Multi-walled Carbon Nanotubes Content Research Articles

Effect of multi-walled carbon nanotubes on the microstructure and properties of Sn-58Bi solder alloys

The influence of multi-walled carbon nanotube (MWCNT) content on the melting properties, wettability, microstructure, and intermetallic compounds (IMCs) of Sn-58Bi-xMWCNT (x = 0, 0.01, 0.02, 0.03, 0.05, and 0.10 wt.%) and the effects of MWCNT on the tensile strength of Cu/Sn-58Bi-xMWCNT/Cu solder joint were analyzed. The results show that MWCNT addition at a small trace amount into Sn-58Bi solder could increase the spreading area of Sn-58Bi solder, refine the solder matrix microstructure, inhibit the growth of interfacial IMCs, and significantly improve the tensile strength of Sn-58Bi solder joints. However, the melting point and melting range remained the same or slightly changed. The wettability of Sn-58Bi alloys increased first and then decreased with the addition of MWCNT. The spreading area and the tensile strength of solder joint were the maximum when the MWCNT content was 0.01 wt.%, and they were 42.23 mm2 and 50.07 MPa, respectively. The reason may be related to the improved microstructure of solder alloys and the morphology of IMCs due to MWCNT addition at trace level.

Effects of the Ratio of Nano-Cu to Hydroxylated MWCNTs on Anticorrosion and Surface Conductivity of Cu/MWCNT Epoxy Coatings on a Steel Substrate

Epoxy coatings provide an economical and practical solution for combating steel corrosion. However, epoxy coatings have poor conductivity, resulting in the accumulation of electrostatic charges. The surface conductivity and anticorrosion properties of epoxy coatings can be improved by adding nano-Cu and hydroxylated multi-walled carbon nanotubes (MWCNTs). This paper investigates the impact of MWCNTs at different concentrations (2.5, 5%) and the ratio of nano-Cu to MWCNTs on the surface conductivity and anticorrosion properties of epoxy coatings on a steel substrate. The findings from the four-probe method of measuring surface resistance indicated that the surface resistivity of steel coated with an epoxy composite of 5% MWCNTs and 65% nano-Cu (Cu65/MWCNT5) was significantly lower, approximately by one order of magnitude, compared to steel coated with a 5% MWCNT (MWCNT5) epoxy coating. When the Cu65/MWCNT5-coated steel was immersed in a 3.5 wt % NaCl solution for 30 days, it was observed that there was a minimal effect on its surface resistivity. The inclusion of a high content of MWCNTs facilitates a more uniform distribution of Cu particles within the epoxy coatings, thereby improving the anticorrosion properties of these coatings on a steel substrate. This was further corroborated by the results of the polarization curves and electrochemical impedance spectroscopy, demonstrating that the Cu65/MWCNT5 epoxy coating on a steel substrate offers exceptional anticorrosion and barrier protection properties. The corrosion rate of steel with a Cu65/MWCNT5 epoxy coating was three orders of magnitude lower than that of steel with a Cu65/MWCNT2.5 epoxy coating, at 4.79 × 10−7 mm/year.

Multifunctional ultra-high performance fibre-reinforced concrete with integrated self-sensing and repair capabilities towards in-situ structure monitoring

Achieving continuous in-situ monitoring of repaired concrete structures has always been a great challenge. Ultra-high performance fibre-reinforced concrete (UHPFRC), featuring superior mechanical capacity, excellent erosion resistance, and long-life cycle, is expected to realize durable, cost-effective, and aesthetically pleasing repairs and possesses tremendous potential for intrinsic self-sensing. This paper presents the multifunctionality of UHPFRC with integrated self-sensing and repair capabilities using multi-walled carbon nanotube (MWCNT). An experimental evaluation on the bond performance and self-sensing properties, including the bond strength and failure patterns by the three-point bending, splitting tensile, and slant shear tests, electrical properties via alternating current impedance spectroscopy test, and electromechanical properties under three-point bending, was conducted through the designed composite layer between concrete substrate and UHPFRC. The microstructure of the interfacial zone was analysed to reveal the bonding mechanism. Results indicate that the addition of MWCNT improved the bond strength between concrete substrate and UHPFRC as MWCNT can enhance the adhesion and cohesion of the interfacial zone through inactive filling effect, as well as the frictional and mechanical interlocks through increased mechanical properties of repair UHPFRC. Moreover, the repair UHPFRC showed remarkable sensing capabilities for the initial cracking, deflection hardening or softening, and fibre pull-out and debonding processes of the composite layers. The optimal content of steel fibre and MWCNT in multifunctional UHPFRC should be 2 vol.% and 0.2 wt.%, respectively, considering the synergistic damage sensing and bonding properties.

