Carbon Nanotube Reinforced Research Articles

Effects of Laser Energy Density on Carbon‐Nanotube‐Reinforced Titanium Composites Printed via Selective Laser Melting

3D‐printing‐reinforced metal matrix composites are a promising avenue for fabricating materials to meet the demands of the 21st century. Ti–6Al–4 V has been a useful material in the aerospace and medical industries for decades due to its incredible strength‐to‐weight ratio, and now its suitability for additive manufacturing has made it even more desirable. One of the leading‐edge reinforcements being studied for metal matrix composites is carbon nanotubes due to their remarkable mechanical properties such as strength and elastic modulus. It is desirable to manufacture advanced metal matrix composites using advanced manufacturing techniques such as selective laser melting. Herein, the effect of 1 vol% carbon nanotube reinforcements on the microstructural evolution and properties of selective‐laser‐melt‐printed Ti64 and the interrelationships with laser energy density, laser power, and laser scan speed are investigated. The effectiveness of reinforcement and influence of printing parameters are assessed via microstructural and porosity analysis, and microhardness testing. Utilizing selective laser melting with a laser energy density of 60 J mm−3, a >99% dense Ti–CNT composite is manufactured with microhardness of 4.75 GPa—a 30% enhancement over its Ti64 counterpart.

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.

Additive Manufacturing of Carbon Nanotube Reinforced Bioactive Glass Scaffolds for Bone Tissue Engineering

Abstract Scaffolds play an essential role in bone healing by providing temporary structural support to the native bone tissue and by hosting bone cells. To this end, several biomaterials and manufacturing methods have been proposed. Among the biomaterials, bio-active glasses have attractive properties as a scaffold material for bone repair. Simultaneously, additive manufacturing (AM) techniques have attracted significant attention owing to their capability of fabricating complex and patient-specific scaffolds. Accordingly, borosilicate bio-active glass (BG-B30) has been used to fabricate the scaffolds using an extrusion-based AM devices in this study. Pluronic F-127 was used as an ink carrier that showed suitable shear thinning behavior for fabrication. The pure BG-B30 scaffold had a compressive strength of 23.30 MPa and was reinforced further with functionalized multiwalled carbon nanotube (MWCNT-COOH) to reduce its brittleness and enhance its compressive strength. When compared to the conventional polymer foam replication technique, the combination of MWCNT-COOH reinforcement and AM resulted in an enhancement of the compressive strength by ∼646% (1.05 MPa to 35.84 MPa). Further, structural analysis using microcomputed tomography revealed that the scaffolds fabricated using AM had better control over strut size and pore size in addition to better network connectivity. Finally, in vitro experiments demonstrated its bio-active behavior by the formation of hydroxyapatite, and the cellular studies revealed good cell viability and osteogenesis initiation. These results are promising for the fabrication of patient-specific CNT-reinforced bio-active glass porous scaffolds for bone tissue engineering applications.

Nonlinear dynamic analysis of FG carbon nanotube/epoxy nanocomposite cylinder with large strains assuming particle/matrix interphase using MLPG method

In this paper, a first known study on the large deformation dynamic behavior of functionally graded carbon nanotube-reinforced (CNTR) nanocomposite cylinder considering the particle/matrix interphase property is presented. The geometrically nonlinear dynamic analysis is carried out using the meshless local Petrov–Galerkin (MLPG) method based on the total Lagrangian approach. The obtained nonlinear time dependent equations are solved using the incremental-iterative Newmark/Newton–Raphson technique. The effective properties of CNTR cylinder is evaluated by employing the three-phase Halpin–Tsai model and rule of mixture. In these models, three constituent phases including nanoparticle, interphase and matrix is considered. It is assumed that CNTs is dispersed in the resin matrix with four different function along the radial direction to obtain the optimum grading pattern. The effects of interphase properties, CNT's weight fraction, CNT distribution pattern and volume fraction exponent on the dynamic characteristics of the cylinder are discussed in details. Numerical results demonstrated the high performance of the proposed MLPG method for geometrically nonlinear dynamic analysis of functionally graded carbon nanotube/epoxy nanocomposites due to its advantage in eliminating the mesh distortion and high capability in FG material modeling. Moreover, it is found that the interphase properties may dramatically affect the dynamic behavior of nanocomposite cylinder especially at the higher CNT volume fractions. So, it is important to consider the interphase properties to correctly model the nanocomposite structures.

