45 results found
Valkova M, Nguyen S, Senokos E, et al., 2023, Current collector design strategies: The route to realising scale-up of structural power composites, Composites Science and Technology, Vol: 236, Pages: 1-9, ISSN: 0266-3538
Multifunctional structural power composites, which combine mechanical load-bearing and electrochemical energy storage, will transform electric vehicle design. This work focuses on structural supercapacitors, based on carbon aerogel-modified carbon fibre electrodes with copper current collectors. In common with many structural power embodiments, scale-up of these devices is currently limited by large internal resistances and the mass associated with current collection. There is a trade-off between the overall resistive power loss and the additional mass for the current collector material. However, in these devices, mechanical integrity is provided by the structural electrodes, allowing a range of collector designs to be considered. Using finite element simulations, these current collection strategies are explored quantitatively across a range of design space variables. The key conductivity parameters were measured experimentally, using the best existing materials, to inform direct current conduction simulations of the electrode/current collector assembly. For the present device configuration, the performance trade-off is governed by the area of the current collector. The most effective near-term strategy for power loss mitigation lies in reducing the contact resistance; however, improvements can also be obtained by modifying the collector geometry. The findings of this paper can be generalised to other structural power composites and monofunctional energy storage devices, which are relevant in many mass-sensitive electrochemical applications.
Senokos E, Anthony DB, Rubio N, et al., 2023, Robust single‐walled carbon nanotube‐infiltrated carbon fiber electrodes for structural supercapacitors: from reductive dissolution to high performance devices, Advanced Functional Materials, Vol: 33, Pages: 1-11, ISSN: 1616-301X
Multifunctional electrodes for structural supercapacitors are prepared by vacuum infiltration of single-walled carbon nanotubes (SWCNTs) into woven carbon fibers (CFs); the use of reductive charging chemistry to form nanotubide solutions ensured a high degree of individualization. The route is highly versatile, as shown by comparing four different commercial nanotube feedstocks. In film form, the pure nanotubide networks (“buckypapers”) are highly conductive (up to 2000 S cm−1) with high surface area (>1000 m2 g−1) and great electrochemical performance (capacitance of 101 F g−1, energy density of 27.5 Wh kg−1 and power density of 135 kW kg−1). Uniformly integrating these SWCNT networks throughout the CF fabrics significantly increased electrical conductivity (up to 318 S cm−1), surface area (up to 196 m2 g−1), and in-plane shear properties, all simultaneously. The CNT-infiltrated CFs electrodes exhibited intrinsically high specific energy (2.6–4.2 Wh kg−1) and power (6.0–8.7 kW kg−1) densities in pure 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) electrolyte. Multifunctional structural supercapacitors based on CNT-coated CFs offer a substantial increase in capacitive performance while maintaining the tensile mechanical properties of the as-received CF-based composite. This non-damaging approach to modify CFs with highly graphitic, high surface area nanocarbons provides a new route to structural energy storage systems.
Anthony DB, Nguyen SN, Qian H, et al., 2023, Silica aerogel infused hierarchical glass fiber polymer composites, Composites Communications, Vol: 39, Pages: 1-7, ISSN: 2452-2139
Hierarchical systems can address the matrix-dominated failures of structural fiber polymer composites. Here, a new synergistic hierarchical structure combines conventional structural glass fibers with a bi-continuous silica-based aerogel matrix; both pure-silica and organically-modified silicate aerogels are demonstrated. When infused with an epoxy matrix, this type of hierarchical architecture showed a marked improvement in mechanical properties: without any loss in modulus, both the compressive strength and the interlaminar shear strength increased by up to 27%, relative to the equivalent glass-fiber reinforced epoxy composite baseline. The bi-continuous network modification strategy uses industrially-relevant infusion techniques, at or near room temperature, and retains a similar final composite density (within 2%). The strategy presented here provides a versatile and readily applicable means to improve state-of-the art continuous fiber reinforced composite systems in compression and offers an opportunity to develop a new generation of composite materials.
