Carbon Nanotube Reinforced Research Articles

Analysis of Progressive Tensile Damage of Multi-walled Carbon Nanotube Reinforced Carbon Fiber Composites by Using Acoustic Emission and Micro-CT

Analysis of Progressive Tensile Damage of Multi-walled Carbon Nanotube Reinforced Carbon Fiber Composites by Using Acoustic Emission and Micro-CT

Thermotropic liquid crystalline polymer reinforced polypropylene composites enhanced with carbon nanotubes for use in fused filament fabrication

AbstractThe objective of this research was to enhance the mechanical properties of wholly thermoplastic composites (WTCs) used in fused filament fabrication (FFF). Multiscale thermoplastic composites, which were based on the use of polypropylene (PP) reinforced with thermotropic liquid crystalline polymer (TLCP) and carbon nanotubes (CNTs), were prepared by a method combining supercritical carbon dioxide (scCO2)‐aided exfoliation and dual‐extrusion technologies. Significant enhancement of tensile properties was observed by using 1 wt% exfoliated CNTs to reinforce WTCs consisting of PP with and without maleic anhydride‐grafted polypropylene (MAPP, 16 wt%). With 1 wt% CNTs and 16 wt% MAPP dual reinforcement, 20 wt% TLCP reinforced WTCs based on PP exhibited 265%, 274%, and 182% improvement in the tensile modulus of the filaments, laid up specimens in the concentric pattern, and laid up specimens in ±45° rectilinear pattern, respectively. For tensile strength, 1 wt% CNTs reinforcement combined with 16 wt% MAPP improved the 20 wt% TLCP reinforced WTC filaments, laid down parts in the concentric pattern, and ±45° rectilinear patterns by 73%, 53%, and 65%, respectively. The tensile modulus and strength of multiscale WTC based on MAPP/PP specimens laid down with a concentric pattern are higher than those reported for PP/40 wt% short carbon fiber and PP/48.5 wt% short glass fiber laid down specimens. The advanced tensile modulus properties of 1 wt% CNTs reinforced WTCs are competitive with 9 wt% continuous carbon fiber reinforced nylon composite materials in FFF. Scanning electron microscopy analysis showed extremely strong interfacial adhesion between the TLCP fibrils and the matrix in multiscale WTC filaments and laid down parts, compared to the WTCs with no CNTs reinforcement. The advanced interfacial adhesion between TLCP fibrils and matrix resulted in an enhancement in the tensile strength. The exfoliated CNTs were premixed with the matrix, but they were trapped at and aligned with TLCP fibrils, which may be the primary reason for tensile modulus enhancement.

Multiscale Toughening of Composites with Carbon Nanotubes—Continuous Multiscale Reinforcement New Concept

Strengthening composite structures for advanced industries such as offshore wind generation is a real issue. Due to the huge dimensions expected for next generation wind-blades, composites based on glass fibers can no longer be used due to the lack of stiffness, whereas composites based on carbon fibers are expensive. Therefore, switching to alternative structural solutions is highly needed. This might be achieved by appropriate use of carbon nanotubes (CNTs) either as fillers of epoxy matrices, especially in inter-plies, or as fillers of epoxy glues used in structural bonding joints. As an example, trailing edges of offshore wind-blades are addressed in the current article, where monolithic bonding holds together the two structural halves and where the risk of sudden and brittle separation of edges while wind-turbines are in service is quite high. This can lead to tedious and very expensive maintenance, especially when keeping in mind the huge dimensions of new generation wind turbine blades that exceed lengths of 100 m. Bond joints and composites inter-plies of the final CNT-reinforced structures will exhibit stiffness and toughness high enough to face the severe offshore environment. In this article, multiscale Finite Element (FE) modeling is carried out to evaluate mechanical properties following the addition of CNTs. To achieve an optimal reinforcement, the effect of inclination of CNTs vs. mechanical loading axis is studied. Two innovations are suggested through this numerical study: The first consists of using homogenization in order to evaluate the effects of CNT reinforcement macroscopically. The second innovation lies in this forward-looking idea to envisage how we can benefit from CNTs in continuous fiber composites, as part of a deep theoretical rethinking of the reinforcement mechanisms operating at different scales and their triggering kinetics. The presented work is purely numerical and should be viewed as a “scenario” of structural composite materials of the future, which can be used both in the offshore industry and in other advanced industries. More broadly and through what is proposed, we humbly wish to stimulate scientific discussions about how we can better improve the performances of structural composite materials.

