Grafted Carbon Fiber Research Articles

Mechanical properties and strain rate effect of graphene oxide grafted carbon fiber modified concrete under dynamic impact load

In order to improve the shortcomings of carbon fiber, such as smooth surface, poor bonding with concrete matrix and easy to pull out under dynamic impact load, graphene oxide is grafted onto the surface of carbon fiber by chemical bonds to prepare graphene oxide grafted carbon fiber (CF-GO). The dynamic impact test on CF-GO modified concrete (CF-GOMC) is carried out by the split hopkinson pressure bar (SHPB) test system, and the mechanical properties and strain rate effect of CF-GOMC under dynamic impact loads are studied. The modification mechanism of CF-GO is analyzed by microscopic tests. The results show that compared with carbon fiber, the surface roughness and surface area of CF-GO increase and CF-GO is more suitable for bonding with concrete matrix. CF-GO can improve the mechanical properties of concrete under dynamic impact load and enhance the strain rate effect of dynamic mechanical properties indicators by preventing crack, bridging, filling and promoting hydration. With the increase of CF-GO content, the dynamic mechanical properties and strain rate sensitivity of CF-GOMC increase first and then decrease. The optimal content of CF-GO is 0.3 %. The improvement effect of CF-GO on the dynamic mechanical properties and strain rate effect of concrete is better than that of carbon fiber. The graphene oxide on the surface of CF-GO makes the interface of CF-GO/concrete matrix compact by improving the mechanical bite force of fiber/concrete matrix and promoting the formation of hydration products on the surface of fiber. The addition of CF-GO does not change the composition of cement hydration products, but promotes the crystal growth of hydration products and optimizes the pore structure of concrete.

Comparison of dynamic mechanical properties of carbon fiber and graphene oxide grafted carbon fiber modified concrete

Graphene oxide grafted carbon fiber (CF-GO) is successfully prepared by the chemical grafting method of “grafting to”. The physical properties, mechanical properties and dispersion effects of carbon fiber and graphene oxide are comparatively studied. Carbon fiber modified concrete (CFMC) and graphene oxide grafted carbon fiber modified concrete (CF-GOMC) are prepared, and the dynamic mechanical properties and fiber/concrete matrix interfaces of CFMC and CF-GOMC are comparatively studied. The results show that the physical and mechanical properties of CF-GO are improved compared with carbon fiber, and the dispersion effect of CF-GO in concrete matrix is better than that of carbon fiber. When the fiber content is the same, the dynamic mechanical properties of CF-GOMC are better than that of CFMC, and the strain rate effect of dynamic mechanical properties indicatoes is stronger than that of CFMC. The strengthening and toughening effect of CF-GO on concrete is better than that of carbon fiber. The carbon fiber/concrete matrix interface exhibits a relatively large porosity, while the CF-GO/concrete matrix interface is well bonded. The graphene oxide on the surface of CF-GO exerts an “expansion bolt” effect, attracting the deposition of hydration product crystals and regulating their crystal structure.

In situ crosslinking of silica aerogel with reactive carbon fiber for high mechanical property, thermal insulation and superhydrophobicity

In this study, a novel silicon hydroxyl groups decorated long carbon chain grafted carbon fiber was synthesized, and a facile fabrication method was developed to produce reactive carbon fiber-silica aerogel composite with chemical crosslinking structure. Scanning electron microscopy images showed that silica aerogel matrix is wrapped on the surface of reactive carbon fibers. The reactive carbon fibers facilitated obstacle in shrinkage, and aerogel composites exhibited microporous behavior with average diameter of about 1.8 nm. Fourier-transform infrared and X-ray photoelectron spectroscopy confirmed the strong interfacial interaction between reactive carbon fibers and silica matrix. The modification mechanism of silicon hydroxyl groups decorated long carbon chain grafted carbon fiber, and the chemical crosslinking in aerogel composite were proposed. The reactive carbon fiber-silica aerogel composites synthesized in this work had been proved to have low density, excellent mechanical property, good tailoring performance, improved thermal stability, low thermal conductivity, high flame retardancy, high thermal insulation property, and superhydrophilicity. Hence, this work provided a theoretical basis for improving the performance and expanding the application of silica aerogel.

