Pitch-based Carbon Fibers Research Articles

Wear Behavior of PAN- and Pitch-Based Carbon Fiber Reinforced Aluminum Alloy Composites under Dry Sliding Condition

Wear Behavior of PAN- and Pitch-Based Carbon Fiber Reinforced Aluminum Alloy Composites under Dry Sliding Condition

等方性ピッチ系炭素繊維フェルトを用いた炭素繊維／炭素複合材料における応力黒鉛化

等方性ピッチ系炭素繊維フェルトを用いた炭素繊維／炭素複合材料における応力黒鉛化

Transient Thermal Tensile Behaviour of Novel Pitch-Based Ultra-High Modulus CFRP Tendons.

A novel ultra-high modulus carbon fibre reinforced polymer (CFRP) prestressing tendon made from coal tar pitch-based carbon fibres was characterized in terms of high temperature tensile strength (up to 570 °C) with a series of transient thermal and steady state temperature tensile tests. Digital image correlation was used to capture the high temperature strain development during thermal and mechanical loading. Complementary thermogravimetric (TGA) and dynamic mechanical thermal (DMTA) experiments were performed on the tendons to elucidate their high temperature thermal and mechanical behaviour. The novel CFRP tendons investigated in the present study showed an ambient temperature design tensile strength of 1400 MPa. Their failure temperature at a sustained prestress level of 50% of the design tensile strength was 409 °C, which is higher than the failure temperature of most fibre reinforced polymer rebars used in civil engineering applications at similar utilisation levels. This high-temperature tensile strength shows that there is potential to use the novel high modulus CFRP tendons in CFRP pretensioned concrete elements for building applications that fulfill the fire resistance criteria typically applied within the construction industry.

피치계 활성탄소섬유를 이용한 페이퍼 제조 및 흡착특성

피치계 활성탄소섬유를 이용한 페이퍼 제조 및 흡착특성

Structural features of various kinds of carbon fibers as determined by small-angle X-ray scattering

The structural features of polyacrylonitrile and pitch-based carbon fibers were analyzed from a comprehensive point of view by X-ray measurements and related techniques. The results indicated that the undulating graphite ribbon with embedded microvoid was the main structural unit for graphitic fibers. The void’s parameters for these fibers could be obtained directly by small-angle X-ray scattering following the classic method deduced based on the typical two-phase system (i.e., Porod’s law, Guinier’s law and Debye’s law). The non-graphitic fibers, however, were composed of two-dimensional turbostratic crystallites in the aggregation of microfibril and thus had a quasi two-phase structure (microfibril, interfibrillar amorphous structure and microvoid embedded within the microfibril). The extended Debye or Beaucage model in this case should be applied in order to obtain the structural parameters. It also revealed that the quasi two-phase system would complete its transformation to two-phase system during high-temperature graphitization. Therefore, the degree of graphitization was speculated to be the essential indicator distinguishing graphitic fibers from non-graphitic ones and would be helpful in understanding the transformation of structural features during the graphitization of carbon fibers.

Electromechanical, self-sensing and viscoelastic behavior of carbon fiber tows

The electromechanical, electrical-resistance-based self-sensing and viscoelastic stress-relaxation phenomena of unsized binderless pitch-based carbon fiber tows have been observed for the first time, using the elastica loop test innovatively modified with four-probe tow electrical resistance measurement. The resistance increases upon fiber breakage and decreases upon stress-relaxation-related fiber rearrangement. With a fixed tensile strain applied, the resistance decreases with time, levelling off after ∼40 s, due to the relative movement of the fibers causing more fiber-fiber contact as the tow relaxes, and indicating viscoelastic stress-relaxation behavior. Minor fiber fracture and inelastic behavior occur more upon loading than unloading. Strain-controlled fatigue loading results in cycle-by-cycle monotonically increasing fraction of fibers broken. Loop major-to-minor axis ratio increase accompanies fiber fracture, which promotes the inelastic behavior. The increase of the fraction of fibers broken upon strain cycling becomes more abrupt when this fraction exceeds 40% and the ratio exceeds 1.4. This fraction increases monotonically with progressively increasing strain amplitude, being gradual at fraction <4% and significant at fraction >4%, with tow failure occurring upon loading from an effectively unloaded state with fraction 22%. For fatigue loading at a relatively high strain amplitude, tow failure occurs upon loading from an effectively unloaded state with fraction 81%.

