Chopped Carbon Fiber Research Articles

Thermal Conductivity of Bentonite Grout Containing Graphite or Chopped Carbon Fibers

The effectiveness of chopped carbon fibers to enhance the thermal conductivity of bentonite-based grout was examined. Fibers of 3 mm and 150 μm in length were added to sodium bentonite and silica sand mixtures at different volumetric concentrations. The thermal conductivity of the resulting composite material was then measured using a non-steady-state needle probe technique. The conductivities of the fibrous materials were compared to bentonite and sand mixtures containing natural flake graphite and milled, compressed exfoliated graphite at corresponding volumetric concentrations. The resulting conductivities for all tested materials increased with the volumetric fraction of additive. However, the 3-mm carbon fibers were more effective as compared to either granular graphite; at a volume fraction of 0.68% the 3-mm fibers were approximately twice as effective as either form of graphite.

Threshold pressure and infiltration behavior of liquid metal into fibrous preform

A dynamic measuring apparatus was developed to investigate the infiltration process of liquid metal into the fibrous preform. 10% (volume fraction) chopped carbon fiber preforms were infiltrated with magnesium alloy under different infiltration pressures. The threshold pressure and flow behavior of liquid metal infiltrating into the preforms were calculated and measured. The microstructure of obtained Cf/Mg composites was observed. The results indicate that the measured threshold pressure for infiltration was 0.048 MPa, which was larger than the calculated value. The infiltration rate increased with the increase of infiltration pressure, but the increase amplitude decreased gradually. The tiny pores in the composites could be eliminated by increasing the infiltration pressure. When the infiltration pressure rose to 0.6 MPa, high quality Cf/Mg composite was obtained.

Determination of the Strengthening Coefficient of Pressure Cast AlSi13Cu2/Chopped Carbon Fibre Composite

Abstract The purpose of the work is the determination of the strengthening coefficient for the AlSi13Cu2 alloy matrix composite reinforced with chopped carbon fibre and produced by high-pressure casting method. This coefficient was determined during the static tensile test using the Ramberg-Osgood equation. The regression relationships between strain and stress were established, serving as a basis for finding the strengthening coefficient values. The measurements and calculations were performed also for the matrix alloy itself, for the purpose of comparison. The examined coefficient decreased with an increase of fibre fraction in the composite. Its value for composite containing 15 vol. % of chopped fibre was found to be lower by 30% than the value determined for matrix alloy, what means the strengthening of the alloy to such a degree.

Effect of carbon nanofiber reinforcement on electromagnetic interference shielding effectiveness of syntactic foam

A novel carbon nanofiber (CNF)-reinforced syntactic foam (CNFRSF) was fabricated. The electrical conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) of CNFRSF with various volume fraction of CNFs (0–2.0 vol%) were evaluated experimentally. The measurement of EMI SE was carried out in a frequency range of 30 MHz to 1.2 GHz. The experimental results showed that the SE of CNFRSF increases with increase of CNFs content and CNF is more effective in providing EMI shielding compared to chopped carbon fiber and long carbon fiber due to the larger aspect ratio. The CNFRSF having 2.0 vol% CNFs has a SE of 25 dB, which is good enough for most practical applications. Compared to CNFs composites, the EMI SE of CNFRSF has been enhanced by the presence of hollow carbon microspheres. The underlying mechanism is discussed in detail.

Flexure Behavior of High Strength Concrete (HSC) Beams Reinforced With Carbon Fiber Reinforced Polymer (CFRP) Rebars With and Without Chopped Carbon Fiber (CCF)

The flexure strength and behavior of high strength concrete beams reinforced with carbon fiber reinforcement (CFRP) rebars with and without chopped carbon fiber (CCF) were investigated by conducting flexural testes on a total of 27 simply supported HSC beams under two symmetrical point loads. The main parameters considered in the study were the reinforcement ratio ρ, compressive strength of the concrete f`c and volume fraction of chopped carbon fiber Vf. It can be seen from the experimental results that the maximum carrying capacity increases as the reinforcement ratio, concrete compressive strength and the volume fraction of copped carbon increases. Crack spacing of the fiber reinforced concrete (FRC) beams was about 20% smaller than plain concrete beams at service load (30% of ultimate load). Addition of fibers significantly improves the system’s ductility; nonetheless the ductility index depends on amount of reinforcement (higher reinforcement allows for lower deformation, thus a lower ductility index) obtained.

