Virgin Carbon Fibers Research Articles

Wind Turbine Blades Using Recycled Carbon Fibers: An Environmental Assessment.

Polymers reinforced with virgin carbon fibers (VCF) are being used to make spar caps of wind turbine (WT) blades and polymers with glass fibers (GF) to make skins of the blade components. Here, we assess the life cycle environmental performance of the hybrid blades with spar caps based on VCF and the shells and shear webs based on RCF (recycled CF) composites (RCF-hybrid). The production of the WT blades and associated reinforced polymers is assumed to occur in Sweden, with their uses and end-of-life management in the European region. The functional unit is equivalent to three blades in an offshore WT with the market incumbent blades solely based on the GF composite or the hybrid option. The RCF-hybrid blades offer 12-89% better environmental performance in nine out of 10 impact categories and 6-26% better in six out of 10 impact categories. The RCF-hybrid blades exhibit optimum environmental performance when the VCF manufacturing facilities are equipped with pollution abatement systems including regenerative thermal oxidizers to reduce ammonia and hydrogen cyanide emissions; spar caps are made using VCF epoxy composites through pultrusion and resin infusion molding, and the blade scrap is mechanically recycled at the end of life. The energy and carbon payback times for the RCF-hybrid blades were found to be 5-13% lower than those of the market incumbents.

Surface engineering of reclaimed carbon fiber (RCF) electrode for superimposed supercapacitor performance

Micrometer-sized carbon fiber (CF) has the advantage in directly serving as flexible electrode or support, while it simultaneously has the disadvantage of the unsatisfactory specific capacitance because of the small specific surface area and low activation. In this work, aerobically reclaimed carbon fiber (RCF) obtained from carbon fiber reinforced polymer (CFRP) is chosen as the subjected electrode, which is surface engineered through a thermal etch process of Cu2O/CuO anchored during a previous hydrothermal process and a subsequent chemical oxidation progress. Due to the circular holes as well as oxygen-containing functional groups on the functionalized CF surface, a superimposed electrochemical performance of functional holey reclaimed carbon fiber (FHRCF) electrode exhibits a specific capacitance of 122.2 F/g at 1 A/g (vs. 0.27 F/g for virgin CF, 31.3 F/g for RCF), and the capacitance retention of 100% after 30,000 cycles. Referring to its symmetrical supercapacitor (SSC), an energy density of 3.84 Wh/kg at the power density of 93.8 W/kg are acquired. This work not only pushes the reclamation of carbon fiber but also supplies μm-scale carbon fiber-based supercapacitor electrode with superimposed electrochemical performance.

Using taguchi approach for investigating mechanical properties of recycled carbon fibre reinforced thermoplastics for injection moulding applications

Demand for carbon fibre reinforced plastic (CFRP) increases due to its popular demand in sectors such as automotive and aerospace. This leads to high volume of manufacturing and end of life CFRP waste. The challenge is to recycle the heterogenous waste and utilise the recycled carbon fibre (rCF) in potential applications, including the injection moulding process. However, the effect of processing parameters such as type of new thermoplastics, filler weight loading and particle size on product mechanical properties is not well understood. This study carried out experimental trials based on L4 Taguchi orthogonal design. It is found that the mechanical and physical properties significantly depend on the selected parameters. Optimisation of the parameters should depend on final application of the product. This study highlights potential use of rCF in reinforcing pure thermoplastics, as well as an alternative material to virgin carbon fibre (CF).

Mechanical characterisation of pneumatically-spliced carbon fibre yarns as reinforcements for polymer composites

An investigation into the mechanical response of pneumatically-spliced carbon fibre yarns as a potential reinforcing material for polymer composites is presented. High strength mechanical connections between carbon fibre yarns are produced by joining short discontinuous tows into longer lengths via fibre entanglement. The effect of altering the number of high-pressure air pulses fired by a commercially available (Airbond 701H) splicing machine, to form the tow-tow connection, on load bearing capacity and linear stiffness is first evaluated on splices between virgin T700SC-24K-50C carbon fibre tows. The best performing spliced configuration is subsequently utilised in reinforcing unidirectional epoxy laminates, which are mechanically characterised, and their properties compared to those of various continuous fibre and chopped strand mat panels. Results presented in this study demonstrate that pneumatic splicing provides a high strength and sustainable solution for reinforcing polymers with discontinuous (approx. >50 mm in length) virgin, off-cut or waste carbon fibre yarns. It is speculated that with further research, quasi-continuous yarns remanufactured by splicing waste fibres could provide a novel material for weaving, braiding, non-crimp fabrics, or use in 3D printing applications.