Shaw C, Anthony D, Garguili J, et al., 2023, Designing bicontinuous silica-epoxy nanocomposites, ECCM20 - The 20th European Conference on Composite Materials, Publisher: Composite Construction Laboratory (CCLab), Pages: 1445-1450
A nanocomposite reinforced with a 3D, connected, stiff framework should offer better performance than a simple dispersion of nanoparticles. Monolithic porous silica can be used as this framework by providing a fully connected but open porous supporting skeleton for reinforcing organic polymers. Infusion of epoxy resin into silica aerogel pores may produce a bicontinuous material that more efficiently exploits the intrinsic properties of each solid phase: bicontinuous aerogel and polymer matrix component. Matrix infusion into an aerogel monolith in principle allows greater silica content than shear mixing (of particles) which is limited by aggregation and high shear viscosities. Silica content is maximised by producing aerogels of unusually high envelope density (0.2 g.cm⁻³ – 0.8 g.cm⁻³).
Anthony D, Woodgate C, Shaw C, et al., 2023, Hierarchical solutions to compressive problems in fibre-reinforced composites, ECCM20 - The 20th European Conference on Composite Materials, Publisher: Composite Construction Laboratory (CCLab), Pages: 1512-1517
Currently, the useable compressive properties of a composite are restricted by set design limits well below the expected intrinsic performance of the materials contained within. The next generation of high-performance fibre-reinforced polymer composites will need to address the challenge of improving the absolute performance of composites in compression. This task requires a rethink of the whole system; not only to address practical limitations of current materials, but their combination, interface, and their architecture. The mechanisms involved do not simply act over the nano-, macro-, or meso-level independently, but are mutually related at the system level, complicating the approach.
Almousa H, De Luca H, Anthony D, et al., 2023, Robust continuous production of carbon nanotube-grafted structural fibres: a route to hierarchical fibre reinforced composites, ECCM20 - The 20th European Conference on Composite Materials, Publisher: Composite Construction Laboratory (CCLab), Pages: 1451-1456
Growth of carbon nanotubes (CNTs) onto the fibre surface by direct chemical vapour deposition (CVD) offers a convenient means to integrate synthesis with assembly. This method delivers the nanostructures where they have the greatest influence on fibre-matrix interface or interphase. However, CVD is usually limited to small batches of short fibre lengths, and can damage the primary properties. Here, we describe a robust process to produce carbon nanotube-grafted-fibres continuously at tow level with a uniform coverage of short (sub-500 nm length), 10-20 nm diameter CNTs. Different CNT growth conditions, such as temperature [650-950 °C], duration [0.72-50 min], line speed [0.6-10 m/h], potential difference [0-1000 V], and reactive gas flow/compositions were investigated. Following optimisation, the fabrication of an entirely “fuzzy” fibre reinforced hierarchical composite was achieved.
Wang J, Anthony DB, Fuentes CA, et al., 2022, Wettability of carbon nanotube-grafted carbon fibers and their interfacial properties in polypropylene thermoplastic composite, Composites Part A: Applied Science and Manufacturing, Vol: 159, Pages: 1-10, ISSN: 1359-835X
The interfacial properties of carbon fiber (CF) reinforced thermoplastic composites depend strongly on the wettability and surface characteristics of the reinforcing fibers, and their compatibility with a chosen matrix. The interface between conventional fibers and thermoplastic matrices is generally weak, due to a lack of specific chemical interaction, especially in the case of polyolefins. Carbon nanotube-grafted-carbon fibers (CNT-g-CF) are considered to be potential reinforcements as they provide additional mechanical interlocking. Commercial CFs were successfully grafted with nanotubes using a continuous, and hence scalable, CVD method. X-ray photoelectron spectroscopy, Wilhelmy wetting measurements, and scanning electron microscopy confirmed the successful grafting and resulting hydrophobic surface chemistry, dominated by van der Waals interactions. The grafted CNTs, with diameters and lengths around 10 nm and 140 nm respectively, were well suited to improve the overall wettability and interfacial shear strength (+53.4 %) of the CNT-g-CF in a polypropylene matrix when compared to as-received unsized CFs.
