Carbon Fiber Bundles Research Articles

Preparation of polyvinyl alcohol-matrix z-pins and tests of their piercing properties

In this study, we developed a molding process for a new type of z-pin applicable to C/C composites. Polyvinyl alcohol (PVA) was adopted as the matrix of z-pins because it has few solid residues when subjected to an inert high-temperature environment. A highly concentrated PVA aqueous solution was prepared to impregnate the carbon fiber bundle. The draw forming method from small-hole-cavity dies was used to mold the PVA-matrix z-pins. Four z-pins with different resin content were made by four dies with the cavity diameters of 0.50, 0.60, 0.70 and 0.80 mm, respectively. The piercing processes and properties of the z-pins were analyzed by piercing them into carbon fiber laminated fabrics. The results showed that the measured value of the PVA resin volume content of the z-pins was slightly larger than the theoretical value. And the z-pin prepared in the molding die with a cavity diameter of 0.70 mm (P7) exhibited the best piercing property with a resin volume content of 45.6%. The maximum compressive stress in the whole piercing process of P7 was the lowest as compared to the z-pins molded by the other dies, and little damage to the piercing tip of P7 was observed after the penetration. In addition, the z-pins can fully pierce laminated fabrics with a thickness of 9 mm.

Polyaniline/graphene/carbon fiber ternary composites as supercapacitor electrodes

An efficient way to make new type of energy storage electrode is to combine different materials to make full use of their respective characteristics. A ternary supercapacitor electrode consisting of polyaniline, reduced graphene oxide (RGO) and carbon fibers (CFs) with high electrochemical performance is reported. A bundle of CFs is wrapped with RGO possessing unique three dimensional porous structure. CFs act as scaffolds in the hybrid materials to ensure a continuous entity, while RGO possesses high specific surface area and provides a large number of pores for the formation of electrochemical double layers. The added polyaniline on RGO sheet surfaces further enhances electrochemical capability of the composite electrode because of its pseudo-capacitance characteristics. Such a ternary supercapacitor electrode takes full advantage of each component and demonstrates the potential as innovative supercapacitors.

Counting carbon fibres by electrical resistance measurement

Electrical Impedance Measurement has been used to measure the diameter of single carbon fibres to within 3% of the actual value measured by Scanning Electron Microscopy (SEM). The precision of the technique developed also allows for the accurate determination of the number of fibres present in a carbon fibre bundle, such data are important for the calculation of fibre tensile strength from the tensile force applied to carbon fibre bundles. The impedance of a single carbon fibre and carbon fibre bundles of up to 20 fibres have been measured, with results showing good agreement with theoretical values. The impedance of multiple lengths of carbon fibres ranging from 80 to 300mm has also been studied, with the impedance being directly proportional to the fibre length, as per electrical theory. This technique will be suitable for determining the number of fibres in a virgin or recycled carbon fibre bundle.

Ablation Behaviors of 3D Fine Woven Pierced Carbon/Carbon Composites

The ablation behaviors of 3D fine woven pierced carbon/carbon (C/C) composites were tested on an arc heater and their ablation morphologies were observed by scanning electron microscopy (SEM). It shows that ablation of 3D fine woven pierced C/C composites tends to start at interfaces, defects and pores. Cracks mainly yield at the boundaries of carbon fiber bundles, interfaces of carbon fiber felts during the ablating processes. The ablation properties of 3D C/C composites in parallel direction are better than that in vertical direction. In addition, the work indicates that the ablation process is mainly controlled by mechanical denudation.

Evaluation of carbon fiber/epoxy interfacial strength in transverse fiber bundle composite: Experiment and multiscale failure modeling

Abstract This work aims at calculating the fiber/matrix interfacial strength in the transverse fiber bundle (TFB) composite. The TFB specimens made up of carbon fiber bundles and epoxy resin were prepared and tested. The multiscale failure analysis based on the Generalized Method of Cells (GMC) was presented and the progressive damage progress of TFB composite under transverse tensile loading was simulated. Interfacial debonding was experimentally and theoretically proved to be the dominated failure mechanism in the TFB test. The interfacial normal strength could be determined by the combination of the experimental and analytical results.