Influences of MWCNT bonding strength on Microstructure, mechanical performance of Alsi10 mg alloy composite

The high strength-to-weight ratio material is becoming essential in various engineering sectors like automotive, structural, aviation, and marine. This investigation is to produce the high strength to lightweight AlSi10Mg alloy composite with 0, 5, 10, and 15 wt% of multi-walled carbon nanotube (MWCNT) as reinforcement through vacuum-assisted liquid state processing. Characteristics-wise, the metal matrix composites are synthesized by using organic, inorganic, and fiber as reinforcement. The developed composites are subjected to physical, microstructural, and mechanical behaviour. The outcome results of the SEM micrograph show good interfacial bonding between AlSi10Mg and MWCNT. The composite contained higher content of MWCNT (15 wt%) and observed maximum tensile strength (192 ± 1.2 MPa) with reduced weight (2.316 g/cc). Tensile strength was increased by 23.87 %, and its weight reduction was 35.89 % compared to unreinforced AlSi10Mg alloy composite. The energy absorption capability was increased significantly (53.84 %) compared to the unreinforced AlSi10Mg composite. The hardness of the composite was found to have a marginal improvement on the increased content of MWCNT.

Unraveling the role of multi-walled carbon nanotubes in a corn-soil system: Plant growth, oxidative stress and heavy metal(loid)s behavior

In the age of nanotechnological advancement, carbon nanotubes (CNTs) are drawing global attention. However, few studies have been published on the crop growth responses to CNTs in heavy metal(loid)s contaminated environments. A pot experiment was conducted to assess the effect of multi-walled carbon nanotubes (MWCNTs) on plant development, oxidative stress, and heavy metal(loid)s behavior in a corn-soil system. Corn (Zea mays L.) seedlings were cultivated in soil containing Cadmium (Cd) and Arsenic (As) that had been primed with 0, 100, 500, and 1000 mg kg−1 MWCNTs. The application of 100 and 500 mg kg−1 MWCNTs improved shoot length by 6.45% and 9.21% after 45 days, respectively. Total plant dry biomass increased by 14.71% when treated with 500 mg kg−1 MWCNTs but decreased by 9.26% when exposed to 1000 mg kg−1 MWCNTs. MWCNTs treatment did not affect Cd accumulation in plants. On the other hand, the bio-concentration factor of As was inversely associated with plant growth (p < 0.05), which was declined in MWCNTs treatments. Oxidative stress was aggravated when plants were exposed to MWCNTs, thus activating the antioxidant enzymes system in the corn. In contrast, TCLP-extractable Cd and As in soil significantly decreased than in the control. Additionally, the soil nutrients were changed under MWCNTs treatments. Our findings also revealed that a particular concentration of MWCNTs can mitigate the toxicity of Cd and As in corn seedlings. Therefore, these results suggest the prospective application of CNTs in agricultural production, ensuring environmental and soil sustainability.

Magnetic Polymer Actuators with Self-Sensing Resistive Bending Response Based on Ternary Polymer Composites.

