Conventional Carbon Fiber Research Articles

Analytical model for RC beams with embedded prestressed Fe-SMAs

Prestressed iron-based shape memory alloy (Fe-SMA) strengthening is an effective means to enhance the performance of reinforced concrete (RC) structures. The applied prestress level significantly influences the strengthening efficiency. However, the absence of a reliable model predicting the applied prestress hinders the efficient design of prestressed Fe-SMA strengthening solutions. To fill this gap, the current study proposes an analytical model, with which a constant zone and a transfer zone are identified in strengthened RC beams. The constant zone, with zero interfacial shear stress, sustains a constant prestress level, while the transfer zone, experiencing non-zero shear stress, gradually reduces the Fe-SMA tensile stress from the prestress level to zero. Validated through experiments, the proposed model accurately predicts the applied prestress levels and prestress-induced deflections in RC beams strengthened with Fe-SMAs and more conventional carbon fiber reinforced polymers (CFRPs). Further analysis reveals that the transfer zone length ranges from 4 to 7 characteristic lengths, and it is proportional to the logarithm of the applied prestress level. Simplifying a constant prestress level within the beam span yields sufficiently accurate prestress analysis.

Optimizing dielectric constant of noncommercial biobased fibres - Acacia Nilotica, Acacia Leucophloea and Prosopis juliflora - For composite applications with selected fillers

In recent decades, most electrical/electronic products possess non – biodegradable components. The expanding consumption of these goods and their eventual disposal pose a serious environmental threat. To cope up with this issue, biodegradable electrical/electronic components using biobased fibres can be an alternative option. The novel exploration of this research work is the usage of underutilized biobased fibres, such as Acacia Nilotica, Acacia Leucophloea and Prosopis Juliflora, as sustainable alternatives to traditional synthetic fibres in natural fibre-reinforced epoxy composites. The novelty lies in the combination of these natural fibres with ceramic fillers like Silicon Carbide, Boron Nitride and Aluminium Oxide, aiming to enhance the composite properties. The objective of the study is to optimize the type of fibre, fibre content (2 wt%, 4 wt% and 6 wt%) and types of fillers (1 wt%) combinations using the Box-Behnken Design to improve the dielectric properties of these composites. Analysis of Variance (ANOVA) is used to evaluate the relevance of each parameter on dielectric constant of the biobased fibre reinforced epoxy composite. The significant outcome is identified that Prosopis Juliflora (6 wt%) combined with Boron Nitride (1 wt%) yields an optimal dielectric constant of 1.11, highlighting the potential of these biobased fibres to serve as effective substitutes for conventional glass and carbon fibres for electrical insulating materials used in switchboards and socket pins to prevent electrical conduction and ensure safety. This research not only contributes to the field of sustainable materials but also addresses critical environmental concerns associated with electric/electronic waste.

Tensile properties of helical carbon fiber tows

The carbon fiber used in the load-bearing structural components often exhibits a relatively low toughness and a limited elongation at the point of failure within its carbon fiber tows. To address this challenge, we introduced a bionic helical structure as an innovative alternative to the conventional straight carbon fiber tows, resulting in a novel material characterized by enhanced strength and toughness. Pioneering a theoretical model, we delved into the effects of the helical angle on the tensile mechanical properties of helical carbon fiber tows for the first time. Subsequently, we conducted experimental trials to validate our theoretical findings and identified an optimal range for the helical angle. The optimized helical angle enhances additional lateral interactions, improving the bonding between the fibers and the resin. The characteristics of the helical structure increase the overall fracture elongation of the fiber tows. Tensile tests revealed a remarkable 10.8 % increase in maximum tensile strength and a significant 46 % enhancement in toughness when the tows were fully impregnated with epoxy resin using this optimal helical angle. Incorporating the helical structures at this optimized angle represents a breakthrough in improving the mechanical properties of carbon fiber tows, offering a unique solution to strike a balance between strength and toughness in carbon fiber composites.