Ultra-Long Pore Fabrication Process by Pulling–Casting in Aluminum Alloy

The main preparation methods of ultra-long pores are carried out by mechanical or special processing over a long time, and by the casting method the aspect ratio of pores is smaller than 2. In the present article, according to weak wettability between carbon fiber and aluminum, carbon fiber was chosen as the pore-forming material then ultra-long pores were fabricated successfully by means of pulling–casting. The experimental result demonstrated that the pore aspect ratio was 495, and pore diameter was about 0.222 mm. Theoretical analysis shows that the effect of surface tension on invalid pore length can be neglected – this value was only 0.01 mm. X-ray diffraction results showed that there was almost no chemical reaction between aluminum and carbon fiber bundles, which means that undamaged carbon fiber was beneficial for pulling. Otherwise, because the carbon fiber was in a loose state previously and there were differences between actual measurement diameter and theory diameter after pore formation, loose carbon fiber bundles were easily pulled and it was helpful to realize ultra-long pore preparation.

Microwave radial dielectric properties of carbon fiber bundle: Modeling, validation and application

The radial dielectric spectroscopy of the carbon fiber bundle (CFB) array/epoxy resin composites have been performed over the frequency range from 8.2 to 12.4GHz. The complex permittivity of the composite increases with the volume fraction, which is attributed to the increase of polarization, and decrease with the CFB diameter along the electric field direction which is ascribed to the increase of depolarization field. A revised Wiener model is proposed for the calculation of the effective permittivity of the composite, and used to extract the radial permittivity of the CFB. The proposed model is validated by the experimental measurements. The proposed model is further applied to derive the radial permittivity of cylinder carbon fiber and analyze the effect of the bundle geometry on the effective permittivity.

Continuous splitting of carbon fibre rovings

Carbon fibres are fabricated in bundles. A single roving contains a minimum of 1000 filaments. Certain applications demand thinner bundles or even single fibres. Single fibres can be used as tool electrodes in electrochemical machining processes. Thinner rovings are needed in sensor applications to raise the electrical resistance of the carbon fibre bundle used as strain sensor. Rovings with a lower filament count cannot be delivered by carbon fibre producers. A splitting technology is therefore needed. A continuous bundle splitting technique was developed. It uses mechanical means, liquid flow and variations in winding force and speed to separate the filaments. The impact of winding parameters and of the liquid flow on the splitting result was quantified in experiments with the developed splitting system. An automatic and continuous splitting of carbon fibre rovings was realised. Smaller bundles of carbon fibre filaments can be provided. There is a solution to satisfy the demand on finer carbon fibre rovings.

Microstructural analysis of a C/SiC ceramic based on the segmentation of X-ray phase contrast tomographic data

Abstract This paper is dedicated to the analysis of 3D data of carbon fiber reinforced silicon carbide ceramics. In the production process of C/SiC, a porous carbon preform reinforced with bundles of carbon fibers is infiltrated with liquid silicon at approximately 1 500 °C. The reaction between liquid silicon and carbon creates a layer of silicon carbide while the silicon vanishes almost completely. This material is able to withstand extremely high temperatures and it is extremely tough with respect to fracture. To increase the efficiency of the costly and time consuming production process, methods for monitoring the quality of the material are helpful. For instance, the thickness of the silicon carbide layer is a valuable measure. Moreover, due to different coefficients of thermal expansion of the components, typically cracks appear during the production process. For effective analysis 3D high resolution image data are necessary that can be acquired by synchrotron computed tomography. In a first image processing step, we segment the 3D image data with a convex optimization approach incorporating spatial regularity. Further, we work on the detection of cracks using an eigenvalue analysis of the 3D Hessian matrix determined in each pixel.

Tensile Properties of Polyimide Composites Incorporating Carbon Nanotubes-Grafted and Polyimide-Coated Carbon Fibers

The tensile properties and fracture behavior of polyimide composite bundles incorporating carbon nanotubes-grafted (CNT-grafted) and polyimide-coated (PI-coated) high-tensile-strength polyacrylonitrile (PAN)-based (T1000GB), and high-modulus pitch-based (K13D) carbon fibers were investigated. The CNT were grown on the surface of the carbon fibers by chemical vapor deposition. The pyromellitic dianhydride/4,4′-oxydianiline PI nanolayer coating was deposited on the surface of the carbon fiber by high-temperature vapor deposition polymerization. The results clearly demonstrate that CNT grafting and PI coating were effective for improving the Weibull modulus of T1000GB PAN-based and K13D pitch-based carbon fiber bundle composites. In addition, the average tensile strength of the PI-coated T1000GB carbon fiber bundle composites was also higher than that of the as-received carbon fiber bundle composites, while the average tensile strength of the CNT-grafted T1000GB, K13D, and the PI-coated K13D carbon fiber bundle composites was similar to that of the as-received carbon fiber bundle composites.

