Recycled Carbon Fiber Research Articles

Adhesives Made from Sulfur Copolymer Composites Reinforced with Recycled Carbon Fiber

Adhesives Made from Sulfur Copolymer Composites Reinforced with Recycled Carbon Fiber

Advances in mechanical and physicochemical performances of recycled carbon fiber reinforced PEKK composites

In recent years, waste storage and recycling have been important issues. All efforts shown in these fields aim to help resolve concerns related to climate change. In this study, recycled CF/PEKK thermoplastic composite materials were reviewed to reduce the environmental impact of materials during the production phase as well as economic costs and ensure product continuity. Comparisons between unprocessed or virgin material and recycled materials were performed by bending and interlaminar shear strength (ILSS) analyses. In addition to mechanical tests, physicochemical tests such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and fiber void ratio (FVC)-porosity tests were conducted. Images of the samples were observed by scanning electron microscopy (SEM) to interpret changes in the structure before and after the recycling. According to the experimental results, it was found that the virgin thermoplastic composite showed 68.05% higher flexural strength and 7.85% higher flexural modulus compared to the recycled thermoplastic composites. The average ILSSs were measured as 81.8 MPa and 64.7 MPa for the virgin and the recycled thermoplastic composites, respectively. Hence, it is obvious that the recycled composites could be used for applications that require less strength and durability. Finally, it was concluded that recyclable materials can be reused in the aero structures.

Recyclable azine polyurethane thermosets and carbon fiber reinforced composites with excellent thermostability and mechanical properties

Carbon fiber reinforced composites (CFRCs) have received increasingly concerns and widely used in high-end applications, owing to their outstanding mechanical properties. Most of the polymers used in CFRCs were thermosets. However, a large number of applications brought enormous wastes due to the stable structure of thermosets which is difficult to degrade or recycle. CFRCs based on dynamic covalent polymers (DCPs) were developed to resolve the recycling problem. Polyurethanes were used for fabricating CFRCs applied in energy absorbing materials, vehicle interiors, sporting goods, and constructing materials, owing to excellent toughness, bonding abilities and low VOCs. Although some recyclable PU CFRCs were developed to resolve the recycling of CFs, there remain the problems of excess catalysts, low chemical resistance or thermostability due to the dynamic feature of DCPs. Herein, a series of azine polyurethane thermosets (APUTs) were prepared from hexamethylene diisocyanate (HDI) trimer and dihydroxy azines with different lengths of carbon chains. The resulting APUTs displayed excellent thermal stabilities with all Td, 5 % exceeding 320 °C, owing to high exchange temperature of azine moieties and high crosslinking density. APUTs-6 showed the highest tensile strength of 36.72 ± 1.18 MPa. APUTs-6 could be easily degraded in 0.1 M acetone/water solution at 50 °C. APUTs-6 showed excellent reprocessing properties and tensile strength could maintain 83.1 % of its initial one. The APUTs-6/CFs composites exhibited excellent mechanical properties, chemical resistance and recyclability. CFs could be readily recycled by acid degradation and maintain excellent mechanical properties. The tensile strength of recycled composites could recover 94.36 % of the original one after two times of recycling. The recovery ratio of tensile strength of recycled CF filaments was 95.7 %. The application of phenyl azine provided a feasible solution for the industrialization of recyclable CFRCs.

Improvement of carbon fiber oxidation resistance by thin ceramic coating using silica particles

Carbon fiber-reinforced plastics have become indispensable materials in energy saving and new energy technologies, such as automobiles, wind power generators, and hydrogen tanks for fuel cells. However, the lack of oxidation resistance limits the high-temperature applications of carbon fibers. In this study, we developed a coating technology for carbon fibers to improve their oxidative resistance. Carbon fibers with silicon carbide coatings were obtained by the adsorption of silica colloids on carbon fibers using electro adsorption, followed by heating. The resulting coating has small thickness and strong chemical connections. The thermogravimetric analysis confirmed that the oxidation start temperature of the coated carbon fibers was higher than that of carbon fibers. Moreover, the mechanical properties of the coated carbon fibers were maintained. Therefore, the proposed coating technology can broaden the application of carbon fibers as the alternative to some SiC fiber applications. Further, it is applicable for recycling carbon fibers to increase their value in terms of thermal oxidation stability.