Fast self-healing zwitterion nanocomposite hydrogel for underwater sensing

Conductive hydrogels have consistently attracted researchers' interests in the past few years. However, challenges still remain in the preparation of hydrogels with self-healing ability and underwater sensing capacity. In this work, we fabricate a novel fully-physically crosslinked nanocomposite hydrogel by incorporating gelatin dispersed carbon nanotubes (CNTs) into poly (sulfobetaine methacrylate) (PSBMA) network. The fully physically crosslinked PSBMA backbone and the nano reinforcement of CNTs endow hydrogel with fast self-healing ability (about 30 s) and good mechanical properties. Additionally, PSBMA/CNTs hydrogels exhibit high strain sensitivity (gauge factor up to 10.35) and pressure sensitivity (up to 0.256 kPa−1) and they can be fabricated as strain and pressure sensors to precisely monitor human movements. Moreover, the PSBMA/CNTs hydrogel sensor can detect human motions underwater owing to the anti-swelling feature. This work provides a feasible method to construct self-healing hydrogel sensors with strain and pressure sensing capacity and paves a way for underwater human motion sensors.

Vibration and damping characteristics of CNTR viscoelastic skewed shell structures under the influence of hygrothermal conditions

The vibration and damping characteristics of carbon nanotubes reinforced (CNTR) skewed shell structure under a hygrothermal environment have been investigated using the finite element method. CNT as reinforcing phase and polymer as matrix phase are considered for the nanocomposites (NCs) based viscoelastic skewed shell structure. Dynamic mechanical analysis is used to conduct the creep test for NCs samples which were fabricated, as per ASTM-D4065 standard, and obtained the viscoelastic properties in the frequency domain under different hygrothermal conditions. The shell geometry is defined by considering an arbitrary coordinate system for the skewed shell structure. Finite element modelling has been done with Serendipity element with five degrees of freedom in all eight nodes. The present formulation is based on Koiter’s shell theory and first-order shear deformation theory is considered to incorporate the transverse shear effect based on Mindlin’s hypothesis. The frequency dependant viscoelastic properties are directly used to obtain the frequency responses of the skewed shell panel using fast Fourier transform (FFT) whereas the transient responses are determined using inverse fast Fourier transform (IFFT). An in-house MATLAB code is developed for the numerical simulation and the accuracy of the proposed formulation is validated with available results in literatures and using ANSYS software. A parametric study has been carried out for the skewing angle and CNT volume fraction on the vibration behaviour of different thin and thick NC skewed shell structures under various hygrothermal conditions.

Analysis of the Morphology and Mechanical Properties of Polymer Composite Materials (PCM) from Silicon Dioxide (SiO<sub>2</sub>) and Multiwalled Carbon Nanotubes (MWNTs) Reinforced Volcanic Stone

The formation of Polymer Composite Materials (PCM) based on mineral stones reinforced with Silicon Dioxide (SiO2) and Carbon Nanotubes (CNTs) using the Squeze Casting Method was carried out to obtain an increase in surface hardness, while the inner side of the elongation remained high. Based on SEM-EDX testing, it is known that the crystalline form of igneous rock and SiO2 is tapered, with large and small variations, CNTs with fine crystalline structures, which can bind well to specimen formation. The results of bending and hardness tests showed that dimensional variations, the aggregate ratio with resin and the addition of CNT and SiO2 reinforcement had the highest hardness 89.55 HD (Hardness of durometer), mixing of silica sand – vulkanic sand had the highest bending strength of 18.7 MPa, the lowest is a mixture of granite-sand of Merapi at 11.63 MPa. The variation of silica sand – volcanic sand has the highest bending strength, the lowest is the mixing of granite-volcanic sand.

