Presence Of Carbon Fibers Research Articles

Self-heating characteristics of electrically conductive cement composites with carbon black and carbon fiber

This study aimed to investigate the self-heating characteristics of electrically conductive cement composites (ECCCs) and propose an effective and affordable mix design for ECCC blocks that are applicable to the accelerated curing of concrete with carbon black and carbon fibers employed as conductive agents. Twelve mix proportions were prepared by varying the carbon black and carbon fiber contents. A voltage application protocol was designed and used to examine the self-heating capacities of the mixtures. The results show that the presence of carbon fibers was critical so that the electrical resistivities of ECCCs with 0.2 vol% carbon fibers were less than 0.16% of that without conductive agents. For a given content of carbon fiber, an increase in the carbon black content up to 0.8 vol% led to a drastic decrease in electrical resistivity, and achieved the highest average surface temperature of ECCC equal to approximately 77 °C. However, the use of 1.2 vol% carbon black caused an increase in the electrical resistivity. Further, the trends were in accordance with the change in the dispersion degree of carbon black, as analyzed via fluorescence microscopy. Finally, two selected ECCC blocks (with 0.4 vol% carbon fiber and 0 vol% or 0.8 vol% carbon black) were tested for the accelerated curing of ordinary cement paste, charged at 25 V DC for 24 h. The cement paste cured using the blocks with 0.8 vol% carbon black attained more hydrated phases, and at least an 11% reduction in porosity at 24 h of curing.

Moisture dependent tensile and creep behaviour of multi-wall carbon nanotube and carbon fibre reinforced, injection moulded polyamide 6 matrix multi-scale composites

a bstract In this study the creep behaviour and its dependence on moisture content in injection moulded hybrid composites reinforced with carbon fibres and carbon nanotubes was investigated. The tensile tests and the scanning electron microscope images confirmed that the presence of carbon fibres helped the uniform distribution of carbon nanotubes in the matrix. In the composites reinforced only with carbon fibres, the creep rate was lower than in any of the composites reinforced with only carbon nanotubes. Synergistic effects were observed when carbon nanotubes were added to the composite besides the carbon fibres: the creep rate was even lower and decreased with the increase in nanotube content. In the composites only reinforced with carbon nanotubes, crystallinity decreased, and moisture absorption increased with increasing nanotube content, but in the hybrid composites, the decrease in crystallinity and moisture absorption was much lower, thus the disadvantageous effect of moisture on the creep rate was much smaller in the hybrid composites.

Mechanical and Thermo-Physical Performances of Gypsum-Based PCM Composite Materials Reinforced with Carbon Fiber

Phase change materials (PCMs) have received extensive attention due to their high latent heat storage density and isothermal behavior during heat charging and discharging processes. The application of PCMs in buildings would match energy supply and demand by using solar energy effectively, thereby reducing building energy consumption. In this study, a diatomite/paraffin (DP) composite was prepared through a vacuum-impregnated process. The thermo-physical performance, thermal stability, chemical structure and thermal reliability of the DP composite were evaluated. To develop a structural–functional integrated energy storage building material, carbon fibers (CF) were chosen as the reinforcing material. The mechanical and thermal properties of CF-reinforced DP/gypsum were examined. It is evident that the flexural strength and thermal conductivity of DP/gypsum containing 1 wt. % CF increased by 176.0% and 20.3%, respectively. In addition, the results of room model testing demonstrated that the presence of CF could enhance the overall thermal conductivity and improve the thermo-regulated performance of DP/gypsum. Moreover, the payback period of applying CF-reinforced DP/gypsum in residential buildings is approximately 23.31 years, which is much less than the average life span of buildings. Overall, the CF reinforced DP/gypsum composite is promising for thermal energy storage applications.

Passive thermal management of a lithium-ion battery using carbon fiber loaded phase change material: comparison and optimization

Phase change materials (PCMs) are currently used for many heat management applications. However, the heat transfer performance of PCMs is limited by their low thermal diffusivities. This is a critical issue for high heat flux applications, such as in thermal management of lithium-ion (Li-ion) batteries. The present work aims at the study of heat transfer enhancement in a cylindrical Li-ion battery thermal management system consisting of a PCM (paraffin) loaded with randomly distributed and radially oriented carbon fibers. The system was simulated numerically under various cooling conditions, including naturally convecting air, in the presence of pure paraffin, and in the presence of carbon fiber loaded paraffin. The results for orderly arranged carbon fibers were compared with those of random distribution. Numerical results indicated that better battery thermal management can be achieved for the radially distributed carbon fiber arrangement in the PCM. The advantage of radial over random distributions can be due to the constant, uniform, and non-agglomerating distribution of carbon fibers under which thermo-physical properties of carbon fibers are better realized in the composite medium. The presence of carbon fibers with thermal conductivity of k=50W/m K in the PCM has caused a more uniform temperature profiles in the radial direction because of the improved thermal conductivities. The results of this research can be used as a guideline for designing battery thermal management system.

