Bone healing under different lay-up configuration of carbon fiber-reinforced PEEK composite plates.

Secondary healing of fractured bones requires an application of an appropriate fixator. In general, steel or titanium devices are used mostly. However, in recent years, composite structures arise as an attractive alternative due to high strength to weight ratio and other advantages like, for example, radiolucency. According to Food and Drug Administration (FDA), the only unidirectionally reinforced composite allowed to be implanted in human bodies is carbon fiber (CF)-reinforced poly-ether-ether-ketone (PEEK). In this work, the healing process of long bone assembled with CF/PEEK plates with cross- and angle-ply lay-up configurations is studied in the framework of finite element method. The healing is simulated by making use of the mechanoregulation model basing on the Prendergast theory. Cells transformation is determined by the octahedral shear strain and interstitial fluid velocity. The process runs iteratively assuming single load cycle each day. The fracture is subjected to axial and transverse forces. In the computations, the Abaqus program is used. It is shown that the angle-ply lamination scheme of CF/PEEK composite seems to provide better conditions for the transformation of the soft callus into the bone tissue.

Polydopamine-induced biomimetic mineralization strategy to generate hydroxyapatite for the preparation of carbon fiber composites with excellent mechanical properties.

Living organisms have developed a miraculous biomineralization strategy to form multistage organic-inorganic composites through the orderly assembly of hard/soft substances, achieving mechanical enhancement of materials from the nanoscale to the macroscale. Inspired by biominerals, this study used polydopamine (PDA) coating as a template to induce the growth of hydroxyapatite (HAP) on the surface of carbon fibers (CFs) for enhancing the interfacial properties of the CF/epoxy resin composites. This polydopamine-assisted hydroxyapatite formation (pHAF) biomimetic mineralization strategy constructs soft/hard ordered structure on the CF surface, which not only improves the chemical reaction activity of the CFs but also increases the fiber surface roughness. This, in turn, enhances the interaction and loading delivery among the fibers and the matrix. Compared to the untreated carbon fiber/epoxy resin (CF/EP) composites, the prepared composites showed a substantial enhancement in interlaminar shear strength (ILSS), flexural strength, and interfacial shear strength (IFSS), with improvements of 45.2 %, 46.9 %, and 60.5 %, respectively. This can be attributed to the HAP nanolayers increasing the adhesion and mechanical interlocking with the CFs to the matrix. This study provides an interface modification method of biomimetic mineralization for the preparation of high strength CF composites.

Reinforcing Efficiency of Recycled Carbon Fiber PLA Filament Suitable for Additive Manufacturing.

The use of 3D printing technology for manufacturing new products based on sustainable materials enables one to take advantage of secondary raw materials derived from recycling. This work investigates the structural performances of 3D printing composite filaments based on polylactic acid (PLA), as a matrix, reinforced by recycled carbon fiber (rCF). Carbon fibers were recovered from industrial scraps by a patented thermal process and used to produce thermoplastic composite filaments for additive manufacturing without any additional treatment and additives. The influence of the recovered carbon fiber (rCF) content on the thermal properties, mechanical properties and microstructure of the composites was studied in the range of 3-20 wt%. The recorded TGA curves exhibited a one-stage weight loss within the temperature range 290-380 °C for all samples and the residual rCF content was in good agreement with the theoretical fiber loading. The Young modulus of the extruded filaments strongly increased below a critical content (5 wt%), while at higher content the improvement was reduced. An increase in the storage modulus of 54% compared to neat PLA 3D printed sample resulted in a printed specimen with a higher rCF content. SEM images highlighted a strong rCF prevailing alignment in the direction of the extrusion flow, creating almost unidirectional reinforcement inside the filament. These findings suggest that homogeneous composite filaments reinforced with well-dispersed recycled CF without additional chemical modification and additives are suitable materials for additive manufacturing. The effect of rCF topological distribution within the material on the mechanical performances has been discussed, highlighting that the isolated fibers could efficiently transfer loads with respect to the percolated 3D network and have been correlated with the microstructure.

Research on the Mechanical and Thermal Properties of Carbon-Fiber-Reinforced Rubber Based on a Finite Element Simulation.

