Waste Carbon Fiber Research Articles

An Investigation on the Feasibility of Fabricating Composites Using Outdated Waste Carbon Fibers and Easily Disposable Polyolefin Resins.

Outdated-waste-carbon-fiber-reinforced olefin composites (oCFOCs) were fabricated with easily disposable polyolefin resins, polypropylene (PP), high-density polyethylene (HDPE), and low-density polyethylene (LDPE), by compressive molding using a hot press. The flexural and impact strengths of the oCFOCs from each respective resin type and oCF content, ranging from 35 to 70 wt.%, were increased by the aging treatment (120 °C and 95% humidity under a pressure of 0.8 MPa) until an aging time of three days, due to improved resin impregnation. For the oCFOC with PP, the hydrogen bond between PP and developed C-O groups due to the aging treatment and the existing silane layer of oCF is considered to assist cohesion between the resin and oCF. In particular, PP and 45 wt.% oCF content were the most effective conditions for improving the oCFOCs’ mechanical properties, in addition to endowing the oCFOCs with good moldability and dimensional stability. Our results demonstrate that durable recycled composites can be manufactured using oCF and PP.

Effect of carbon fiber waste on steel corrosion of reinforced concrete structures exposed to the marine environment

This study experimentally investigates the possibility of using chopped carbon fiber waste for mitigating steel corrosion in reinforced concrete structures. Chopped carbon fiber waste was surface treated with epoxy to address the uniform dispersal of soft chopped carbon fiber into the cement mixture and prevent galvanic coupling between chopped carbon fiber and steel bars. The steel corrosion of reinforced concrete structures with different chopped carbon fiber percentages has been analyzed via electrochemical corrosion measurements, load-displacement curves and microscopy observation analysis. reinforced concrete beams were subjected to sustained point loading, a mass fraction of 3.5% Sodium Chloride marine wet-dry cycle and 50 °C environments for 360 days. A decrease in corrosion rate was observed in the beams with chopped carbon fiber waste compared to the control beams without chopped carbon fiber. The decreased corrosion rates in beams with 2.5% and 5% chopped carbon fiber (mass fraction of cement) were approximately 20% and 10%, respectively, compared to the beams without chopped carbon fiber. The ultimate strength of beams with 2.5% chopped carbon fiber and 5% chopped carbon fiber was increased by 25% and 17% compared to the control beams. Therefore, chopped carbon fiber waste could be used in reinforced concrete structures for reducing corrosion activity.

Undergraduate Research Program to Recycle Composite Waste

With the rapid growth in the manufacturing industry and increased urbanization, higher amounts of composite material waste are being produced, causing severe threats to the environment. These environmental concerns, coupled with the fact that undergraduate students typically have minimal experience in research, have initiated the need at the UAE University to promote research among undergraduate students, leading to the development of a summer undergraduate research program. In this study, a recycling methodology is presented to test lab-fabricated Carbon-Fiber-Reinforced Polymer (CFRP) for potential applications in industrial composite waste. The work was conducted by two groups of undergraduate students at the UAE University. The methodology involved the chemical dissolution of the composite waste, followed by compression molding and adequate heat treatment for rapid curing of CFRP. Subsequently, the CFRP samples were divided into three groups based on their geometrical distinctions. The mechanical properties (i.e., modulus of elasticity and compressive strength) were determined through material testing, and the results were then compared with steel for prompt reference. The results revealed that the values of mechanical properties range from 2 to 4.3 GPa for the modulus of elasticity and from 203.7 to 301.5 MPa for the compressive strength. These values are considered competitive and optimal, and as such, carbon fiber waste can be used as an alternate material for various structural applications. The inconsistencies in the values are due to discrepancies in the procedure as a result of the lack of specialized equipment for handling CFRP waste material. The study concluded that the properties of CFRP composite prepreg scrap tend to be reusable instead of disposable. Despite the meager experimental discrepancies, test values and mechanical properties indicate that CFRP composite can be successfully used as a material for nonstructural applications.