Investigation of recycled carbon fiber-reinforced ultrafine-grain carbon-matrix composites

To broaden the usefulness of recycled carbon fibers and develop the high value-added product, the recycled carbon fiber-reinforced carbon-matrix composites were prepared using ultrafine-grain coke as a filler and coal tar pitch as a binder via a liquid mixing process. A comprehensive study and investigation of the microstructures and properties of recycled carbon fibers and composites were conducted. It was found that the recycled PAN-based carbon fiber (rPCF) outperformed the recycled rayon-based carbon fiber (rRCF) in terms of fiber integrity and pitch-coated effect in the recycling and forming processes. By relieving thermal stress, lowering stacking pores, and inhibiting the growth of shrinkage pores, the rCF can promote the sintering of the green body. The flexural strength of rPCF-reinforced carbon-matrix composite (30.70 MPa) and rRCF-reinforced carbon-matrix composite (20.75 MPa) increased by 60.6% and 8.6% than that of pristine carbon-matrix composite (19.11 MPa), respectively. The difference in mechanical properties between rPCF-reinforced carbon-matrix composite and rRCF-reinforced carbon-matrix composite is attributed to the mechanical interlock mechanism and fiber pull-out mechanism. This work provides a propagable, affordable, and environment-friendly idea for recycling waste carbon fiber and producing recycled carbon fiber reinforced composites.

Analysis of Mechanical Properties of Recycled Carbon Fiber-reinforced Plastics according to Recycled Carbon Fiber Contents

Analysis of Mechanical Properties of Recycled Carbon Fiber-reinforced Plastics according to Recycled Carbon Fiber Contents

Analysis of Mechanical Properties of Recycled Carbon Fiber Reinforced Plastic using Isostatic Pressure

Analysis of Mechanical Properties of Recycled Carbon Fiber Reinforced Plastic using Isostatic Pressure

Towards highly homogeneous self-regulating heating of smart nanocomposites

Smart self-regulating heating devices utilising the positive temperature coefficient (PTC) effect have shown great potential in advancing applications across healthcare, soft robotics, and energy-efficient manufacturing. However, achieving homogeneous resistive heating within such temperature self-controllable nanocomposites remains a significant challenge, falling short of meeting the requirements of advanced heating systems. This study explores and evaluates multiple innovative strategies aimed at enhancing the temperature uniformity of PTC nanocomposites. By identifying and analysing the primary physical mechanisms behind the inhomogeneous heating observed in conductive polymer composites, we propose a series of targeted strategies, ranging from customised material formulations to novel electrode configurations. Recycled carbon fibres have also been explored and upcycled as an effective solution for homogenous self-regulating heating. Through a comprehensive analysis of experimental results, the effectiveness of each strategy has been evaluated with a significantly improved temperature uniformity (from 32.6 to 2.7 % variation at 125 °C), providing valuable insights for the design and development of advanced self-regulating heating devices based on conductive polymer nanocomposites, while offering promising prospects for achieving more energy-efficient and uniform heating in various industrial applications.

Evaluation and optimization of flexural properties of anisotropic recycled carbon fiber card web reinforced thermoplastic hollow beams

The flexural properties of hollow beams are influenced by both the structural morphologies and the level of anisotropy of the materials. Card web carbon fiber-reinforced thermoplastics (CWTs), recognized as a promising composite for fabrication with recycled carbon fiber, demonstrate control over fiber alignment and robust mechanical properties, characterized by a wide distribution of fiber lengths. In this study, square-shaped, tube-shaped, and hat-shaped hollow beams are modeled with different geometries. Calculations are performed on different input data featuring CWTs with varying fiber alignments using a modified Mori-Tanaka model, and the results are verified with experimental data. The effects of fiber alignment, beam geometries, and beam types on the flexural properties of CWT hollow beams are evaluated and compared with unidirectional (UD) carbon fiber composites, aluminum alloys, and steel beams. The highest levels of flexural stiffness and specific flexural stiffness (indicative of the most effective lightweight property) in square-shaped and tube-shaped hollow beams were observed in CWTs with higher fiber alignment. The hat-shaped beams achieved the highest level of flexural properties at a relatively lower fiber alignment level. Comparisons with 1 mm wall-thickness steel hollow beams indicated that CWTs with specific fiber alignments could achieve a weight reduction of over 50 % while maintaining the same flexural stiffness. This performance surpasses that of UD composites and aluminum alloys.