Evaluation of Thermo-Mechanical and Wear Behavior of Short Carbon Fibre Vinyl-Ester Filled Homogenous and Their Functionally Graded Composites

Abstract The paper presents the processing and mechanical characterization of chopped carbon fibre reinforced homogenous and functionally graded vinyl ester composites and also reports on their sliding wear characteristics respectively. The sliding wear characteristics are studied with the help of POD test employing the design of experiments approach based on Taguchi's orthogonal arrays. Dynamic mechanical analysis is carried out of the investigated homogenous/FGMs composites to investigate the overall stiffness/flexibility, so as to improve the specific wear rate. Present study reveals that graded composite possess good mechanical and wear characteristics compared to homogenous composites. SEM confirms the graded dispersion of carbon fibre in the matrix.

The reaction behavior of carbon fibers and TaC at high temperatures

Chopped carbon fibers (CFs) and TaC particles were dispersed uniformly and then sintered at temperatures of 1773, 2123, 2298, 2473 and 2823 K, respectively. The effect of sintering temperature on the microstructure of CFs was investigated. The results showed that the reaction between CFs and TaC particles was controlled by solid diffusion. When the temperature was lower than 1773 K, mainly carbon diffused into TaC. However, Ta diffused into the CFs while carbon diffused into TaC particles and then precipitated as graphite when the sintering temperature was above 2123 K. During the process, the structure of TaC was not influenced. The preferential crystalline orientation of the graphite precipitated from TaC particles increased with the increase of sintering temperature. The R value determined by Raman spectra decreased from 0.12 to 0 as the temperature increased from 2123 to 2823 K, meaning the formation of perfect graphite crystallites.

Design and Manufacturing of a Laminated Composite Bicycle Crank

This paper presents the design and manufacturing process of a carbon fibre composite bicycle crank by using the compressionmoulding (CM) technology. Bulk moulding compound (B.M.C.)was manufactured by mixing strands (>1”) of chopped carbon fibres in a mixer with polyester resin. The crank body is treated as a composite sandwichstructure, where the interior is a short fibre layer (B.M.C.) while the exterior is coated with a main long fibre layer andan inner reinforcing layer near the metallic interface ring of the crank.The composite material was hot pressed and manufactured into crank body to reduce most of its weight. In the CMprocess, the long and short fibre layers were joined together by a metallic interface ring. Its characteristics include base composite material, interface ring, hollow square inner wall and exterior projected rib. The inner reinforcing layer provides the maximum bending strength and to reduce stress concentration of themetallic interface ring- to-crank attachment. The FEM model was then calibrated on the basis of the constituent material characterization and the definition of suitable boundary conditions in order to achieve a reliable simulation of the experimental tests and optimum design. Several designs of composite cranks were given to demonstrate the feasibility and applications of the proposed method.

Self-Sensing Hybrid Composite Rod with Braided Reinforcement for Structural Health Monitoring

Enhancing the performance and lightness of different structures has already been achieved by the employment of fibre reinforced composite materials. Nowadays, a new challenging perspective is being given to these materials by the inclusion of non-metallic conductive components. This emerging technology will lead to multifunctional composites with possible applications in structural health monitoring and traffic monitoring. The aim is to avoid corrosion problems from metallic components, as well as to eliminate the need of expensive equipments used for the health monitoring of large infrastructures. In the present research, the strain-sensing capability of a core-reinforced hybrid carbon fibre/glass fibre braided composite has been investigated in order to develop continuous monitoring system. The characterization of sensing behaviour was performed with the help of an instrumental set-up capable of measuring the change in electrical resistance with mechanical stresses applied to the samples. The effect of core composition (carbon fibre/glass fibre weight ratio) on the strain sensitivity of the braided composites has been studied in order to find out the optimum composition for best sensing capability. Among the three compositions studied (23/77, 47/53 and 100/0), composites with lowest amount of carbon fibre showed the best strain sensitivity with gauge factors up to 23.4 at very low flexural strain (0.55%). Attempts have also been made in this research to develop a piezoresistive matrix for the braided composites in order to further enhance their strain sensitivity. For this purpose, the strain sensing capability of an unsaturated polyester matrix dispersed with chopped carbon fibres (1mm and 3 mm lengths) at various weight % (0.5, 0.75 and 1.25%) was evaluated in order to find out their optimum length and concentration. It was observed that chopped fibres with different lengths showed similar strain sensitivity, which however, improves with the decrease in their concentrations.