The comprehensive performance of rubber products could be significantly improved by the addition of functional fillers. To improve research efficiency and decrease the experimental cost, the mechanical and thermal properties of carbon-fiber-reinforced rubber were investigated using finite element simulations and theoretical modeling. The simplified micromechanical model was constructed through the repeatable unit cell with periodic boundary conditions, and the corresponding theoretical models were built based on the rule of mixture (ROM), which can be treated as the mutual verification. The simulation results suggest that, in addition to the fiber volume fraction Vfc increasing from 10% to 70%, the longitudinal Young's modulus, transversal Young's modulus, in-plane shear modulus, longitudinal thermal expansion coefficient, and transversal thermal expansion coefficient changed from 2.31 × 1010 Pa to 16.09 × 1010 Pa, from 0.54 × 107 Pa to 2.59 × 107 Pa, from 1.66 × 106 Pa to 10.11 × 106 Pa, from -4.98 × 10-7 K-1 to -5.89 × 10-7 K-1, and from 5.72 × 10-4 K-1 to 1.66 × 10-4 K-1, respectively. The mechanism by which Vfc influences the properties of carbon-fiber-reinforced rubber was revealed through the distribution of Von Mises stress. This research will contribute to improving the performance of carbon-fiber-reinforced rubber and promote its application.

Electrophysical Characteristics of Acrylonitrile Butadiene Styrene Composites Filled with Magnetite and Carbon Fiber Fillers.

With the rapid development of wireless communication technologies and the miniaturization trend in the electronics industry, the reduction of electromagnetic interference has become an important issue. To solve this problem, a lot of attention has been focused on polymer composites with combined functional fillers. In this paper, we report a method for creating an acrylonitrile butadiene styrene (ABS) plastic composite with a low amount of conductive carbon and magnetic fillers preparation. Also, we investigate the mechanical, thermophysical, and electrodynamic characteristics of the resulting composites. Increasing the combined filler amount in the ABS composite from 1 to 5 wt % leads to a composite conductivity growth of almost 50 times. It is necessary to underline the temperature decrease of 5 wt % mass loss and, accordingly, the composite heat resistance reduction with an increase in the combined filler from 1 to 5 wt %, while the thermal conductivity remains almost constant. It was established that electrodynamic and physical-mechanical characteristics depend on the agglomeration of fillers. This work is expected to reveal the potential of combining commercially available fillers to construct effective materials with good electromagnetic interference (EMI) protection using mass production methods (extrusion and injection molding).

Study on Low Temperature Cracking Resistance of Carbon Fiber Geogrid Reinforced Asphalt Pavement Surface Combined Body.

Currently, there are limitations in the research on the use of carbon fiber geogrids to prevent low-temperature cracking in asphalt pavements. This study aims to comparatively investigate the effects of carbon fiber-based geogrid type and dense-graded asphalt concrete mixture (AC) surface combined body (SCB) type on the low-temperature cracking resistance of reinforced asphalt pavement through low-temperature bending damage tests. Two geogrid types were prepared: a carbon fiber geogrid (CCF) and a glass/carbon fiber composite qualified geogrid (GCF). Two SCB types were studied: AC-13/AC-20 and AC-20/AC-25. The results show that the improvement in the flexural tensile strength of CCF is similar to that for GCF. Moreover, under reinforced conditions, the improvement in the low-temperature cracking resistance of AC-20/AC-25 is better than that for AC-13/AC-20 by 16.26-24.57%. Based on the analysis, the reasonable ratio range of the aperture sizes to the major particle sizes in the dense gradation can achieve a more effective interlocking effect. This can improve the low-temperature cracking resistance of carbon fiber-based geogrid-reinforced samples. Then, increasing the bending absorption energy is a key way of improving the low-temperature cracking resistance of carbon fiber-based geogrid reinforcements. Eventually, the fracture type of carbon fiber-based geogrid-reinforced samples is a mixed plastic-brittle fracture. These results can provide a reference for the road failure analysis of geogrid-reinforced asphalt pavement.

A Modeling Framework for the Thermoforming of Carbon Fiber Reinforced Thermoplastic Composites.

A comprehensive modeling framework for the thermoforming of polymer matrix woven laminate composite was developed. Two numerical indicators, the slip path length and traction magnitude, have been identified to be positively correlated to matrix smearing and wrinkling defects. The material model has been calibrated with picture-frame experimental results, and the prediction accuracy for intra-ply shear and thickness distribution was examined with measurements of the physically formed parts. Specifically, thickness prediction for most locations on the formed parts was accurate within an 11.6% error margin. However, at two points with significant intra-ply shear, the prediction errors increased to around 20%. Finally, a parametric study was conducted to determine the relationship between various process parameters and the quality of the formed part. For the trapezoidal part, orienting the laminate at 45 degrees to the mold axis reduces the likelihood of matrix smear and wrinkling defects. Although this laminate orientation yielded a greater spatial variation in part thickness, the thickness deviation is lower than that for the 0-degree orientation case. Two forming analyses were conducted with ramp rates of 25 mm/s and 80 mm/s to match the equipment's operational limits. It was observed that higher forming rates led to a greater likelihood of defects, as evidenced by a 15% and 10% increase in the formed part areas with longer slip paths and higher traction magnitudes, respectively. It was discovered that shallower molds benefit from faster ramp rates, while deeper molds require slower rates to manage extensive shearing, stretching and bending. Faster forming rates lead to smaller thickness increases at high intra-ply shear regions, indicating a shift from intra-ply shear to out-of-plane bending due to the visco-plastic effect of the molten laminate and can negatively impact part quality. Lastly, it was shown that a well-conceived strategy using darts could improve the part quality by reducing the magnitude of the defect indicators.

Analysis of the Tensile Properties and Probabilistic Characteristics of Large-Tow Carbon Fiber-Reinforced Polymer Composites.

Large-tow carbon fiber-reinforced polymer composites (CFRP) have great application potential in civil engineering due to their low price, but their basic mechanical properties are still unclear. The tensile properties of large-tow CFRP rods and plates were investigated in this study. First, the tensile properties of unidirectional CFRP rods and plates were studied, and the test results of the relevant mechanical properties were statistically analyzed. The tensile strength of the CFRP rod and plate are 2005.97 MPa and 2069.48 MPa. Second, the surface of the test specimens after failure was observed using a scanning electron microscope to analyze the type of failure and damage evolution process. Finally, the probabilistic characteristics of the mechanical properties were analyzed using normal, lognormal, and Weibull distributions for parameter fitting. Quasi-optimality tests were performed, and a probability distribution model was proposed for the mechanical properties of large-tow CFRP rods and plates.

Nanostructured Transition Metal Oxides on Carbon Fibers for Supercapacitor and Li-Ion Battery Electrodes: An Overview.

Nowadays, owing to the new technological and industrial requirements for equipment, such as flexibility or multifunctionally, the development of all-solid-state supercapacitors and Li-ion batteries has become a goal for researchers. For these purposes, the composite material approach has been widely proposed due to the promising features of woven carbon fiber as a substrate material for this type of material. Carbon fiber displays excellent mechanical properties, flexibility, and high electrical conductivity, allowing it to act as a substrate and a collector at the same time. However, carbon fiber's energy-storage capability is limited. Several coatings have been proposed for this, with nanostructured transition metal oxides being one of the most popular due to their high theoretical capacity and surface area. In this overview, the main techniques used to achieve these coatings-such as solvothermal synthesis, MOF-derived obtention, and electrochemical deposition-are summarized, as well as the main strategies for alleviating the low electrical conductivity of transition metal oxides, which is the main drawback of these materials.

Efficient Sequestration of Cesium Ions Using Phosphoric Acid-Modified Activated Carbon Fibers from Aqueous Solutions.

In this study, acid-modified activated carbon fibers (ACF-Ps) were synthesized by phosphorylation. Three different types of ACF-based adsorbents functionalized with PO43-, P2O74-, or P3O105- ions, namely, ACF-P1, ACF-P2, and ACF-P3, were prepared by phosphorylating ACF with trisodium phosphate (Na3PO4), sodium dihydrogen pyrophosphate (Na2H2P2O5), and sodium tripolyphosphate (Na5P3O10), respectively, and utilized as adsorbents to remove cesium ions (Cs+) from aqueous solutions. Among the tested adsorbents, ACF-P3 exhibited the highest Cs+ adsorption capacity of 37.59 mg g-1 at 25°C and pH 7 which is higher than that of ACF (5.634), ACF-P1 (19.38 mg g-1), and ACF-P2 (30.12 mg g-1) under the same experimental conditions. More importantly, the Cs+ removal efficiencies of ACF-P3 (82.90%), ACF-P2 (66.2%), ACF-P1 (34.2%) were 29.3-, 23.4-, and 12.11-fold higher than that of un-treated ACF (2.83%). The results suggested that the phosphorylation with Na5P3O10 is highly suitable for Cs+ adsorption which effectively functionalizes ACF with a greater number of phosphate functional groups. Adsorption and kinetic data well-fitted the Langmuir isotherm and pseudo-second-order model, respectively, which indicated the monolayer adsorption of Cs+ onto ACF-P1, ACF-P2, and ACF-P3 which were largely controlled by chemisorption. Overall, phosphoric acids containing different phosphate-based polyanions (PO43-, P2O74-, or P3O105-) enriched -OH and/or -COOH surface functional groups of ACF in addition to P-containing surface groups (P=O, C-P-O, C-O-P, and P-O) and facilitated the Cs+ adsorption through surface complexation and electrostatic interactions.

Novel multifibrillar carbon and oxidation-stable carbon/ceramic hybrid fibers consisting of thousands of individual nanofibers with high tensile strength.

In this study, multifibrillar carbon and carbon/ceramic (C/SiCON) fibers consisting of thousands of single nanofibers are continuously manufactured. The process starts with electrospinning of polyacrylonitrile (PAN) and PAN/oligosilazane precursors resulting in poorly aligned polymer fibers. Subsequent stretching leads to parallel aligned multifibrillar fibers, which are continuously stabilized and pyrolyzed to C or C/SiCON hybrid fibers. The multifibrillar carbon fibers show a high tensile strength of 911 MPa and Young's modulus of 154 GPa, whereas the multifibrillar C/SiCON fibers initially have only tensile strengths of 407 MPa and Young's modulus of 77 GPa, due to sticking of the nanofibers during the stabilization in air. Additional curing with electron beam radiation, results in a remarkable increase in tensile strength of 707 MPa and Young's modulus of 98 GPa. The good mechanical properties are highlighted by the low linear density of the multifibrillar C/SiCON fibers (~ 1 tex) compared to conventional C and SiC fiber bundles (~ 200 tex). In combination with the large surface area of the fibers better mechanical properties of respective composites with a reduced fiber content can be achieved. In addition, the developed approach offers high potential to produce advanced endless multifibrillar carbon and C/SiCON nanofibers in an industrial scale.

A Study on the Surface Oxidation Pretreatment and Nickel Plating Mechanism of Carbon Fiber.

This study explores the effects of various temperatures on the surface modification of carbon fibers, as well as the effect of differing voltages and currents on the morphology, deposition rate, and thickness of the Ni plating layers. Post-treatment characterization of the samples was conducted utilizing scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods, thus facilitating a discussion on the mechanism of Ni plating. The findings demonstrate that at a temperature of 500 °C, the carbon fiber surface exhibits the highest concentration of functional groups, including hydroxyl (-OH), carboxyl (-COOH), and carbonyl (-C=O), resulting in the most efficacious modification. Specifically, exceeding 500 °C leads to significant carbon fiber mass loss, compromising the reinforcement effect. Under a stable voltage of 7.5 V, the Ni-plated layer on the carbon fibers appear smooth, fine, uniform, and complete. Conversely, at a voltage of 15 V, the instantaneous high voltage induces the continuous growth of Ni2+ ions along a singular deposition point, forming a spherical Ni-plated layer. In addition, a current of 0.6 A yields a comparatively uniform and dense carbon fiber coating. Nickel-plated layers on a carbon fiber surface with different morphologies have certain innovative significance for the structural design of composite reinforcements.

Towards Sustainable and Fire-Safe Thermosets Using Phosphorus-Containing Covalent Adaptable Networks.

Dynamic covalent chemistry is a promising strategy for developing recyclable thermosets and their carbon fiber reinforced composites, in line with the goal of green and sustainable development. However, a significant challenge lies in balancing the dynamic reversibility and the desired service performances, such as thermal, mechanical properties, and flame retardancy. It has hindered the broader application of dynamic materials beyond the initial proof of concept. This concept provides an overview of the current state of research on phosphorus-containing covalent adaptable networks (CANs), highlighting key designing and regulating principles for tailoring comprehensive properties including flame retardancy, mechanical and thermal properties, as well as dynamic behaviours such as malleability, reprocessability and degradability. Finally, new frontiers and opportunities in developing high-performance sustainable CANs-based thermosets and their carbon fiber composites for structural engineering applications are prospected.

Experimental Proof of Principle of 3D-Printed Microfluidic Benthic Microbial Fuel Cells (MBMFCs) with Inbuilt Biocompatible Carbon-Fiber Electrodes.