Casting of micro- to macroholes in Al components

A new pore forming process for the casting of microarray holes in Al components was proposed. This pore forming process depended on both the poor wettability of C and Al, and high strength of extension of carbon fibre. In contrast to conventional pore forming methods, such as mechanical or special process, the proposed method did not require any additional sophisticated equipment and acquired super large aspect ratio by casting. Aiming at demonstrating the feasibility and making comparative superiority of the proposed pore forming method, pore forming principle and the regularities of aperture were studied. The results show molten aluminium pore formed around the carbon fibre bundle. The actual diameter of holes is almost 20% larger than that of the theoretical value, the average aspect ratio of holes reaches 290 and the average diameter of holes is ∼0·222 mm under the influence of loose quantity.

Ablative and Mechanical Properties of C/C–ZrC Composites Prepared by Precursor Infiltration and Pyrolysis Process

C/C–ZrC composites with continuous ZrC matrix were prepared by precursor infiltration and pyrolysis process using zirconium-containing polymer. Ablation properties of the composites were investigated by oxyacetylene flame with heat flux of 2380 and 4180 kW/m2, respectively. The results showed that C/C–ZrC composites exhibited excellent ablation resistance under the heat flux of 2380 kW/m2 for 120 s and a tree-coral-like ZrO2 protective layer formed after ablation. However, when the heat flux increased to 4180 kW/m2, the maximum temperature of ablated surface reached 2500 °C and a strong degradation of ablation resistance was observed due to the weak bonding between the formed ZrO2 layer and the composites. The flexural strength of C/C–ZrC composites was 110.7 ± 7.5 MPa. There were a large number of carbon fiber bundles pull-out, and the composites exhibited a pseudo-plastic fracture behavior.

Microvoid evolution in carbon fibers during graphitization for the preparation of carbon/carbon composites

Polyacrylonitrile-based carbon fiber bundles, with two sides fixed, were heated in a graphitization furnace with temperature profiles similar to those used in the preparation of carbon/carbon composites. The microstructure of the microvoids formed was characterized by small-angle X-ray scattering and high resolution transmission electron microscopy (HR-TEM). Results showed that the average radius of gyration of the microvoids decreases, and their length, width, cross-sectional area and volume fraction decrease followed by a slight increase with increasing temperature, with the minima found at around 2300 °C. The HR-TEM images showed that the microvoids were formed by stacking defects of the carbon layers. The ordering of the amorphous carbon layers accounted for the initial decrease of size and volume fraction of the voids with increasing temperature, while the growth and ordering of the layers at high temperatures gave rise to increases in their size and volume fraction. [New Carbon Materials 2013, 29(1): 41–46]

Microvoid evolution in carbon fibers during graphitization for the preparation of carbon/carbon composites

Polyacrylonitrile-based carbon fiber bundles, with two sides fixed, were heated in a graphitization furnace with temperature profiles similar to those used in the preparation of carbon/carbon composites. The microstructure of the microvoids formed was characterized by small-angle X-ray scattering and high resolution transmission electron microscopy (HR-TEM). Results showed that the average radius of gyration of the microvoids decreases, and their length, width, cross-sectional area and volume fraction decrease followed by a slight increase with increasing temperature, with the minima found at around 2300 °C. The HR-TEM images showed that the microvoids were formed by stacking defects of the carbon layers. The ordering of the amorphous carbon layers accounted for the initial decrease of size and volume fraction of the voids with increasing temperature, while the growth and ordering of the layers at high temperatures gave rise to increases in their size and volume fraction.

B-5 炭素長繊維束で成形したチェーンスプロケットの自転車長期間実走試験(サイクリング1)

It ran 2920km making the chain sprocket for the bicycle for trial purposes with 3K carbon fiber bunch and being include the public road in ten months of three years at rain. The chain made of the carbon fiber bundle reinforced plastic sprocket, the addendum was not a loss and was worn out. The measurement of the consumption calorie measurement and the pedal output became possible by installing the heart beat meter and the pedal power meter in cycle computer with the GPS function. It made comparative study with extra super-duralumin A7075 sprocket for the performance evaluation of the CFRP sprocket. The pedal rotation output increased by an increase of the average speed on a smooth road, the average speed exceeded, the pedal rotation output of CFRP exceeded that of A7075 at 10 km/h or more, and the pedal rotation output of the CFRP sprocket was 50% increase in 25 km/h of it of A7075. The pedal output increased by an increase of the average speed in the CFRP sprocket and the A7075 sprocket on non-pavement road and the difference was not seen by both. The CFRP sprocket was a constant pedal output in the climbing up the slope examination of 9% inclination regardless of the average speed. However, a pedal output high for the average speed to decrease in the A7075 sprocket was needed. The CFRP sprocket is suitable for climbing up the slope.