A multifunctional polymer-based composite has been designed based on poly(vinylidene fluoride) (PVDF) as polymer matrix and cobalt ferrite (CoFe2O4, CFO) and multiwalled carbon nanotubes (MWCNTs) as fillers, allowing to combine magnetic and electrical responses. The composites were prepared by solvent casting with a fixed 20 wt % concentration of CFO and varying the MWCNTs content between 0 and 3 wt %, allowing to tailor the electrical behavior. The morphology, polymer phase, and thermal and magnetic properties are nearly independent of the MWCNT filler content within the polymer matrix. On the other hand, the mechanical and electrical properties strongly depend on the MWCNT content and a maximum d.c. electrical conductivity value of 4 × 10-4 S·cm-1 has been obtained for the 20 wt %CFO-3 wt %MWCNT/PVDF sample, which is accompanied by an 11.1 emu·g-1 magnetization. The suitability of this composite for magnetic actuators with self-sensing strain characteristics is demonstrated with excellent response and reproducibility.

Effect of electron beam irradiation on thermal stability and crystallization behavior of flexible copolyester/multiwalled carbon nanotubes nanocomposites

AbstractPoly(butylene adipate‐co‐terephthalate) (PBAT), a biodegradable copolyester, was used as the polymer matrix to prepare nanocomposites with multiwalled carbon nanotubes (MWCNT) by melt‐mixing followed by hot‐pressing. The PBAT/MWCNT nanocomposites were exposed to electron beam (EB) irradiation, and thermal stability, melting and crystallization behavior of irradiated and unirradiated nanocomposites were comparatively investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. TGA results reveal increased thermal stability (up to 17°C) and maximum degradation temperature (Tmax) (up to 15°C) of PBAT/MWCNT nanocomposites, attributed to the high thermal stability of MWCNT and good MWCNT–PBAT interfacial interactions. However, the activation energy for thermal degradation (Ea) decreased with the presence of MWCNT in comparison to neat PBAT regardless of the MWCNT concentration. Both the thermal stability and Tmax of irradiated nanocomposites decreased by 3°C despite the crosslinking which can be attributed to successive minor irradiation‐induced polymer degradation, while Ea remained unchanged. Declined melting temperature (Tm), enthalpy of crystallization, enthalpy of melting and crystallinity of nanocomposites with the presence of MWCNT suggest the formation of less perfect crystals. Meanwhile, their increased glass transition temperature (Tg) and crystallization temperature (Tc) are due to the increased rigidity of PBAT chains and a reduced crystallization process in the presence of MWCNT, respectively. Similarly, reduced crystallinity and values of Tm and Tc of EB‐irradiated nanocomposites by 4.1%, 9.6%, and 7.5%, respectively, signifying the presence of PBAT‐crosslinks resulting in crystal defects.

Effects of MWCNTs content and dry density on hydro-structural characteristics of bentonite during drying and wetting

Bentonite has been an essential component of geosynthetic clay liners due to its low hydraulic conductivity, which has been used as a barrier against hazardous pollutants in landfills. During the drying and wetting processes caused by high temperatures and leachate in landfills, the hydro-structural characteristics of bentonite vary as the moisture content change. This article investigates the effect of dry density and multi-walled carbon nanotubes (MWCNTs) content on the soil shrinkage characteristic curve (SSCC), the soil free-swelling characteristic curve (SFSCC), the soil water characteristic curve (SWCC), and microstructure of bentonite during the drying and wetting processes. Experimental results indicate that the addition of MWCNTs can slow down the volume variation of bentonite at the normal shrinkage stage and at the initial swelling stage and improve the water retention capacity in the low suction range. Meanwhile, reducing bentonite’s dry density can increase the void ratio during drying, decrease the void ratio during wetting, and improve the water retention capacity in the low suction range. Dry density and MWCNTs content both have no influence on the SSCC at the residual shrinkage stage and the zero shrinkage stage, the SFSCC at the residual swelling stage, and the SWCC at the high suction range.