Free Vibration Analysis of Cylindrical Micro/Nano-Shell Reinforced with CNTRC Patches

This paper studies free vibration analysis of cylindrical micro/nano shell made from a mixture of ceramic/metal, reinforced with some carbon-nanotube-reinforced (CNTRC) patches, based on shear deformation theory and nonlocal elasticity theory. Extended rule of mixture and power law model are utilized to find effective properties of composite patches and the ceramic/metal core, respectively. The main aim of this work is to investigate the effect of characteristics of attached CNTRC patches on the free vibration responses. It is concluded that some important parameters such as number and angle of composite patches as well as their volume fraction, and some geometric parameters have significant influence on the free vibration responses.

Forced Nonlinear vibration and bifurcation analysis of circular cylindrical nanocomposite shells using the normal form

The current paper focuses on investigating the effect of different distribution types of single-walled carbon nanotube (SWCNT) reinforcement and the volume fraction of CNTs on the nonlinear vibration of simply supported nanocomposite circular cylindrical shells. The governing equations are derived for uniform and three kinds of FG distribution of CNTs utilizing the extended mixture rule and Hamilton principle in cylindrical coordinate employing a classical nonlinear shell theory. The considered 1:1 internal resonance between asymmetric driven and companion vibration modes profoundly influences the frequency responses’ nonlinear characteristics. Then by the aids of the Airy stress function and the Galerkin method, the motion equations turn into several nonlinear nonhomogeneous ODEs. Finally, the bifurcation analysis is carried out based on various parameters using the normal form method. Three stable, unstable, and quasi-period regions concerning the locations of saddle nodes, pitchfork bifurcation, and torus points at the limit cycle around the resonance condition would differ due to change the structure of the nanocomposite shells, viscous damping coefficient, and the amplitude of the concentrated external force. The perturbation method’s accuracy is compared against the Runge–Kutta 4th order method’s results validated by available data.

Study on Properties of Multi Walled Carbon Nanotube Reinforced Aluminum Matrix Composite through Casting Technique

Composite materials are defined as material systems consisting of mixture of or combination of two or more micro constituents insoluble in each other and differing in form and or material composition. In this study Metal Matrix Composite (MMCs) has been produced using stir casting method for performing the mechanical properties. Most of the engineering industries want light and better mechanical properties of components; this can be achieved by MMCs of Aluminium because of its excellent performance. In this research work we fabricate the Aluminium by liquid route. Here Al 7075 is used as a base metal and Multi Walled Carbon Nanotubes (MWCNT) used as sub metal with various percentages. Experiments were conducted to analyze microstructure, hardness & tensile strength. By using optical microscope and Scanning Electron Microscope (SEM) we analyze the sample specimens are well dispersion in MWCNT with AA 7075. Hardness and tensile strength increases with increasing of wt. %. Hardness of material increases with increase in percentages of MWCNT, whereas tensile strength of the material increases with increase in percentages of MWCNT and Elongation reduces

Optimization of Process Conditions for Continuous Growth of CNTs on the Surface of Carbon Fibers

Grafting carbon nanotubes (CNTs) is one of the most commonly used methods for modifying carbon fiber surface, during which complex device is usually needed and the growth of CNTs is difficult to control. Herein, we provide an implementable and continuous chemical vapor deposition (CVD) process, by which the novel multiscale reinforcement of carbon nanotube (CNT)-grafted carbon fiber is prepared. After exploring the effects of the moving speed and growth atmosphere on the morphology and mechanical properties of carbon nanotubes/carbon fiber (CNTs/CF) reinforcement, the optimal CVD process conditions are determined. The results show that low moving speeds of carbon fibers passing through the reactor can prolong the growth time of CNTs, increasing the thickness and density of the CNTs layer. When the moving speed is 3 cm/min or 4 cm/min, the surface graphitization degree and tensile strength of CNTs/CF almost simultaneously reach the highest value. It is also found that H2 in the growth atmosphere can inhibit the cracking of C2H2 and has a certain effect on prolonging the life of the catalyst. Meanwhile, the graphitization degree is promoted gradually with the increase in H2 flow rate from 0 to 0.9 L/min, which is beneficial to CNTs/CF tensile properties.