Influence of Carbonisation Temperatures on Multifunctional Properties of Carbon Fibres for Structural Battery Applications

AbstractCarbon fibres are multifunctional materials considered for the realisation of structural battery electrodes. Processing conditions affect the carbonaceous microstructure of carbon fibres. The microstructure dictates the fibre‘s mechanical properties, i. e. modulus and strength, as well as its electrochemical capacity. Here, carbon fibre processing conditions are investigated to identify the effect of carbonisation temperature on carbon fibre multifunctionality. Different thermal conditions during carbonisation are considered, while keeping the precursor material, applied tension, and oxidation temperature constant. The carbonaceous microstructure of fibres is investigated via wide‐angle x‐ray scattering (WAXS) and transmission electron microscopy (TEM) analyses to determine the effect of the carbonisation temperature. Mechanical and electrochemical tests are performed to characterise carbon fibre multifunctionality with respect to mechanical and electrochemical performance. A moderate trade‐off between mechanical and electrochemical performance is demonstrated, where the elastic modulus and strength decrease and the electrochemical capacity increase with reduced carbonisation temperature. Here, for the studied temperature interval, the elastic modulus and strength is found to drop up to 7 % with a 15 % increase in capacity. Thus, fibres customised for targeted multifunctionality within a limited design space can be realised by careful selection of the processing conditions in conventional carbon fibre manufacture.

Microcracking resistance of 3D printed fibre composites at cryogenic temperatures

Thermoplastic composites present considerable promise for 3D printing cryogenic fuel storage tanks, offering enhanced recyclability and repairability compared to thermoset composites. However, a significant knowledge gap remains regarding their ability to withstand cryogenic environments without suffering ply cracking, especially the effects of high thermal residual stresses and voids on the microcracking resistance of 3D printed composites. This study investigates the microcracking behaviour of continuous carbon fibre reinforced thermoplastic (CFRTP) composites fabricated through extrusion-based 3D printing. Three-point bending tests were conducted to assess the microcracking resistance of the as-printed and heat-treated composites at room and cryogenic temperatures. The results reveal that the nylon-based CFRTP composites printed at room temperature exhibit a remarkable ability to withstand an applied strain of 0.60 % without ply cracking at liquid nitrogen temperature. This performance surpasses that of conventional carbon fibre reinforced epoxy composites, which typically experience ply cracking even at zero applied strain. Some of the microcracks were traced back to manufacturing defects, which could be fused by a post-heat treatment at 180℃ for 60 minutes. Unexpectedly, however, the treatment reduced the ply-cracking strain to 0.40 % at the liquid nitrogen temperature. Computational micromechanical modelling revealed that this unexpected decline in ply-cracking resistance resulted from the increased thermal residual stresses induced by the heat treatment. The findings of this study suggest that 3D-printed thermoplastic composites exhibit robust resistance to microcracking at cryogenic temperatures, making them a promising solution in the quest for sustainable lightweight cryogenic fuel storage solutions.

Highly thermally conductive composites of graphene fibers

Carbon fiber-based polymer composites have rich electric and thermal functions, the merit of weight lightness to meet important applications in thermal management. Graphene fiber, a newly emerged carbonaceous fiber, features high thermal conductivity that surpasses conventional carbon fibers. For the realistic applications of graphene fiber, fiber composite is one necessary form but still remains unexplored. Here, we prepared graphene fiber based polymer composites and achieved high specific thermal conductivity up to 363 W∙cm3∙m−1∙K−1∙g−1, outperforming composites of mesophase pitch-based carbon fiber. Graphene fiber composites with a fiber content of 59 vol% have a low density of 1.53 g∙cm−3 and high axial thermal conductivity of 553 W∙m−1∙K−1. For the high breakage elongation of graphene fiber, graphene fiber composites can be fabricated to adapt sharp curvature structures. This work develops polymer composites of graphene fiber and their high thermal conductivity can have extensive applications in thermal management.

An ingenious synergistic solid lubricant of copper and graphite for exceptional wear resistance of the SCF/PTFE/PEEK composite

In this work, the conventional short carbon fiber (SCF)/polytetrafluoroethylene (PTFE)/polyetheretherketone(PEEK) (SCF/PTFE/PEEK) composite was elected as the matrix, copper and graphite micron flakes were further blended to prepare PEEK self-lubricating composites. At a pressure of 12 MPa and a speed of 0.5 m/s, with a graphite content of 7.5 wt% and copper of 2.5 wt% (Gr7.5Cu2.5), the composite exhibited a COF of 0.23 and the lowest wear rate of 4.1 × 10−7 mm3/Nm. Physicochemical analysis of the worn surface of the steel ring revealed that the introduction of appropriate amounts of copper facilitated the tribo-physicochemical reaction during the rubbing process, which favored the formation of a thin and tough transfer film of Gr7.5Cu2.5 on the worn surface of the steel ring.