Heterogeneous Thermoset/Thermoplastic Recycled Carbon Fiber Composite Materials for Second-Generation Composites

With an increase in the use of carbon fiber composites in the aerospace and automobile industry a collateral issue of what to do with end-of-life carbon fiber composites has risen. In this study, we successfully developed a second-generation composite using a heterogenous mixture of thermoset and thermoplastic recycled carbon fiber composites (CFCs). The recovered vinyl ester and epoxy CFCs (thermosets) were characterized using thermogravimetric analysis. Adhesive performance was evaluated through double lap shear tests by melt-bonding a thermoplastic polyether ether ketone (PEEK) CFC to either the thermoset epoxy or vinyl ester CFC. The waste carbon fiber composites were also mechanically milled and classified through screening techniques. The resulting milled materials were used to form and produce composite panels through high temperature compression molding. The influence of particle size and platen temperature were evalauted through mechanical testing. Results indicate that melt-bonding with the vinyl ester/CFC exhibited significantly higher lap shear strength values than that between epoxy/CFC and PEEK. Findings also show that adding thermoset CFCs to the thermoplastic system (PEEK) enhanced the flexural properties of composites.

Valorization of carbon fiber waste from the aeronautics sector: an application in Li-ion batteries

Recycled carbon fibers coming from the aerospace industry are integrated as the backbone of a high energy density free-standing electrode.

Simulation based characterization of recycled carbon fiber reinforced plastics in a rod specimen

Abstract This paper aims to characterize recycled carbon fiber reinforced plastics through simulations and predict the behavior of Polyamide 6 (Nylon 6) and Polypropylene (PP) when reinforced with short carbon fibers. By modeling ASTM 638D test specimen and simulating injection molding on Moldflow software, a fiber orientation factor was obtained. This factor was used to predict the tensile strength of the fiber reinforced plastics using modified Kelly-Tyson equation. Digimat software was further used to predict the young’s modulus and micro-analysis of the carbon fiber reinforced plastics. These mechanical properties were calculated for variations in the fiber content (by volume) and fiber length. An efficient CFRP recycling method and the corresponding characterization of the recycled composite can provide a solution to the problem of excessive carbon fiber waste generation and find newer applications for the recycled polymers, thus provide alternatives to the traditionally used materials.

Electrical percolation and fluidity of conductive recycled mortar cement: graphite powder: recycled sand with addition of industrial waste carbon fiber

The use of recycled materials, such as the fine recycled aggregate made from concrete waste and carbon fiber (CF) product of industrial waste, for the manufacture of conductive recycled mortars (CRM), transforms the mortar base cement normally made with cement:sand in a sustainable multifunctional material, conferring satisfactory mechanical and electrical properties for non-structural uses. This action provides ecological benefits, reducing the use of natural fine aggregates from rivers and the amount of concrete waste deposited in landfills resulting from construction waste. In this investigation the effect of the addition of CF on electrical properties in hardened, wet and dry state, electric percolation in dry state and fluidity of the wet mixture of a cement based CRM was evaluated: fine recycled aggregate: graphite powder, CRM specimens with dimensions of 4 × 4 × 16 cm. were manufactured for 3, 7 and 28 days of age and sand/cement ratios = 1.00, graphite/cement = 1.00, water/cement = 0.60 and CF = 0.1, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0% compared to the weight of cement. The results demonstrated the effect of the addition of CF in CRM, reducing fluidity of the mixtures due to the opposition generated by its physical interaction of CF with recycled sand or recycled fine aggregate and graphite powder (GP), in its case, placing the electric percolation percolation at 0.30% and 0.45% of CF for CRM with and without GP, respectively. Increases in electrical conductivity (EC) without the presence of GP are defined by the contact between the CF and the conductive paths formed. In contrast, with the presence of GP, the EC is defined by the contact between the CF and the GP simultaneously, forming conductive routes with greater performance in its EC.

Sustainable use of recycled carbon fiber reinforced polymer and crumb rubber in concrete: mechanical properties and ecological evaluation

To mitigate the potential environmental pollution of discarded tires and waste carbon fiber reinforced polymer (CFRP), the present study investigates the feasibility of collaborative use of these recycled materials, which is called recycled CFRP fiber reinforced rubberized concrete (RFRRC). Specifically, eight different mixes are designed, considering different fiber dosages (0%, 0.5%, 1.0%, and 1.5% by volume) and different rubber contents (0% and 10% by volume). Subsequently, the flowability, compressive and flexural strengths, and impact resistance of the RFRRC are discussed. Experimental results show that the compressive strength of the mixed composites is slightly improved, while the ductility, flexural toughness, impact resistance and energy absorption capacity are significantly enhanced. Ecological evaluation of the RFRRC is conducted through case studies of an individual building and regional buildings. Evaluation results indicates that CO2 emissions can be substantially reduced through the application of RFRRC in construction fields. The application of RFRRC not only can improve the mechanical properties of concrete, but also is of great benefit to ecological environment.