Microbial fuel cells (MFCs) represent a promising avenue for sustainable energy production by harnessing the metabolic activity of microorganisms. In this study, a novel design of MFC-a Microfluidic Benthic Microbial Fuel Cell (MBMFC)-was developed, fabricated, and tested to evaluate its electrical energy generation. The design focused on balancing microfluidic architecture and wiring procedures with microbial community dynamics to maximize power output and allow for upscaling and thus practical implementation. The testing phase involved experimentation to evaluate the performance of the MBMFC. Microbial feedstock was varied to assess its impact on power generation. The designed MBMFC represents a promising advancement in the field of bioenergy generation. By integrating innovative design principles with advanced fabrication techniques, this study demonstrates a systematic approach to optimizing MFC performance for sustainable and clean energy production.

Investigation of the nanostructure and nanomechanical properties of the interphase in carbon fiber reinforced polyamide-6 composite.

Carbon fiber reinforced polyamide-6 (CF/PA-6) composites have been widely applied in automobile, aerospace, and biomedical industries for their high mechanical properties, high thermal resistance and recyclability. On the purpose of finding ways to improve the interfacial properties, the investigation of the nanostructure and nanomechanical properties of the interphase in CF/PA-6 composites were essential. In this study, MD simulation was carried out to show the interfacial formation and nanostructure of the CF/PA-6 composite model directly at the atomic level and compute the radial distribution function, interfacial energy, total energy. Then the nanomechanical properties of the CF/PA-6 composite, such as interfacial thickness, interfacial modules, interfacial adhesion, were investigated by AFM PF-QNM model. The changes of the radical distribution function and energies over the MD simulation time indicated that the PA-6 chains adsorbed and then regularly folded on the CF surface, displaying the interfacial crystallization of the CF/PA-6 composite model. What stood out in the AFM PF-QNM tests were the abrupt decreasing of the interfacial modulus and the sharp increasing of the interfacial adhesion from those of the carbon fiber to those of the PA-6. The average interfacial thickness of the CF/PA-6 composite was 72 nm. Consistent with the simulation results, the interfacial properties were distinct from the properties of the carbon fiber and PA-6, owning to the adsorption and orderly folding of the PA-6 chains on the CF surface and the changes of the RDF and energies.

Online monitoring of pre-crack initiation in carbon fiber-reinforced thermoplastic composites by an ultrasonic cutting tool using high-speed optical imaging and infrared thermography.

The ultrasonic-assisted manufacturing process is a promising machining approach for composite materials as it exerts less force, making it ideal for the aerospace and automotive sectors. This work reports about the pre-crack initiation in carbon fiber reinforced (CF)/ poly-ether-ether-ketone (PEEK) composite under ultrasonic frequency at room temperature. An iron-based cutting tool matching the system's resonance frequency (20 kHz) was used to perform the ultrasonic pre-cracking. In this novel work, the pre-cracking of CF-PEEK is considered as the initial step for a complete fiber layer separation, which holds the key for circularity options in high-performance aerospace composites. State-of-the-art high-speed camera and infrared thermography were combined to monitor the crack initiation and propagation. By online monitoring, the different stages involved in the pre-cracking process, its temperature evolution, and consequently the dissipated energy during pre-cracking under ultrasonic frequency were evaluated. The results showed that oscillation amplitude had a significant influence on the determined pre-crack depth and measured global temperature and energy compared to cutting force. The measured global temperature data indicates that pre-cracking occurred in the solid state with a temperature well below the glass-transition temperature of PEEK. However, the local temperature at the contact between the sample and sonotrode could have been much higher during ultrasonic cutting which needed further investigation. The computed global dissipated energy and temperature were only reliable at the pre-crack initiation site due to the limitation in the infrared thermography system.

Lignin-Based Carbon Fiber/Epoxy Resin Biocomposites with Excellent Fire Resistance and Mechanical Properties.

Carbon fiber (CF)-reinforced epoxy resin (EP) composites are lightweight materials with excellent comprehensive performance. However, the flammability of EP and the poor interfacial bonding between CF and EP are two key disadvantages that limit their further applications. Here, a kind of water-soluble lignin-based CF sizing agent (ELBEDK) is prepared through hydrophilic modification of enzymatic lignin, which can significantly enhance the interfacial interaction between CF and EP. Additionally, a highly efficient intumescent flame retardant (LMA) is prepared. The EP, enzymatic lignin, LMA and CF sized ELBEDK are compounded to obtain the fire-safety CF reinforced composites (SCF/FEP/L). The flame retardancy of SCF/FEP/L with 7% LMA (SCF/FEP7) reached V-0 rating. Moreover, SCF/FEP/L with 7% LMA and 15% lignin (SCF/FEP7/L15) present an limiting oxygen index (LOI)of 30.2% and V-0 of UL-94. Specifically, the total smoke production and the heat release rate are 47.8% and 46.81% lower than that of SCF/EP, respectively, indicating the improved smoke suppression and flame retardancy. The IFSS and flexural strength of SCF/FEP7/L15 are improved to be 59.4 MPa and 511.1 MPa, respectively. This study presents a simple approach to fabricate low-cost high performance lignin-based flame retardant CF/EP biocomposites with wide application potential.