Unveiling thereinforcement potentiality of MWCNTs architecture towards the improvement of microstructural vis-a-vis mechanical and thermo-mechanical properties of pressureless sintered MgAl2O4 spinel ceramic composite

The study presented in this work focuses on the preparation of composites made of multi-walled carbon nanotubes (MWCNTs) and magnesium aluminate spinel through a pressureless sintering technique. The effects of sintering temperature and MWCNTs content on the densification behavior and mechanical properties of the composite were investigated in detail. The results revealed that the composite exhibited improved densification behavior, enhanced mechanical performance and decent control at the microstructural refinement with increasing MWCNTs content up to 0.75 wt%. The superior mechanical properties obtained in case of sintered composite were attributed to the synergetic toughening mechanisms involving the fiber pull out, cracks bridging and cracks deflection effects of reinforcing phases, observed as a resultant effect of strong interfaces with the matrix phase. The crystalline structural arrangement obtained from the XRD and Raman spectral analysis of the composites structure also satisfies the attainment of the promising reinforcement potential of the nanotubular structure. Most importantly, the study also exemplified the subsidiary interference of a surface decorative coating on the MWCNTs structure with the MgAl-binary oxide network. The strategic grafting of the oxide protective shell and the consequent development of a robust interfacial bridging network between the matrix and reinforcement phase regulated the energy dissipation characteristic for fiber debonding. This, in turn, restricted the crack growth phenomenon during mechanical loading, and thereby ultimately contributing to the enhanced fracture toughness, reduced thermal expansion co-efficient and augmented thermo-mechanical performance of the evolved spinel-based composite structure

Improvements in the lateral crushing behavior of syntactic foam‐filled glass fiber reinforced polymer tubes by the addition of straight and helical multiwalled carbon nanotubes

AbstractTo diminish the brittleness of glass fiber reinforced polymer tubes and syntactic foams, a novel composite tube filled with syntactic foam was proposed, in which thin‐walled tubes were reinforced by ribs and the syntactic foam core reinforced with multiwalled carbon nanotubes (MWCNTs). The influence of the ribs and the type and content of MWCNTs on the lateral crashworthy characteristics of composite tubes was investigated. Crushing experimental results indicated that the ribs contributed to improving the crashworthy performance for both hollow and foam‐filled tubes. The effect of the ribs on the energy absorption was more pronounced for the hollow tubes. Incorporation of straight or helical MWCNTs lead to improvement of the crush resistance and energy absorption for foam‐filled tubes. With the same MWCNT content, the peak load and absorbed energy of specimens with helical MWCNTs were nearly 14% and 13% higher than those of specimens with straight MWCNTs, respectively. Furthermore, analytical models were proposed to predict the load–displacement responses for foam‐filled tubes in the linear‐elastic, postcrushing, and foam‐compaction stages. The predicted results agreed well with experimental results. The resulting composite tubes are potential light‐weighted and crashworthy structures, which could be applied as collapsible energy absorbers in engineering fields.

Flexible MWCNT/Silk fibroin film decorated with Pt NPs for electrochemical glucose sensors

Flexible glucose sensor has become a research focus of continuous blood glucose detection methods because it can easily and quickly detect the glucose content in human body fluids. We prepare a multi-walled carbon nanotube (MWCNT)/Silk Fibroin (SF) flexible film, decorated with platinum nanoparticles (Pt NPs) and loaded with glucose oxidase (GOx) to construct a Pt-MWCNT/SF glucose sensor. A flexible conductive film with an electrical conductivity of 8.5 × 10−5 S/m is prepared by controlling the content of MWCNT. The maximum breaking strength and elongation at the break of MWCNT/SF film are 19.12 MPa and 192%. The Pt-MWCNT/SF glucose sensor has excellent conductivity stability under mechanical deformation and accurately detects glucose in the presence of other biomolecules. The linear range of glucose response is 0.1 to 3.75 mM, and the sensitivity is 8.09 μA/mM·cm2. The biological electrode constructed based on MWCNT/SF film has excellent flexibility, which is expected to be integrated with other electronic devices for monitoring and managing human health.