Exploration of Properties of Al 6060/CNT Metal Matrix Nanocomposites

Nowadays the use of composites in all most all manufacturing sectors is developing rapidly and is likely to increase more rapidly shortly. Aluminum alloy is playing a greater role in all engineering fields. Modern mechanical parts require superior properties, the material available in pure form do not have the required mechanical properties such as strength, hardness, corrosion resistance, etc. A Composite is formed by two or more physically and chemically distinct substances and which is fabricated to enhance the distinctiveness of base metal. The Present work has focused on properties of Carbon nanoTubes (CNTs) reinforced aluminum metal matrix Al 6060; Nanocomposites. These Nanocomposites are fabricated by using the stir casting method by varying the CNT reinforcement with a multi-walled size 10 to 15 nm weight percentage (0.3%, 0.7%, and 1%) of the Al 6060 matrix. To study its properties, the fabricated specimens are tested for mechanical properties. The properties of the Nanocomposites are found to be greatly influenced by the increase in weight percentage of reinforcement. With the mixing of different weight proportion reinforced particles by stir casting process properties of Tensile, Flexural, Impact, and hardness strength of composites are increased. The experimental values obtained from tests more useful in the development of Nanocomposites for different applications.

Preparation of carbon/silica composite aerogel and application of fire insulation

In order to improve the disadvantages of aerogel brittleness and easy structural destruction during drying, carbon/silica dual network aerogel composites were constructed by copolymerizing carboxylated carbon nanotubes and tetraethyl orthosilicate decomposition products on chitosan templates. The composites were characterized by microscopic morphology and structural properties. The results show that the bulk carbon/silica aerogel composites can be prepared by freeze-drying through the reinforcement of chitosan templates and carbon nanotubes. The N2 adsorption and desorption curves of the composites show a type IV curve. The thermal conductivity of the material is only 0.0375 W/(m*K) at higher temperatures, which does not change much compared to that at room temperature (0.0312 W/(m*K)).

Mechanical properties of multiwalled-carbon-nanotubes reinforced poly(methyl methacrylate): Effect of UV-irradiation

The reinforcement of carbon nanotubes (CNTs) to polymer plays a critical role in the potential applications of polymer-based composites in sensing, actuating and structural health monitoring technologies. In this work, we study the irradiation effects of ultraviolet (UV) light on the glass transition temperature and mechanical deformation of multiwall-carbon-nanotube reinforced poly(methyl methacrylate) (PMMA-MWCNT composites) as a function of the weight percentage of MWCNTs in a range of 0–0.7 wt%. Increasing the weight percentage of MWCNTs from 0.3 wt% to 0.7 wt% slightly increases the glass transition temperature of the PMMA-MWCNT composites. The glass transition temperature, elastic modulus and tensile strength of the UV-irradiated pure PMMA are less than the corresponding ones without the UV irradiation. The glass transition temperatures of the PMMA-MWCNT composites for the weight percentage of MWCNTs ranging from 0.3 wt% to 0.7 wt% are relatively independent of the UV-irradiation for the UV-dose used in this work. We propose a simple equation to calculate the effective modulus of the PMMA-MWCNT composites. Both the toughness and elongation of the PMMA-MWCNT composites without UV-irradiation are larger than the corresponding ones of the same composite with the UV irradiation.