X-ray scattering tensor tomography based finite element modelling of heterogeneous materials

Among micro-scale imaging technologies of materials, X-ray micro-computed tomography has evolved as most popular choice, even though it is restricted to limited field-of-views and long acquisition times. With recent progress in small-angle X-ray scattering these downsides of conventional absorption-based computed tomography have been overcome, allowing complete analysis of the micro-architecture for samples in the dimension of centimetres in a matter of minutes. These advances have been triggered through improved X-ray optical elements and acquisition methods. However, it has not yet been shown how to effectively transfer this small-angle X-ray scattering data into a numerical model capable of accurately predicting the actual material properties. Here, a method is presented to numerically predict mechanical properties of a carbon fibre-reinforced polymer based on imaging data with a voxel-size of 100 μm corresponding to approximately fifteen times the fibre diameter. This extremely low resolution requires a completely new way of constructing the material’s constitutive law based on the fibre orientation, the X-ray scattering anisotropy, and the X-ray scattering intensity. The proposed method combining the advances in X-ray imaging and the presented material model opens for an accurate tensile modulus prediction for volumes of interest between three to six orders of magnitude larger than those conventional carbon fibre orientation image-based models can cover.

In Situ Ceramization of Nanoscale Interface Enables Aerogel with Thermal Protection at 1950 °C.

Conventional carbon fiber felt-reinforced aerogel composites are often used as lightweight thermal protection systems (TPSs) for aerospace craft. However, due to their poor oxidation resistance, they have gradually failed to handle increasingly harsh thermal environments. In this work, a nanoscale composite coating interface of SiC-ZrC ceramic precursor is first constructed on the fiber surface. Subsequently, using the coated fiber felt as a three-dimensional skeleton and through polymerization-induced phase separation, an aerogel composite with excellent thermal protection in extreme thermal environments is prepared. Owing to the in situ ceramization of this nanoscale interface at ultrahigh temperatures, the back temperature of the 12 mm thick aerogel is only 147 °C after exposure to an oxyacetylene flame at 1950 °C for 70 s. Meanwhile, the central region of the aerogel recedes by only 7%. Not only does this work provide a way to enhance aerogels by constructing a self-ceramizable nanoscale interface it is also expected that the developed aerogel composite can be applied in the ultrahigh-temperature thermal protection of future aerospace craft.

Assessing sustainability and green chemistry in synthesis of a Vanillin-based vitrimer at scale: Enabling sustainable manufacturing of recyclable carbon fiber composites

Sustainable manufacturing of carbon fibre (CFs) reinforced polymer (CFRP) composites featured technically by low-cost and rapid manufacturing techniques, use of renewable materials, and non-destructive recycling process. By developing an inherently recyclable thermoset, this research bridges between these three components of sustainable manufacturing by focusing on a fast cured vanillin-based Schiff base polyimide network in all-solid state. In this study, a multifunctional vanillin-based monomer was synthesised at scale in water which can be cured using a diamine without requiring any organic solvent. A CFRP was fabricated using this newly developed Schiff base polymer using compression moulding technique, and its mechanical and thermal/fire performance were compared to a CFRP made of a commercially available automotive grade epoxy resin. The resulting Schiff base CFRP composite demonstrated exceptional fire retardancy, complemented by remarkable tensile strength and modulus values of 427 MPa and 45 GPa, respectively. These characteristics meet the criteria for a broad spectrum of high-performance applications. In contrast to conventional CF reclaiming processes, a novel and efficient chemical recycling approach was introduced, enabling the delamination of CF layers containing the Schiff base network without requiring the separation and purification of the polymer matrix. This approach facilitates the low-cost remanufacturing of new CFRP composites with mechanical performance comparable to the original composite. Finally, green chemistry matrices as well as simplified life cycle assessment (LCA)-like approaches, including the EcoScale and GREEN MOTION rates, were employed to evaluate the efficiency and environmental impact of the CFRP manufacturing process.