Impact response of nanoparticle reinforced 3D woven spacer/epoxy composites at cryogenic temperatures

Fiber-reinforced polymer composites serving in harsh conditions must maintain their performance during their entire service. The cryogenic impact is one of the most unpredictable loading types, leading to catastrophic failures of composite structures. This study aims to examine the low-velocity impact (LVI) performance of 3D woven spacer glass-epoxy composite experimentally under cryogenic temperatures. LVI tests were conducted under various temperatures ranging from room temperature (RT) to −196°C. Experimental results reveal that the 3D composites gradually absorbed higher impact energies with decreasing temperature. Besides, the effect of multi-walled carbon nanotube and SiO2 nanofiller reinforcements of the matrix on the impact performance and the damage characteristics were further assessed. Nanofiller modification enhanced the impact resistance up to 30%, especially at RT. However, the nanofiller efficiency declined with decreasing temperature. The apparent damages were visually examined by scanning electron microscopy to address the damage formation. Significant outcomes have been achieved with the nanofiller modification regarding the new usage areas of 3D woven composites.

Free vibration analysis of carbon nanotube RC nanobeams with variational approaches

There is not enough mixed finite element method (MFEM) model developed for dynamic analysis of carbon nanotube reinforced (CNTRC) composite beams in the literature. In the present study, free vibration analysis of functionally graded carbon nanotube reinforced composite (FG-CNTRC) nanobeams is carried out in the framework of variational formulations. The rule of mixture is employed to estimate the effective material properties of single-walled CNT reinforced nanobeams. Four kinds of CNT distribution of un-axially aligned reinforcement material are investigated in the through-thickness direction of the nanobeams. There are the uniform distribution (UD) and functionally graded distributions FG-O, FG-X and FG-Ʌ of CNTs in the thickness direction of the nanobeams (z axis direction) are assumed here for the analysis. The Hamilton

Increasing the resistance to interlayer shear of composite materials due to the modification of carbon fabric fibers with carbon nanotubes

Interlaminar shear strength is an important characteristic of the characteristics of composite structures. This article presents the results of an experimental study of the role of carbon nanotube reinforcement of a fibrous filler of carbon fabrics in increasing the interlayer shear strength of composite articles made of carbon fiber reinforced plastics. Studies were conducted using dry roving carbon twill weave (Twill type grade: 3K, 2 x 2 Twill Weave Carbon Fiber Fabric, 5.7 Oz/Sq Yd, 50 “Wide,.012” Thick, and 3K, 2 x 2 Twill Weave).The creation of carbon composite materials based on a polyester matrix with additional reinforcement using grown carbon nanotubes (CNTs) on filler fibers has been proposed and investigated. It is shown that with a uniform distribution of CNTs on filler fibers, the interlayer shear resistance increases by 60%.

Modeling of density of state for polyethylene–nanotubes nanocomposites

AbstractAt the nanoscale system, the efficiency of carbon nanotube (CNT) reinforcement between the CNTs and polymer matrices in terms of interfacial load transferring is assessed for both nonfunctionalized and functionalized interfaces. The simulations of the mechanical properties (stress–strain) of polyethylene (PE)/CNT nanocomposites by the molecular dynamics are currently an area of discussion in the literature. In this work, PE considered as a thermoplastic material is studied, in which the characterization of its nanoscale load transfer has been carried out through the classification of representative nanoscale interface elements for nonfunctionalized CNTs for the diverse values of lengths and diameters. First, the main evaluations based on the density functional theory and the molecular dynamics method were used with the aim to examine the effect of PE monomers. Then, the effect of the diameter of CNTs with nonfunctionalization content on the electronic and mechanical properties of single‐walled carbon nanotubes was examined. The findings reveal that the density of states highlights the absence of orbital hybridization between the PE monomers and nanotubes, whereas the Mulliken charge analysis depicts that the PE polymer produces a positive charge that is directly proportional to the number of monomers with many chains of PE and different diameters of CNTs. The decrease in diameters implies an increase in nanocomposites stress. In addition, the results show that the reinforcements in the longitudinal direction are more promising than those in the transverse direction.