Multifunctional cementitious composite: Conductive and auxetic behavior

This research focused on developing an innovative multifunctional cementitious material with both conductive and auxetic properties simultaneously. This novel cement-based metamaterial has different applications, ranging from piezoresistivity to structural energy dissipation. The cementitious composite (CC) with an auxetic structure were produced using additive manufacturing techniques. The study involved analyzing different cementitious compositions, including Ultra High-Performance Concrete (UHPC) formulation tailored for both high strength and workability, and flexible mortar. Both types of composites were combined with two types of fibers: recycled carbon and Polyvinyl Alcohol (PVA). Uniaxial compression tests, conductivity, piezoresistivity by load cycles, and Digital Image Correlation (DIC) analysis were carried out on the auxetic cementitious composite (ACC). Among these tested cementitious composites (UHPC and flexible mortar) reinforced with PVA and recycled carbon fibers, only the flexible mortar with carbon fibers achieved the desired multifunctional properties. This success with flexible mortar and carbon fibers suggests promise for this combination. Conversely, UHPC composites with PVA fibers, with or without additional carbon fibers, failed to achieve the targeted functionality. As a result, both piezoresistivity and auxetic properties were achieved. From the auxetic behavior results, the Poisson’s ratio reached -67.5%. This implies that if compressed longitudinally, the specimen is shortened transversely (auxetic behavior) by up to 67.5%. This finding stands out compared to traditional construction materials like concrete and steel, which typically exhibit much lower strain recoveries (15–30%). On the other hand, the specific deformation energy absorption of the auxetic specimen reached 0.076 Jcm3. Moreover, the resistivity reached the small magnitude of 0.15 Ωm at 50 Hz, proving to be a conductive composite. The gauge factor of 4.26 indicates that it can be used as a self-sensing concrete. This innovative cementitious composite opens new possibilities for future applications that require materials with conductive and auxetic behaviors.

FDM 3D printed MXene/Recycled carbon fibre reinforced polylactic acid composites: Interface optimization, toughening and enhanced electromagnetic shielding performance

Polylactic acid (PLA), a rapidly emerging bio-based plastic, faces challenges in reinforcement due to its weak mechanical properties and poor interface adhesion with carbon fibre surfaces. This study introduces an MXene/recycled carbon fibre (rCF) reinforced PLA 3D printing material, prepared through electrostatic self-assembly of MXene and recycled carbon fibre. MXene addition significantly enhances the fibre-substrate interface bonding in fibre-reinforced PLA filaments. This results in the printed parts displaying enhanced toughness, the flexural strength achieved of 105.45 MPa, modules of 5.98Gpa, and notched impact strength of 7.12 kJ/m2, realizing 15.6 %, 112.1 %, and 31.8 % improvements, respectively in comparison to pure PLA. Additionally, the modified PLA demonstrates absorption-dominated superior electromagnetic shielding performance. This research offers a viable approach for enhancing recycled carbon fibre-reinforced thermoplastic PLA and insights into designing sustainable, structurally, and functionally integrated composites.

High‐performance, semi‐bio‐based degradable epoxy resins and their application to recyclable carbon fiber composites

AbstractEpoxy resins containing dynamic covalent networks enable recycling of carbon fiber composites. However, the simultaneous realization of high performance and mild condition recycling of composites is still a challenge. In the present work, we mixed citric acid epoxy resin with bisphenol A epoxy resin to form a hybrid resin (DER) that meets the requirements of medium temperature curing epoxy resin, and prepared a carbon fiber reinforced resin composite material (DER@CF) that can rapidly degrade and recycle carbon fibers under mild conditions. The Tg of the DER was 125.67 °C, and the tensile strength (79.63 MPa) was comparable to that of the bisphenol A epoxy resin (79.90 MPa). It degraded rapidly after 2 h in ethylene glycol solution at 120 °C. The tensile strength of DER@CF was 825 MPa, and clean fibers could be obtained after 8 h of treatment in ethylene glycol solution at 120 °C. The results of SEM, Raman and tensile tests showed that the recycled fibers were similar to the original fibers in terms of morphology, chemical structure and mechanical properties. © 2024 Society of Chemical Industry.

Effects of UV-C exposure on composite materials made of recycled carbon fibers

Carbon fiber-reinforced polymers are widely used in space applications since they combine outstanding mechanical properties with low material density. However, the development of composite components involves raw materials that are becoming increasingly scarce and contributes significantly to carbon emissions during the manufacturing process. Indeed, the fabrication of fibers is energy-intensive and requires very high temperatures, high costs, and usually precursor materials derived from fossil fuels. In addition to the negative environmental impact due to the manufacturing process, there are critical issues related to the disposal of components fabricated using carbon/glass fiber composites. Therefore, the use of efficient recycling strategies becomes necessary, according to economic reasons and legislation. The recycled fibers exhibit different properties from virgin fibers, generally lower, due to adverse effects of the current recycling methods. In this study, we investigated the potential application of recovered carbon fibers in satellite platforms, using recycled fibers from our laboratory obtained with a subcritical solvolysis method that we have previously developed. Composite materials reinforced with recycled and virgin carbon fibers were exposed to UV-C, and the effects of irradiation were analyzed in terms of structural performance, surface morphology, and chemical modifications of the samples. Results were used to evaluate the possibility of effectively using recycled fibers in space applications, without significant loss of performance.