Grinding, Melting and Reshaping of EoL Thermoplastic Polymers Reinforced with Recycled Carbon Fibers

This article assesses the technical feasibility of a recycling process based on grinding, melting and re-shaping of carbon fibers (CFs) reinforced thermoplastic polymers, in order to obtain new products that can be introduced in different markets, depending on mechanical properties retained. The idea at the basis of our study is that this kind of recycling process lies at the edge of the stages of recycling and re-use of materials, considering that the latter is preferable when considering the waste management hierarchy. Lower cost and similar mechanical strength of virgin CFs allowed the spread of recycled CFs in the automotive sector in the form of composite materials. Taking into account the Directive 2000/53/EC that sets out measures to prevent and limit waste from end-of-life (EoL) vehicles and their components, and ensures that where possible this is reused, recycled or recovered, we considered worth to investigate the recyclability of composite materials made with recycled CFs when they will reach the state of EoL materials. Considering this premise, an additional scope of this paper is therefore to provide some useful information about the possibility to perform a multiple closed loop recycling of rCF thermoplastic composites. Experiments carried out demonstrated that re-shaping of composites is technically feasible. Some square plates were produced without any setback. The mass balance of the recycling process demonstrated that about 88% of the EoL material can be recovered. Calculation of energy consumption showed that approximately 16 MJ are necessary in the treatment of 1 kg of EoL composites.

Fully recyclable, flame-retardant and high-performance carbon fiber composites based on vanillin-terminated cyclophosphazene polyimine thermosets

Carbon fiber reinforced polymer composites (CFRPs) have been widely applied in various high-tech fields because of their superior performance. However, with the increasing consumptions of CFRPs, the nondestructive recycling of expensive carbon fibers (CFs) and the reduction of fire-hazards are highly desirable for the sustainable and safe utilization of CFRPs. Herein, a fully recyclable CFRPs with high flame retardance was newly designed by incorporating the vanillin-terminated phosphazene monomer (HVP) into the polyimine binder material. The six-functional HVP monomer makes the polyimine thermosets have a high crosslinking density and high P/N content, thereby ensuring the excellent flame retardancy and mechanical performances of the resulted composites. And the preparation of this kind of composites just need simple hot-pressing at lower temperature and shorter time, which is more energy-saving and efficient. Owing to the degradable imine bonds, the nondestructive closed-loop recycling of CFs and HVP monomers from the composites are achieved under mild conditions, which is extremely vital to preserve the structure of virgin CFs and HVP functional monomer. The regenerated CFRPs displayed same performance with that of fresh ones, and it also could be reprocessed and repaired within few minutes at elevated temperatures. More importantly, due to the rational combination of cyclophosphazene and imine bond, the excellent synergistic effect of gas phase and condensed phase during combustion endows the composites with superior flame retardancy. This work prepared bio-based recyclable, flame-retardant CFRPs, offering a green, sustainable and fire-safe strategy for designing eco-friendly high-performance composites. ● A vanillin terminated cyclophosphazene (HVP) was synthesized through a facile one-step reaction ● Dynamic polyimine resin for CFRP was prepared by HVP and D230 without catalyst. ● High recyclability and flame retardance are simultaneously attained in this CFRP. ● The comprehensive properties of recycled CFs are same with that of virgin ones. ● Near total flame-retardant monomer HVP could be retrieved.

Recent Progress in Carbon Fiber Reinforced Polymers Recycling: A Review of Recycling Methods and Reuse of Carbon Fibers.