Pitch-based carbon fibers from coal tar or petroleum residue under the same processing condition

Spinnable pitches and carbon fibers were successfully prepared from petroleum or coal pyrolysis residues. After pyrolysis fuel oil (PFO), slurry oil, and coal tar were simply filtered to eliminate the solid impurities, the characteristics of the raw materials were evaluated by elemental analysis, 13C nuclear magnetic resonance spectrometer, matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF-MS), and so on. Spinnable pitches were prepared for melt-spinning carbon fiber through a simple distillation under strong nitrogen flow, and further vacuum distillation to obtain a high softening point. Carbon fibers were produced from the above pitches by single-hole melt spinning and additional heat treatment, for oxidization and carbonization. Even though spinnable pitches and carbon fibers were processed under the same conditions, the melt-spinning and properties of the carbon fiber were different depending on the raw materials. A fine carbon fiber could not be prepared from slurry oil, and the different diameter carbon fibers were produced from the PFO and coal tar pitch. These results seem to be closely correlated with the initial characteristics of the raw materials, under this simple processing condition.

The effect of the spinning conditions on the structure of mesophase pitch-based carbon fibers by Taguchi method

Taguchi’s experimental design was employed in the melt spinning of molten mesophase pitch to produce carbon fibers. The textures of the obtained carbon fibers were radial with varied crack angles, as observed by scanning electron microscopy and polarized optical imaging. The diameter, crack angle, preferred orientation, and tensile modulus of the produced samples were examined to investigate the influence of four spinning variables. The relative importance of the variables has been emphasized for each characteristic. The results show that thicker carbon fiber can be obtained with a smaller entry angle, a higher spinning temperature, a reduced winding speed, and an increased extrusion pressure. The winding speed was found to be the most significant factor in relation to the fiber diameter. While it was observed that thicker carbon fiber generally shows improved preferred orientation, the most important variable affecting the preferred orientation was found to be the entry angle. As the entry angle decreased from 120° to 60°, the shear flow was enhanced to induce more ordered radial alignment of crystallite planes so as to obtain carbon fibers with a higher degree of preferred orientation. As a consequence, the crack angle was increased, and the tensile modulus was improved.

Preparation of pitch based carbon fibers using Hyper-coal as a raw material

A cost-effective method for producing an isotropic pitch-based carbon fiber using the 1-methylnaphthalene (MN) soluble fraction of Hyper-coal (HPC) was newly developed. The extent of MN fractionation was controlled by altering the fractionation temperatures. The MN soluble fraction obtained from HPC at 60 °C had excellent spinnability after the removal of volatile matter by thin layer evaporation. Additionally, the fiber that was subsequently derived from the MN soluble fraction had satisfactory mechanical properties with an averaged tensile strength of 1150 MPa after heating to 800 °C for 5 min.

A study on grid-stiffened multi-functional composite structures with radiation spot shielding

This paper deals with alternative multi-functional structures by using grid-stiffened composite panel with excellent bending stiffness and lightweight characteristics. The grid-stiffened multi-functional structure can provide an array of available rooms for integrating multiple electronic circuitries into structure with ease. The substrate fabrication process was proposed and the grid-stiffened multi-functional structure equipped with several electronics and interfaces was built up. In order to improve the thermal conduction capability, pitch-based carbon fibers were applied to facesheet of the multi-functional structure. The spot shielding technique was also proposed to enhance the radiation shielding at the selective region sensitive to radiation, and the lightweight radiation spot shielding plate was fabricated with multi-layered laminate of CFRP and tungsten foil. The radiation shielding effectiveness of the multi-functional structure with spot shielding plate was demonstrated by proton beam irradiation test. Through the test, it was found that the radiation spot shielding plate has comparable proton-shielding performance to aluminum but more lightweight characteristics than aluminum. Grid-stiffened MFS with radiation spot shielding can be an effective measure for accommodating lots of electronics into structure, providing dramatic mass and volume savings in spacecraft design.

Effect of Hybrid Surface Modifications on Tensile Properties of Polyacrylonitrile- and Pitch-Based Carbon Fibers

Recent interest has emerged in techniques that modify the surfaces of carbon fibers, such as carbon nanotube (CNT) grafting or polymer coating. Hybridization of these surface modifications has the potential to generate highly tunable, high-performance materials. In this study, the mechanical properties of surface-modified polyacrylonitrile (PAN)-based and pitch-based carbon fibers were investigated. Single-filament tensile tests were performed for fibers modified by CNT grafting, dipped polyimide coating, high-temperature vapor deposition polymerized polyimide coating, grafting-dipping hybridization, and grafting-vapor deposition hybridization. The Weibull statistical distributions of the tensile strengths of the surface-modified PAN- and pitch-based carbon fibers were examined. All surface modifications, especially hybrid modifications, improved the tensile strengths and Weibull moduli of the carbon fibers. The results exhibited a linear relationship between the Weibull modulus and average tensile strength on a log-log scale for all surface-modified PAN- and pitch-based carbon fibers.