The effect of processing in a SHF electromagnetic field on the moisture absorption of cured polymer composite materials

Comparative studies of moisture absorption by cured polymer composite materials (PCM) under conditions of being in a climate chamber for 7 days, previously subjected to short-term exposure to a SHF electromagnetic field with a frequency of 2.45 GHz, have been performed. It has been found that processing with an energy flux density (17-18) x104 mW/cm2 for 2 minutes contributes to a significant decrease in moisture absorption, which is expressed in a decrease in weight change after the presence of carbon fiber and fiberglass prototypes in the chamber compared with control samples by 16.7 and 25%, respectively. The reason for this result, determined on the basis of microstructure analysis, presumably lies in the reduction of the pore size and the increase in the relief of agglomerates, which increases the resistance to liquid penetration. Taking into account the previously established positive effect on improving the strength of PCM processed in a SHF electromagnetic field, the results obtained confirm the feasibility of using this method as a finishing technological operation in the production of PCM products.

Characterization of Continuous‐Wave Laser Heating Ignition of Ammonium Dinitramide‐Based Ionic Liquids with Carbon Fibers

AbstractAmmonium dinitramide–based energetic ionic liquid propellants (ADN‐EILPs) exhibit the advantages of high energy density, low toxicity, and handling safety, and are therefore promising monopropellants. Herein, we characterized the ignition of ADN‐EILPs induced by CW laser heating in the presence of carbon fibers, clarifying the effect of laser power and suggesting that ignition reproducibility is influenced by the difference of ADN‐EILP osmotic state in carbon fibers or carbon fiber configuration. The observed ignition behavior allowed one to conclude that (i) high‐power CW laser heating causes the formation of bubbles on the surface, which disturbs further heating; and (ii) an Arrhenius‐type relationship exists between ignition delay and heating rate, suggesting that the strategy of foreshortening ADN‐EILP ignition delay by increasing CW laser power has certain limits.

Evaluation of mechanical properties of polytherimide reinforced carbon/glass/ aramid hybrid composites

Composites are quite competent in mechanical strength than metals. Due its high strength to weight ratio, light weight, take over the need of metal which were exhaustively used in the manufacturing of the structure of automobile and aircraft.In this research, the effect of mechanical properties, i.e. tensile and flexural strength on hybrid composites fabricated using woven carbon fabric, glass fabric and aramid fabric (Kelvar 29) and has been studied. Composites were fabricated using a compression molding technique. Tensile strength varies from 148 MPa to 501 MPa, flexural strength varies from 11 MPa to 19 MPa and hardness of the sample varies from 54D to 96 D. The tensile test and flexural test is carried based on ASTM D638 and ASTM D790 specification respectively. Scanning electron microscopic (SEM) images were used to analyze the surface morphology of the developed composites. The study concluded that the presence of carbon fiber in the composites results in better mechanical properties of the composite material.

Effect of Strengthening of Steel Beams with Variable Length by Using Carbon Fiber

In this research, four steel beams were fabricated and tested to understand the influence of their strengthening (by using carbon fiber) with various span lengths on load deflection, load-strain, and ultimate load responses. All tested beams have the same cross-sectional area, and they are all strengthened by using intermediate stiffeners and cover steel plate at top flange to insure that failure will occur at the bottom flange. The tested steel beams are divided into two groups according to their clear span lengths 1400 and 1900 mm, and each group is subdivided into two beam cases based on whether they are strengthened by carbon fiber or not. From this study, it was found that the load deflection and load-strain curves for the beams strengthened by carbon fiber are stiffer than the original beams (without carbon fiber) with similar clear span lengths (this behavior was more obvious with smaller lengths). Moreover, the load deflection and load-strain responses have shown that beams became stiffer when the effective length is reduced (with and without carbon fiber), and this behavior was more apparent with the beams strengthened by carbon fiber. On the contrary, from the results of ultimate load of the beams, it can be concluded that the percentage of increase in ultimate load for the beam strengthened by carbon fiber is increased with the decrease in its span length. One could also conclude that when the effective length decreases, the ultimate load was increased and the percentage of this increasing is magnified with the presence of carbon fiber.

