Recycled Carbon Fiber Research Articles

Enhancing Mixing and Thermal Management of Recycled Carbon Composite Systems by Torsion-Induced Phase-to-Phase Thermal and Molecular Mobility.

A novel torsion screw has been proposed to resolve the inadequate control of mass transfer and the thermal management of two component polymer blends and their carbon fiber composites. The novel torsional screw distinctly introduced radial flow in the torsion screw channel, which is a significant improvement over the flow pattern developed by the conventional screw. The heat transfer and mixing behavior of melt mixtures are enhanced by adapting screws with torsion elements compared with the traditional screw elements. Heat transfer efficacy in the polypropylene–polystyrene bi-phasic extrusion process improved with the increase in torsion element numbers. An increased number of newly designed torsional elements also improved the dispersion of minor phase in bi-phase polypropylene–polystyrene composition and their carbon fiber composites. The unique flow pattern induced by the torsion elements shows a synergistic effect on the melt-phase mass flow and the thermal flow field facilitating phase-to-phase thermal and molecular mobility and enhanced fiber orientation, crystallinity and mechanical properties of composite made from recycled carbon fiber/polypropylene. Microtomographs of recycled carbon fiber demonstrated the extraordinary ability of a torsion screw element to orient carbon fiber in both axial and radial directions.

Comparative life cycle energy analysis of carbon fibre pre-processing, processing and post-processing recycling methods

The use of carbon fibre reinforced polymers (CFRP) faces high energy consumption of carbon fibre production and a lack of recycling. Increasing the use of recycled carbon fibres (rCF) to substitute virgin carbon fibres (vCF) can improve the sustainability of the carbon fibre industry. Nonetheless, the most impactful area of CF recycling on the quality of recycled CFRP (rCFRP) is unclear. In this study, a life cycle energy analysis compares the Primary Energy Demand (PED) of an rCFRP automotive roof panel with different CF recycling methods in the pre-processing, processing and post-processing stage. Results indicate that retaining CF architecture during the pre-processing stage reduces the cradle-to-gate energy demand of an rCFRP roof panel by 26.3%. Fibre realignment in the post-processing stage leads to 11.4% higher cradle-to-gate energy consumption of an rCFRP roof panel, despite improvements in the stiffness of rCFRP. This study demonstrates the significant impact of the pre-processing and post-processing stages of CF recycling on the quality and production energy demand of rCFRP. Moreover, improvement in the architecture of rCF leads to a more significant conservation of energy during rCFRP component production than preserving the tensile properties of rCF.

High performance epoxy composites prepared using recycled short carbon fiber with enhanced dispersibility and interfacial bonding through polydopamine surface-modification

The critical issue and challenge in reusing recycled carbon fiber (rCF) was to fully exerting its outstanding properties via an efficient and environmental-friendly way. In this study, the strengthening effects of polydopamine surface-modified recycled short CF (pDop-rSCF) on mechanical, thermo-mechanical, electrical and electromagnetic properties of epoxy (EP)-based composites were systematically evaluated. The dispersibility of pDop-rSCF in suspension used for fabricating nonwoven mat was quantitatively characterized with crowding factor N, dispersion coefficient β and fractal dimension D. Significant enhancements were achieved in tensile and flexural properties, interlaminar shear strength, storage modulus and electromagnetic interference shielding capability of EP composites reinforced with pDop-rSCF nonwoven mat, which was primarily ascribed to chemically strengthened interfacial bonding between pDop-rSCF and EP matrix and the increased connectivity among pDop-rSCFs with excellent dispersion.

Tensile properties of recycled carbon fibers subjected to superheated steam treatment under various conditions

A new treatment condition involving superheated steam (SHS) was proposed to achieve optimal carbon fiber recovery with a minimal decrease in fiber strength. Unidirectional carbon fiber reinforced sheets were exposed to SHS at 650 °C for 1 h with the addition of N2 or CO2 as process gas. The recovery was assessed based on mass change and using thermogravimetry and differential scanning calorimetry. The results showed that the addition of N2 efficiently suppressed the decrease in fiber strength and achieved optimal recovery. Weibull parameters indicated that lower strength fibers tended to present a narrower strength distribution. The observation of fracture surfaces and oblique sections indicated that the presence of intrinsic defects and corrosion of surface crystallites under the oxidative condition are responsible for the deterioration of and the changes in the distribution of strength.