Significant reduction in stabilization temperature and improved mechanical/electrical properties of pitch-based carbon fibers by electron beam irradiation

Carbon fibers are produced using an electron beam, which can reduce the temperature and time in their stabilization processes compared with the existing processes that use heat treatment. Pitch fibers with a stabilization index (SI) of more than 90% are obtained under a lower heat treatment temperature after an electron beam irradiation of 3000kGy. It is contributed that electron beam irradiation facilitates dehydrogenation and the introduction of oxygen. Carbon fibers stabilized under the conditions of 3000kGy and 250°C show 563MPa and 69GPa for tensile strength and Young's modulus, respectively. In addition, the electrical conductivity of carbon fibers is approximately 600S/cm with SI of more than 84%. Therefore, the electron beam reduces the time and energy required to stabilize the pitch fibers, and electron beam-treated carbon fibers show excellent tensile strength and electrical conductivity.

Characterization of defects in carbon fiber-reinforced plastics by inverse heat conduction analysis using transfer matrix between layers

In this study, inverse analyses of the defects in carbon fiber-reinforced plastics (CFRPs) are performed using the transfer matrix approach. The material properties used in the calculation were obtained on the basis of mixture laws for epoxy resin and carbon fibers. The accuracy of the inverse analysis was confirmed by calculations employing numerical models of CFRP plates with PAN-based and pitch-based carbon fibers containing defects. The inverse analysis was conducted based on the temperature distribution of CFRP laminates with PAN-based carbon fibers, which was obtained by infrared measurements. The analyses successfully estimated the positions of defects, and the effectiveness of the transfer matrix method for CFRPs was demonstrated through the inverse analysis.

炭素繊維のねじり-引張特性の評価

Torsional-tensile, dynamic torsional pendulum oscillation and static rotary tests of carbon mono-filament were carried out. Two high performance carbon fibers，a PAN-based and a pitch-based, were chosen for these tests. From static rotational behavior of carbon and glass series connected filament, shear stress-strain diagram of carbon fiber is determined. On the diagram, the PAN-based carbon fiber exhibits a very linear shear stress-shear strain relationship up to the torsional fracture. On the other hand, the pitch-based carbon fiber shows the linear relationship up to a point. Beyond the point, increasing shear strain, slope of the τ/γ (torsional stiffness) is decreased. However, for each carbon fiber, it does not show any plastic torsional deformation, that is, it is perfectly elastic until fracture. In other words, the torsional deformation is completely recovered when the torque is reduced at every torsional deformation stage. The mono-filament of carbon fiber is tensioned until fracture with fixing torsional strain. The torsional-tensile strength of the PAN-based carbon fiber shows that increasing torsional strain, the tensile strength decrease by insensible degrees with the small torsional strain and rapidly decrease coming up to the torsional fracture strain. The torsional-tensile strength of the pitch-based carbon fiber does not change until a torsional strain, and after then decreased rapidly. Tensile rigidity is gradually decreased, increasing torsional strain, and decreased sharply at closing torsional fracture strain. The ratios of anisotropic measure of strength by the tensile strength to the torsional strength are smaller than the ratios of elasticity by the tensile modulus to the torsional modulus. This torsional-tensile test method is useful in order to evaluate strength and structural anisotropy of fiber materials.

Pitch-Based Carbon Fibre-Reinforced PEEK Composites: Optimization of Interphase Properties by Water-Based Treatments and Self-Assembly

This work addresses the challenging fibre-matrix compatibilization and interface adhesion improvement of poly(etheretherketone) (PEEK) composites reinforced with pitch-based carbon fibre. An innovative and environmentally friendly method, inspired both by supramolecular “layer-by-layer” (LBL) assembly and by the composition of adhesive proteins in mussels was designed to modify the carbon fibre surface and improve the composites transverse properties by supramolecular interactions. The results proved that few sensitive carbon surfaces can be selectively modified by stable polyelectrolyte complexes and catechol amine polymer partners dispersed in water in such a way that a sizing treatment can be applied by techniques as simple as immersion or spraying procedure. It was shown that the combination of these solutions self-organized to form thin deposits containing compatibilization and/or crystallization promoter partners, thought transcrystallinity, onto carbon surface. This approach is an innovative and environmentally-friendly method which improves fibre-matrix interface quality in terms of compatibilization, adhesion and mechanical properties.