Agricultural and industrial wastes applied on the high performance energy storage devices

Driven by population growth, the destruction of the environment and the energy demand continue to increase dramatically. This study uses garlic skin and carbon fiber from agricultural and industrial wastes to prepare energy storage devices. Carbon quantum dots (CQDs) were obtained from garlic skin using high-temperature pyrolysis. The specific capacitance of the gel electrolyte could be effectively increased with a small number of CQDs doping. A methylcellulose-based carbon fiber-electrode was prepared by grinding and depositing the industrial recycled carbon fiber onto a biodegradable methylcellulose substrate. The methylcellulose-based recycled carbon fiber-electrode has the highest specific capacitance, energy density, and power density, which are 155 F/g, 10 Wh/kg, and 4047 W/kg, respectively, at a scan rate of 0.02 V/s, and demonstrates excellent performance, such like high specific capacitance, low internal resistance as well as rapid charge and discharge characteristics, which may have potential to replace the expensive carbon nanotubes and graphenes. The electrodes were made from recycled carbon fiber, the gel electrolyte with garlic CQDs, and a separator assembled into a sandwich structure to form supercapacitors. The capacity retention rate of the supercapacitor still retained 96 % of its initial value after 2000 cycles of charge and discharge testing at a constant current of 0.20 mA. This demonstrates the supercapacitor prepared in this study with competitive power density, energy density, high rate capability, and excellent life cycle stability by combining the garlic skin and carbon fiber from agricultural and industrial wastes, highlighting the enormous potential of agricultural and industrial wastes for energy storage applications.

Investigation of alignment and layup optimization of recycled carbon fiber mats on mechanical and electromagnetic shielding properties of composites

AbstractExcellent recycled carbon fiber (rCF) was obtained using a thermally activated oxide semiconductor process. An alignment device was manufactured based on wet‐laid technology. It was used to investigate the effect of various alignment nozzle parameters on the degree of alignment of rCF mats. The mechanical, electrical conductivity and EMI shielding properties of composites reinforced by rCF mats with different layup structures were analyzed. The results showed that the optimal alignment parameters for rCF aligned mats included a convex nozzle shape, a nozzle diameter of 3 mm, a nozzle channel length of 50 mm, a nozzle up‐and‐down diameter ratio of 7:1, a nozzle departure height of 20 mm. These settings achieved a preferential alignment degree (PAD) of 93.07%. The design of layup structures for rCF mats with optimized fiber alignment fully exploits the material's anisotropic characteristics. The rCF‐0/EP composite material exhibited the highest tensile strength (195.45 MPa), while the rCF‐04/EP composite material not only demonstrated the highest flexural strength (247.95 MPa) but also showed excellent electromagnetic interference (EMI) performance (47.97 dB). The results of the research laid a theoretical foundation and provides scientific guidance for high‐value reuse of rCF.Highlights Utilized rCF as a reinforcing material for CFRP composites. Preparation of rCF aligned mats with high PAD. Effect of different layup structures on rCF aligned mat reinforced composites. rCF aligned mats improve mechanical properties and EMI properties of composites.

Transformation of waste carbon fiber prepreg into sustainable composites: Application in the automotive industry components

AbstractCarbon fiber (CF) prepregs are employed in the manufacture of many different aeronautical structural and non‐structural components. Following the cure of the prepregs in molds, trimming is generally used to give the final shape to the components. Considering the aircraft's vast surface area and the use of multiple prepreg layers in each component, an extensive amount of carbon fiber prepreg is discarded. The unique characteristics of carbon fibers render this CF waste highly valuable and requires its efficient recycling. Cured waste CF prepregs were milled and processed in this research to produce chopped carbon fibers for use in the novel composite development. The matrix material used in the composites was selected as recycled polypropylene sourced from old surgical masks, which highlighted the sustainability of the developed composites. To enhance the quality of the fiber‐matrix interface and improve the impact resistance of the composites an anhydride‐grafted polyethylene (Fusabond) was employed in small quantities. From mechanical characterizations, synergistic effects of the fillers were observed. Besides, compositions containing CF and Fusabond are found more impact resistant than neat matrix. In addition, the use of carbon fibers increased fracture toughness of the matrix through various mechanisms including fiber bridging, fiber pullout, and matrix plastic deformation identified by scanning electron microscopy fractography. Thermomechanical characterizations using dynamic mechanical analysis revealed that carbon fiber raises the neat matrix's glass transition temperature. The developed materials are intended to be employed in the automotive industry to produce inner fender liners, with an optimal composition determined by an optimization research.Highlights Carbon fiber (CF) derived from aerospace fresh scraps significantly improved the mechanical properties of the polymer matrix. Anhydride‐grafted polyethylene incorporation remarkably enhanced the impact resistance of the polymer. CF demonstrated a bridge effect and improved the fracture toughness of the composites. The use of recycled CF presents encouraging prospects in the automotive industry for the production of inner fender liners.