Enhancing strength and stiffness of composite joint through co-cure technique

The co-cure manufacturing process effectively merges the various composites parts in wings, fuselage, and frames in aerospace applications. The current study investigates the combined effects of co-cure manufacturing technique and multi-wall carbon nanotubes (MWCNTs) reinforcement on shear strength and fundamental natural frequency of single lap joints (SLJs). In continuation, results were compared with SLJs fabricated through co-bonding and secondary bonding. Shear analysis affirmed that SLJs prepared using co-cure manufacturing technique along with 0.25 wt% MWCNT addition increased the shear strength by 104.25 %, 88.2 % while comparing with co-bonded and secondary bonded joints, respectively. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicated uniform dispersion of 0.25 wt% MWCNTs increased the joint strength, deviated crack propagation path, formation of shear bands and uneven surfaces in the adhesive layer. The experimental modal analysis revealed that 0.25 wt% CNT addition with co-cured manufacturing technique enhanced fundamental natural frequency, whereas higher wt.% MWCNT addition increased the damping factor of lap joint due to nanoparticle agglomeration increased the interaction between adhesive and adherend.

Dynamic Response of Multilayered Polymer Functionally Graded Carbon Nanotube Reinforced Composite (FG-CNTRC) Nano-Beams in Hygro-Thermal Environment.

This work studies the dynamic response of Bernoulli–Euler multilayered polymer functionally graded carbon nanotubes-reinforced composite nano-beams subjected to hygro-thermal environments. The governing equations were derived by employing Hamilton’s principle on the basis of the local/nonlocal stress gradient theory of elasticity (L/NStressG). A Wolfram language code in Mathematica was written to carry out a parametric investigation on the influence of different parameters on their dynamic response, such as the nonlocal parameter, the gradient length parameter, the mixture parameter and the hygro-thermal loadings and the total volume fraction of CNTs for different functionally graded distribution schemes. It is shown how the proposed approach is able to capture the dynamic behavior of multilayered polymer FG-CNTRC nano-beams under hygro-thermal environments.

Dynamic Analysis of Multi-Stepped Functionally Graded Carbon Nanotube Reinforced Composite Plate with General Boundary Condition

This study presents the multi-stepped functionally graded carbon nanotube reinforced composite (FG-CNTRC) plate model for the first time, and its free and forced vibration is analyzed by employing the domain decomposition method. The segmentation technique is employed to discretize the structure along the length direction. The artificial spring technique is applied to the structural boundary and piecewise interface for satisfying the boundary conditions and the combined conditions between subplates. Based on this, the boundary conditions of subdomains could be considered as a free boundary constraint, reducing the difficulty in constructing the allowable displacement function. Since all the structures of subdomains are identical, the allowable displacement functions of them can be uniformly constructed using the two-dimensional ultraspherical polynomial expansion. The potential energy function of the plate is derived from the first-order shear deformation theory (FSDT). The allowable displacement function is substituted into the potential energy function, and then the natural frequencies and mode shapes of the multi-stepped FG-CNTRC plate are decided by using the Rayleigh–Ritz method. The accuracy and reliability of the proposed method are confirmed by the results of the previous literature and finite element method (FEM). On this basis, the influences of the geometric and material parameters on free and forced vibration of the multi-stepped FG-CNTRC plate are also studied.

Damping characteristics of carbon nanotube reinforced epoxy nanocomposite beams

In this paper, theoretical and experimental studies are carried out to investigate the damping characteristics of carbon nanotube (CNT) reinforced epoxy nanocomposite beams. A modified Biot model is proposed to simulate the frequency-dependent damping characteristics of CNT reinforced epoxy nanocomposites and implemented into the finite element model for composite beams. The natural frequencies and modal damping ratios of CNT reinforced epoxy beams are predicted using the proposed finite element model. Then, CNT reinforced epoxy beam specimens are fabricated, upon which dynamic mechanical analysis and vibration tests are carried out. Comparison studies between theoretical and experimental results show that modified Biot model proposed here is more accurate than the original one in predicting loss factors of CNT reinforced epoxy nanocomposites. It is revealed that the damping ratios associated with the first three vibration modes of composite beam specimens initially increase and then decrease with the increment of CNT weight ratio. The first order damping ratio with 0.4 wt% CNT reinforcement has the maximum value of 0.591%, which is improved by 41% compared with that of pure epoxy.

A Combination of Enhanced Mechanical and Electromagnetic Shielding Properties of Carbon Nanotubes Reinforced Cu-Ni Composite Foams.

