•Recent updates in recycling carbon fibre reinforced composites are reviewed.•Mechanical, thermal and chemical methods along with influential parameters are discussed.•The methods of manufacturing ...yarns and nonwovens from dry carbon fibre scraps are reviewed.•The environmental impacts of processing CFRC wastes are discussed.
Carbon fibre reinforced composites (CFRC) continue to play a key role in the growth and development of many weight sensitive industries. However, their proliferation has raised increasing concerns regarding the required practices and strategies to deal with these expensive engineered structures at the end of their life cycle. This has brought into focus the need to develop more sustainable and efficient recycling solutions for these products. Similarly, the necessity of managing dry carbon fibre scraps generated during the manufacturing process of CFRC has attracted more attention in recent years. This review article provides an overview on recent advances in recycling CFRC as well as processing dry carbon fibre scraps. Influential parameters, advantages, drawbacks, and possible environmental impacts of the main technologies of processing CFRC waste including mechanical, thermal (pyrolysis and fluidised bed), and chemical (solvolysis and low temperature chemical processing) will be evaluated. Their potential effects on mechanical characteristics and surface chemistry of fibres are assessed. Moreover, recent processing methods of dry and semi-finished carbon fibre scrap are also reviewed. Specific attention is paid to the recent developments in producing hybrid yarns and nonwovens made of waste carbon fibre. The methodologies developed in this area, their processing conditions, as well as other important findings are discussed. This review paper provides a valuable platform for researchers and decision makers working in the field of carbon fibre by providing a clearer picture on the options available to recycle CFRC, and the methods of developing value-added products using waste carbon fibre.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The development of a hierarchically engineered micro-nano hybrid composite system is described. A spray coating technique has been utilized as an effective way to deposit carbon nanotubes (CNTs) onto ...carbon fibre prepregs with good control of network formation and the potential for localization. Compared to more traditional approaches of introducing CNTs into epoxy matrices for enhancing composite properties, this technique has benefits in terms of its simplicity and versatility, as well as the potential for industrial scale-up. The effectiveness of the technique is demonstrated by the extremely low CNT loading (0.047wt.%) needed to significantly increase the Mode-I fracture toughness of the carbon fibre laminates by about 50%, which is so far the largest reported improvement for such extremely low concentrations of non-functionalized CNTs. In-situ damage sensing has also been presented for the monitoring of structural health of these nano-engineered composite laminates upon loading, and a systematic analysis of sensing signals is performed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
By adding glass fibres to carbon fibre composites, the apparent failure strain of the carbon fibres can be increased. A strength model for unidirectional hybrid composites was developed under very ...local load sharing assumptions to study this hybrid effect. Firstly, it was shown that adding more glass fibres leads to higher hybrid effects. The hybrid effect was up to 32% for a hybrid composite with a 10/90 ratio of carbon/glass fibres. The development of clusters of broken fibres helped to explain differences in the performance of these hybrid composites. For 50/50 carbon/glass hybrids, a fine bundle-by-bundle dispersion led to a slightly smaller hybrid effect than for randomly dispersed hybrids. The highest hybrid effect for a 50/50 ratio, however, was 16% and was achieved in a composite with alternating single fibre layers. The results demonstrate that thin ply hybrids may have more potential for improved mechanical properties than comingled hybrids.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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► Main recycling technologies for carbon fibre reinforced plastics (CFRPs). ► Advantages and disadvantages for each technology. ► Focus on the chemical recycling of CFRPs using a ...solvolysis process in near- and supercritical fluids. ► REcycling Carbon fibre reinforced COmposites (RECCO) project.
This paper presents the main technologies for recycling carbon fibre reinforced plastics, focusing on the chemical recycling using the supercritical fluids technology. The conventional technologies of carbon fibres recycling are described with their advantages and drawbacks. After a brief introduction on the specific properties of supercritical fluids and some of the green associated technologies, the development of the chemical recycling of carbon fibre reinforced plastics by solvolysis in near- and supercritical fluids is reviewed. Research efforts on the technology have shown great results at the lab-scale and should then contribute to the development of this process at the industrial scale in a near future.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The integration of piezoelectric materials onto carbon fiber (CF) can add energy harvesting and self‐power sensing capabilities enabling great potential for “Internet of Things” (IoT) applications in ...motion tracking, environmental sensing, and personal portable electronics. Herein, a CF‐based smart composite is developed by integrating piezoelectric poly(3,4‐ethylenedioxythiophene) (PEDOT)/CuSCN‐coated ZnO nanorods onto the CF surfaces with no detrimental effect on the mechanical properties of the composite, forming composites using two different polymer matrices: highly flexible polydimethylsiloxane (PDMS) and more rigid epoxy. The PDMS‐coated piezoelectric smart composite can serve as an energy harvester and a self‐powered sensor for detecting variations in impact acceleration with increasing output voltage from 1.4 to 7.6 V under impact acceleration from 0.1 to 0.4 m s−2. Using epoxy as the matrix for a CF‐reinforced plastic (CFRP) device with sensing and detection functions produces a voltage varying from 0.27 to 3.53 V when impacted at acceleration from 0.1 to 0.4 m s−2, with a lower output compared to the PDMS‐coated device attributed to the greater stiffness of the matrix. Finally, spatially sensitive detection is demonstrated by positioning two piezoelectric structures at different locations, which can identify the location as well as the level of the impacting force from the fabricated device.