Rapidly reprocessable, degradable epoxy vitrimer and recyclable carbon fiber reinforced thermoset composites relied on high contents of exchangeable aromatic disulfide crosslinks

With large quantities of waste carbon fiber reinforced polymer (CFRP) composites generated, the development of recycling routes for CFRP composites have been driven by both environmental and economic factors. Vitrimer materials provide exciting opportunities to recycle thermosets and CFRP composites, since they can be thermally reprocessed without losing their permanently cross-linked networks. However, the poor mechanical properties, additional catalyst and time-consuming recycling process still limit their applications. Herein, the authors proposed an epoxy vitrimer with high contents of exchangeable aromatic disulfide crosslinks to overcome these limitations. This epoxy vitrimer exhibited outstanding properties with the glass transition temperature (Tg) of 147 °C and the tensile strength of 63.1 MPa. Upon heating, it released the stress from deformation more rapidly without any catalyst, resulting from the high contents of disulfide crosslinks in the network. Meanwhile, the networks exhibited excellent reprocessability and were more readily degraded by thiols. Moreover, this epoxy was applied as matrix to prepare recyclable CFRP composites. By dissolving the epoxy matrix efficiently, the carbon fibers embedded were recycled rapidly and they still exhibited outstanding mechanical properties when being reused to form CFRP composites. Results from this study may promote the wide development of cost-efficient recyclable composites in automotive, wind power and aeronautical industries.

Influence of adding discontinuous and dispersed carbon fiber waste on concrete performance

Waste generated in carbon fiber manufactures, such as products in end-of-life, still have limited options of reuse. Therefore, new recycling alternatives are required before expected disposal increases occur in the coming years. This study aims to justify a new carbon fiber recycle method and to understand how carbon fibers corroborate improvements in the transition zone in concrete by controlling crack propagation during mechanical loading. Cylindrical concrete specimens were prepared with cement consumption of 370 kg/m³, water-cement ratio of 0.5, and addition of 2% carbon fiber waste in relation to the cement mass. Despite a lower workability in the fresh state, the mechanical performance of the new composite was improved in compressive strength and tensile strength, as shown by a 28-day test result. In order to explain the relationship of structure and property of the new composite, images of the fibers and fractured surfaces of the concrete were evaluated by scanning electron microscopy (SEM). The carbon fiber acts directly on the concrete cracking mechanism at the moment of rupture, restraining the formation of large cracks from microcracks and maintaining the transition zone of the coarse aggregate adhered to the matrix. The addition of carbon fiber waste into the concrete is potentially positive, for providing mechanical improvements that will reduce the maintenance needs and, consequently, increase the durability of concrete structures and the sustainability of constructions.

Reclamation of carbon fibers and added-value gases in a pyrolysis-based composites recycling process

Carbon fibers reclamation from waste composites by pyrolysis is developing fast. Pyrolysis allows the reclamation of the fibers by thermal decomposition of the polymeric resin, but the material value of these resins is not yet recovered. In this research work, the possibility of obtaining high-value gaseous fractions by treating the vapors generated in the decomposition of a poly(benzoxazine) containing carbon fiber waste composite has been studied. The experiments have been carried out in a lab-scale facility consisting of two reactors in series. In the first reactor, the pyrolysis of the waste is carried out at 500 °C, while in the second reactor the vapors coming from the first reactor are treated at 900 °C. Such treatment enables to triple the amount of gas in comparison to conventional pyrolysis. Besides, this gas contains 56% by volume of H2, which means the recovery of approximately 60% of the hydrogen contained in the resin. On the other hand, clean carbon fibers with mechanical properties within commercial values have been also obtained.

Research on Process Parameters for Recycling CF/EP Composites by Thermal Excitation of Oxide Semiconductor

There has a great economic and environmental significance for recycling high performances carbon fibers from the waste carbon fiber reinforced polymers. This paper presented a novel method for recycling carbon fiber (CF)/epoxy resin (EP) composites by thermal excitation oxide semiconductor; the effects of process parameters including the temperature, processing time, concentration and flow of O2 on decomposition rate of resin matrix was analyzed; through some methods of analysis and testing such as micro-morphology, monofilament tensile strength, Raman spectra, the effects of process parameters on morphology, mechanical property and surface chemistry of the recycle carbon fibers were investigated; the components of the gas products were investigated by gas chromatography. The research findings provided theoretical foundations for estimating the process parameters and understanding the general law of resin matrix decomposition.