M1101 ナノ粒子を添加した炭素繊維強化複合材料の摩擦・摩耗特性とメカニズムの把握(GS4,11,13 耐摩耗性向上,修士研究発表セッション)

M1101 ナノ粒子を添加した炭素繊維強化複合材料の摩擦・摩耗特性とメカニズムの把握(GS4,11,13 耐摩耗性向上,修士研究発表セッション)

ピッチ系炭素繊維強化アルミニウム合金複合材料の諸特性

ピッチ系炭素繊維強化アルミニウム合金複合材料の諸特性

等方性ピッチ系炭素繊維の構造と空気酸化挙動

等方性ピッチ系炭素繊維の構造と空気酸化挙動

Influence of MWCNTs on Fracture Toughness of MWCNTs/Nickel-Pitch Fiber/Epoxy Composites

ABSTRACT: The influence of MWCNTs on fracture toughness properties of MWCNTs/Nickel-Pitch Fibers/epoxycomposites (MWCNTs/Ni-PFs/epoxy) was investigated according to MWCNTs content. Nickel-Pitch-based carbonfibers (Ni-PFs) were prepared by electroless nickel-plating. The surface properties of Ni-PFs were determined byscanning electron microscopy (SEM) and X-ray photoelectron spectrometry (XPS). The fracture toughness ofMWCNTs/Ni-PFs/epoxy was assessed by critical stress intensity factor ( K IC ) and critical strain energy release rate( G IC ). From the results, it was found that the fracture toughness properties of MWCNTs/Ni-PFs/epoxy were enhancedwith increasing MWCNTs content, whereas the value decreased above 5 wt.%. MWCNTs content. This was probablyconsidered that the MWCNTs entangled with each other in epoxy due to an excess of MWCNTs. Key Words: Pitch Fibers, Multi-walled Carbon Nanotubes (MWCNTs), Electroless Nickel-plating, Epoxy Composites,Fracture Toughness 1. INTRODUCTION These days, pitch-based carbon fibers (pitch fibers) havereceived considerable attention due to their advantages such ashigh carbon yield, low cost, and good graphitizability that arecharacteristic of pitches derived from coal tar or petroleum.These excellent properties of pitch fibers are transferred tomatrix through their interface. Accordingly most of pitch-based carbon fibers reinforced composite properties are con-trolled by interfacial adhesion between pitch fibers and matrixresins [1,2]. Carbon nanotubes (CNTs) are a typically nanofillers andwere discovered as fullerene-related structures by Iijima atNEC laboratory of Tsukuba in 1991 [3]. Carbon nanotubesalso have several excellent properties including electronic con-ductivity, thermal conductivity, corrosion resistance, highstrength, Young's modulus and so on [4-6]. In this study, epoxy matrix was reinforced with Pitch fibersand multi walled carbon nanotubes (MWCNTs) to enhancethe fracture toughness of the composites. In order to improveinterfacial adhesive strength between fillers and matrix resins,the filler surface is commonly modified by numerous surfacetreatments [7-9]. Therefore the pitch fibers and MWCNTswere electrolessly nickel-plated and acidic treated, respectively.The objective of this study is to evaluate the influence ofMWCNTs on the fracture toughness of MWCNTs/Ni-PFs/epoxy composites. The pitch fiber surfaces were characterizedby SEM and XPS to confirm the morphology of the fiber sur-faces and the elemental compositional changes. The criticalstress intensity factor (

Enhancing the tensile strength of isotropic pitch-based carbon fibers by improving the stabilization and carbonization properties of precursor pitch

A unique isotropic pitch composed of linear chains of polycondensed aromatic molecules was synthesized through the bromination and subsequent dehydrobromination of mixed naphtha-cracked oil (NCO) and quinoline-insoluble free coal tar (CT). Isotropic pitch-based carbon fibers obtained from the co-carbonization of an NCO/CT mixture via bromination and dehydrobromination exhibited an unprecedentedly high tensile strengths and elongations at break of 1800 and 2050 MPa, and 3.2 and 2.8% following carbonization at 800 and 1100 °C for 5 min, respectively. The aromatic components derived from the co-carbonization process were primarily condensed cyclic compounds containing four or five aromatic rings. These substructures enhanced the tensile strength of the carbon fibers up to 2050 MPa, which is a level much higher than that reported for carbon fibers derived from naphtha-cracked oil-based isotropic pitch. TOF-MS analyses indicated that the molecular weight of the NCO/CT derived pitch was higher than that of the NCO derived pitch. Both isotropic pitches exhibited Bingham behavior above their softening temperatures. However, the linear chains of the higher aromatic units of the NCO/CT derived pitch resulted in a higher degree of shear-thinning than was observed with the NCO derived pitch, resulting in a higher degree of molecular orientation during spinning.