Strength, toughness and interface modification of graphene oxide grafted carbon fiber modified concrete

Graphene oxide grafted carbon fiber (CF-GO) is prepared by "grafting to" chemical graft method. The elements and chemical bonds on the surface of CF-GO are characterized by XPS test, which confirms the successful preparation of CF-GO, and the monofilament tensile strength of CF-GO is tested. The dispersion effect of CF-GO under different dispersion methods is compared, and CF-GO modified concrete (CF-GOMC) is prepared. The strength and toughness of CF-GOMC are tested and compared with those of carbon fiber modified concrete. In addition, the modification mechanism of CF-GO on fiber/concrete matrix interface is analyzed by SEM-EDS test. The results show that the monofilament tensile strength of CF-GO increases by 22.22% compared with that of carbon fiber. When dispersing with high-efficiency water reducer combined with ultrasonic wave, the dispersion effect of CF-GO is the best, the resistivity of CF-GOMC is the minimum, and the strength is the maximum. CF-GO can improve the strength and toughness of concrete, and its improvement effect is better than carbon fiber. The optimal contents of CF-GO and carbon fiber are 0.3% and 0.2% respectively. Graphene oxide on the surface of CF-GO enhances the fiber/concrete matrix interface physically and chemically by improving the mechanical interlocking force between CF-GO and concrete matrix and promoting the formation of hydration products on the surface of CF-GO. Moreover, the content of C-S-H crystal at the CF-GO/concrete matrix interface increases.

Fabrication and luminescence properties of rare earth complex grafted carbon fiber

Luminescence enhanced carbon fibers are important materials for sensing technology. In this work, rare earth Europium (Eu3+) complexes are successfully grafted onto carbon fiber (CF) and endue the CF fluorescence characteristics. The results show that the Eu-complex grafted onto CF (CEuCF) obtained sharp red emission attributed to 5D0→7F1 and 5D0→7F2 of Eu3+. The surface roughness of CF changed after fluorescence properties were given to them. With the increasing of Eu content, the fluorescence intensity of CF increased first and then decreased, and reached the highest value when the molar ratio of Eu was 2 mmol. The energy transfer in the CEuCF was also discussed in detail. Enduing CF luminous properties could broaden its application areas.

High performance and durable graphene-grafted cathode for electro-Fenton degradation of tetramethyldecynediol

A novel reduced graphene oxide grafted carbon fiber (rGO-CF) cathode for electro-Fenton was prepared using a simple thermal treatment method and applied to the degradation of tetramethyldecynediol (TMDD), a massively used non-ionic surfactant. Electrochemical characterization demonstrated that the new cathode possessed high electroactive surface area (1387.1 cm2 g−1), low electron-transfer resistance (0.198 Ω) and high activity for oxygen reduction. With these excellent properties, rGO-CF achieved 122.1 mg L−1 of H2O2 accumulation, 45 % higher than with the unmodified cathode (84.2 mg L−1). Compared to the unmodified cathode, rGO-CF doubled the TMDD degradation rate and increased the 2-hour mineralization yield from 49.4 % to 84.0 %. Most importantly, rGO-CF exhibited excellent stability verified over 1000 cycles of cyclic voltammetry and 5 runs of electro-Fenton experiments. A degradation pathway for the oxidation of TMDD is proposed. With ease of fabrication, stability and affordable cost, the new electrode shows tremendous potential for practical applications.

Direct electrochemical grafting of crystalline PAEK macromolecule on carbon fiber to enhance the interfacial properties of PEEK/CF composites

Electrochemical grafting of diazonium salts have been applied to improve interfacial properties of carbon fiber and matrix resin. However, these graft modifications are still limited to general-purpose carbon fiber reinforced resin matrix composites such as epoxy. In this research, the direct grafting of Poly (aryl ether ketone) (PAEK) macromolecule on carbon fiber was achieved with mild condition. Firstly, aniline was introduced into Poly (ether ether ketone) (PEEK) as pendent group to improve solubility and amino terminated group was introduced as precursor of diazonium salt. Then the graft was conduct through diazonium salt reduction. After modification, the aniline side group could be hydrolyzed off to recover crystallinity. To further analyze the graft, single molecular-force spectroscopy was introduced to investigate the surface of carbon fiber. Impressively, the extension curve suggested the PAEK macromolecule had been attached to surface through strong interaction. Combined this with XPS data, it was believed that the graft was a success. As a result, the grafted polymer along with the polymer that physically absorbed on carbon fiber in electrolyte can cooperate to strengthen the interface. The interfacial shear strength of the grafted carbon fiber and PEEK increased from 42.27 MPa to 97.33 MPa by 130.26%. The improvement mainly originated from the covalent bonding that connected the carbon fiber and the graft coating layer as well as the great compatibility between the graft coating layer and the matrix resin. These results also demonstrated the possibility to graft high performance polymers on carbon fiber through one-step modifications.

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.

Improving delamination resistance of carbon fiber reinforced polymeric composite by interface engineering using carbonaceous nanofillers through electrophoretic deposition: An assessment at different in‐service temperatures

AbstractIn this article, modification of carbon fiber surface by carbon based nanofillers (multi‐walled carbon nanotubes [CNT], carbon nanofibers, and multi‐layered graphene) has been achieved by electrophoretic deposition technique to improve its interfacial bonding with epoxy matrix, with a target to improve the mechanical performance of carbon fiber reinforced polymer composites. Flexural and short beam shear properties of the composites were studied at extreme temperature conditions; in‐situ cryo, room and elevated temperature (−196, 30, and 120°C respectively). Laminate reinforced with CNT grafted carbon fibers exhibited highest delamination resistance with maximum improvement in flexural strength as well as in inter‐laminar shear strength (ILSS) among all the carbon fiber reinforced epoxy (CE) composites at all in‐situ temperatures. CNT modified CE composite showed increment of 9% in flexural strength and 17.43% in ILSS when compared to that of unmodified CE composite at room temperature (30°C). Thermomechanical properties were investigated using dynamic mechanical analysis. Fractography was also carried out to study different modes of failure of the composites.

Wettability of thermoplastic and thermoset polymers with carbon nanotube grafted carbon fiber

In this experimental study the wetting behavior of unsized and carbon nanotube (CNT) grafted carbon fibers is assessed with various polymers. Thermoset epoxy and two thermoplastics (polypropylene and polycarbonate) are tested. Sessile drop method and drop-on-fiber method are employed to quantify the wettability of various fiber/polymer combinations. Contact angle measurements based on the above two methods give insights into the effectiveness of various polymers to wet different types of carbon fiber fabrics and single fiber filaments. Moreover, the effect of CNT length and density on the wettability of carbon fibers is ascertained by synthesizing nanotubes on the fiber surface for varying time durations (10–30 min). CNT grafting reduces the contact angle of the polymer drop with carbon fiber; however, too much growth of nanotubes on the fiber surface leads to improper impregnation of the polymer into the carbon fabric. While polypropylene shows better wetting characteristics with unsized and CNT grafted carbon fibers, polycarbonate shows poor wettability.

Chemically Grafting Carbon Nanotubes onto Carbon Fibers for Enhancing Interfacial Properties of Fiber Metal Laminate.

This paper primarily investigates the effects of chemically grafted modified carbon fibers on the bonding properties of fiber metal laminates (FMLs). Relative elemental content on the carbon fibers’ surface was performed via X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was utilized to observe the material microstructure. The effect of chemically grafted carbon fibers on the bond strengths of FMLs was experimentally investigated through lap joint testing. The carbon nanotubes (CNTs) grafting concentration and curing conditions of the samples were also investigated. The test results demonstrate that grafting concentrations of 0.1, 0.2, and 0.3 mg/mL CNT solution increased the bond strength of the cured samples under vacuum conditions by 63.51%, 87.16%, and 71.56%, respectively. In addition, the bond strengths of vacuum-cured samples were also increased.

Surface functional treatment of carbon fiber with ultra wide potential range in neutral electrolyte for high performance supercapacitor

Abstract In this study, the oxygen-rich functional groups grafted carbon fiber cloth electrode (OCC) was successfully fabricated by activating carbon fiber cloth (CC) in strongly corrosive and oxidative environment, and the content of oxygen functional groups on surface of OCC can be easy controlled through different activation time. Surprisingly, the OCC electrode possesses an ultra wide potential range of −1.2 − 1.2 V in neutral electrolyte that is impossible to achieve in acidic or alkaline aqueous electrolyte, and the assembled symmetric supercapacitor device (SSD) exhibits a large operating voltage of 2.2 V. What's more, SSD presents high energy density of 0.87 mW·h cm−3 at power density of 5.5 mW cm−3 and superior cycling stability (86.8% of capacitance retention after 10,000 cycles). This study may provide a facile and available method for fabricating and designing flexible electrode with high performance.

Influence of cryogenic temperature on mechanical behavior of graphene carboxyl grafted carbon fiber reinforced polymer composites: An emphasis on concentration of nanofillers

Recently, there have been rapid advances in the use of Carbon fiber reinforced polymer (CFRP) composites in cryogenic applications. Graphene-based nanofillers are under the limelight as an ideal material for being used as nanofillers in multi-scale fiber reinforced composites because of their various exotic properties. Electrophoretic deposition (EPD) of graphene-based nanofillers on carbon fiber is an attractive technique to improve the quality of the interface of CFRP composites. In the present study, the effect of nano-filler concentration in the EPD bath on the mechanical behavior of Graphene carboxyl (G-COOH) grafted CFRP composites was evaluated both at room temperature and cryogenic temperature. Experimental results showed that out of three different concentrations (0.5 g/L, 1.0 g/L, 1.5 g/L) used, 1.5 g/L has shown the best mechanical behavior at both room temperature (RT) and cryogenic temperature (CT). At RT testing maximum improvement of 25.383% and 7.287% was observed in interlaminar shear strength (ILSS) and flexural strength (FS) respectively. At CT, the highest improvement of 20.780% and 5.347% in ILSS and FS was observed respectively. Scanning electron microscope was used to carry out the fractography of failed samples to understand the dominant mode of failure.

Antistatic and microwave shielding performance of polythiophene-graphene grafted 3-dimensional carbon fibre composite

The current attempt reports the fabrication of polythiophene (PTh) grafted 3-dimensional carbon fibre composite by in-situ emulsion polymerization of thiophene (Th) monomer on carbon fibre (CF) and with graphene as filler. The antistatic studies of polythiophene-graphene grafted carbon fibre composites exhibit static charge decay period in the order of 0.2–0.5 s at 10% cut-off of high corona voltage. EMI shielding effectiveness of the composites in Ku-band illustrates a shielding effectiveness of microwaves from −15 dB to −30 dB. The shielding and antistatic performance of polythiophene-graphene grafted carbon substrate composite confirm that composite can be employ as efficiently for the protection of static charge and utilize in wrapping of electronic equipments.

Influence of Unsizing and Carbon Nanotube Grafting of Carbon Fibre on Fibre Matrix Interfacial Shear Strength of Carbon Fibre and Polyamide 6

Carbon Fibre Reinforced Thermoplastics (CFRTP) are expected to be applied to the automotive industry instead of CFRP which require curing time, due to the expected short production cycle time of CFRTP, which is using thermoplastic as a matrix. We reported that the grafting of carbon nanotubes (CNTs) on the carbon fibre improves the fibre matrix interfacial shear strength. In our process to graft CNTs on carbon fibre, chemical vapour deposition (CVD) method was used and Ni, which was used as the catalyst, was electrically plated onto carbon fibres. Since commercially available carbon fibre was sized, which may affect the plating behaviour of Ni, the effects of sizing agents on CNT deposition have to be clarified. In this study, Ni for catalytic metal was plated by electrolytic plating using a watt bath on spread PAN-based carbon fibre and unsized carbon fibre, and the influence of the sizing agent to the distribution of Ni was evaluated. The morphological observation of carbon fibre and single fibre pull-out test were conducted to clarify the influence of sizing agent on the CNT deposition and the interfacial shear strength between the CNT grafted carbon fibre and Polyamide 6 (PA6). Uniform distribution of small sized Ni particles can be obtained on unsized carbon fibre and uniform Ni particles results in uniform CNT distribution. The CNT grafted unsized carbon fibre showed higher interfacial shear strength with PA6 than that of sized carbon fibre.

Effects of Temperature on the Fibre Matrix Interfacial Shear Strength of Carbon Nanotube Grafted Carbon Fibre Reinforced Heat Resistant Resin

Transportation sector is required to reduce CO2 emissions as environmental problems are becoming more serious. Carbon fibre reinforced thermoplastic (CFRTP) are expected to be applied to the structural parts of automobiles and aircrafts because of their superior mechanical properties such as high specific strength, high specific stiffness and high recyclability. One of the problems in using CFRTP for the structural parts is heat resistance, and it is necessary to clarify the mechanical properties under their service environmental temperature. The tensile strength of CFRTP at high temperatures decreases with temperature rise. The fibre matrix interfacial shear strength is reported to be improved by grafting of carbon nanotubes (CNTs) on the surface of carbon fibre. In this study, in order to clarify the effects of temperature on the fibre matrix interfacial shear strength of CNTs grafted carbon fibre reinforced PPS resin, single fibre pull-out test was conducted. While the interfacial shear strength of CNT grafted-CF/PPS is higher than that of As-received-CF/PPS at 25 °C, no significant difference was found in the interfacial shear strength of As-received-CF/PPS and CNT grafted-CF/PPS at 80 °C.

Resistance welded thermoplastic composites joint strengthened via carbon nanotubes from flame: interface strength, mechanical properties and microstructure

Carbon nanotube (CNT)-grafted carbon fibers (CFs) were used as the interlayer heating element for resistance welding of glass fabric reinforced polyetherimide (GF/PEI) composite laminates to enhance the strength of the joints of GF/PEI. The effects of CNTs on the wettability of PEI resin on the CF surface and the interfacial microstructure and mechanical properties of welded joints were investigated. The CNTs were grown in situ on the surface of the CFs by a flame method, and their structures and morphologies were characterized by Raman spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM). PEI resin solution exhibits better wettability on CNTs-grafted CF surface with the help of capillary action. The interfacial shear strength (IFSS) of the CF/PEI resin and the SEM images of the bonding interface show a stronger binding effect between CNTs-grafted CFs and PEI resin. The mechanical property of the joints was evaluated by the tensile test of single lap shear strength (LSS). The LSS values increased first and then decreased with welding time (tw), and the optimum LSS of the joint with CNTs was increased by 23.6% to 32.5MPa in comparison with that of the joint without CNTs when tw was 60 s.