Flexural and flame retardance properties of multi-walled carbon nanotubes/glass fibre/epoxy hybrid composites

The effect of different multi-walled carbon nanotubes (MWCNTs) wt.% loading on the flammability, water absorption, thermal stability and flexural properties of glass fabric reinforced epoxy composites is reported in this paper. The pristine MWCNTs were dispersed in water, using arabic gum (GA) as a dispersing agent. Then, the suspension was sprayed onto the glass fibre (GF). Hybrid composites with and without MWCNTs were fabricated using hand lay-up and vacuum bagging techniques. Based on standard fire testings such as limiting oxygen index (LOI) and horizontal burning (UL94HB), it was observed that the composites were able to self-extinguish, even at low amounts of MWCNTs. Increase in the MWCNTs content produced a concurrent increase in the LOI of the composites which reached a maximum value of 31.30 ± 1.22% at 1 wt% MWCNT. The thermal stability was investigated using thermogravimetric analysis (TGA) and it was found that the addition of MWCNTs improved thermal stability, and increased the fire-retardance of the glass fabric reinforced epoxy (GF/EP) composites. The highest composite flexural strength (150 MPa) and flexural modulus (12 GPa) were attained at 0.5 wt% MWCNT. Above 0.5 wt%, a drop in strength and modulus was observed. The results from this study showed that the use of hybrid reinforcement containing MWCNTs can help to significantly improve the flame retardance, water absorption, and mechanical properties of reinforced composites by incorporating optimum amount of MWCNTs.

Experimental investigation on a solar parabolic collector using water-based multi-walled carbon-nanotube with low volume concentrations

A limited experimental work was on multi-walled carbon nanotube (MWCNT)—water nanofluid with surfactant in the solar parabolic collector at low volume concentrations. At high-volume concentrated nanofluid, the pressure drop was more due to an increase in the viscosity of the working fluid and an increase in the nanoparticle cost; hence it is not economical. This report attempted to use Sodium Dodecyl Benzene Sulfonate (SDBS) surfactant in the low-volume concentrated MWCNT-water nanofluid to establish effective heat transfer in solar parabolic collector applications. The stable MWCNT-water nanofluid was prepared at 0.0158, 0.0238, and 0.0317 volume concentrations. The experiments were conducted from 10:00 to 16:00 at 6, 6.5 and 7 L/min flow rates concerning ASHRAE Standards. At the 7 L/min flow rate of the working fluid, having a minimum temperature difference between the working fluid and absorber tube leads to better heat transfer. The increased volume concentration of MWCNT in the water enhances the surface area interaction between water and MWCNT nanoparticles. This results in maximum solar parabolic collector efficiency at 0.0317 vol% with a 7 L/min flow rate and 10–11% higher than the distilled water.

Coaxial structured Bi2S3–SnS2-MWCNT hybrid nanocomposite with its improved thermoelectric properties

Bismuth(III) sulfide (Bi2S3), tin(IV) sulfide (SnS2), and a multi-walled carbon nanotube (MWCNT) are prepared as a hybrid composites (Bi2S3–SnS2-MWCNT) using a simple hydrothermal method. The as-prepared hybrid composite exhibit n-type thermoelectric (TE) characteristics and an enhanced power factor (PF) value. Bi2S3–SnS2 composites are anchored to the surface of MWCNT and form a coaxial structure. The nanostructure formation through bonding between these different materials is confirmed via scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The TE properties of the Bi2S3–SnS2-MWCNT composite is improved by changing the Bi2S3, SnS2 and MWCNT content. The maximum PF (∼150.8 μ·W/m·K2) was obtained for Bi2S3–SnS2-MWCNT composite with Bi:Sn ratio of 7:3 and 2 wt% of CNT. The highest PF values were ∼34 and ∼58 times higher than the PF of Bi2S3 and SnS2 at room temperature. The synthesized Bi2S3–SnS2-MWCNT hybrid nanocomposite can provide important components for fabrication CNT-based TE composites with high conversion efficiency, further advancing TE device.

Recovery of Pure Water, Salicylic Acid Crystals, and Paracetamol using PVDF-MWCNT Membranes by Membrane Distillation-crystallization

Membrane distillation-crystallization (MDC) is presented as a novel technique in the treatment of waste concentrated water which produces valuable crystals along with pure water. In the present study, multi-walled carbon nanotubes (MWCNT)/polyvinylidene fluoride (PVDF) flat sheet membranes were prepared via the wet phase inversion method and applied in MDC for the treatment of pharmaceutical waste. The pure and modified membrane surface properties are characterized with the help of SEM, FTIR, and contact angle measurement. The present work reported the effect of MWCNT content and feed temperature on the MDCperformance and measured pure water flux and pharmaceutical compounds recovery. The observed maximum permeate flux and crystal recovery for Salicylic acid system was 5.5 kg/m2h and 50%, respectively for PVDF+0.5% CNT membrane and 5 kg/m2h and 48%, respectively for pure PVDF. Also, for paracetamol system it was 3.9 kg/m2h and 41% for PVDF +0.5% CNT membrane and 3.5 kg/ m2h and 38% for pure PVDF. Obtained results show that MDC has good potential in treating pharmaceutical waste.