Commercial and recycled carbon/steel fibers for fiber-reinforced cement mortars with high electrical conductivity

The paper aims to provide a comprehensive study on the compositional optimization of high-conductive multifunctional fiber-reinforced cement mortars (FRCMs). Therefore, the effects of three different fiber types: virgin carbon fibers (VCFs), recycled carbon fibers (RCFs), and brass-plated steel fibers (BSFs), added at a broad range of concentrations, as 0.05%, 0.1%, 0.2%, 0.4%, 0.8%, 1.2%, and 1.6% by volume, on the mechanical, electrical and durability properties of FRCMs have been compared. The results showed that RCFs increase the flexural and tensile splitting strength up to 100%, whereas BSFs improve the compressive strength by 38%. Moreover, the fibers decrease both the capillary water absorption and the drying shrinkage by 39%. Electrical conductivity tests show that RCFs decrease the electrical resistivity of mortars up to one order of magnitude, in addition to a percolation threshold between 0.1 and 0.2 vol%.

Integration of rCF in resin transfer pressing process

A new composite manufacturing process, resin transfer pressing, is introduced in this paper. In this process, nonwoven fabrics made of recycled carbon fibers are oversaturated with thermoset resin, i.e. they contain excess resin. The oversaturated nonwoven fabrics are prefabricated and used as resin carrier in a press process, where they are placed in a heated mold together with a dry textile-based preform. During pressing, the resin is pressed out and transferred from the nonwoven into the non-impregnated preform and hence impregnates the whole reinforcement. This study examines the oversaturation of nonwoven fabrics, the resin transfer pressing laminate manufacturing and the surface quality of the laminates. The ability of a nonwoven fabric to be oversaturated with resin is defined by the saturation degree, which was determined as up to 12 for glass fiber nonwoven fabrics and up to 60 for recycled carbon fiber nonwoven fabrics. Different laminates are manufactured by resin transfer pressing, and the impregnation quality is evaluated. With an optimized stacking sequence, a pore content <1% was achieved. The use of recycled carbon fiber nonwovens in the resin transfer pressing process leads to a less wavy surface compared to a wet compression molding manufactured laminate, showing a decrease of waviness Wz25 of 11% minimum.

Improved hydrogen gas production in microbial electrolysis cells using inexpensive recycled carbon fibre fabrics

Growing energy demands of wastewater treatment have made it vital for water companies to develop less energy intensive processes for treating wastewater if net zero emissions are to be achieved by 2050. Microbial electrolysis cells (MECs) have the potential to do this by treating water and producing renewable hydrogen gas as a product, but capital and operational costs have slowed their deployment. By using recycled carbon fibre mats, commercially viable MECs can brought closer to reality, where recycled carbon fibre anode MECs treating real wastewater (normalised ~3100 L d−1) were producing 66.77 L H2 d−1 while graphite felt anode MECs produced 3.65 L H2 d−1 per 1 m3 reactor, anodes costing £5.53 m−2 and £88.36 m−2 respectively, resulting in a total anode cost saving of 93%. This could incentivise the development of larger pilot systems, opening the door for generating greater value and a more sustainable wastewater treatment industry.

Recycling of carbon fiber composites in carbon-bonded alumina refractories

This study investigates the feasibility of recycling carbon fiber reinforced polymer (CFRP) composites in carbon-bonded alumina refractories. For this purpose, different procedures for pretreatment and separation of recyclable CFRP composites were examined. The influence of pretreatment, dimensions and condition of the CFRPs on physical, mechanical, and thermo-mechanical properties of carbon-bonded alumina refractories were evaluated.The CFRP fractions were classified by sieving and partly treated by means of mechanical and thermal methods. The mechanical approach describes a simple method to obtain short fibers along with a reusable fiber dust. By thermal treatment in an oxidizing atmosphere, the carbon fibers can be easily separated from the polymer matrix. Carbon-bonded alumina bricks of industry standard with CFRPs of different length and treatment and partly silicon as antioxidant were produced and compared to the respective reference without CFRPs.The addition of recycled CFRPs to carbon-bonded alumina refractories resulted in a modified microstructure consistent with open porosity and altered mechanical properties at room temperature. The microstructural change in the refractory material provoked by recycled CFRPs < 1mm increased the high-temperature Young's modulus up to 200%. The addition of mechanically treated and short CFRPs resulted in enhanced creep resistance at high temperature. Thus, different treatment methods of CFRPs exhibit promising recycling approaches for reusing carbon composites in carbon-bonded refractories by improving thermo-mechanical properties and simultaneously operating as final repository.

말레산 무수물 그래프트 폴리프로필렌이 재생 탄소섬유 보강 폴리프로필렌에 미치는 영향

말레산 무수물 그래프트 폴리프로필렌이 재생 탄소섬유 보강 폴리프로필렌에 미치는 영향

Closing the circle with recycled carbon fiber

A UK company has recently increased its capacity for parts using recycled carbon fiber prepreg. I spoke to Prodrive Composites about the potential for this market in a variety of industries.