Piezoelectric poly(3,4‐ethylenedioxythiophene) (PEDOT)/CuSCN‐coated ZnO nanorods are integrated with carbon fibers to produce a smart composite. Both flexible polydimethylsiloxane (PDMS)‐coated devices and carbon fiber/epoxy devices serve as impact sensors generating up to 7.6 and 3.53 V, respectively. Using epoxy as the matrix to produce an impact sensing panel enables spatially sensitive detection exhibiting excellent ability for energy harvesting and self‐powered sensing.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This study develops a novel procedure combining topological design and fibre placement paths based on average load transmission trajectories for high load-bearing capacity of 3D-printed carbon fibre ...reinforced composite parts. First, a two-stage topological design procedure is established to acquire the optimal topology for confining maximum stress and minimising structural compliance. Second, based on calculations for the average load transmission trajectories within the optimal topology, continuous carbon fibre placement paths are defined for 3D-printing with fused filament fabrication (FFF). Experimental studies are performed for topologically designed short cantilever and three-point-bending specimens to characterise the reinforcement effect of short carbon fibre (SCF, vol% = 15%) and continuous carbon fibre (CCF, vol% = 35%) on specimens printed with pure polyamide (PA). The CCF increases the stiffness and the magnitude of peak load of the cantilever specimens by 1198% and 1633%, respectively, while the increments are 569% and 293%, respectively, for three-point-bending specimens, showing the significant impact of the procedure. The SCF also increases the stiffness and peak load of the both structural configurations but to a much lesser degree.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Classifying the type of damage occurring within a structure using a structural health monitoring system can allow the end user to assess what kind of repairs, if any, that a component requires. This ...paper investigates the use of acoustic emission (AE) to locate and classify the type of damage occurring in a composite, carbon fibre panel during buckling. The damage was first located using a bespoke location algorithm developed at Cardiff University, called delta-T mapping. Signals identified as coming from the regions of damage were then analysed using three AE classification techniques; Artificial Neural Network (ANN) analysis, Unsupervised Waveform Clustering (UWC) and corrected Measured Amplitude Ratio (MAR). A comparison of results yielded by these techniques shows a strong agreement regarding the nature of the damage present in the panel, with the signals assigned to two different damage mechanisms, believed to be delamination and matrix cracking. Ultrasonic C-scan images and a digital image correlation (DIC) analysis of the buckled panel were used as validation. MAR’s ability to reveal the orientation of recorded signals greatly assisted the identification of the delamination region, however, ANN and UWC have the ability to group signals into several different classes, which would prove useful in instances where several damage mechanisms were generated. Combining each technique’s individual merits in a multi-technique analysis dramatically improved the reliability of the AE investigation and it is thought that this cross-correlation between techniques will also be the key to developing a reliable SHM system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The interface quality between the reinforcement and the host matrix plays a key role in the mechanical performance of Carbon Fibre/Epoxy Resin (CFRP) composites. In most cases, an adequately strong ...interfacial bond is induced chemically either by the oxidation of the carbon fibre (CF) surface and/or by means of mechanical interlocking (friction). Here, a mild chemical process involving CF's functionalization via an epoxidation reaction at room temperature (RT) is being proposed. By immersing the CF in an organic solution (chloroperoxybenzoic acid in dichloromethane), the outer surface is functionalized with oxygen moieties, such as epoxy rings, at optimized grafting densities. The room-temperature method described here is more advantageous that other oxidative treatments since it is cost-effective, environmentally friendly and does not damage the fibre surface. Furthermore, as detected by Laser Raman microscopy a considerable 2.3-fold increase of the maximum interfacial shear stress was observed for the treated CF/Epoxy systems as compared to the pristine-untreated-samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Natural structures such as nacre show an outstanding balance of strength and toughness, despite comprising mainly brittle constituents; this is a highly desirable combination of properties scarcely ...seen in synthetic composites. In this study, carbon fibre-reinforced polymer (CFRP) laminates mimicking the structure of nacre (‘brick-and-mortar’) were manufactured using the automated tape laying (ATL) technique, as a means of enhancing their interlaminar properties and fracture toughness. The interlaminar fracture toughness of the bio-inspired CFRP laminates was measured via double cantilever beam (DCB) and three-point bending end-notched flexure (3ENF) tests. The results indicated increments of up to 32% and 92%, respectively, in the interlaminar fracture toughness when compared with that of conventional continuous CFRP samples. In addition, the translaminar fracture toughness of the developed nacre-inspired CFRPs was measured through a compact tension (CT) test, which revealed increments of up to 30%. Finally, different reinforcement mechanisms were analysed to understand the effect of the ‘brick-and-mortar’ structure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of carbon fibre (CF) on the mechanical and thermal properties of graphene foam (GF)/polydimethylsiloxane (PDMS) composites was investigated. The CFs with different weight percentages (2, ...4, 6, 8 and 10 wt%) were thoroughly dispersed in the PDMS matrix using a high-speed shearing and stirring method and then the GF was filled with the mixture. The CF/GF/PDMS composites were characterized in terms of microstructure, mechanical and thermal properties using various testing techniques. The results reveal that the addition of CF observably improved the mechanical and thermal properties of GF/PDMS composites. For 10 wt% CF/GF/PDMS composite, the tensile strength and Young's modulus are increased by 52% and 71% respectively compared with GF/PDMS composite. In addition, its thermal conductivity reaches 0.55 Wm−1 K−1, i.e., an increase by about 41% and 162% compared to GF/PDMS composite and pure PDMS, respectively. SEM images show a strong interfacial bonding between CF and PDMS.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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