Composite produced from rice husk and chopped carbon fiber without using any binders

A composite was fabricated from agricultural waste and industrial waste, namely rice husk (RH) and carbon fiber (CF) ends. A mixture of powdered RH and chopped CFs was molded into a slab by means of hot pressing without the use of any binders, after which some samples were subjected to a post-heating process. The physical properties of bulk density, Shore hardness, bending strength, and compressive strength of composites produced at different heating temperatures and various CF fractions were subsequently evaluated. The coefficient of kinetic friction and specific wear rate at the surfaces of these composites in contact with a SUS304 stainless steel ball were also ascertained. Unfilled (CF-free) composites heated to 1000°C displayed the greatest mechanical strength and optimal sliding properties, superior to the CF filled samples, resulting from the densification of the molded lignocellulosic elements in RH. However, this densification was accompanied by a large thermal shrinkage, causing a large molding error. The composite that contained 20% (by mass) CF and which was not subjected to a post-heating process turned out to be subject to only a minor molding error (∼1%), but was characterized by satisfactory mechanical and sliding properties: bulk density 1.19g/cm3, Shore hardness 76.1HS, bending strength 41.2MPa, compressive strength 150.2MPa, kinetic friction coefficient 0.19, and specific wear rate of 2.6×10−9mm2/N. Filling CFs into composites that were then treated with a post-heating process at 800–1200°C reduced their mechanical and sliding properties, which is associated with a difference in the thermo-mechanical properties between CFs and the RH matrix.

Study on Short Carbon Fiber Asphalt Concrete Marshall

The addition of chopped carbon fiber will effect on the pavement performance of asphalt concrete and reinforce and crack-resistance the concrete. The type, length and mixture of pitch carbon fiber have a significant impact on chopped carbon fiber asphalt concrete. This article discusses the effect of carbon fiber on the Marshall of concrete short asphalt, visits the change of Marshall Index, chooses the best short-cut ratio of concrete with carbon fiber asphalt and asphalt and gives guidance to the design of chopped carbon fiber asphalt concrete and construction.

Studies on Properties of Epoxy Resin Base Piezoelectricity Damping Carbon Fiber Composite Materials

Damping Materials Have Been Wildly Used in Aerospace, Traffic, Construction Fields and so on. The Piezo-Damping Materials Have Received much Attention due to the Novel Energy Loss Mechanism. In this Paper, Piezo-Damping Composite Materials Were Prepared from the Epoxy Resin (EP) as the Resin Matrix, Nano Lead Titanate (Nano-PT) Ceramics as Piezoelectric Material and Chopped Carbon Fibers (CF) as Conductive Materials. The Mechanical and Damping Properties of the Composites Were Analyzed by Mechanics Test, DMA and Vibration Beam Method. The Results Showed that when the Nano-PT Content Was 60% of EP and CF Content Was 0.25% of EP, the Composite Got the Better Mechanical Properties. Form DMA, the Loss Factor (tanδ) Peak Reached 0.58. Damping Temperature Range △T (tanδ>0.3) Was about 36.3°C. In Comparison, Damping Loss Factor Measured by Vibration Beam Method Was 0.82.

Effects of random chopped fiber on the flexural strength and toughness of reaction bonded silicon carbide composite

Chopped carbon fibers were introduced into the SiC/C suspensions to enhance the mechanical behaviors of reaction bonded silicon carbide ceramics. The effects of fiber fraction on the flexural strength and fracture toughness were investigated. No preferred fiber orientation was observed on the fracture surface of the green body. This implies a homogeneous dispersion of chopped fiber in the composite. XRD analysis indicates a complete siliconization of both carbon particles and carbon fiber during liquid silicon infiltration. The flexural strength and fracture toughness increase with chopped fiber ranging from 10vol.% to 30vol.%. This improvement derives from the fiber pullout, fiber debonding as well as crack deflection. The consequent decline at fiber fraction of 40vol.% is resulted from the siliconization of chopped fiber and the increase of residual silicon.

The dynamic response of carbon fiber-filled polymer composites

The dynamic (shock) responses of two carbon fiber-filled polymer composites have been quantified using gas gun-driven plate impact experimentation. The first composite is a filament-wound, highly unidirectional carbon fiber-filled epoxy with a high degree of porosity. The second composite is a chopped carbon fiber- and graphite-filled phenolic resin with little- to-no porosity. Hugoniot data are presented for the carbon fiber-epoxy (CE) composite to 18.6GPa in the through-thickness direction, in which the shock propagates normal to the fibers. The data are best represented by a linear Rankine-Hugoniot fit: Us = 2.87 + 1.17 × up(ρ0 = 1.536g/cm 3 ). The shock wave structures were found to be highly heterogeneous, both due to the anisotropic nature of the fiber-epoxy microstructure, and the high degree of void volume. Plate impact experiments were also performed on a carbon fiber-filled phenolic (CP) composite to much higher shock input pressures, exceeding the reactants-to- products transition common to polymers. The CP was found to be stiffer than the filament-wound CE in the unreacted Hugoniot regime, and transformed to products near the shock-driven reaction threshold on the principal Hugoniot previously shown for the phenolic binder itself. (19) On-going research is focused on interrogating the direction-dependent dyanamic response and dynamic failure strength (spall) for the CE composite in the TT and 0 ◦ (fiber) directions.

Effect of Water Absorption on Some Electrical and Dielectrical Properties of Epoxy Resin Reinforced with Chopped Carbon Fibers

In thi s research, we s tudy a.c electrical conductivity (σa.c (ω) ) and dielectric properties (dielectric constant (έ), and dissipation factor ( tanδ) ), with frequency change (10 2 -10 7 Hz) for the epoxy resin and composites reinforced with chopped carbon fiber ,prepared by hand lay –up method (EP +5% CF), (EP +10% CF), (EP +15% CF), (EP +20% CF), Were measured electrical conductivity of epoxy and composites with frequency change and at room temperature the results showed a.c electrical conductivity dependence with frequency relationship σ ( ω)=Aω s to the values of the exponential factor (s)of less than one all samples, and adopted the theory of filtration for the interpretation of data conductivity for composites reinforced with carbon fibers was selected epoxy+20% C.F showed a higher electrical conductivity (13.6 * 10 -7 (ohm.cm) -1 ). The composites were immersed in water at room temperature for 6, 10,15,20,27 days. The results showed that the electrical conductivity of ( σ ( ω)) increasing with increasing weight gain(M%) due to water absorption. Itwas found that dielectric constant increases when the percentage moisture absorption increase, whereas dielectric constant (έ) is dependent on capacity of composite materials.

Contact Analysis of Prosthetic Knee Joint Using ANSYS

The objective of this study is to determine the best materials for the tibia/femoral combination of the prosthetic knee joint using commercial available FEM software. Insertion of these joints in human should not result in too much of discomfort and postoperative treatment. Further, the life and performance of the artificial joints is of prime concern. During activation, contact is established between tibia and femoral components leading to stresses at the interface, which in turn dictates the performance of these joints. The intensity of the developed stresses at the interface depends on several important factors such as the materials used for tibia/femoral components and the load acting on the bearing surfaces of the joint. To ensure reduction in the stress intensity, it is of utmost importance to select the best materials for tibia/femoral combination. In this regard, FEM the most powerful and widely accepted numerical tool to predict the state of stress is currently gaining importance in optimization of design of knee joint. In the light of the above, this paper discusses the modeling and finite element analysis of prosthetic tibia/femoral joint with different material combinations. The materials like stainless steel, titanium alloy and alumina ceramic are considered for the femoral component. Polyethylene and polyethylene chopped carbon fiber composite are considered for the tibial insert. The three dimensional model was developed using PRO E software for sagittal radius of 40 mm and 0 degree flexion angle, while load was varied from 500-2667N. An explicit finite element was generated using hyper mesh software and was solved by ANSYS. For a given load, a considerable reduction in the stress intensity at the interface of femur made of alumina ceramic and tibia made of polyethylene chopped carbon fiber composite have been observed when compared with other combinations of materials investigated.

The Effect of Flexion Angle and Sagittal Radius on Femorotibial Contact Stresses

The artificial knee joint need to satisfy and meet certain design requirements in addition to being biocompatible. These being the design of the flexion angle and sagittal radius of the prosthetic knee for specific activities such as walking and exercising. Day to day physical activities do result in generating frequent contacts between the femur and tibia leading to stresses at the interface of the femorotibial joint. These stresses on exceeding certain limit do result in damage of the tibia which acts as bearing surface carrying loads during each of the knee activity. Hence, prediction and minimization of the stresses at the knee interfaces is the key issue to ensure high performance knee joints. In the light of the above, the stresses at the knee interfaces are computed using commercially available FEA software (ANSYS 10). The three dimensional model was developed using PRO E software for sagittal radius of 40, 50 and 60 mm. The flexion angles considered are 0, 20 and 40 degrees. A load of 500N was considered. It is observed that the stress intensity increases with increase in flexion angle and sagittal radius for all the material combinations of the prosthetic knee joint. Further, alumina ceramic femur and polyethylene chopped carbon fiber composite tibia exhibits the least stress levels at all the studied sagittal radius and flexion angles.

Thermal insulation by heat resistant polymers for solid rocket motor insulation

A new method for the development (design, fabrication, and characterization) of asbestos-free rubbers for use as rocket motor insulators is presented. Such insulation is based on chopped carbon fiber (CCF) and aramid fiber in pulp form asreinforcement for ethylene propylene diene monomer (EPDM) along with ammonium polyphosphate (AP) flame retardant agent. Six millimeters long CCFs and/or Kevlar pulp (KP) are dispersed in the EPDM polymeric matrix to obtain a homogenous master batch for curing. The new method involves the development of two types of prepregs andthe lamination of these types of prepregs. The first one consists of CCF/EPDM/AP (50 phr CCF) and the second type of prepreg KP/EPDM/AP (30 phr KP). Laminates composed of six alternative layers of these prepregs have been shown to exhibit better thermal, mechanical, physical, and ablative properties than their non-laminated counterparts.

Warpage and mechanical properties of film insert molded parts with composite substrate

Mechanical properties of chopped carbon fiber (CF) reinforced PC/ABS composites were investigated. Tensile strength and elastic modulus of the composites were enhanced with increasing CF contents. On the contrary, impact strength of the composite was decreased with increasing CF fraction. Film insert molding was introduced in order to improve impact strength. Film insert molded composite specimens have higher impact strength than conventional injection molded composite specimens because inserted film acted as a cushion to absorb the impact energy. Large warpage which was observed after molding and known as a disadvantage of the film insert molded part can be prevented by controlling the amount of filled CFs. Therefore, fiber reinforcement and film insert molding can be applied simultaneously to reduce warpage of the film insert molded part and enhance impact strength of the CF reinforced composite.

탄소섬유 강화 반응소결 탄화규소의 탄소섬유 첨가량에 따른 기계적 특성 변화

The composite added with surface-coated chopped carbon fiber showed the microstructure of a 3 dimensional discretional arrangements. The fiber reinforced reaction bonded silicon carbide composite, containing the 50 vol% carbon fiber, showed the porosity of 1/2 . As the content of carbon fiber was increased from 0 vol% to 50 vol% in the composite, fracture strength was decreased due to the increase of carbon fiber, which has a less strength than SiC and molten Si. On the other hand, the fracture toughness was increased with increasing the amount of carbon fiber. According to the polished microstructure, carbon fiber was shown to have a random 3 dimensional arrangement. Moreover, the fiber pull-out phenomenon was observed with the fractured surface, which can explain the increased fracture toughness of the composite containing high content of carbon fiber.