The rapid increase in the application of carbon fiber reinforced polymer (CFRP) composite materials represents a challenge to waste recycling. The circular economy approach coupled with the possibility of recovering carbon fibers from CFRP waste with similar properties to virgin carbon fibers at a much lower cost and with lower energy consumption motivate the study of CFRP recycling. Mechanical recycling methods allow the obtention of chopped composite materials, while both thermal and chemical recycling methods aim towards recovering carbon fibers. This review examines the three main recycling methods, their processes, and particularities, as well as the reuse of recycled carbon fibers in the manufacture of new composite materials.

Re-use potential of carbon fibre fabric recovered from infusible thermoplastic CFRPs in 2nd generation thermosetting-matrix composites

The research presented here attempts to assess the potential for re-using carbon fibre (CF) fabrics recovered from recycling infusible acrylic thermoplastic carbon fibre reinforced polymer composites (CFRPs) in a universal manner, i.e. by combining with a wide variety of matrices to manufacture 2nd generation composite laminates by resin infusion. The 2nd generation composites have been compared in terms of bulk and interfacial properties against counteparts processed with virgin carbon fibre fabric infused with the same matrices. Generally, an increase in damping (tanδ) was observed in all 2nd generation composites, which can be attributed to a residual thin thermoplastic layer present on the recovered fibres. The interfacial adhesion of the 2nd generation composites was investigated by shear tests and scanning electron micsoscopy, and also appears to be less influenced by the type of matrix.

Catalyst-free self-healing bio-based vitrimer for a recyclable, reprocessable, and self-adhered carbon fiber reinforced composite

Carbon fiber reinforced composites (CFRPs) have the problems of over-reliance on petroleum-based products and difficult recycling of Carbon fibers (CFs). To solve these problems, a degradable Epoxidized menthane diamine–adipic acid (EMDA–AA) vitrimer matrix for CFRPs is obtained from bio-based menthane diamine and adipic acid. Owing to the rigid six-membered ring structure of EMDA, the EMDA–AA vitrimer matrix exhibits good mechanical properties. With the autocatalysis of tertiary amines in the EMDA–AA vitrimer, the vitrimer network can achieve topological rearrangement via dynamic transesterification reactions without additional catalysts. The fabricated vitrimer exhibits excellent self-healing, shape memory and reprocessing properties. Moreover, EMDA–AA–CF composite with EMDA–AA epoxy vitrimer as the matrix resin shows excellent reprocessing, shape memory and self-adhesive properties. In addition, the EMDA–AA vitrimer matrix resin can be rapidly degraded into polyols by amination reaction with ethanolamine under mild conditions, resulting in the efficient recycling of Carbon fibers (CFs). Scanning electron microscopy, Raman spectroscopy, and tensile tests show that the recycled CFs have almost the same chemical structure and mechanical properties as the virgin CFs. This study can assist in the preparation of green and high-strength CFRPs using recyclable bio-based epoxy vitrimer matrices and provide a strategy for efficient recycling of CFs from CFRPs.

High temperature tensile, compression and creep behavior of recycled short carbon fibre reinforced AZ91 magnesium alloy fabricated by a high shearing dispersion technique

The present study seeks the feasibility of using short carbon fibres recycled from polymer matrix composites as alternative to virgin carbon fibres in the reinforcement of magnesium alloys. The microstructures, high temperature mechanical and creep properties of AZ91 alloy and its composites with various recycled carbon fibre contents (2.5 and 5 wt.%) and lengths (100 and 500 μm) were investigated in the temperature range of 25–200 °C. The microstructural characterization showed that the high shear dispersion technique provided the cast composites with finer grains and relatively homogenous distribution of fibres. The materials tested displayed different behaviour depending on the type of loading. In general, while enhancements in the mechanical properties of composites is attributed to the load bearing and grain refinement effects of fibres, the fluctuations in the properties were discussed on the basis of porosity formation, relatively high reinforcement content leading to fibre clustering and interlayer found between the matrix and reinforcement compared to those of AZ91 alloy. The compressive creep tests revealed similar or higher minimum creep rates in the recycled carbon fibre reinforced AZ91 in comparison to the unreinforced AZ91.