Valkova M, Anthony DB, Kucernak ARJ, et al., 2022, Predicting the mechanical behaviour of structural supercapacitor composites, Composites Part A: Applied Science and Manufacturing, Vol: 156, ISSN: 1359-835X
Multifunctional structural power composites may transform transport electrification, and other applications, but require performance and reliability improvements. Computational modelling has the potential to accelerate their development and deployment. This work addresses the lack of predictive models for the mechanical behaviour of structural supercapacitor composites exploiting carbon aerogel-modified carbon fabric electrodes. The elastic behaviour was investigated using finite element analysis of quasi-meso-scale periodic unit cell models, considering the effects of constituent properties, defects, stacking geometry, and boundary conditions. Nanoindentation was used to evaluate the Young’s modulus of carbon aerogel. Parametric modelling demonstrated a strong influence of the ply offset and matrix materials on the composite elastic properties. The initial numerical results overpredicted the actual performance measured from tensile and in-plane shear experiments in the literature. Optical, scanning electron and micro X-ray imaging revealed extensive pre-cracking and voidage in the physical laminates. Additional computational investigations showed that the pre-cracks were associated with a degradation of shear stiffness. The remaining performance gap was attributed to voidage. The present study highlights that challenges for mechanical performance and its prediction stem from the presence of processing defects and a lack of in-situ material data. Nevertheless, the models identify the potential of hierarchical laminates containing aerogels to generate sizable performance improvements, both in multifunctional and purely structural contexts.
Pernice MF, Qi G, Senokos E, et al., 2022, Mechanical, electrochemical and multifunctional performance of a CFRP/carbon aerogel structural supercapacitor and its corresponding monofunctional equivalents, Multifunctional Material, Vol: 5
Anthony DB, De Luca HG, Almousa H, et al., 2022, Carbon Nanotube-grafted Carbon Fiber Production: A Scaling Challenge
Qi G, Nguyen S, Anthony DB, et al., 2021, The influence of fabrication parameters on the electrochemical performance of multifunctional structural supercapacitors, Multifunctional Materials, Vol: 4, ISSN: 2399-7532
Multifunctional structural supercapacitors based on carbon fibre electrodes (CF) and structural electrolytes (SEs) can realise multifunctionality by simultaneously bearing load and providing electrochemical energy storage. Structural supercapacitor constituents (i.e. electrodes and electrolytes) have undergone significant development to enhance their electrochemical and mechanical properties. However, the fabrication of fully functional devices presents a number of practical challenges to achieve optimal multifunctional properties, particularly those associated with assembly and lamination. This work investigated the effect of separator selection and processing parameters on the electrochemical performance of structural supercapacitors, as well as evaluating the repeatability of the SE filming process. Two layers of glass fibre fabrics were the most effective separator for preventing short-circuiting of the structural supercapacitors. The weight fraction of the SE matrix had a significant effect on the capacitance, energy and power of the structural supercapacitors. By addressing such fabrication challenges, high performance structural supercapacitors can be manufactured with greater reproducibility and at larger scales such that they are suitable for integration in industrial applications.