Processing of waste carbon and polyamide fibers for high-performance thermoplastic composites: Modifications to the auto-leveling system to enhance the quality of hybrid drawn sliver

The auto-leveling system of a modern draw frame is widely used for conventional fibers to develop homogeneous, uniform, and defect free drawn slivers. This auto-leveling system also improves the quality of tapes and hybrid yarn structures by eliminating mass irregularities in hybrid sliver. However, the existing auto-leveling system exerts very high loads on feedstock, thus diminishing the quality of waste carbon in the delivered sliver. The aim of the present study was to process hybrid sliver based on waste carbon and polyamide fibers on a modern draw frame and modify the auto-leveling system to enable the damage-free processing of carbon fiber. For this purpose, hybrid card slivers were processed on an industrial draw frame with auto-leveling system. The different auto-leveling parameters, e.g., scan roller width and scan roller load, were modified and optimized for the uniform and damage-free processing of hybrid sliver. Results revealed that the scan roller load has a significant influence on the quality of waste carbon fiber in hybrid sliver. A uniform hybrid sliver ensures the reproducibility of unidirectional tapes and hybrid yarn at industrial scale, while simultaneously maintaining the quality of recycled carbon fiber-reinforced thermoplastics.

Processing of waste carbon and polyamide fibres for high-performance thermoplastic composites: influence of carding parameters on fibre orientation, fibre length and sliver cohesion force

The processing of waste carbon fibre on carding machine for the developments of nonwovens, tapes and hybrid yarn structures is an emerging trend. These structures are widely used to enhance the performance efficiency of recycled carbon fibre reinforced thermoplastic composites. The aim of the research presented in this study is to process waste carbon fibre on a carding machine and to investigate the influence of different carding parameters on waste carbon fibre. For this purpose, card slivers composed of waste carbon and polyamide fibres were developed on a double cylinder card machine by varying technical parameters. Then, effect of these parameters on card sliver quality was assessed in terms of fibre orientation, fibre length and sliver cohesion force. Results revealed that fibre orientation and fibre length is significantly affected by technological parameters carding zones, whereas the sliver cohesion force is significantly affected by the speed of feed roller and doffer.

Recent developments in the processing of waste carbon fibre for thermoplastic composites – A review

The aim of this paper is to highlight recent developments in the processing of waste carbon fibre for thermoplastic composites. Initially, injection moulding and nonwoven technologies have been used to integrate waste carbon fibres into fibre-reinforced thermoplastic composites. Recently, tape and hybrid yarn spinning technologies have been developed to produce tape and hybrid yarn structures from waste carbon fibre, which are then used to manufacture recycled carbon fibre-reinforced thermoplastics with much higher efficiency. The hybrid yarn spinning technologies enable the development of various fibrous structures with higher fibre orientation, compactness and fibre volume fraction. Therefore, thermoplastic composites manufactured from hybrid yarns possess a good potential for use in load-bearing structural applications. In this paper, a comprehensive review on novel and existing technologies employed for the processing of waste carbon fibre in addition to different quality aspects of waste carbon fibre is presented.

Characterization of carbon fibers recovered through mechanochemical-enhanced recycling of waste carbon fiber reinforced plastics

In this study, we present the characterization of the carbon fibers recovered from the mechanochemical-enhanced recycling of carbon fiber reinforced fibers. The objectives of the study were to investigate the effect of our modified recycling method on the interfacial properties of recovered fibers. The reinforced plastics were recycled; the recycling efficiency was determined and the recovered fibers were sized using 1 wt% and 3 wt% concentration of (3-aminopropyl)triethoxysilane. We characterized the morphologies utilizing the electron spectroscopy for chemical analysis (ESCA), atomic force microscopy (AFM), FTIR-attenuated total reflection (ATR) spectroscopy and scanning electron microscopy (SEM). Although the surface of the fibers had no cracks, there was evidence of contaminations which affected the interfacial properties and the quality of the fibers. Results showed that the trends in the recovered and virgin fibers were similar with an increase in sizing concentration. The results highlighted the perspectives of increasing the quality of recovered fibers after the recycling process.