Impacts of ZnO and multi-walled carbon nanotubes (MWCNTs) on biological parameters of the Oriental river prawn Macrobrachium nipponense De Haan, 1849 (Decapoda: Caridea: Palaemonidae)

Abstract Nanomaterials (NMs) mainly settle on bottom sediments and accumulate in the benthos of aquatic communities. Decapod crustaceans, being deposit-omnivorous feeders, are appropriate biological models to assay the biological effects of NMs. The present study evaluated the effects of ZnO and multi-walled carbon nanotubes (MWCNTs) NMs separately and in combination on the activities of antioxidant enzymes on crustacean hyperglycemic hormone (CHH), hematology, reproductive performance, and hepatopancreas lesions the Oriental river prawn, Macrobrachium nipponense De Haan, 1849 [De Haan, 1833–1850]. We essayed concentrations of ZnO (0, 1, 10, 30, 50 mg l–1) and MWCNTs (0, 5, 10, 15, 20 mg l–1) and two higher concentrations of the NMs were compared in combined treatments. Both NMs showed dose-dependent effects on reproductive parameters of M. nipponense, especially the fertilization rate of eggs. Inter-molt and inter-spawn periods were postponed and reproduction stopped in 50 ppm ZnO and 15 and 20 ppm MWCNTs treatments. Our findings showed that the release of crustacean hyperglycemic hormone (CHH) and superoxide dismutase (SOD) enzyme activity are directly related to the NMs levels independently as well as in combination. NMs did not show any effect on the activities of alanine transaminase (ALT) and aspartate transaminase (AST) enzymes in muscle tissue independently, but the combined effects of the activities of these enzymes were significant. NMs caused hepatocyte enlargement, melanization, apoptosis, and necrosis damages in the hepatopancreas of prawns. The findings showed that ZnO and MWCNTs NMs have strong adverse biological effects on M. nipponense, and that this species is an appropriate bio-indicator and bio-monitor organism for NMs contaminations in the freshwater aquatic environments.

Impact behaviour of MWCNTs reinforced YSZ and Al2O3 ceramic-nanocomposites prepared via vacuum hot-pressing technique

Materials for structure-based aerospace applications are on high demand throughout the globe. Owing to its high strength to weight ratio and high stiffness, composites are potential candidates in aerospace, turbine and military applications. This paper concentrates on the impact behaviour of two nanoceramic composites - yttria stabilized zirconia (YSZ) and aluminium oxide (Al2O3) reinforced with multi-walled carbon nanotubes (MWCNTs) prepared via vacuum hot-pressing at 1600 °C with a pressure of 30 MPa at varying MWCNTs contents (1, 3 & 5 wt.%). The composite tiles were examined for impact behaviour using gas gun at different velocities (50, 100 & 200 ms−1). The results indicated that composites with 1 wt% MWCNTs reinforced YSZ demonstrated lower penetration compared to other composites owing to its higher interfacial bonding between MWCNTs and YSZ. On the other hand, alumina reinforced MWCNTs showcased a higher depth of penetration due to weak van der Waals force of attraction between MWCNTs and alumina. The reinforcement of CNTs up to 3 wt.% worked as threshold for improvement in impact behaviour for ceramics whereas penetration values increase with increase of MWCNTs.