Surface modification of carbon fibers for enhanced electromagnetic absorption

The exceptional chemical and physical properties of carbon fiber make it highly promising for utilization in the field of wave-absorbing materials. However, the low magnetic loss and high complex permittivity of conventional carbon fiber materials limit their use in wave-absorbing materials. Hence, this study presents the synthesis of a FeCoNi/N-doped carbon coating/SCF composite with a distinctive microstructure by an in-situ reduction process. The successful formation of this unique architecture was confirmed through various characterization techniques. The composite material displayed both magnetic and dielectric characteristics. It showed an effective bandwidth spanning 14.77 GHz with a reflection loss (RL) of − 10 dB or less. In addition, it attained the minimum RL value of − 50.5 dB at a distance of 3.5 mm. The composite material is hypothesized to show great potential in electromagnetic wave absorption.

Enhanced electrochemical hydrogen storage performance of Co9S8 material by doping with cobalt nanoparticles embedded hollow porous carbon nanofibers

Co-axial electrospinning has been regarded as an effective technology to fabricate hollow or core/shell nanofibers. Herein, co-axial electrospinning was carried out employing polymethyl methacrylate (PMMA) and polyacrylonitrile (PAN) as the core and shell components. Cobalt acetate was used as the cobalt source. The cobalt nanoparticles embedded hollow porous carbon fibers (Co/HCNF) were obtained after electrospinning and subsequent carbonization process. For comparison, the conventional carbon fibers (CNF), hollow carbon fibers (HCNF), and cobalt nanoparticles modified carbon fibers (Co/CNF) were also synthesized. Co9S8 material was manufactured via mechanical alloying. By adjusting the types of carbon fibers, a series of carbon fibers modified Co9S8 composites were obtained by ball milling and their electrochemical hydrogen storage properties were studied. As a result, the Co9S8 + Co/HCNF electrode showed the higher discharge capacity of 603.3 mAh/g than CNF, HCNF, Co/CNF modified Co9S8 and conventional Co9S8 electrodes. The Co nanoparticles within Co/HCNF provided high electrocatalytic activity. The special hollow porous structure and high specific surface area of Co/HCNF increased the conductivity, offered more electrochemical active sites and rapid channel for charge transfer. Moreover, Co9S8 + Co/HCNF also demonstrated improved high-rate dischargeability (HRD), capacity retention and kinetics properties. An advantageous solid-solid interface may be generated between Co9S8 and Co/HCNF, serving as a beneficial electron conduction path and facilitating the hydrogen diffusion, thereby enhancing the electrode performance of Co9S8 material.

A review of high-performance carbon nanotube-based carbon fibers

With the growing importance of high-performance carbon fibers (CFs), researches have been conducted in many applications such as aerospace, automobile and battery. Since conventional CFs which were made from polyacrylonitrile, pitch and cellulose display either high tensile strength or high modulus properties due to structural limitations, it has been a challenge to develop CFs with both tensile strength and modulus with high conductivity. Therefore, various studies have been conducted to obtain high-performance multifunctional CFs. Among them, 1-dimensional carbon nanotubes (CNTs) have been used commonly to make CFs because of high mechanical and conducting properties. In this review, the recent development of CFs was introduced briefly, and CNT-based composite CFs were introduced. Many efforts are being made to create high-performance CFs by combining various carbon nanomaterials and polymers, which can have potential to be utilized in aerospace, defense and other industries. The those fibers may be nextgeneration high-performance fibers due to both high strength and high modulus as well as high conducting properties. The challenges and outlook for commercialization of CNT-based CFs are addressed in terms of aspect ratio of CNTs, solvent recycling, and mass-production.