Fibre hybrid composites consisting of discontinuous waste carbon fibre and continuous glass filaments developed for load-bearing structures with improved impact strength

The aim of this research is to improve the impact strength of composites manufactured from discontinuous waste carbon fibre (CF). For this purpose, novel multi-material hybrid yarns with a core-sheath structure are developed from a mix of waste CF and polyamide 6 (PA 6) fibre (60 mm) that is combined with continuous glass filaments in the core and PA 6 fibre in the sheath. The tensile and Charpy impact properties of the unidirectional hybrid composites produced from the developed multi-material hybrid yarns are compared with those of a non-hybrid composite reinforced exclusively with waste CF. Results revealed that the impact strength of hybrid composites can be augmented by 50.5% by adding only 6 vol% of glass filaments to waste CF. An increase of 18.4% in impact strength can be achieved in hybrid composites if the total fibre volume content is identical with that of non-hybrid composites.

Carbon fiber waste incorporation in blast furnace slag geopolymer-composites

This work evaluates the properties of geopolymer-composites based on blast furnace slag with additions of a carbon fiber waste coming from the aircraft industry. Two parameters were considered: slag/waste ratio (100/0, 80/20 and 60/40) and nature of activating solution (8 M NaOH and sodium silicate). Open porosity and compressive strength were analysed. Geopolymers were also subjected to a sulphuric attack and thermal resistance test (compressive strength after 105, 300, 500 and 700 °C was assessed). Porosities increased and compressive strengths decreased as the slag was replaced by the carbon fiber waste. A positive effect of the carbon fiber waste on the acid attack was observed mainly due to the created porosity which could generate space to calcium-sulphate products precipitation. CFW incorporation improved the thermal resistance since higher porosity could provide channel to increase heat dissipation.

Improvement of the chemical recycling process of waste carbon fibre reinforced plastics using a mechanochemical process: Influence of process parameters.

We present the experimental results of an optimal recycling method for waste carbon fibre reinforced plastics (CFRPs) that is based on the application of a set of unit mechanochemical processes. The objectives of this study were to highlight the influence of process factors that are inherent in the chemical recycling process of waste CFRP. We investigated the influence of the soaking period, the application of a catalyst and impurities on the recycling process and recovery efficiency of the waste CFRP. Different combinations of the unit mechanochemical processes were investigated, and the effectiveness of the combination was analysed. The chemical recycling process was conducted using benzyl alcohol under ordinary pressure at initial solvent temperatures lower/equivalent to its flash point temperature. Experimental results showed that the solvent temperature increased up to boiling temperature levels when the mechanochemical process was initiated, thereby enhancing the mechanochemical process. The presence of impurities did not influence the recovery rate. Likewise, this experimental study highlighted the importance of accounting for the soaking period during the chemical recycling process: an extended soaking period resulted in a higher recovery rate, a lower portion of undissolved solids and recovered fibres of better quality. This research highlighted the significance of choosing the proper combination for the chemical recycling process as well as the benefits of recycling the waste CFRP with negligible application of the catalyst.

Investigation of Interfacial and Mechanical Properties of Various Thermally-Recycled Carbon Fibers/Recycled PET Composites

The mechanical and interfacial properties were evaluated for carbon fiber reinforced composites (CFRC) manufactured using thermally recycled waste carbon fiber and recycled polyethylene terephthalate (PET). The mechanical properties of the recycled fiber were determined and compared to those of neat fibers using the single-fiber tensile test. The surfaces of the recycled and neat carbon fiber were examined and compared using FE-SEM and dynamic contact angle measurements. A goal of the study was to determine the applicability of industrial use of recycled CF and/or recycled PET in CFRC. Mechanical properties were measured using short beam and tensile tests. These properties were observed to be correlated with crystallinity. The interfacial properties between the recycled carbon fibers and recycled PET were evaluated using the microdroplet test. At low temperature residual resin remained on the recycled CFs surface resulting relatively the low interfacial properties. At excessively high temperatures, oxidation occurred, on the CFs surface, which also resulting in relatively poor low mechanical properties. The optimal treatment condition was 500 °C, where the surface was relatively clean and the reduction in mechanical properties was minimized.