck coefficients and figures of merit (FOMs). The present study focuses on the effect of interfacial electrical and thermal conductivities, the volume fraction of CNTs and their inclination on the effective electrical and thermal conductivities and thermoelectric performance. It is interesting to report that effective conductivities strongly depend on interfacial conductance in composites where CNTs are transverse to electrical current and heat flow. Interfaces with electrical and thermal conductance less than 103 S m−2 and 107 W m−2 K−1 respectively isolate CNTs from the matrix. This reduces the effective properties, while the conductivities increase with the CNT content if interfacial conductance is more than these specified values. It was also established that the effective Seebeck coefficient and FOM increase with interfacial electrical conductance, while decreasing with an increase in interfacial thermal conductance. Additionally, the effect of inclination on the electrical and thermal conductivities of composites, the effective Seebeck coefficient and the FOM were analysed. It can be concluded from the study that the Seebeck coefficient and FOM of thermoelectric composites are increased if the CNTs are lying perpendicular to the heat and electrical current flow.

Deflection and Buckling behaviour of simply supported nanocomposite beams under FSDT approach

Due to their high strength-to-weight ratio, carbon nanotube (CNT) reinforced polymer composites are being considered as one of the most promising nanocomposites which can improve the performance when used in structural applications. The deflection and buckling behavior are the most important parameters needs to be considered in the design of structural members like beams, plates and shells. In the present paper the elastic constants of CNT reinforced polymer composites has been evaluated by using Mori-Tanaka micromechanics approach. Knowing the elastic properties of CNT reinforced polymer composites, an analytical study is being conducted to investigate the deflection and buckling behaviour of nanocomposites beams for different CNT volume fractions at different boundary conditions using first order shear deformation theory. The effect of stacking sequence and CNT radius on the deflection and buckling of beam is also been presented. This study is being conducted primarily with an intension to examine the stiffening effect of CNTs when used in polymer composites as reinforcement.

Mechanical characterization of carbon nanotubes based polymer composites using indentation tests

Abstract In this paper, instrumented indentation testing was used to determine the elastic mechanical properties of multiwall carbon nanotubes (CNTs) reinforced polymer composites. A finite element analysis model for simulating micro-indentation test was developed using ABAQUS software and confronted to experimental tests. It seems that CNTs reinforced polymer composites shows an improved of mechanical properties. The microstructure of indentation mark has been evaluated using scanning electronic microscopes and compared with the microstructure of numerical models. It results that adding small amount of CNTs improves the fracture interfacial rigidity and can stop micro-cracks evolution.

Elastic behavior of CNT-reinforced polymer composites with discontinuities in CNT configurations

A numerical study has been made towards the effective elastic properties estimation of carbon nanotubes and carbon nanotube reinforced composite using finite element modelling (FEM). First, the elastic properties of Carbon nanotube (CNT) were predicted by considering that carbon atoms as nodes and carbon-carbon bonds as beam elements with linear and isotropic behaviour. It was observed that elastic properties of CNT predicted by FE analysis were in good agreement with previous data. Carbon atom vacancy defects were also included to investigate the adverse effect on elastic modulus of SWCNTs. To explore the macroscopic elastic behaviour of CNT in a finite densely packed polymer resin, a representative volume element (RVE) was selected instead of whole composite material in which the polymer resin was modelled as continuum material while CNT as an equivalent long fibre. FE results of RVE manifest that the CNT volume fraction and waviness have significant effect on elastic modulus of CNT reinforced polymer composite. An analytical formulation in terms of elastic properties and waviness ratio was also introduced in this study for waviness analysis. Moreover, the elastic properties of wavy CNT reinforced composite was compared with analytical outcomes. We extended present RVE model to incorporate the effects of CNTs agglomeration on the elastic behaviour of CNT-reinforced polymer composites. It was observed that anticipated elastic results not only depended on the volume fraction of CNTs, but also on the CNTs geometry, waviness and agglomeration.

Stress transfer properties of carbon nanotube reinforced polymer composites at low temperature environments

Stress transfer properties of carbon nanotube reinforced polymer composites at low temperature environments

New processing method to fabricate high-performance carbon-nanotube/polyvinyl alcohol composite films

Bad dispersion, low volume fraction, and poor alignment of long carbon nanotubes (CNTs) in a polymer matrix are the main reasons for the disappointing performance of CNT reinforced polymer composites. Here, we report a novel technique for the preparation of high performance CNT/Polyvinyl alcohol (PVA) composite films, involving continuous production of a hollow cylindrical CNT assembly from a tubular reactor and its in-situ deposition on a paper substrate wrapped on a winding drum under the spray of a PVA solution. The distribution, alignment and loading of CNTs in the composite film are easily tailored by changing the winding rate and the PVA concentration in the spray solution. It is found that the properties of the prepared film are strongly dependent upon the CNT loading in the film. At the optimal high CNT loading of 56.8 wt%, the tensile strength has reached 3.16 GPa, and electrical conductivity 1322 S cm−1. This combination of mechanical and electrical properties is superior to any other CNT/polymer composites developed to date. In terms of its versatility and simplicity, the reported process paves a new way for continuous production of high-performance CNT reinforced composites.