Substitution of virgin carbon fiber with low-cost recycled fiber in automotive grade injection molding polyamide 66 for equivalent composite mechanical performance with improved sustainability

Recycled carbon fiber has historically proven challenging to integrate into composite manufacturing due in no small part to the low-density, randomly oriented, discontinuous fiber format that results from typical recycling. Discontinuous fiber requires the use of alternative technologies than those traditionally applied to continuous fiber (e.g., hand lay-up, winding). Extrusion compounding is one such applicable technology, but material transfer into the system requires alternative feeding equipment or the use of an altered procedure as trialed in this research. In this study, an injection molding compound for automotive applications was prepared with recycled carbon fiber and compared against an existing commercial compound. Input fibers and molded compound were evaluated for mechanical performance, while relevant variables such as compounded fiber alignment and aspect ratio were compared to the existing baseline material to confirm a like-for-like composite material structure. Analysis indicates that recycled fiber performs similarly to virgin fiber reinforcement, demonstrating that recycled fiber may be a viable drop-in replacement for short-fiber discontinuous applications.

Multicriteria performance evaluation of fiber-reinforced cement composites: An environmental perspective

Cement composites have the intrinsic drawback of low flexural strength and crack endurance. Many studies have been conducted to improve the mechanical performance of cement composites by employing commercially available fibers, but less attention has been paid to the environmental impacts associated with these fibers. Therefore, this study aims to evaluate and compare the performance of different fiber reinforced cement composites (FRCCs) based on their mechanical strength, environmental impact potential, and cost. For this purpose, the overall performance of six different fiber (such as Recycled carbon fiber (rCF), Basalt Fiber (BF), Glass fiber (GF), Polypropylene fiber (PPF), Polyvinyl alcohol fiber (PVAF), and Virgin carbon fiber (vCF)) reinforced cement composites were evaluated. Results revealed that the flexural strength of recycled carbon fiber reinforced cement composite (M-rCF) was highest among all other FRCCs. Moreover, depending on the environmental impact category, the lowest impacts were employed by M-rCF and M-PPF. At the same time, the minimum production cost was associated with M-PPF. Therefore, a multicriteria decision technique was employed to evaluate the overall performance of all the FRCCs. Based on the performance score, the FRCCs can be ranked as: M-rCF > M-PPF > M-BF > M-GF > M-PVAF > M-vCF.

Evaluation of recycled carbon fibre/epoxy composites: Thermal degradation behaviour of pyrolysed and virgin carbon fibres using thermogravimetric analysis

The recycling of carbon fibres is a critical step in the reutilization of carbon fibres in a closed-loop economy. Evaluation of the recovered fibres regarding their mechanical properties, purity of the fibre surfaces and thermal stability are key points when exploring new high performance applications. This publication reports about the investigation of the thermal stability of pyrolysed carbon fibres and virgin fibres alone and in composite materials using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). A commercial pyrolysed woven fabric (unaltered in length) was processed like virgin high tenacity carbon fibre to investigate the recycling potential of unchopped fibres and demonstrate their recycling without further down-cycling. Identical components of virgin and pyrolysed fibres were manufactured. These composite materials as well as the fibres solely were compared regarding their thermal degradation behaviours as a function of heating rates as well as temperature ranges in different gas environments. For further analysis of the data a kinetic study was performed. In addition, light microscopy and SEM imaging was used to visualize and investigate the samples. A slight shift to lower temperatures in thermal decomposition behaviour of the pyrolysed carbon fibres was observed. The decomposition of the matrix was similar in the TGA measurements but possibly, due to the missing sizing and lower fibre orientation a higher mass fraction of resin as well as higher activation energy values were calculated. The degradation of the carbon fibre fraction showed the largest variation. This is assumed to be due to the carbon fibre crystal structure but for verification, additional work needs to be performed.