Simultaneous evaluation of tensile strength and interfacial shear strength of short length carbon fibers using fragmentation test

Novel procedure is proposed for simultaneous evaluation of fiber tensile strength and interfacial shear strength of carbon fiber based on fragmentation test. Polyamide 6 was utilized as a matrix polymer. Relation between defect density λ and fiber strain εf was derived. Stepwise strain was applied to the specimen and increment of λ against εf was measured at each step. Accumulation of several test results gave smooth increment of λ till saturation. From the linear region in the double-logarithm plot of λ against εf, Weibull parameters for fiber strength were estimated. Somewhat higher fiber strength was observed by the proposed method as compared with that from the single fiber tensile test. The interfacial shear strength estimated from the saturated λ value (λ∞) and the measured fiber strength was comparable to the reported values, indicating the versatility of the proposed method. The proposed procedure could also be applied to the short carbon fiber length specimen, showing the applicability for the evaluation of recycled carbon fibers.

Recycling carbon and glass fiber polymer matrix composite waste into cementitious materials

Recycling options for fiber polymer matrix composites (FPMCs) are limited since they typically cannot be re-used or re-processed. One source of FPMCs is the utility industry, which is increasingly using hybrid carbon and glass FPMC core high voltage (HV) conductors for energy transmission. As there are currently no recycling methods for these composite cores, we investigated if hybrid carbon and glass FPMC waste could be recycled as an admixture for cementitious materials in order to improve their properties for seawater applications. We assessed the compression strength of ordinary Portland cement (OPC) with 6% wt of various FPMC admixtures before and after accelerated salt-water aging. The experimental part of this research was strongly supported by molecular dynamics simulations (MD) to examine the effect of FPMC admixtures on moisture diffusion in OPC. It was established that recycled finely ground FPMC admixtures can provide a benefit to cementitious materials by decreasing void content and slowing the diffusivity of corrosive compounds such as salt water.

Development of a new hybrid yarn construction from recycled carbon fibres for high-performance composites: Part IV: Measurement of recycled carbon fibre length

Due to the increasing application of carbon fibre–reinforced plastics, the use of recycled carbon fibres can help reduce the tremendous amount of carbon fibre waste growing worldwide. In this context, the processing of longer recycled carbon fibres (&gt;40 mm mean length) into hybrid yarn constructions offers a promising solution. The characterisation of recycled carbon fibre length is essential for textile processes. However, to suit the atypical fibre characteristics of recycled carbon fibres compared to standard natural or man-made-fibres, the development of an adequate measuring technique is required. Investigations on the state of the art suggest that an adapted fibrograph method might pose an appropriate measuring system. Therefore, new test equipment and an alternative image analysing method based on pixel greyscale values were developed. To enable a calibration process, different samples with cut carbon fibre from carded and drafted slivers were intensively tested and compared. In addition, an adapted reference method was investigated by combining single fibre measurement and image processing techniques. In a final step, recycled carbon fibres samples with unknown fibre length were tested. Results proved that the presented measuring system is adequate for the testing of longer recycled carbon fibres in webs or slivers. All measured values were close to the measured reference length values (deviation ±4%).

Mechanical Properties of Bio-Based Epoxy Composites Reinforced with Hybrid-Interlayer Ramie and Recycled Carbon Fibres

The growing environmental concerns have led to attention on bio-based composite materials, such as the natural fibres, recycled carbon fibres and bio-based resins. Herein, the bio-based epoxy composites were reinforced with ramie fibre (RF) and recycled carbon fibre (rCF) via inter-layer hybridisation. The dynamic mechanical analysis, tensile, flexural and impact properties characterisation were conducted to analyse the mechanical behaviour of the specimens. Also, the morphology of fractured surface after mechanical tests was studied under a scanning electron microscope. When the volume ratio between RF and rCF was varied from 100/0 to 0/100, the flexural and tensile strength of composites was significantly increased, while the impact strength was reduced. Thus the maximum values of flexural strength (182 MPa) and tensile strength (165 MPa) were observed for rCF reinforced composite, whilst impact strength of 24 kJ/m2 was found for RF reinforced composite. Furthermore, the values of storage and loss modulus were increased with the rCF incorporation due to a greater degree of restriction with the addition of rCF into the matrix. The hybridisation was able to combine the specific properties of RF and rCF and optimise the mechanical performance of composites. Therefore, the alternative low-cost green composites are prepared which can replace synthetic materials for semi-structural applications.