A milliliter-scale yeast-based fuel cell with high performance

Microbial fuel cells are attracting attention as one of the systems for producing electrical energy from organic compounds. We used commercial baker's yeast (Saccharomyces cerevisiae) for a glucose fuel cell because the yeast is a safe organism and relatively high power can be generated in the system. In the present study, a milliliter (mL)-scale dual-chamber fuel cell was constructed for evaluating the power generated by a variety of yeasts and their mutants, and the optimum conditions for high performance were investigated. When carbon fiber bundles were used as an electrode in the fuel cell, high volumetric power density was obtained. The maximum power produced per volume of anode solution was 850W/m3 under optimum conditions. Furthermore, the power was examined using seven kinds of yeast. In Kluyveromyces marxianus, not only the power but also the power per consumed glucose was high. Moreover, it was suggested that xylose is available as fuel for the fuel cell. The fuel cell powered by K. marxianus may prove to be helpful for the effective utilization of woody biomass.

Effects of carbon matrix on microstructure and properties of 3-D C/ZrC composites prepared by reactive melt infiltration

Three-dimensional braided carbon fiber-reinforced ZrC matrix composites, 3-D C/ZrC, were fabricated by reactive melt infiltration process at 1200°C. Phenolic resin and asphalt were used as carbon precursors, and the effects of carbon matrix on microstructure and properties of the 3-D C/ZrC composites were investigated. The composites fabricated with asphalt showed a higher ZrC yield of 37.5±1.0vol% and better anti-ablative properties, with a mass loss rate of 0.8±0.3mgs−1 and a linear recession rate of 0.0006±0.0002mms−1. However, the use of phenolic resin could provide better mechanical properties of the obtained composites, including a flexural strength of 285.4±9.7MPa, an elastic modulus of 76.2±4.0GPa and a fracture toughness of 8.9±0.8MPam1/2. The main reason for the superior mechanical properties is the preservation of carbon fiber bundles in the phenolic resin based composites.

Tensile properties of 4D braided carbon/carbon composites produced from carbon fiber bundles and carbon rods

4D preforms woven with carbon fiber bundles and carbon rods were densified by repeated pitch impregnation, carbonization and high temperature treatment to obtain 4D-C/C composites. The tensile properties were investigated at room temperature when tension was applied in the carbon rod direction ( Z direction). The strain and stress under tensile load were measured, and the surface morphologies of specimens after tensile failure were observed by scanning electron microscopy. Results indicate that the tensile strengths of the composite were controlled by interfacial shear strength between the carbon rod and the carbon matrix. The carbon rods were pulled out entirely from matrix after tensile failure, indicating that the material was not sufficiently reinforced by the carbon rods. Numerous micro-cracks were found on the surface of specimens after tensile failure. These were perpendicular to the load direction and equally spaced by a distance of about 2 mm. The damage model of 4D-C/C is similar to that of 1D-C/C. [New Carbon Materials 2013, 28(4): 300–306]

A Pre-Stitching Method to Manufacture Z-Pins Reinforced Woven Ceramic Matrix Composite Laminates

Z-pins reinforced 2D ceramic matrix composites (CMCs), integratedly designed new materials, are developed to enhance 2D CMCs through-thickness in the form of Z-pins and to ensure significant increase in interlaminar fracture toughness, delamination resistance and impact resistance, and Z-pins reinforced 2D CMCs have much application. A manual pre-stitching method is developed to make holes in the graphite fixture to control Z-pins row spacings and to introduce yarns of 3000 T300 carbon fibers bundle into a preform. Z-pins reinforced woven CMCs for research were manufactured successfully by repeatedly using chemical vapor infiltration (CVI) to infiltrate SiC matrix into woven preform and carbon fiber sutures. It is shown that this method of manufactured Z-pins reinforced woven CMC is feasible.

Nonaqueous Atomic Layer Deposition of Aluminum Phosphate

Aluminum phosphate was deposited onto bundles of carbon fibers and flat glassy carbon substrates using atomic layer deposition by exposing them to alternating pulses of trimethylaluminum and triethylphosphate vapors. Energy dispersive X-ray spectroscopy (EDXS) and solid state nuclear magnetic resonance (SS-NMR) spectra confirmed that the coating comprises aluminum phosphate (orthophosphate as well as other stoichiometries). Scanning electron microscopic (SEM) images revealed that the coatings are uniform and conformal. After coating, the fibers are still separated from each other like the uncoated fibers. Thermogravimetric analysis (TGA) indicates an improvement of oxidation resistance of the coated fibers compared to uncoated fibers.