Carbon nanotubes (CNTs) reinforced double-layered Cu-Ni composite foams (Cu-Ni/CNT foams) were prepared through chemical plating and electrodeposition, for the purpose of combining enhanced mechanical and electromagnetic shielding properties. The microstructure characterization revealed a quite uniform dispersion of the CNTs embedded in the metal layers, even after heat treatments. The property testing showed the compressive strength, energy absorption capacity and electromagnetic shielding effectiveness (SE) of Cu-Ni/CNTs foams were significantly improved, as compared to Cu-Ni foams. The heat treatments of the composite foams resulted in an interdiffusion of the Cu and Ni layers, causing an increase of compressive strength and a slight decrease of average SE. The possible mechanisms of the property evolution are discussed.

Tribological Behavior of Carbon Nanotubes Reinforced High Velocity Oxy-Fuel Sprayed WC-20 wt.% Co Coatings

Tribological Behavior of Carbon Nanotubes Reinforced High Velocity Oxy-Fuel Sprayed WC-20 wt.% Co Coatings

The effect of uncertainty sources on the dynamic instability of CNT-reinforced porous cylindrical shells integrated with piezoelectric layers under electro-mechanical loadings

In the present study, the influence of the propagation of different uncertainty sources on the dynamic stability of a sandwich carbon nanotube-reinforced (CNT) cylindrical shell under a pulse axial load is investigated. The core of the cylindrical shell is composed of a porous metal matrix reinforced with CNTs. The core is surrounded by piezoelectric layers. Five distributions of CNT reinforcements in the shell thickness are considered in this study. Moreover, it is assumed that the shell rests on an elastic foundation. Two dynamic curves and the Chebyshev model are combined to examine the dynamic stability probability of functionally-graded carbon nanotube-reinforced cylindrical shells surrounded by piezoelectric layers (FG-CNT-P). The stability of the shell is investigated under both mechanical dynamic load and electrical potential. The effective material properties of the functionally graded carbon nanotube shells are estimated through a micromechanical model based on the extended rule of mixture. The virtual work method based on Sanders’ nonlinear theory and the higher-order shear deformation theory is used to derive the dynamic equilibrium equations of the CNT cylindrical shells surrounded by piezoelectric layers and an elastic medium. The Fourier differential quadrature method is used to solve these equations. The analysis results are presented in terms of the probabilistic density functions (PDFs) of the buckling loads of the composite shells. Accordingly, the probabilistic distributions of the buckling loads of the shells corresponding to the first three modes of buckling are overlapping. Hence, the first mode of buckling determined in a deterministic study may not always be the dominant failure mode of the structure. Consequently, a great attention is paid to this phenomenon and the effects of different factors on it. Finally, the sensitivities of the critical loads of the FG-CNT-P cylindrical shells to different sources of uncertainty are assessed through a sensitivity analysis.

The bonding performances of carbon nanotube (CNT)-reinforced epoxy adhesively bonded joints on steel substrates

Carbon nanotubes (CNTs) are generally considered as a promising particle reinforcement of incorporating advanced properties and characteristics into epoxy nanocomposites. This paper investigated the bonding performances of CNT-reinforced epoxy adhesively bonded joints on steel substrates using the single lap shear (SLS) tests. The bonding performances (including bonding strength, fracture strain, toughness, and failure mode) were studied with three adhesive thicknesses (1 mm, 0.5 mm, and 0.25 mm) and three CNT weight fractions (0%, 0.375%, and 0.75%). The experimental results indicated that thinner bondlines and higher CNT additions could significantly improve the bonding performances and modify the failure mode of CNT-reinforced epoxy adhesively bonded joints. However, the effects of adhesive thickness became less significant with the increase of CNT weight fractions. In addition, the plastic behaviour of CNT-reinforced epoxy, CNTs pulling-out, and the aggregation of CNTs were observed by scanning electron microscopy (SEM) image analysis on the fracture surfaces of CNT-reinforced epoxy adhesively bonded joints, indicating the potential effectiveness of the CNT reinforcement.