De Luca H, Anthony D, Greenhalgh E, et al., 2020, Piezoresistive structural composites reinforced by carbon nanotube-grafted quartz fibres, Composites Science and Technology, Vol: 198, Pages: 1-12, ISSN: 0266-3538
Nano-engineered fibre/matrix interfaces can improve state-of-the-art fibre-reinforced composites. Grafting carbon nanotubes (CNTs) to high temperature quartz glass fibres produces “hairy” or “fuzzy” fibres, which combine reinforcements at micrometre and nanometre length scales. Fuzzy quartz fibres were produced continuously, reel-to-reel, on whole tows, in an open chemical vapour deposition reactor. The resulting uniform coverage of 200 nm long CNTs increased the interfacial shear strength with epoxy (90.3 ± 2.1 MPa) by 12% compared to the commercially-sized counterpart, as measured by single fibre pull-out tests. The improved interfacial properties were confirmed at the macroscale using unidirectional hierarchical bundle composites, which exhibited a delayed onset of fibre/matrix debonding. Although the quartz fibres are electrically insulating, the grafted CNT create a conductive path, predominantly parallel to the fibres. To explore the applicability for structural health monitoring, the resistivity was recorded in situ during mechanical testing, and correlated with simultaneous acoustic emission data. The baseline resistivity parallel to the fibres (ρ0 = 3.9 ± 0.4 × 10−1 Ω m) displayed a linear piezoresistive response (K = 3.64) until failure at ca. 2.1% strain, also referred to as "gauge factor”, a two-fold improvement over traditional resistance strain gauges (e.g. constantan). Hierarchical, fuzzy quartz fibres, therefore, simultaneously enhance both structural and sensing performance, offering multifunctional opportunities in large composite parts.
Senokos E, Anthony D, Nguyen S, et al., 2020, Manganese dioxide decorated carbon aerogel/carbon fibre composite as a promising electrode for structural supercapacitors, 22nd International Conference on Composite Materials 2019 (ICCM22), Publisher: Engineers Australia, Pages: 1-8
Manganese dioxide electrochemically deposited onto carbon aerogel/carbon fibres (CAG/CF) shows a great potential as an electrode material in multifunctional structural supercapacitors. MnO₂ nanowires grown by a pulse potentiometric method provide a large enhancement in capacitive performance of the carbon electrodes and symmetric supercapacitor devices based on the hybrid material.
Valkova M, Anthony DB, Kucernak ARJ, et al., 2020, Predicting the compaction of hybrid multilayer woven composite reinforcement stacks, Composites Part A: Applied Science and Manufacturing, Vol: 133, ISSN: 1359-835X
A meso-scale finite element modelling strategy was developed to investigate the effect of hybridisation on the compaction response of multilayer stacks combining glass and carbon dry woven fabrics. It is expected that the electrochemical-mechanical properties of emerging multifunctional hybrid composites are strongly dictated by the morphology of the compacted reinforcements, yet no investigations into their compressibility have been reported. Model predictions were evaluated against compressibility measurements for monolithic and hybrid fabric stacks. The ply offset had a major influence on the predicted internal morphologies and fibre content, contributing to experimental variability thereof. Optical microscopy and micro X-ray computed tomography imaging indicated greater likelihood of intermediate ply offsets in physical specimens, over limit case model idealisations. Compressibility was slightly reduced in the hybrid multilayer stacks studied in this work. The model outputs presented are being used to analyse the electrochemical-mechanical response of hybrid woven structural power composites.
Lee WJ, Paineau E, Anthony DB, et al., 2020, Inorganic nanotube mesophases enable strong self-healing fibers, ACS Nano, Vol: 14, Pages: 5570-5580, ISSN: 1936-0851
The assembly of one-dimensional nanomaterials into macroscopic fibers can improve mechanical as well as multifunctional performance. Double walled aluminogermanate imogolite nanotubes are geo-inspired analogs of carbon nanotubes, synthesized at low temperature, with complementary properties. Here, continuous imogolite based fibers are wet spun within a polyvinyl alcohol matrix. The lyotropic liquid crystallinity of the system produces highly aligned fibers with tensile stiffness and strength up to 24.1 GPa (14.1 N tex⁻¹) and 0.8 GPa (0.46 N tex⁻¹), respectively. Significant enhancements over the pure polymer control are quantitatively attributed to both matrix refinement and direct nanoscale reinforcement, by fitting an analytical model. Most intriguingly, imogolite-based fibers show a high degree of healability via evaporation induced self assembly, recovering up to 44%, and 19% of the original fiber tensile stiffness and strength, respectively. This recovery at high absolute strength highlights a general strategy for the development of high-performance healable fibers relevant to composite structures and other applications.