Life cycle assessment and energy intensity of CFRP recycling using supercritical N-butanol

Recycling carbon fiber reinforced polymer (CFRP) waste is unavoidable for the sustainable manufacturing and cost reduction of CFRP products. Supercritical fluid technology is an emerging chemical method for recycling CFRP waste, but its energy intensity and environmental implication are limited understanding. In this paper, the energy intensity and environmental impact of supercritical fluid technology were quantitatively assessed in CFRP recycling process. Then, the life cycle assessment (LCA) method was used to analyse the life cycle environmental impact of CFRP in two scenarios, scenario (a) using conventional waste disposal method, while scenario (b) with CFRP waste recycling process. The results show that the energy consumption of CFRP waste recycling is 49.21 MJ/kg using the supercritical n-butanol method, which is far lower than that of virgin carbon fiber production (286 MJ/kg). Scenario (b) with CFRP waste recycling has a lower impact than scenario (a) at nine environmental impact categories, including a 26% reduction of global warming potential. Besides, the energy consumption of the supercritical n-butanol method is 31% lower than that of the steam thermolysis method (71.64 MJ/kg) in recycling 1 kg of CFRP waste, which validates that the supercritical n-butanol method is a potential strategy for recycling CFRP waste.

Ultrafast carbon nanotubes growth on recycled carbon fibers and their evaluation on interfacial shear strength in reinforced composites

The global demand for products manufactured with carbon fibers (CFs) has increased in recent years; however, the waste generated at the end of the product lifetime has also increased. In this research, the impact of the addition of carbon nanotubes (CNTs) on the interlaminated resistance of recycled carbon fibers (RCFs) was studied. In this work, a recycling process of the composite material was applied via thermolysis to obtain the CFs, followed by the growth of CNTs on their surface using the Poptube technique. The recycling temperature were 500 °C and 700 °C; and ferrocene and polypyrrole were used to grow CNTs on CFs surface. CNTs were verified by Raman spectroscopy and scanning electron microscopy (SEM). Finally, to determine the interlaminar resistance, a double cantilever beam (DCB) test was performed. The results indicate that with Poptube technique, CNTs can be grown on RCFs using both impregnations. Thermolysis recycling process at 500 °C allowed CFs without resin residues and without visible damage. The DCB tests showed a decrease in the fracture resistance in mode I loading of 34.9% for the polypyrrole samples and 29.3% for the ferrocene samples compared with the virgin carbon fibers (VCFs) samples with a resistance of 1052.5 J/m2.

UV-Assisted 3D Printing of Polymer Composites from Thermally and Mechanically Recycled Carbon Fibers

Despite the growing global interest in 3D printed carbon fiber reinforced polymers, most of the applications are still limited to high-performance sectors due to the low effectiveness–cost ratio of virgin carbon fibers. However, the use of recycled carbon fibers in 3D printing is almost unexplored, especially for thermoset-based composites. This paper aims to demonstrate the feasibility of recycled carbon fibers 3D printing via UV-assisted direct ink writing. Pyrolyzed recycled carbon fibers with a sizing treatment were firstly shredded to be used as a reinforcement of a thermally and photo-curable acrylic resin. UV-differential scanning calorimetry analyses were then performed to define the material crosslinking of the 3D printable ink. Because of the poor UV reactivity of the resin loaded with carbon fibers, a rheology modifier was added to guarantee shape retention after 3D printing. Thanks to a customized 3D printer based on a commercial apparatus, a batch of specimens was successfully 3D printed. According to the tensile tests and Scanning Electron Microscopy analysis, the material shows good mechanical properties and the absence of layer marks related to the 3D printing. These results will, therefore, pave the way for the use of 3D printed recycled carbon fiber reinforced polymers in new fields of application.