The use of functionalized carbon xerogels in cells growth

In the present study carbon xerogels are used for the first time to study the fibroblast cell growth. For that, carbon xerogel microspheres are synthesized and thereafter functionalized with carbon nanofibers followed by the 1,3-dipolar cycloaddition of azomethine ylides (the so called “Prato reaction”) or the addition of aryl diazonium salts (the so called “Tour reaction”) to improve its wettability. The presence of nanofibers produces a huge improvement of the functionalization degree (59 versus 372 μmol/g for pristine carbon spheres and carbon spheres with 30% of carbon nanofibers, respectively) in spite of the blockage of the carbon spheres porosity caused after the nanofibers growth. This improvement was explained on the base of the increase of the number of probable active sites for the addition reactions (CC bonds) and the accessibility to these active sites (accessible surface area) by the presence of nanofibers. These high functionalization degrees reflect a promising potential of these materials in biomedical applications. Toxicity results obtained using a fibroblast cell line showed that samples are biocompatible for this kind of cells and that the presence of carbon fibers on the surface of the spheres increases the cells proliferation in a high extend reaching in some case values around 150% regarding the control. This study evidences that carbon aerogels could be interesting materials in biological applications, an unexplored field for this type of materials, being biocompatible, favouring the proliferation of cells and achieving high functionalization degrees.

Strength and Wear Behavior of Mg Alloy AE42 Reinforced with Carbon Short Fibers

In addition to the advantage of the lightweight of magnesium alloys, magnesium composites have moderate strength and elastic modulus. The proposed application of magnesium composites as diesel truck pistons makes it necessary to assess their wear performance. Little research data have been discussed on wear behavior of Mg alloy AE42 matrix and its composites. Thus, this paper reports wear behavior of magnesium alloy AE42 (Mg–Al–Mn—RE; rare earth) and its composite AE42-C, which contains 23 vol% of randomly oriented carbon short fibers. Materials characterization, including density measurements, hardness testing, microstructures investigation, and compression testing at temperatures of 25, 150, and 300 °C, were conducted. Wear tests were performed under various loads and sliding distances. Wear mechanisms were also proposed based on the examination of worn surfaces using optical microscopy and scanning electron microscopy equipped with EDX (energy-dispersive X-ray spectrometry) analysis system. The hardness of AE42-23 vol% C composite is twice the hardness of the Mg matrix alloy AE42. Significant improvements to yield stress and compressive strength at temperatures of 25, 150, and 300 °C of the composite versus the AE42 alloy are achieved. Wear resistance of the composite is improved considerably versus that of the Mg alloy AE42 at the various sliding distances. Smearing of graphite on the worn surface produces a lubricating film that delays change from mild to severe wear of the composite, especially at high loads. EDX analysis of the worn surface shows oxidation of the matrix alloy at higher wear loads, and this mechanism decreases in the presence of carbon fibers under the same loads. Abrasive wear, oxidation, and plastic deformation are the dominant wear mechanisms for the alloy matrix AE42, whereas mainly abrasive wear is the wear mechanism of AE42-23 vol% C composite under the proposed testing conditions.

Effect of carbon fiber volume fraction on 6H to 4H-SiC polytype transformation

ABSTRACTIn this study, polycrystalline α-SiC composed of 55.7 wt.% 6H-SiC, 35.1 wt.% 4H-SiC with different volume fractions of carbon fibers (0–5–10–15–20%) was successfully sintered by spark plasma sintering technique at 2000°C and 35 MPa of applied pressure. The micrographs obtained from scanning electron microscopy revealed that the sintered samples were composed of equiaxed SiC grains. Results indicated that the presence of carbon fibers retarded the SiC densification process, decreased their relative densities and increased their porosity. Additionally, according to quantitative phase analysis by the Rietveld method during the sintering step, it was found that the 6H to 4H transformation has taken place. Increasing the carbon fibers content accelerated this trend as the sample containing 20 vol.% carbon fiber was consisted of 85.5 wt.% 4H-SiC.