Investigating the effect of carbon nanotubes and graphene oxide on water/crude oil separation efficiency in polystyrene nanofiber membrane

In recent years, carbon-containing nanofibrous membranes have been used for oil separation purposes due to their superhydrophobicity, high specific area, high porosity, low basis weight, and selectivity. This work aims to study the effect of different carbon-based materials including multi-wall carbon nanotubes (MWCNT) and graphene oxide (GO) on the water/crude oil separation efficiency of electrospun polystyrene (PS) nanofibrous membrane. In the following, an experiment based on factors including the concentration of PS, the concentration of MWCNT, the concentration of GO, and the type of crude oil (heavy and light) which comes to a total sample of 32 is performed. After selecting the best combination of the factors, the optimum sample is chosen to be used as double and triple-layer membranes in the same condition as the main experiment. The results showed that the optimum membrane of 20 wt% of PS, 1.5 wt% of MWCNT, and 15 of either heavy or light oils can lead to about 90% separation efficacy. Furthermore, both doubled and tripled membranes showed approximately 99.99% separation efficacy. However, tripled layered membrane demonstrated lower flux (335.10 for heavy oil and 450.19 for light oil) than doubled one (350.32 for heavy oil and 525.13 for light oil) due to its higher thickness.

Hygrothermal degradation of MWCNT/epoxy brittle materials under I/II combined mode loading conditions: An experimental, micro structural and theoretical study

The effects of carboxylated multi-walled carbon nanotubes (MWCNTs) are studied experimentally and theoretically on mixed-mode (I/II) fracture behavior of epoxy resin at the presence of hygrothermal aging conditions. In this paper, the mixed-mode fracture of MWCNT/epoxy is experimentally measured using Short Beam Bending (SBB) samples with different crack inclination angles (α) ranging from pure mode I (i.e., α = 0°) to pure mode II (i.e., α = 39°). To examine the effects of hygrothermal aging conditions and water barrier properties of MWCNTs, four groups of samples including a group of neat epoxy specimens, and three groups of MWCNT/epoxy specimens (with 0.1, 0.3, and 0.5 wt% of MWCNTs) were manufactured and immersed into hot deionized water for 15 days at 60 °C temperature and similarly four groups were placed at room temperature conditions (26 °C and 25–35% relative humidity) for 15 days. According to the experimental results, toughening the epoxy resin by incorporating nanotubes with 0.1, 0.3, and 0.5 wt% of MWCNTs improved the fracture toughness at both environmental conditions, but the highest fracture toughness was obtained for composition containing 0.3 wt% nanoparticles. The variations of fracture loads were dependent on the ambient environment, MWCNTs content, and mode mixity. The relationship between the obtained experimental results, microstructure and morphology of fracture in the tested samples was also investigated. In addition, the load-carrying capacity of the SBB samples made of the neat and MWCNTs modified epoxy material was also predicted well using a two-term based fracture model called Generalized Maximum Tangential Stress (GMTS) criterion.

Piezoresistive response of carbon nanotube and carbon fiber/epoxy composites under cyclic loading

Maintaining the mechanical properties and long-term operational safety is considered the main challenge for composite materials under cyclic loading. This work presents mechanical performance of tri-component composites based on multiwall carbon nanotubes (MWCNTs), carbon fibres (CFs) and epoxy resin, and their electrical conductance property for applications like strain gauges. As a result of incorporation of MWCNTs into the epoxy resin in the composite’s morphology, their electrical, mechanical and piezoresistive performance can indicate the self-sensing of carbon fiber reinforced epoxy resin matrix (CF/Epoxy matrix) composites; and thus its influence has been systematically examined. The inclusion of multiwall carbon nanotubes increased the resin bonding to the surface of the CF’s leading to an increased electrical conductivity and mechanical performances. The piezoresistive performance was significantly influenced by the amount of MWCNTs added to the resin, where the Gauge Factor (GF) with respect to the MWCNTs concentration under cyclic tensile and cyclic bending were in the range of 0.6∼1.5 and 2.5∼5.5 respectively. Moreover, the piezoresistive behaviour of the composite samples showed reasonable sensitivity, stability, and reversibility under cyclic mechanical loading, and the samples withstood more than 500 cycles of load without detectable loss in performance. The exceptional mechanical, electrical and piezoresistive performance and easy manufacturing process of the tri-component composites make them attractive for applications such as self-monitoring structural components.