Nanocone-shaped Ni-electroplated carbon fiber composite films for electromagnetic shielding applications

This study developed a series of lightweight composite films with adjustable reflectivity and superior mechanical properties. Carbon fiber (CF) was electroplated with both conventional and nanocone-shaped Ni coatings to create Ni-plated carbon fiber (CF@Ni), which was then further classified into conventional Ni carbon fiber (CF@CN) and nanocone-shaped Ni carbon fiber (CF@NN). CF@Ni fibers were sheared and filtered to produce Ni-plated carbon fiber fabric (CFF@Ni), which was then encapsulated in polyimide resin (PI) to form the final thin film materials (CF@Ni/PI). The shielding performance and mechanical properties of these CF@Ni/PI thin films have been comprehensively investigated. The study found that the nanocone-shaped Ni-plated samples exhibited superior performance. Absorption loss was dominant when a relatively low amount of Ni-plated carbon fiber was added, while reflection loss dominated when a relatively high amount was added. Adding 0.3 g of nanocone-shaped Ni carbon fiber created a 1.2 mm thin film with a shielding effectiveness of 71 dB and a tensile strength of 22.4 MPa. Additionally, the thin film demonstrated excellent flexibility and durability. Due to its exceptional mechanical properties and flexibility, this composite film holds significant potential in the fields of microelectronics and intelligent electronic devices.

Interfacial and interlayer enhancement of highly hydrophilic dual-affinity waterborne polyurethane sizing agent acting on carbon fiber/epoxy resin composites

Dual-affinity waterborne polyurethane (WPU) sizing agents with different solid concentrations were designed to achieve two-stage interfacial properties of carbon fiber (CF) and epoxy resin (EP) reinforced composites. The effects of hydrophilic monomer content on the emulsion dispersion of WPU sizing agents and the thermal properties of the coating films were investigated, and the best performing component was selected as the sizing agent of CF to prepare WPU treated-CF. The analysis focuses on the changes of surface morphology and roughness, ionic group types, tensile strength of CF before and after WPU sizing, and the interfacial properties, interfacial strengthening mechanism of CF/EP composites. Compared with conventional commercial CF, the WPU treated-CF shows a 4 % increase in surface free energy and a noticeable improvement in surface roughness and morphology. The wettability, compatibility and adhesion of WPU treated-CF/EP composites were improved according to the strong polar “similarity intermiscibility” between the strong polar functional groups in WPU and EP. Most importantly, the interfacial shear properties (IFSS) of WPU treated-CF/EP composites were improved by 17.2 % and the interlaminar shear properties (ILSS) were improved by 23.8 %. The dual-affinity WPU sizing agent optimizes the practical effect of CF/EP composites for applications such as instrument components and surface coatings used in new energy vehicles, high-speed rail trains, aerospace and provides a boost to the development of new environmentally friendly high-performance chemical coatings.

Fabrication of Graphitized Carbon Fibers from Fusible Lignin and Their Application in Supercapacitors.

Lignin-based carbon fibers (LCFs) with graphitized structures decorated on their surfaces were successfully prepared using the simultaneous catalyst loading and chemical stabilization of melt-spun lignin fibers, followed by quick carbonization functionalized as catalytic graphitization. This technique not only enables surficial graphitized LCF preparation at a relatively low temperature of 1200 °C but also avoids additional treatments used in conventional carbon fiber production. The LCFs were then used as electrode materials in a supercapacitor assembly. Electrochemical measurements confirmed that LCF-0.4, a sample with a relatively low specific surface area of 89.9 m2 g-1, exhibited the best electrochemical properties. The supercapacitor with LCF-0.4 had a specific capacitance of 10.7 F g-1 at 0.5 A g-1, a power density of 869.5 W kg-1, an energy density of 15.7 Wh kg-1, and a capacitance retention of 100% after 1500 cycles, even without activation.

Using Harris Hawk algorithm for experimental study on the hole dilation mechanism during Micro-machining (μM) of Graphene nanoplatelets/Carbon fiber (GnP/C) reinforced polymeric composite