Improved mechanical performance of three-dimensional woven glass/epoxy spacer composites with carbon nanotubes

Three-dimensional polymer composites offer various features and design options due to their hollow structure and lightweight. However, to exploit their advantages, it is a must to improve their structural features and mechanical performances including out-plane direction. Although introducing thermoplastic fillers between the plies or multilayered design addresses on this critical issue, the benefits offered by the nanoparticles with superior mechanical properties come a step forward as an another engineering solution. Based on this motivation, the goal of this study is to investigate the impact of multiwalled carbon nanotubes on the mechanical and thermomechanical performances of three-dimensional woven glass/epoxy spacer composites. Therefore, multiwalled carbon nanotubes at various content were introduced into epoxy matrix, and the multiwalled carbon nanotubes–epoxy mixture was infused to three-dimensional woven fabric with the vacuum-assisted resin transfer method. The obtained results indicated that the three-point bending strength and modulus were enhanced up to 25 and 80% for warp direction and enhanced up to 44 and 85% for weft direction with carbon nanotube addition, respectively. Tensile strength developed in the warp direction by 7%, while the strength value in the weft direction did not change. The tensile strain values for warp and weft directions enhanced up to 19 and 12% with carbon nanotube addition, respectively. In addition, thermomechanical analysis has revealed that the glass transition temperature and storage modulus were also improved. Particle dispersion detection with color measurement and scanning electron microscopy analyses revealed the effectiveness of the ultrasonic mixing on the dispersion of carbon nanotubes in the epoxy matrix. The consequences of carbon nanotube addition on microscale morphology were discussed based on the fracture morphologies to nanoscale and microscale toughening mechanisms in the existence of carbon nanotube reinforcement.

Fabrication of Carbon Nanotubes and Rare Earth Pr Reinforced AZ91 Composites by Powder Metallurgy

It can be known from a large number of research results that improving the dispersibility of CNTs can effectively optimize the mechanical properties of the corresponding metal matrix composites. However, the crucial issue of increasing the bonding of CNTs and the matrix is still unsolved. In this paper, a novel method was developed to increase interfacial bonding strength by coating titanium oxide (TiO2) on the surface of CNTs. The rare earth Pr and TiO2@CNTs-reinforced AZ91matrix composites were successfully fabricated by powder metallurgy. Hot press sintering and hot extrusion of the milled powder was performed. After hot extrusion, the influence of TiO2@CNTs on the microstructure and mechanical properties of the composites were investigated. The results showed that the coating process can improve the distribution of CNTs in Mg alloy. The CNTs refined the grains of the matrix, and the CNTs were presented throughout the extrusion direction. When the TiO2@CNTs content was 1.0 wt.%, the yield strength (YS), ultimate tensile strength (UTS), and elongation of the alloy attained maximum values. The values were improved by 23.5%, 82.1%, and 40.0%, respectively, when compared with the AZ91 alloy. Good interfacial bonding was achieved, which resulted in an effective tensile loading transfer at the interface. CNTs carried the tensile stress and were observed on the tensile fracture.

Experimental Novel Investigation of Electrostatic Charged Multi Walled Carbon Nanotubes Reinforced Epoxy Based Polymer Composite

Experimental Novel Investigation of Electrostatic Charged Multi Walled Carbon Nanotubes Reinforced Epoxy Based Polymer Composite

3D Printed Hierarchical Honeycombs with Carbon Fiber and Carbon Nanotube Reinforced Acrylonitrile Butadiene Styrene

The mechanical properties of Fused Filament Fabrication (FFF) 3D printed specimens of acrylonitrile butadiene styrene (ABS), ABS reinforced with carbon fibers (ABS/CFs) and ABS reinforced with carbon nanotubes (ABS/CNTs) are investigated in this paper using various experimental tests. In particular, the mechanical performance of the fabricated specimens was determined by conducting compression and cyclic compression testing, as well as nanoindentation tests. In addition, the design and the manufacturing of hierarchical honeycomb structures are presented using the materials under study. The 3D printed honeycomb structures were examined by uniaxial compressive tests to review the mechanical behavior of such cellular structures. The compressive performance of the hierarchical honeycomb structures was also evaluated with finite element analysis (FEA) in order to extract the stress-strain response of these structures. The results revealed that the 2nd order hierarchy displayed increased stiffness and strength as compared with the 0th and the 1st hierarchies. Furthermore, the addition of carbon fibers in the ABS matrix improved the stiffness, the strength and the hardness of the FFF printed specimens as well as the compression performance of the honeycomb structures.