Carbon fibers recovery from CFRP recycling process and their usage: A review

Carbon fiber is a popular polymer reinforcing material for forming carbon fiber reinforced polymer composites (CFRP) as a construction material under high loading. The use of this composite has spread in various fields of technology with a quite large production volume annually. Consequently, when the life span of the composite has run out it will leave composite waste and brought up CFRP recycling cases as a dare for scientists and engineers. Research on carbon fiber reclamation from CFRP materials has been carried out with the main purpose of taking and reusing carbon fiber. Several CFRP recycling methods have been investigated in laboratories and applied successfully to business but the capacity of production is not comparable with the addition of CFRP composite waste each year. High recycling energy is one of the main reasons constrained this waste recycling business. Recycled carbon fiber (r-CF) also shows a decrease in performance compared to virgin carbon fiber (v-CF) with a varied distribution of degradation according to the recycling method applied. However, reuse of r-CF in the form of short fibers in a composite materials under medium and low loads has been thoroughly tested and applied with promising results as a reinforcement for new composites

Gasification Char and Used Foundry Sand as Alternative Fillers to Graphene Nanoplatelets for Electrically Conductive Mortars with and without Virgin/Recycled Carbon Fibres

Structural health monitoring to assess the safety, durability and performance of structures can be performed by non-destructive methods such as the measurement of impedance in self-sensing cement-based elements. Cement-based materials, like mortars and concretes, generally have high electrical resistivity but the addition of carbon-based fillers and fibres decreases their electrical resistivity and thus enhances their self-sensing capabilities. In this study, two waste carbon-based fillers, namely, used foundry sand and gasification char were compared to commercial graphene nanoplatelets and used to produce self-sensing cement mortars, both with and without recycled or virgin carbon fibres. The mortars were tested in terms of their mechanical and electrical properties as well as their propensity to capillary water absorption. The results demonstrate that gasification char alone is the best carbonaceous waste for decreasing the electrical resistivity (−42%) and water absorption (−17%) of mortars, while their compressive strength remains unaltered. Moreover, although there is a slight reduction in compressive strength and an increase in water suction when gasification char is coupled with fibres, the combination of fillers and fibres has a synergistic effect in decreasing mortars’ electrical resistivity, especially when recycled carbon fibres are used (−80%).

Recycling of polymeric composites from industrial waste by pyrolysis: Deep evaluation for carbon fibers reuse

The use of polymeric composite on transport applications as reinforcement material has been increased due to the low fuel consumption when replacing heavier materials. It is estimated that 170,000 tons of polymeric composites will be discarded by 2025, and recycling processing for carbon fibers recovery is required to save primary energy and reduce waste. Among the current techniques, pyrolysis processing has been most effective. On the other hand, innovation must maintain the structure for reuse since physical and mechanical properties are important for recycled materials. For this reason, the goal of the present study was the recycling of polymeric composite by pyrolysis. The recovered carbon fibers were analyzed in SEM and EDS to verify surface defects compared with virgin carbon fibers. The effect of temperature, time, and atmosphere were investigated. Results showed that at 550 °C for 1 h, it was possible to obtain free carbon fibers from the polymeric matrix. After the pyrolysis process in this condition, the fibers had no pores, material fracture, and carbonization. This paper contributes to the widening and systematizing knowledge on effectiveness and understanding polymeric composites recycling for carbon fiber recovery, maintaining its structure for reuse.

Recycling of carbon fibers from unsaturated polyester composites via a hydrolysis-oxidation synergistic catalytic strategy

Unsaturated polyester resins (UPRs) composites have many industrial applications, such as fan blades in wind energy. However, the stable cross-linked polymer networks of resin matrix lead to large numbers of composite wastes that are difficult to recycle. Developing an efficient approach to explore the recovery of high-value fiber from composites is thus imperative. In this paper, an efficient and mild hydrolysis-oxidation synergistic catalytic strategy was proposed to efficiently recycle carbon fibers from UPRs composites by selectively cleaving chemical bonds of UPRs. Ester bonds in UPRs were cleaved by using hydrolysis of 80% hydrazine hydrate along with NaOH. Afterwards, the cleavage of carbon-carbon bonds was accomplished via the Fenton reaction for the purpose of complete degrading UPRs. The result figured that UPRs could be efficiently degraded at 100 °C below via this hydrolysis-oxidation strategy. Interestingly, applying the strategy, the recovery of carbon fibers from UPRs composites was investigated. The reclaimed carbon fibers kept their original surface microscopic morphology, chemical structure and tensile strength almost close to the virgin carbon fibers. This strategy opens up a new way for efficient and mild degradation of thermosets.