Flexible Wearable Sensors Based in Carbon Nanotubes Reinforced Poly(Ethylene Glycol) Diglycidyl Ether (PEGDGE): Analysis of Strain Sensitivity and Proof of Concept

The electromechanical capabilities of carbon nanotube (CNT) doped poly(ethylene glycol) diglycidyl ether (PEGDGE) have been explored. In this regard, the effect of both CNT content and curing conditions were analyzed. The electrical conductivity increased both with CNT content and curing temperature due to the lower gel time that leads to a lower reaggregation during curing. More specifically, the percolation threshold at 160 and 180 °C curing temperatures is below 0.01 wt.%, and this limit increases up to 0.1 wt.% at 140 °C for an 8 h curing cycle. Moreover, the strain monitoring capabilities were investigated, and the effect of contact resistance was also analyzed. The electrical contacts made with silver ink led to higher values of gauge factor (GF) but presented some issues at very high strains due to their possible detachment during testing. In every case, GF values were far above conventional metallic gauges with a very significant exponential behavior, especially at low CNT content due to a prevalence of tunneling mechanisms. Finally, a proof of concept of fingers and knee motion monitoring was carried out, showing a high sensitivity for human motion sensing.

Influence of carbon nanotubes reinforcement on the structural feature and bioactivity of SiO2–Al2O3–MgO–K2CO3–CaO–MgF2 bioglass

Influence of carbon nanotubes reinforcement on the structural feature and bioactivity of SiO2–Al2O3–MgO–K2CO3–CaO–MgF2 bioglass

Molecular dynamics simulation study of wear-resistant mechanism of UHMWPE composites reinforced by CNTs with different configuration directions

The water-lubricated stern tube bearing carried on the extreme working like heavy-duty, low-velocity and starting operation condition, the interface of water-lubricated bearing always suffers from the severe abrasive wear. Carbon nanofibers have been widely used as additives to enhance the properties of composites used in water-lubricated bearings. Therefore, it is important to determine and characterize the wear-resistant mechanisms of composites reinforced with carbon nanofibers. In this work, molecular dynamics (MD) simulation is employed to investigate the mechanical and tribological properties of ultra-high molecular weight polyethylene (UHMWPE) composites and determine the interactions and wear mechanisms of the UHMWPE composites from the atomic level perspective. Three-layer models (Cu–Composites-Cu) were developed to simulate the deformation and wear process of the composites. The effect of three different directions of the carbon nanotubes (CNTs) on the mechanical and tribological properties of the composites was calculated and analyzed. The results demonstrated that, compared to that of the pure UHMWPE, after CNT reinforcement, the shear modulus of the three CNTs/UHMWPE composites increased by 28.04%, 42.22%, and 47.4%, respectively, while the wear rate decreased by 16.91%, 41.05%, and 47.37%, respectively. When the CNTs are perpendicular to both the sliding direction and the top Cu layer can significantly reinforce the matrix materials and provide better mechanical and tribological properties. This study provides a theoretic basis for the structural design and performance enhancement of water-lubricated bearings.

Influence of carbon nanotube reinforcement on the heat transfer coefficient, microstructure, and mechanical properties of a die cast Al-7Si-0.35Mg alloy

Al-7Si-0.35Mg or A356 alloy is most widely used in aircraft and automobile industries owing to its high strength to weight ratio. This alloy has been reinforced with a 1 wt% carbon nanotube (CNT) to improve its properties in this investigation. First, A356/1 wt% CNT powders were ball milled in the presence of ethanol and subsequently consolidated using gravity die casting. Ball milling was effective in achieving homogeneous dispersion of CNT. The microstructural study revealed the segregation of the Al4C3 phase at the grain boundary. This mechanism is known as grain boundary precipitation. Also, the grain size has decreased by ~44%. Next, the casting-die interfacial heat transfer coefficient (IHTC) has been evaluated using Beck's inverse heat transfer algorithm. With the reinforcement, the IHTC has increased by ~2.5%, which indicates the rise in heat transfer rate during solidification. Then, the experimental and theoretical tensile properties of A356 were correlated using simulation software. The experimental results showed the synergistic effect of grain size, Al4C3, and IHTC improving yield strength by ~19.8%, ultimate tensile strength by ~14.13%, elongation by 7%, and hardness ~22%. Therefore, a meagre 1 wt% CNT has improved the heat transfer rate of the melt as indicated by IHTC values. This effect was further corroborated by evaluating the thermal conductivity of the sample. The thermal conductivity has improved by 10% that resulted in finer grain size of the sample. Therefore, such reinforced alloys are expected to display higher strength demanded in various industrial applications.