Influence of phenylphosphonic amide on rheological, mechanical and flammable properties of carbon fiber/RTM6 composites

Abstract The aim of this work was to study the influence of a high efficient halogen-free phenylphosphonic amide flame retardant (FP1) to epoxy resin (brand name RTM6) on the rheological, mechanical and water absorption properties of the carbon fiber/RTM6 epoxy composite (CFR). With a 8 wt% loading FP1 in RMT6, the processing of CFR/FP1 was able to use the equal condition with that of CFR since the viscosity of RTM6 was maintained at a similar level in the minimum viscosity temperature region. The addition of FP1 showed negligible impacts on the interlayer share strength (ILSS) and in-plane share strength (IPSS) of CFR. The interfacial strength between RTM6 matrix and carbon fiber was decreased due to the impact of FP1 on cross-linking density and polarity of RTM6. The flame retardant efficiency of FP1 showed difference in presence of carbon fiber or not in RTM6. RTM6/FP1 (8 wt%) had a LOI value of 38%, achieved a V-0 rating at thickness of 3.2 mm in UL 94 test and showed 60% reduction in peak of heat release rate. RTM6/carbon fiber/FP1 (8 wt%) had a LOI of 43%, while it showed reduced performance in UL 94 and cone calorimeter tests.

INFLUENCE OF ENERGY ON PHASE COMPOSITION OF END-PRODUCT OBTAINED BY VACUUM-FREE ELECTRIC ARC SYNTHESIS OF CUBIC SILICON CARBIDE

The paper describes the scientific and technical basis of the vacuum-free plasma method for obtaining silicon carbide realized by DC arc discharge between graphite electrodes. In a series of experiments the energy supplied to the system was changed by increasing the duration of arc discharge with the constant value of current intensity (165 A); two precursor types were used: a mixture of silicon powder with X-ray amorphous carbon in the microfiber form in the first case and with carbon powder in the second case; the mass ratio in the initial mixture was Si:C = 2:1. As a result of the evaluation of the synthesis product quantitative composition, the experimental parameters that allow to achieve the maximum content of the target silicon carbide phase (up to 45%) are determined. Moreover, it was possible to determine the parameters when the only impurity phase in the product was graphite; as a result, the purification of the product from unbound carbon and thereby obtaining silicon carbide with ~99% content was successfully performed by atmospheric furnace heating at a temperature of 900 °C. This result is ensured by two factors: the presence of carbon fibers in the initial reagents mixture and a sufficient level of the supplied energy of about 216 kJ/g.

Synthesis and properties of calcium hydroxyapatite/carbon fiber composites

Composites comprising micrometer-sized carbon fibers (CFs) and biocompatible nanocrystalline calcium hydroxyapatite Ca10(PO4)6(OH)2 (HA, NCHA), containing 1.0, 2.0, and 5.0 wt % CFs, have been synthesized in the course of precipitation from aqueous solutions in the Ca(OH)2–H3PO4–CF–H2O system. Some physicochemical characteristics of the precursor CFs and synthesis products have been determined using chemical, X-ray diffraction, and thermal analyses, IR spectroscopy, and scanning and transmission electron microscopy. An analysis of composition–synthesis conditions–structure–particle size–property correlations indicates that the presence of CFs in HA/CF composites strongly decreases the sizes and modifies the habit of NCHA. A rise of CF content in the HA/CF composite is accompanied by a decrease in particle size and a rise in solubility of NCHA.

Influence of Stacking Sequence on the Impact and Postimpact Bending Behavior of Hybrid Sandwich Composites

A new hybrid sandwich structure was developed by using carbon, e-glass, and s-glass fabrics as reinforcement materials, an epoxy resin as the matrix material for face sheets, and a PVC foam as the core material. Six different configurations were prepared. Sandwich composites plates with different stacking sequences were subjected to low-speed impacts will energies of 7.5, 15, and 22.5 J. Their impact response is analyzed and reported in terms of the peak load as a function of impact energy. After impact tests, 3-point bending tests were conducted to determine the bending behavior of the sandwich composites after impacts in terms of their flexural strength. The results obtained showed that the use of carbon fabrics in the face sheets increased the peak loads for all the impact energies considered. The presence of carbon fibers in skin regions increased the flexural strength of the composites, but e-glass fibers decreased this strength.

Low temperature fabrication & photocatalytical activity of carbon fiber-supported TiO2 with different phase compositions

Crystalline TiO2 nanoparticles with different phase compositions were fabricated on carbon fibers. The fabrication is achieved at low temperature. The process includes the treatment of Ti(OH)4 with hydrogen peroxide in the presence of carbon fibers. Neither additional acids nor bases, or additives are used during the process. Carbon fibers prior to and after TiO2 loading are characterized by FE-SEM, XRD, and UV–vis absorption spectroscopy. The photocatalytic activity was assessed via photocatalytic degradation of methyl orange solution, and found to be phase composition-dependent & pH dependent. Carbon fibers loaded with mixed-phase TiO2 led to the best photocatalytic performance. HRTEM reveals the anatase/rutile heterojunction which helps explain the high efficiency of photocatalysis. They have been demonstrated to be re-usable in the continuous photocatalytic degradation process.