The effect of graphene oxide grafted carbon fiber on mechanical properties of class G Portland cement

As described in the research, CFs were reinforced by graphene oxide (GO) and prepared by grafting-to technology and this new graphene oxide modified carbon fiber (GO-CF) showed excellent adhesion properties to cement material, which was with excellent mechanical properties and analyzed by infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). To deeply explore the reinforcement mechanism of graphene oxide to CFs, not only were scanning electron microscopy analysis and X-ray diffraction (XRD) analysis conducted, but triaxial strain-stress mechanical performance tests, a dynamic simulation to subsurface operation environment, were also utilized to confirm the mechanical effect of GO-CFs to cement. The results showed that GO-CF reinforced cement (GOCFRC) exhibited excellent compressive strength performance with GO of only 0.4% BWOC content. And cement compressive strength increased to over 1.18 times that of pure cement after 14-day curing period. Above all, the new kind of reinforced cement material showed superior toughness compared to pure cement. Its flexural tensile strength increased by 38.81% in 3-day curing period, 38.65% in 7-day curing period, and 41.76% in 14-day curing period. Furthermore, it displayed excellent triaxial stress-strain toughness compared to pure cement: Young’s modulus increased to 150.9%, ultimate stress increased to over 121%, and ultimate strain increased to about 267%. Excellent compatible interface adhesion performance of new carbon fiber was detected through SEM analysis. Via this research, the application mechanism of GO reinforced cement material was improved, and a new type of carbon fiber reinforced cement (CFRC) with higher mechanical performance was developed.HighlightsGraphene oxide (GO) was used for the surface properties modification of carbon fiber.Graphene oxide (GO) can significantly increase the mechanical behaviors of carbon fiber.Graphene oxide-carbon fibers (GO-CFs) can significantly increase the mechanical behaviors of cement.The influence that GO-CF had on the mechanical integrity of the cement was discovered (SEM).The reinforcing mechanism that GO-CF had on the oil-well cement was discussed in detail.

Improved tensile strength of carbon nanotube-grafted carbon fiber reinforced composites

Increased tensile strength of carbon nanotube (CNT)-grafted carbon fiber (CF) composites has been reported, but the mechanism of this increase is not yet clear. In this study, CNT-grafted CF unidirectional (UD) and woven composites were fabricated using a low-temperature chemical vapor deposition (CVD) and resin transfer molding. Two types of CNTs (short and thin, long and thick) were successfully grown and grafted to CFs without degrading the CFs in the preforms. The CNT-grafted CFs exhibited increased interfacial shear strength (IFSS) similarly regardless of the CNT type. Interestingly, however, long and thick CNT-grafted CF UD and woven composites exhibited significant increases in tensile strength (about 20% and 30%), suggesting other mechanisms besides increased IFSS. The splitting crack initiation under the mixed mode condition was quantitatively characterized for the CNT-grafted CF UD composites, demonstrating that long and thick CNTs delayed the splitting crack initiation. Delayed fiber splitting and increased IFSS were concluded to be the main sources of increased tensile strength of CNT-grafted CF composites.

Interfacial shear strength of carbon nanotubes based hybrid composites: effect of loading rate

Interfacial interaction is investigated between the two basic constituents in carbon fiber reinforced plastics (CFRPs). Efforts have been made to quantify the interfacial shear strength (IFSS) between individual carbon fiber (CF) and epoxy matrix in CFRPs by performing single fiber micro-droplet debond test. Initially, IFSS of the epoxy composites reinforced with unsized carbon fiber (HCF) is assessed. Study is then extended to assess the IFSS of carbon nanotubes (CNTs) based CFRP hybrid composites. The hybrid composites are prepared by reinforcing epoxy matrix with CNT grafted carbon fibers (CNTCF). The versatile, simple and time effective method of chemical vapor deposition is used to synthesize CNTs directly on the surface of CF. IFSS is found to enhance after the inclusion of grafted CNTs in CFRP composites. Keeping in mind the application view point of CFRPs to put up with varying loads, effect of loading rate on the IFSS of CFRPs is also examined. To this end, both HCF/epoxy and CNTCF/epoxy composites are debonded at cross-head rates varying by two orders of magnitude and IFSS is compared. Finally, scanning electron microscopy of debonded fibers is carried out to understand the interfacial failure mechanism in various composites.