Multifunctional electromagnetic wave absorbing carbon fiber/Ti3C2TX MXene fabric with superior near-infrared laser dependent photothermal antibacterial behaviors.

Developing multifunctional materials which could simultaneously possess anti-bacterial ability and electromagnetic (EM) absorption ability during medical care is quite essential since the EM waves radiation and antibiotic-resistant bacteria are threatening people's health. In this work, the multifunctional carbon fiber/Ti3C2Tx MXene (CM) were synthesized through repeated dip-coating and following in-situ growth method. The as-fabricated CF/MXene displayed outstanding EM wave absorption and highly efficient photothermal converting ability. The minimum reflection loss (RL) of -57.07 dB and ultra-broad absorption of 7.74 GHz could be achieved for CM composites. By growth of CoNi-layered double hydroxides (LDHs) sheets onto MXene, the absorption bandwidth for carbon fiber/Ti3C2Tx MXene layered double hydroxides (CML) could be reach 5.44 GHz, which could cover the whole Ku band. The excellent photothermal effect endow the CM composites with excellent antibacterial performance. The antibacterials tests indicated that nearly 100 % bactericidal efficiency against E. acoil and S. aureus was obtained for the CM composite after exposure to near-infrared region (NIR) irradiation. This work provides a promising candidate to combat medical device-related infections and EM pollution.

Entropy-Engineered Middle-In Synthesis of Dual Single-Atom Compounds for Nitrate Reduction Reaction.

Despite the immense potential of Dual Single-Atom Compounds (DSACs), the challenges in their synthesis process, including complexity, stability, purity, and scalability, remain primary concerns in current research. Here, we present a general strategy, termed "Entropy-Engineered Middle-In Synthesis of Dual Single-Atom Compounds" (EEMIS-DSAC), which is meticulously crafted to produce a diverse range of DSACs, effectively addressing the aforementioned issues. Our strategy integrates the advantages of both bottom-up and top-down paradigms, proposing an insight into optimizing the catalyst structure. The as-fabricated DSACs exhibited excellent activity and stability in the nitrate reduction reaction (NO3RR). In a significant advancement, our prototypical CuNi DSACs demonstrated outstanding performance under conditions reminiscent of industrial wastewater. Specifically, under a NO3- concentration of 2000 ppm, it yielded a Faradaic efficiency (FE) for NH3 of 96.97%, coupled with a mass productivity of 131.47 mg h-1 mg-1 and an area productivity of 10.06 mg h-1 cm-2. Impressively, even under a heightened NO3- concentration of 0.5 M, the FE for NH3 peaked at 90.61%, with a mass productivity reaching 1024.50 mg h-1 mg-1 and an area productivity of 78.41 mg h-1 cm-2. This work underpins the potential of the EEMIS-DSAC approach, signaling a frontier for high-performing DSACs.

Dynamic Covalent Bonds Enabled Carbon Fiber Reinforced Polymers Recyclability and Material Circularity.

Due to their remarkable features of lightweight, high strength, stiffness, high-temperature resistance, and corrosion resistance, carbon fiber reinforced polymers (CFRPs) are extensively used in sports equipment, vehicles, aircraft, windmill blades, and other sectors. The urging need to develop a resource-saving and environmentally responsible society requires the recycling of CFRPs. Traditional CFRPs, on the other hand, are difficult to recycle due to the permanent covalent crosslinking of polymer matrices. The combination of covalent adaptable networks (CANs) with carbon fibers (CFs) marks a new development path for closed-loop recyclable CFRPs and polymer resins. This review summarizes the most recent developments of closed-loop recyclable CFRPs from the unique paradigm of dynamic crosslinking polymers, CANs. These sophisticated materials with diverse functions, oriented towards CFs recycling and resin sustainability, are further categorized into several active domains of dynamic covalent bonds, including ester bonds, imine bonds, disulfide bonds, boronic ester bonds, and acetal linkages, etc. Finally, the possible strategies for the future design of recyclable CFPRs by combining dynamic covalent chemistry innovation with materials interface science are proposed.