Cation-exchange membrane modified by inorganic short fibres

Ion-exchange membranes have been used in separation processes, for example, electrodialysis, electrodeionisation and electrophoresis. Preparation of a new type of heterogeneous ion-exchange membrane with improved mechanical properties is described in the paper. Heterogeneous cation-exchange membranes reinforced by short carbon fibres (1 mm) were prepared with different amount of the fibres and ion-exchange resin. Fibres and ion-exchange resin were compounded with polyethylene matrix in two steps. Membrane foil was formed by extrusion. Electrochemical properties of the membranes like electric resistance, permselectivity and counterion-transfer number were measured. Microstructure and morphology of the membranes were assessed by light microscopy. Properties of reinforced membranes were compared with unreinforced membrane in all cases. Results clearly show that electrochemical properties depend on amount of the ion-exchange resins and are not negatively affected by presence of carbon fibres. Light microscopy has provided evidence of absence of large fibre clusters. Fibres are uniformly distributed throughout the volume of the membrane.

Properties of freshly mixed carbon fibre reinforced self-consolidating concrete

This study examined the effects of discrete pitch-based carbon fibres on the fresh properties of self-consolidating concrete. Different carbon fibre reinforced self-consolidating concrete mixtures were produced incorporating 0%, 0.25%, 0.5%, 0.75% and 1% carbon fibres by concrete volume with two water-to-binder ratios (0.35 and 0.40). The flowing ability (filling ability and passing ability) of the concrete mixtures was determined with respect to slump flow, J-ring slump flow, and T50 slump flow time. The segregation resistance of the concrete mixtures was evaluated by using the sieve stability test. Visual stability index (VSI) was also used to assess the segregation resistance of concrete. Moreover, the freshly mixed concrete mixtures were tested for air content and unit weight. The hardened concretes were tested by a Scanning Electron Microscope to observe the distribution of fibres. Test results revealed that the increased amount of carbon fibres decreased the filling ability and passing ability of concrete. However, carbon fibres had no adverse effects on the segregation resistance of concrete. Also, no significant air entrapment occurred in the presence of carbon fibres. Carbon fibres were well-distributed and they slightly decreased the unit weight of concrete.

Thermal conversion of carbon fibres/polysiloxane composites to carbon fibres/ceramic composites

The aim of this work is to investigate the thermal conversion of carbon fibres/polysiloxane composites to carbon fibres/ceramic composites. The conversion mechanism of four different resins to the ceramic phase in the presence of carbon fibres is investigated. The experiments were conducted in three temperature ranges, corresponding to composite manufacturing stages, namely up to 160 °C, 1000 °C and finally 1700 °C. The study reveals that the thermal conversion mechanism of pure resins in the presence of carbon fibres is similar to that without fibres up to 1000 °C. Above 1000 °C thermal decomposition occurs in both solid (composite matrix) and gas phases, and the presence of carbon fibres in resin matrix produces higher mass losses and higher porosity of the resulting composite samples in comparison to ceramic residue obtained from pure resin samples. XRD analysis shows that at temperature of 1700 °C composite matrices contain nanosized silicon carbide. SEM and EDS analyses indicate that due to the secondary decomposition of gaseous compounds released during pyrolysis a silicon carbide protective layer is created on the fibre surface and fibre–matrix interface. Moreover, nanosized silicon carbide filaments crystallize in composite pores. Owing to the presence of the protective silicon carbide layer created from the gas phase on the fibre–matrix interface, highly porous C/SiC composites show significantly high oxidation resistance.

Localized thermal analysis of carbon fiber‐reinforced polypropylene composites

AbstractThe effect of carbon fiber (CF) and annealing temperature on polypropylene (PP) microstructure was studied. The crystalline state of polymer matrix was found to be a strong function of thermal history. The effect of annealing temperature on the microstructure evolution of PP in the presence of CFs was characterized by using X‐ray diffraction, DSC and localized thermal analysis. The melting behavior of CF‐reinforced PP composite was strongly dominated by the thermal history and was weakly influenced by the presence of CFs. The interface between a CF and PP matrix was found to be weak. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers