Carbon Fiber Content Research Articles

Negative permittivity behavior of carbon fibre/alumina ceramic composites prepared by hot-press sintering

Although metals are the most common conductive functional phase in metacomposites preparation, one-dimensional carbon fibre (CF) is an ideal alternative. In this paper, ceramic composites with CFs homogeneously dispersed in an alumina matrix were prepared using a hot press sintering process. The impact of CF contents on the microscopic morphology, electrical conductivity and negative permittivity behavior of the composites was systematically investigated. The conductivity of the composites increased with increasing CF contents, and their impedance modulus subsequently decreased. The conductivity mechanism of the composites transformed from a hopping conductivity to a metal-like conductivity. With the increase in CF contents above the percolation threshold, the composites showed a negative permittivity behavior at the frequency range from 1 kHz to 10 MHz. The negative permittivity of the metacomposites was attributed to the plasma oscillations of free electrons in the three-dimensional CF networks, and the corresponding dispersion characteristics were in agreement with the Drude model. The plasma oscillation frequencies of ceramic composites moved to higher frequencies with increasing CF content in the composites, and the absolute value of negative permittivity also increased. These findings can be useful for clarifying the realization and regulation mechanism of negative permittivity, which greatly facilitates the development of ceramic-based metacomposites.

Cyclic (phenylene sulfide) treated carbon fiber for facile preparation of high performance PEEK based anti-wear composites

Improving the surface activity of carbon fiber (CF) via a sizing agent is an efficient approach to enhance the performance of CF reinforced polymer composites. However, the conventional sizing agents usually readily decompose at high temperature. In this work, a novel heat resistant sizing agent is coated directly on the CF surface by in-situ thermal ring-opening polymerization of cyclic phenylene sulfide oligomers (CPS) in air. Studies indicate that the novel sizing agent is oxygenated poly (phenylene sulfide) (PPS), possessing high temperature stability. Properties of the PPS sized CF (CF-CT) filled PEEK based composite are investigated by using the original CF/PEEK composite as a reference. The results reveal that the CF-CT composite exhibit significantly higher tensile strength, lower average friction coefficient and wear rate when CF content exceeds 20 wt%. It is reasonably ascribed to the stronger interface interaction between the PPS sized CF and PEEK, which effectively promotes the enhancement effect of CF in the composite material.

Additive Manufacturing of Carbon Fiber Reinforced Plastic Composites: The Effect of Fiber Content on Compressive Properties

The additive manufacturing (AM) of carbon fiber reinforced plastic (CFRP) composites continue to grow due to the attractive strength-to-weight and modulus-to-weight ratios afforded by the composites combined with the ease of processibility achievable through the AM technique. Short fiber design factors such as fiber content effects have been shown to play determinant roles in the mechanical performance of AM fabricated CFRP composites. However, this has only been investigated for tensile and flexural properties, with no investigations to date on compressive properties effects of fiber content. This study examined the axial and transverse compressive properties of AM fabricated CFRP composites by testing CF-ABS with fiber contents from 0%, 10%, 20%, and 30% for samples printed in the axial and transverse build orientations, and for axial tensile in comparison to the axial compression properties. The results were that increasing carbon fiber content for the short-fiber thermoplastic CFRP composites slightly reduced compressive strength and modulus. However, it increased ductility and toughness. The 20% carbon fiber content provided the overall content with the most decent compressive properties for the 0–30% content studied. The AM fabricated composite demonstrates a generally higher compressive property than tensile property because of the higher plastic deformation ability which characterizes compression loaded parts, which were observed from the different failure modes.

Investigation of influence of printing parameters on the quality of 3D printed composite structures

Composites reinforced with short or continuous carbon fibres are used for very wide applications. Additive manufacturing technologies allow to print very complex shapes of product reducing costs and production time. It is very well known that composite structures used for aerospace applications should have a minimum void volume and high fibre content; however, additive manufacturing of polymer – fibre composites with known mechanical properties and other parameters such as fibre content and void volume is extremely challenging. Understanding how the printing parameters influence the mentioned properties is a key in order to minimize void volume and improve mechanical characteristics. In this study, tensile properties of unidirectional 0° 3D printed composites were investigated. Two main printing parameters: layer height and line width were changed. Voids volume in the printed samples were studied by using computed tomography (CT) and matrix dissolution methods. Voids volume average in the samples fluctuates from 18.5% to 27.5% according CT results and have significant dependency on printing parameters: layer height and line width. After matrix dissolution, carbon fibre content was determined. Results showed that weight percentage of carbon fibre content fluctuates from 13.4% to 19.1% and depends on printing parameters. It has been determined that tensile properties are most influenced by layer height of the samples. Moreover, research results highlight that composites properties can be optimized by changing 3D printing process parameters.

Negative permittivity behavior in carbon fibre/silicon nitride ceramic composites prepared by spark plasma sintering

Carbon/ceramic composites with adjustable electrical properties can be promising candidates for electromagnetic metamaterials with negative permittivity. Herein, silicon nitride (Si3N4) ceramic composites incorporated with carbon fibres (CFs) were prepared via spark plasma sintering. The fibres were randomly distributed in the ceramic matrixes, and their amounts had a great influence on the microstructure, electrical conductivity, dielectric behaviour, and impedance response of the CF/Si3N4 composites. As the CF content was low, the ceramics with isolated CFs showed a dielectric type of conductivity, along with a capacitive character and positive permittivity. When the CFs were more sufficient to contact or overlap each other in the ceramics, the formation of CF networks endowed the ceramics with a metallic type of conductivity and inductive character. A plasma-type negative permittivity behaviour was observed in these ceramics and was imputed to the low-frequency plasmonic state of free electrons in the formed CF networks. The Drude model was applied to make a precise description of the negative permittivity behaviour. As the CF content increased, the plasma frequency (negative-positive transformation frequency of permittivity) of the ceramics shifted to a higher frequency, and their absolute magnitudes of negative permittivity also increased. Furthermore, equivalent circuit models were utilized to interpret the impedance response of the ceramics, which demonstrated that the negative permittivity was linked to the inductive character. This work provides support for developing ceramic-based metamaterials with tunable negative permittivity that is desirable for many applications.

Warp deformation model of polyetheretherketone composites reinforced with carbon fibers in additive manufacturing

Fused deposition modeling (FDM) provides a promising technique for the small-batch fabrication of highly customized objects. The required performance of FDM far exceeds the performances of conventional manufacturing methods. However, the temperature difference that occurs during FDM generates internal stress, which causes warp deformation and affects formed sample quality. Hence, identifying the influencing factors of warp deformation is the key to improving the forming quality of FDM samples. In this work, PEEK/short carbon fiber (CF) composites were prepared by using the FDM method, the warp deformation formula was derived, and the warp deformation mechanism was obtained. Results showed that the material linear expansion coefficient, forming chamber temperature, and forming size had considerable effects on warp deformation. Moreover, CF could improve the warp deformation of the PEEK/CF composites because of their low Poisson’s ratio and high thermal conductivity. The addition of CF could reduce the residual stress of the composites and improve warp deformation. In addition, annealing could improve the tensile and bending mechanical properties of the PEEK/CF composites. Specifically, after 3 h of heat treatment at 190 °C, the tensile and bending mechanical properties of the composites reached 10.7% and 11.6%, respectively. Crystallinity analysis revealed that the mechanical properties of the PEEK/CF composites strongly depended on their crystallinity. High cooling temperature rates were associated with low crystallinity, tensile strengths, and elastic moduli. DMA analysis showed that the addition of CF could improve the high-temperature resistance of the PEEK/CF composites as reflected by the higher glass transition temperature of the composites than that of the pure PEEK resin. Porosity analysis showed that the CF content could tailor the pore size and distribution. The study reported here provides a reference for improving the forming quality and mechanical properties of PEEK/CF composites fabricated through FDM.

Additive manufacturing of continuous carbon fiber reinforced epoxy composite with graphene enhanced interlayer bond toward ultra‐high mechanical properties

AbstractContinuous carbon fiber reinforced polymer composites (CFRPCs) exhibiting superior mechanical properties have emerged as high‐performance engineering materials for various industrial applications. Additive manufacturing (AM) of CFRPCs enables production of customized structures with superior mechanical properties at a low cost and has gained tremendous popularity. In the present study, a novel AM technique namely laser‐assisted laminated object manufacturing (LA‐LOM) is proposed for producing CFRPCs using prepreg sheets with continuous carbon fiber reinforcement. The interfacial properties of the bonded prepreg sheets are critical for the performance of the additively manufactured CFRPCs. We further introduce graphene as a modifier between the prepreg sheets to improve the mechanical properties of the CFRPCs. It is shown that low porosity (0.38%), high concentrations of continuous carbon fibers (63 wt. %), and improved interfacial bonding strength contribute to excellent mechanical properties. For the composite structure ([0°]s fiber arrangements), in which 0.5 mg/ml graphene is introduced as interface modifier, the lap shear strength, tensile strength, and tensile modulus are 18 MPa, 2940 MPa, and 170 GPa, respectively, and the flexural strength and modulus are 1310 MPa and 140 GPa, respectively. The tensile strength and modulus outperform all AM‐produced structures reported in literature, including carbon fiber composites and metals and metal alloys. Meanwhile, the increases are observed in the lap shear strength by 25%, flexural strength by 10%, and flexural modulus by 27%, as well as tensile strength by 7% and modulus by 6%, compared to specimens without graphene reinforcement. This composite architecture design, involving laminated continuous carbon fiber reinforced prepreg sheets and graphene‐modified interfaces, provides a readily scalable manufacturing method toward excellent properties and this method can be further explored in industrial applications.

Preparation and thermophysical properties of graphite flake-carbon fiber coreinforced copper matrix composites

Graphite flake-carbon fiber coreinforced copper matrix composites were prepared by vacuum hot pressing technology. The carbon fibers were dispersed ultrasonic in alcohol and then mixed with graphite flake and alloys powder (Zr and Cu) for hot pressing sintering. The effects of the carbon fiber content on the microstructure, bending strength and thermal conductivity of the composites were investigated. The results show that the interface of the composites is well bonded. When the volume fraction of carbon fiber is 1%–3%, the carbon fiber can be uniformly dispersed in the matrix, and the bending strength of the composites can be improved effectively. When the volume fraction of carbon fiber is 2%, the bending strength reaches a maximum of 152 MPa, which is an increase of 60% compared with that of the composites without carbon fiber. However, an excessive addition of carbon fiber (4% or more) leads to an uneven distribution of carbon fiber, and the bending strength of the composites decreases. When the volume fraction of carbon fiber is 2%, the thermal conductivity of the composite is 597 W·m−1·K−1. The acoustic mismatch model (AMM) associated with the Digimat MF module is able to predict the thermal conductivity of the anisotropic multiphase composites.

Mechanical, Fracture, and Microstructural Assessment of Carbon-Fiber-Reinforced Geopolymer Composites Containing Na2O.

For a sustainable environment, geopolymer (GPO) paste can be used in the construction industry instead of Portland cement. Nowadays, sustainable construction and high-efficacy composites are demanding. Therefore, in the present investigation, the mechanical and microstructural efficacy of carbon-fiber-reinforced fly ash-based GPO with different percentages of nano-sodium dioxide (NS) were studied. The investigated percentages of NS were 0%, 1%, 2%, 3%, and 4%. For all the samples, the carbon fiber content was kept the same at 0.5% by weight. Different percentages of NS for all five fabricated GPO composite pastes were assessed with scanning electron microscopy (SEM). Various mechanical parameters of GPO—the compressive strength, toughness modulus, hardness, toughness indices, impact strength, fracture toughness, flexural strength, and elastic modulus—were evaluated. The results revealed that the use of 3% NS was the most effective for ameliorating the mechanical, microstructural, and fracture behavior of GPO. The use of 3% NS in carbon-fiber-reinforced GPO paste showed the maximum improvements of 22%, 46%, 30%, 40%, 14%, 38.4%, 50.2%, 31%, and 64% for the compressive strength, flexural strength, elastic modulus, toughness modulus, hardness, compressive stiffness, bending stiffness, fracture toughness, and impact strength, respectively. The SEM study showed that the inclusion of NS improved the microstructure and delivered a denser GPO paste by improving the interfacial zones and quickening the polymerization reaction.

Influence of iron ore tailings by-product on the mechanical and electrical properties of carbon fiber reinforced cement-based composites

This research evaluated the feasibility of using iron ore tailings (IOTs) to produce functional conductive composite materials as cement-based sensors based on carbon fiber (CF) reinforced cement composite. In this study, recycled IOTs are used as an alternative material to natural fine aggregate (0%, 30%, and 60%). Nine mixtures were produced. The effects of CF and IOTs content on mechanical properties and electrical conductivity were investigated; Based on the digital image correlation (DIC) system, the stress sensing ability of the specimen was evaluated and the strain field distribution was extracted; According to the results of compressive stress sensing, a predictive compressive stress model was proposed, and the ratio of fractional changes of resistivity (FCR) with unit stress and CF content were fitted; The pore size distribution was studied using nuclear magnetic resonance (NMR) technology; Besides, scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to analyze the microscopic morphology and crystal phase composition. The experimental results revealed that the appropriate IOTs content could improve the pore size distribution and the mechanical properties, which is a maximum increase of 28.12% compared with the plain cement (PC). The DIC strain field distribution shows that the excessive IOTs could increase the brittleness of the matrix, and XRD crystal phase analysis showed that the calcium silicate hydrate (CSH) gel is reduced and the bond with CF is weakened. The addition of CF significantly reduces the resistivity of the composites by an order of magnitude, and the self-sensing capability can be increased by 3 times. The compression stress sensitivity has a linear relationship with the amount of CF, which can be used to predict the compression stress sensing efficiency. It is expected to develop industrial waste IOTs as an effective conductive filler to promote the wider use of CF conductive composite materials.

Study on the conductivity of carbon fiber self-sensing high ductility cementitious composite

The self-sensing high ductility cementitious composite that integrates high ductility and sensing performance has a unique advantage in structural health monitoring . The study of the electrical conductivity is significant for analyzing the sensing performance. In this paper, the high ductility self-sensing cementitious composite was developed by adding carbon fibers (CFs) into high ductility cementitious matrix . The percolation threshold and the effects of curing age, moisture content and temperature on the conductivity of the material were analyzed. The conductive behavior was also analyzed by equivalent circuit model and electrical impedance spectroscopy (EIS). The results revealed that the percolation threshold is 0.7 wt%. When the CF content is lower than the percolation threshold, the conductivity decreases with the increase of curing age, but increases with the increase of moisture content and temperature. The material conductive behavior is caused by the joint action of ionic conduction and electronic conduction of conductive fillers . When the CF content is higher than the percolation threshold, the effects of curing age and temperature are weakened, and the moisture effect has disappeared. The electronic conduction dominates the conductive behavior. It was also concluded that the equivalent circuit model can be applied to describe the conductive behavior. • The conductivity of CF self-sensing cementitious composite were studied. • The curing age, moisture and temperature affecting the conductivity were discussed. • The conductive behavior were discussed by electrical impedance spectroscopy. • The equivalent circuit model (CR(RQ)(RW)) were obtained.

Thermal Properties according to Content and Alignment of Carbon Fiber in Cu Matrix Composite Reinforced with Chopped Carbon Fiber

Thermal Properties according to Content and Alignment of Carbon Fiber in Cu Matrix Composite Reinforced with Chopped Carbon Fiber

Mechanical and Electrical Characteristics of Lightweight Aggregate Concrete Reinforced with Steel Fibers.

There is increased interest in applying electromagnetic (EM) shielding to prevent EM interference, which destroys electronic circuits. The EM shielding’s performance is closely related to the electrical conductivity and can be improved by incorporating conductive materials. The weight of a structure can be reduced by incorporating lightweight aggregates and replacing the steel rebars with CFRP rebars. In this study, the effects of lightweight coarse aggregate and CFRP rebars on the mechanical and electrical characteristics of concrete were investigated, considering the steel fibers’ incorporation. The lightweight coarse aggregates decreased the density and strength of concrete and increased the electrical conductivity of the concrete, owing to its metallic contents. The steel fibers further increased the electrical conductivity of the lightweight aggregate concrete. These components improved the EM shielding performance, and the steel fibers showed the best performance by increasing shielding effectiveness by at least 23 dB. The CFRP rebars behaved similarly to steel rebars because of their carbon fiber content. When no steel fiber was mixed, the shielding effectiveness increased by approximately 2.8 times with reduced spacing of CFRP rebars. This study demonstrates that lightweight aggregate concrete reinforced with steel fibers exhibits superior mechanical and electrical characteristics for concrete and construction industries.

Development of Reinforcement Grout Materials Based on Blast Furnace Slag according to the Content of Reinforcement Fiber

The grouting is used to reinforce soft ground and to prevent the leakage of water in the soil. The objective of the study is to enhance the compressive strength of grout materials by using reinforcing fibers and to increase the strength of soil using blast furnace slag powder. For this purpose, cement was replaced with the blast furnace slag powder by 30 to 60%. Furthermore, for comparison of carbon fibers with aramid fibers, each fiber was added by 0, 0.5, and 1.0% of the weight of material. As the contents of carbon fibers and aramid fibers increased, the uniaxial compressive strength increased. This is due to the interlocking of fibers in the grout material that increased the uniaxial compressive strength. Moreover, the grout material reinforced with aramid fibers showed an increase of uniaxial compressive strength by at least 20% compared to the carbon fibers. An environmental assessment was done through a heavy metal leaching test and a pH test. The test result reveals that about 50% of chromium (VI) leaching decreased as 30% more blast furnace slag powder was used but the pH test shows about 0.5 pH increased as 30% more blast furnace slag powder was used. Further study is necessary for the pH test.

A Three-Dimensional Activated Carbon Electrode with Carbon Fiber Felt Framework and Ordered Macropores for Enhanced Capacitive Deionization Performance

Capacitive deionization (CDI) is a promising energy-efficient electrochemical water treatment technology and a scalable electrode having high mass loading is an essential imperative to the success of this technology. A thick CDI electrode was constructed by loading activated carbon particles as the electroactive material into a three-dimensional framework fabricated from a mixture felt of conductive carbon fiber serving as an electron transfer channel and removable yak hair functioning to provide an ion transport pathway. The carbon fiber reduces the electrode electrical resistance and the ultimately removed yak hair creates an ordered macropore array that provides an ion reservoir as well as a conduction channel for reducing ion transport distance inside the electrode. The resulting composite electrode with an optimal carbon fiber and yak hair content shows a specific capacitance of 219.27 F g-1 at 0.1 A g-1 and reaches salt adsorption capacity of 15.75 mg g-1 and average salt adsorption rate of 17.10 mg g-1 h-1 with more than 50% retention after 200 cycles. The designed three-dimensional composite exhibits enhanced deionization and long-term stability that is believed to be a low-cost and simple assembly solution for achieving a high mass loading and scalable electrode for the industrial CDI applications.

Carbon fiber-reinforced polyamide composites with efficient stress transfer via plasma-assisted mechanochemistry

Carbon fiber-reinforced polymers (CFRPs) show excellent mechanical strength and lightweight. However, conventional CFRPs require high loading of carbon fibers (CFs) to improve their mechanical properties due to poor polymer–CF interfacial adhesion. We propose a dry and ecofriendly method to fabricate high-performance CFRPs by improving interfacial adhesion. The plasma-assisted mechanochemistry (PMC) process can create physical and chemical linkages between polymers and carbon fillers via application of a mechanical force and plasma treatment. We use carbon nanotubes as bridge materials to increase the effective interfacial area and promote mechanical interlocking. The PMC-treated CFRPs exhibit reduced C-factor and increased degree of entanglement, indicating efficient stress transfer the polymer to the filler. Additionally, the PMC process can provide the significantly improved mechanical properties of CFRPs even at low CF loading. Notably, the PMC-treated CFRPs showed continuously increasing tensile strength, Young's modulus, and elongation at break with increasing CF content up to 30 wt%, which has not been observed previously for CFRPs. As a result, the tensile strength, Young's modulus, and elongation at break of the PMC-treated composites with a CF content of 30 wt% increased by 47.1%, 43.0%, and 91.7%, respectively, compared to those of the conventional composites. We believe that this simple approach opens a new route to the fabrication of high-performance CFRPs exhibiting extraordinary mechanical properties.

Electrical properties of 3D printed continuous carbon fibre composites made using the FDM process

Fused deposition modelling (FDM) is an additive manufacturing process for the 3D printing of continuous fibre-thermoplastic composite laminates. The electrical conductivity of continuous carbon fibre (CF)-nylon filaments and laminates printed with a Markforged MarkTwo® FDM machine is experimentally investigated. The axial electrical conductivity of single filaments measured before, during and following the FDM process reveal a large reduction (∼40%) due mostly to breakage of carbon fibres. The electrical conductivity of 3D printed laminates made by the layer-by-layer deposition of the single filaments were determined in the longitudinal, transverse and through-thickness directions, and compared to the electrical properties of a hot moulded composite with a near-equivalent carbon fibre content. The longitudinal conductivity of the 3D printed laminate was only ∼50% that of the hot moulded composite, and this was due mostly to fibre breakages caused by the FDM process. However, the transverse and through-thickness electrical conductivities of the 3D printed laminate were higher (∼13 times and ∼3 times, respectively) than the hot moulded composite due to higher fibre waviness causing increased fibre-to-fibre contact which aids the flow of electrical current in these two directions.

Influence of rigid particles on thermal conductivity enhancement of polydimethylsiloxane composite during spatial confining forced network assembly

AbstractIn order to meet the heat dissipation requirements of electronic equipment, a variety of methods for preparing thermally conductive polymer composites have been proposed. In this article, highly thermal conductive polydimethylsiloxane (PDMS) composites were prepared by combining the spatial confining forced network assembly (SCFNA) method with adding rigid particles (RPs). The orthogonal experiments were designed to verify the effects of short carbon fiber (SCF) content, glass bubble (GB) content, GB particle size and composite thickness on the thermal conductivity (λ) of SCF‐GB/PDMS composite. In addition, the λ and shapes of different RPs (including GB, SiO2, AlN, glass fiber [GF]) also play vital roles in λ enhancements of SCF‐RP/PDMS composites. The mechanical properties of SCF‐RP/PDMS composites were different with various RPs contents, and the SCF‐GB/PDMS composite presented the largest elongation at break (70%) and the best mechanical flexibility. The SCF‐GB/PDMS composite with a low GB content of 5 vol% can not only greatly improve the λ, but also ensure its excellent mechanical properties.

Application of Broadband Laser-Ultrasonic Spectroscopy for Nondestructive Testing of the Porosity in Carbon Fiber Reinforced Plastics with Various Volume Contents of Carbon Fibers

Application of Broadband Laser-Ultrasonic Spectroscopy for Nondestructive Testing of the Porosity in Carbon Fiber Reinforced Plastics with Various Volume Contents of Carbon Fibers

Determination of the influence of a filler on the properties of composite materials based on polytetrafluorothylene for tribosystems of mechanisms and machines

This paper reports a comprehensive laboratory study into the thermophysical, physical-mechanical characteristics, and tribological properties of the designed composite materials based on polytetrafluoroethylene. In the structures of machines and mechanisms, a significant role belongs to the tribological conjugations made from polymeric and polymer-composite materials. The reliability of machines, in general, depends to a large extent on the reliability of movable connections. Composite materials of nonmetallic origin have a low cost, they are resistant to most aggressive chemicals and are capable of operating under conditions without lubrication. It was established that the characteristics and properties of materials must be adapted to the working conditions of separately considered tribological conjugations. The mechanisms of thermal destruction have been established, both in the basic material and the carbon fiber based on it. It was found that carbon fiber, regardless of its content (quantity) in the polymer-composite material based on polytetrafluoroethylene, is mainly oriented perpendicular to the force application plane. It was found that with an increase in the carbon fiber content from 10 to 40 % by weight, the heat capacity decreases by 16‒39 % compared to the main material. The optimal operating modes for the designed composite materials have been substantiated on the basis of a pv factor: under a dry friction mode – up to 4 MPa∙m/s; at friction with lubrication – up to 36.4 MPa∙m/s. The dependence has been established of the friction coefficient on the operating modes of a composite material based on polytetrafluoroethylene containing 20 % by weight of carbon fiber when lubricated with oil and water. The results reported here make it possible to synthesize the physical-mechanical characteristics and tribological properties of composite materials in accordance with the required modes of tribological conjugation.