This article highlights the hole generation mechanism in the Graphene nanoplatelets/Carbon fiber (GnP/C) reinforced polymeric composite. The lower conductivity of conventional carbon fiber reinforced polymer (CFRP) composites restricts the μEDM (Micro Electrical discharge machining) test. This limitation is overwhelmed by adding highly conductive GnP powder in the CFR (epoxy) polymer composites. The generation of the drilled hole is possible through the increase in the electrical conductivity of the samples. During μEDM, in order to examine the quality of machined holes in terms of hole dilation (HD), different process constraints such as voltage (80, 120, 160 V), pulse on time (30, 40, 50 s), and weight percentage of GnP (0.25, 1, 1.75%) are evaluated (HD). The hole dilation was significantly influenced by GnP concentration and voltage alteration during the micromachining process. Analysis of Variance (ANOVA) results confirmed that the GnP concentration (67.51%) was the most prominent factor affecting hole dilation. The high-resolution microscopy test was performed to investigate the hole machined surface and damages occur during the micromachining test. The variation in the thermal nature of carbon fabric and resin generates internal stress between the composite material, which results in micro-cracks developed in the laminates. The varying parameters were controlled and optimized through a recently developed nature-inspired metaheuristics algorithm based on the conduct of Harris Hawk (HH). The optimal parametric condition for the hole dilation is voltage (level 1–80 volt), pulse duration (level 1–30 μs), and GnP concentration% (Level 1–0.25). The findings of the validation test demonstrate the application potential of the proposed Harris Hawk algorithm.

Study on new process of electroless copper plating pretreatment on carbon fiber surface

In general, conventional carbon fiber surface pretreatment, with palladium, silver, and other precious metals as activators, increases its surface activity by initiating redox reactions for metallization, whereas it exhibits a high cost and poor economy. In this study, copper-nickel mixed colloids with low cost served as the activators, and sodium borohydride (NaBH4) and sodium hydroxide (NaOH) were employed as sensitizing reducing agents to successfully plate copper on the surface of carbon fibers. Subsequently, the morphology of the treated samples was characterized through SEM and XPS to explore the pretreatment process of the carbon fiber surface. The results indicated that the carbon fiber exhibited the optimal debinding effect at 55°C and the heating time was longer than 120 min. The result indicated that coarsening effect of 65% concentrated nitric acid was the optimal. The activation effect of copper-nickel mixed colloid was the optimal, and the surface quality of the coating was the optimal.

Temperature field evolution and thermal-mechanical interaction induced damage in drilling of thermoplastic CF/PEKK – A comparative study with thermoset CF/epoxy

Although new generation carbon fibre reinforced thermoplastic (CFRTP) such as carbon fibre reinforced polyetherketoneketone (CF/PEKK) is a promising sustainable alternative to the conventional thermoset carbon fibre reinforced plastic (CFRP), there is a lack of literature regarding its machining performance. This is the first study unveiling the machining temperature evolution during drilling of CF/PEKK and its potential impact on the associated material damages. Through a comparative study with the thermoset CF/epoxy, the disparate drilling performance of the two composites has been uncovered, and the results were found to be closely related to the materials' thermal/mechanical properties. Specifically, CF/PEKK produces continuous chips due to its excellent ductility and thermal sensitivity, whereas CF/epoxy produces segmented chips due to its brittle nature. CF/PEKK generates up to 40 N (50.5 %) higher thrust force, 87.6 °C (98.9 %) higher hole wall temperature and 61.1 °C (48.8 %) higher chip temperature than that of CF/epoxy. This has been correlated to the longer tool-chip contact length of CF/PEKK and its unique chip morphology. Despite the greater thrust force/temperature generation, CF/PEKK shows 55.7 % lower delamination damage as compared to CF/epoxy, and this is owning to its excellent interlaminar toughness. This study establishes a more in-depth understanding into the drilling performance of thermoplastic CF/PEKK and thermoset CF/epoxy and also provides guidance on the high performance manufacturing of next generation composites.

AFP tool path planning for manufacture of variable stiffness composites

Variable stiffness composites (VSC) demonstrate enhanced mechanical properties compared to conventional carbon fiber reinforced plastics (CFRP). Finite element analysis (FEA) is used to optimize layup directions, which need to be transformed into viable tool paths for automated fiber placement (AFP) processes. Manufacturing defects such as wrinkles, gaps, and overlaps should be handled. In this study, a novel path planning algorithm is developed for variable steering in AFP. The fiber directions are clustered and for each cluster a reference curve is fitted as B-Spline, where manufacturing constraints are considered. The proposed tool path planning approach is successfully demonstrated in a case study.