Monitoring the Hydration Process in Carbon Nanotube Reinforced Cement-Based Composites Using Nonlinear Elastic Waves

There is currently an increased need for associating construction material properties and behavior with the nature of their microstructure. One of the major issues in this context is the need for understanding the curing process in freshly poured cement-based materials. This is particularly important when nanoreinforcement materials, such as carbon nanotubes, are used to enhance the mechanical behavior and multifunctionality of the final structure. The solidification point, at which the state of liquid suspension transmutes to the solid state, is of particular interest since it greatly influences the load-bearing capacity of the cement-based material and its structural behavior at the long term. The main purpose of the present work is to develop a reliable method for monitoring the hydration process during the early stages of freshly poured cementitious composites enhanced with carbon nanotubes. This methodology is based on the use of nonlinear elastic waves. To achieve this goal, a combination of contact ultrasonics with noncontact optical detection was used. The detection method for evaluating the setting process is based on the assessment of higher-harmonic amplitudes of an ultrasonic wave, with a given frequency, propagating through the cementitious material. It was observed that the material nonlinearity changes significantly during the hardening process, compared to velocity or attenuation measurements which are based on linear acoustics. These changes were more noticeable as the concentration of carbon nanotubes in the cement matrix increases, indicating that higher harmonics are more susceptible to minute microstructural changes.

Characterization of the 3YSZ/CNT/HAP coating on the Ti6Al4V alloy by electrophoretic deposition.

In this article, the effects of the simultaneous addition of the 3mol % yttria-stabilized zirconia (3YSZ) and carbon nanotubes (CNTs) reinforcements on different properties of the natural hydroxyapatite (HAP) coating were studied. The electrophoretic deposition (EPD) process was implemented to prepare thin coatings on the Ti6Al4V substrate. The coatings were then sintered at 1000 ° C under vacuum for 2hr and the mechanical properties of them were studied by the nano-indentation method. The microsture and phase content of the coatings were investigated by the scanning electron microscope and X-ray diffraction methods, respectively. The electrochemical properties of the samples were studied by potentiodynamic polarization and electrochemical impedance spectroscopy. The biocompatibility of the coatings was evaluated by the MTT test under standard conditions. It was found that the proper voltage and duration for the deposition of the coatings were 20 V and 4min, while the longer deposition time of up to 6min. Was tolerable in the coatings containing 5wt % of the CNTs. The hardness and Young's modulus of the coatings were improved significantly by the siumultaneous addition of 3YSZ and CNTs, but the effect of nanotubes was more prominent. It was also found that the composite coating had marginally lower biocompatibility, as compared to the natural HAP, which was probably due to their lower roughness. The corrosion resistance of the HAP was not affected by the presence of 3YSZ particles, while the addition of CNTs improved the corrosion resistance of the coatings.

Fabrication of carbon nanotube reinforced aluminum alloy composites by vacuum-assisted infiltration technique

Carbon nanotube (CNT) reinforced 6063 aluminum (Al) matrix composites were fabricated by vacuum-assisted infiltration of molten 6063 Al alloy into a CNT preform to enhance compressive mechanical properties. Preforms were produced with different amounts of chemically functionalized CNTs to obtain three different CNT reinforcement ratios (0.25, 0.50, and 0.75 wt.%). In addition to the investigation of properties throughout all stages of the preparation of the CNTs, CNT preforms and fabricated composites by various methods of analysis, all steps of the composite fabrication process, as well as the compressive mechanical test results of CNT/6063 Al composites are all discussed. Approximately 250% and 280% increases in the yield and ultimate compressive strength, respectively, are achieved with low-purity CNT addition. Consequently, it is confirmed from the micrographs that the mechanical enhancements of the composites are mainly interrelated with the successful bridging of CNTs in the matrix material. Meanwhile, it is observed that both the modified Halpin-Tsai model and the modified Halpin-Tsai model developed with a dispersion-based prediction model results match with experimental results. Overall results can be accepted as developmental stages of significant progress in the CNT preform reinforced metal matrix composites field.