Pyrolytic Recycling of Carbon Fibers from Prepregs and Their Use in Polyamide Composites

Carbon fibers composites are well-known as high tech materials but are also recognized as a problem after use as they have to be deposited in landfills. Pyrolysis is an attractive process for recycling carbon fibers from used composites as well as offcuts from prepregs. Pyrolysis of carbon fiber composite prepregs is carried out in a pilot plant with a single screw reactor. The pyrolysis products, carbon fibers and pyrolysis vapor are fully characterized. Variation of pyrolysis temperature is carried out to obtain carbon fibers with the best possible surface properties. In order to compare the mechanical properties of the recycled carbon fibers with virgin material, composite materials with polyamide are produced and their properties compared.

Joule heating of dry textiles made of recycled carbon fibers and PA6 for the series production of thermoplastic composites

Processing carbon fiber reinforced thermoplastic parts includes heating to form the thermoplastic matrix. The needed heat can be applied externally or internally to the preform. One possibility to generate intrinsic heat involves the use of carbon fibers as a resistive element to induce joule heat. So far, most research efforts have been based on contacting continuous carbon fibers on both ends to melt the thermoplastic matrix of a pre-impregnated preform. The objective of this project is to use a dry hybrid yarn textile in a one-step process to impregnate and rapidly consolidate the dry textile in less than a minute. The desired molding process is based on joule heating of carbon fibers due to an applied current in the transverse fiber direction. This article focuses on the detection of the involved macroscopic parameters. The first composites produced by means of this new method exhibit a high potential with heating times of 15 s, a void fraction below 1%, and flexural properties comparable to the state of the art.

Carbon nanotubes synthesized on the surface of recycled carbon fibers by catalytic chemical vapor deposition for revalorization of degraded composite materials

There is a clear need to develop a sustainable use of composite materials; high-performance composite materials like carbon-epoxy systems are of special interest because of their wide range of applications and their high intrinsical value. Even though the technology for recycling thermoset composite materials has been developed, and the recovery of carbon fibers from composite materials is feasible, there is still to some extent, a degradation of the recovered carbon fibers; thus, a revalidation of the recycled carbon fibers with improved properties is highly desirable for a new life cycle in high-performance composites and components; thereupon, revalorization of the recovered carbon fibers by anchorage and growth of carbon nanotubes directly on the surface of the fibers via assembly of graphene-cap mechanism on nickel nanoparticles is an attractive technological approach for integral recycling of composite materials. These revalorized carbon fibers with carbon nanotubes are potential candidates for novel composites with exceptional mechanical, thermal, and electrical properties. In this research, catalytic chemical vapor deposition method was used for the synthesis of carbon nanotubes on the recycled fibers under influence of carbon source, temperature. Carbon nanotubes were produced by decomposing whether ethanol or isopropanol as a carbon source at temperatures ranging from 800 to 600 °C in an inert atmosphere. Fibers used as a substrate in this research are actually recovered carbon fibers from a carbon-epoxy composite component reaching end-of-life via pyrolysis. All experimental results were characterized using scanning electron microscopy corroborating the synthesis and morphology of the carbon nanotubes on the carbon fibers; Raman spectroscopy corroborated synthesis of multiwall carbon nanotubes; pseudo-mechanical testing confirmed that the nanotubes have a good anchorage to the carbon fiber surface, making this novel revalorized fiber a potential reinforcement for new high-performance composite materials.

Анализ факторов, влияющих на свойства вторичного углеродного волокна и материалов, полученных с его применением

For recycling of increasing volumes of waste of composites, in particular carbon plastics, it is necessary to develop technologies for the extraction and application of recycled carbon fiber. At the same time there is a scientific and practical task to choose a such conditions of fiber extraction which will allow to keep desirable values of its physical and chemical characteristics as high as possible and comparable with primary fiber. This paper presents an analysis of the factors affecting the properties of secondary carbon fiber and materials obtained with its use throughout its life cycle.

Mechanical Properties and Fracture Surface Analysis of Vinyl Ester Resins Reinforced with Recycled Carbon Fibres

This work is focused on the mechanical characterization and fracture surfaces analysis of thermosetting polymers reinforced with short, randomly oriented, recycled carbon fibres (rCFs). This work aims at evaluating fibre/matrix adhesion between recycled CFs - reclaimed via pyrolysis followed by controlled oxidation of the pyrolytic char - and different polymer matrices, namely epoxy and vinyl ester resins. The latter is the main focus in this work, being amongst the most widely used thermosetting resins in SMC processes, which are the typical target for short rCFs. The evaluation of the properties of this new recycled carbon fibre reinforced polymer (rCFRP) has been via thermogravimetric analysis, dynamic mechanical analysis, stress/strain tests in tensile mode, and a subsequent analysis of the fracture surfaces by means of images analysis obtained by macrophotography, Optical Microscopy and Scanning Electron Microscopy. The comparison amongst the results allowed to evaluate the influence of the polymer nature and of the adhesion quality between fibres and polymeric matrix, mainly on the mechanical properties of the rCFRPs.

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.