Assessing cellular responses to milled recycled carbon fiber in alveolar macrophages

Assessing cellular responses to milled recycled carbon fiber in alveolar macrophages

Effects of recycled carbon fibers on mechanical and piezoresistive properties and environmental impact in alkali-activated cementitious materials

The development of alkali-activated cementitious materials (AAM) reinforced with recycled carbon fiber (rCF) is of remarkable significance due to its cost-effectiveness compared to virgin carbon fiber, along with the sustainable reuse of solid waste serving as AAM. This study explores the integration of rCF and solid waste Ground Granulated Blast Furnace Slag (GGBS), aiming for cleaner construction practices. A novel approach involving a high-viscosity one-part GGBS slurry ensured homogeneous rCF dispersion, resulting in alkali-activated slag (AAS) mortars with outstanding overall performance at minimal dosage. At a minimum dosage of 0.1 vol%, rCF significantly enhanced flexural strength by 53.42% and reduced drying shrinkage by over 20%. The uniformly dispersed rCF acts as nucleation sites, boosting early compressive strength without compromising long-term performance. Furthermore, the connected rCF network established an exceptionally low percolation threshold (0.125 vol%) and demonstrated promising piezoelectric properties under cyclic loading, illustrating its potential as self-sensing concrete elements. Additionally, life cycle analysis (LCA) underscored the environmental benefits of rCF and GGBS, revealing their potential to remarkably cut carbon emissions (75.36%) and reduce costs (36.5%). These findings provide valuable insights into the development of rCF-reinforced self-sensing mortar with superior mechanical properties, showcasing the substantial potential of rCF in driving the construction industry toward carbon neutrality.

Improving the interfacial adhesion between recycled carbon fibres and polyphenylene sulphide by bio-inspired dopamine for advanced composites manufacturing

Polyphenylene sulphide composites with recycled carbon fibres are of high interest due to their promising mechanical properties. Poor interface adhesion between recycled carbon fibre and thermoplastic matrix, however, remains a major problem in composite manufacturing. Herein, a novel one-step method using bio-inspired copolymerisation of dopamine to graft silica nanoparticles onto the carbon fibre surface is reported. Comprehensive investigations were conducted to fabricate the treated carbon fibre and characterise the modified samples by analysing the surface morphology and functional groups. The experimental results reveal that the network of bio-inspired adhesive polydopamine and nanoparticles adhering to the fibres can improve inter-laminar shear strength by 28.4% in the resulting composites. In addition, dynamical mechanical analysis results prove that the interfacial bonding at the fibre/matrix interface provides good resistance to thermal cycling. This novel approach introduces the functional groups on the recycled carbon fibre surface, leading to an improvement of surface energy and wettability between the carbon fibres and polyphenylene sulphide matrix and constitutes a robust and green approach to the manufacturing of advanced composites.

Micromechanical Modelling of the Deformation Mechanisms of Friction-Spun Yarn from Recycled Carbon Fibres

The growing use of carbon fibre-reinforced polymers (CFRP) results in an increased amount of CF waste from offcuts or end-of-life components. A promising method to reuse the waste fibre materials in a structural component with excellent mechanical properties is the processing of recycled CF (rCF) and thermoplastic fibres into hybrid yarns. Spinning of friction spun yarns consisting of more than 90% rCF and containing almost no thermoplastic fibres that are suitable for thermoset composites, currently leads to high fibre damage and low yarn quality and is, therefore, addressed in this project. The technology is reported in another paper. One of the limiting factors for drapability of textiles is the stretchability of continuous fibres and draping of the semi-finished textile products for complex geometries is still error-prone. Friction spun yarns exhibit significantly higher yarn elongations due to sliding mechanisms between the fibres. The deformation properties of friction spun yarns are significantly influenced by fibre-fibre interactions and depend on a variety of process and material parameters. In the following, micromechanical finite element models of the spun yarns are created by using beam elements. Monte Carlo method is used to model local variabilities in the yarns. The models are then used to simulate yarn behaviour under deformation and to investigate the influence of various process parameters.