Clancy AJ, Anthony DB, De Luca F, 2020, Metal mimics: lightweight, strong, and tough (nano)composites and nanomaterial assemblies, ACS Applied Materials & Interfaces, Vol: 12, Pages: 15955-15975, ISSN: 1944-8244
The ideal structural material would be high strength and stiffness, with a tough ductile failure, all with a low density. Historically, no such material exists, and materials engineers have had to sacrifice a desired property during materials selection, with metals (high density), fibre composites (brittle failure), and polymers (low stiffness) having fundamental limitations on at least one front. The ongoing revolution of nanomaterials provides a potential route to build on the potential of fibre-reinforced composites, matching their strength while integrating toughening behaviours akin to metal deformations all while using low weight constituents. Here, the challenges, approaches, and recent developments of nanomaterials for structural applications are discussed, with an emphasis on improving toughening mechanisms – often the neglected factor in a field which chases strength and stiffness.
Nguyen S, Anthony DB, Qian H, et al., 2019, Mechanical and physical performance of carbon aerogel reinforced carbon fibre hierarchical composites, Composites Science and Technology, Vol: 182, ISSN: 0266-3538
Carbon aerogel (CAG) is a potential hierarchical reinforcement to improve the matrix-dominated mechanical properties of continuous carbon fibre reinforced polymer (CFRP) composites in both multifunctional and purely structural applications. When using CAG to reinforce a polyethylene glycol diglycidyl ether (PEGDGE) matrix, the interlaminar shear strength, compressive modulus and strength increased approximately four-fold, whilst the out-of-plane electrical conductivity increased by 118%. These mechanical and electrical performance enhancements significantly improve the multifunctional efficiency of composite structural supercapacitors, which can offer weight savings in transport and other applications. However, CAG also has the potential to reinforce conventional continuous CF composites in purely structural contexts. Here, CAG reinforcement of structural epoxy resin composites marginally increased compressive (1.4%) and tensile (2.7%) moduli respectively, but considerably reduced compressive, tensile and interlaminar shear strengths. Fractographic analysis shows that the reduced performance can be attributed to poor interfacial adhesion; in the future, alternative processing routes may resolve these issues to achieve advances in both moduli and strengths over conventional structural CFRPs.
Anthony D, Nguyen S, Senokos E, et al., 2019, Hierarchical carbon aerogel modified carbon fiber composites for structural power applications, 22nd International Conference on Composite Materials 2019 (ICCM22), Publisher: Engineers Australia, Pages: 1-7
The desire to reduce overall weight in devices is a key driver for perpetual material development; the ability to combine composites with energy storage functions/capabilities which simultaneously provide structural integrity has the potential to supersede monofunctional components. To achieve this ambition, the multifunctional structure must perform both mechanical and energy storage functions sufficiently, but often there is a trade off in performance which is a significant challenge to overcome. Carbon aerogels have been shown to contribute positively to (electro-chemical double layer) capacitive performance due to an increased surface area in multifunctional carbon fiber based composite electrodes, but have also been shown to reduce mechanical properties; the addition of nanoscale reinforcers, such as carbon nanotubes, graphene or alike, with their superlative electrical and mechanical properties are proposed to address these concerns and create a truly hierarchical structure suitable for structural power applications.
Lee WJ, Clancy AJ, Fernandez-Toribio JC, et al., 2019, Interfacially-grafted single-walled carbon nanotube / poly (vinyl alcohol) composite fibers, CARBON, Vol: 146, Pages: 162-171, ISSN: 0008-6223
Clancy A, Sirisinudomkit P, Anthony D, et al., 2019, Real-time mechanistic study of carbon nanotube anion functionalisation through open circuit voltammetry, Chemical Science, Vol: 10, Pages: 3300-3306, ISSN: 2041-6520
The mechanism of the functionalisation of reduced single walled carbon nanotubes with organobromides was monitored byopen circuit voltammetry throughout the reaction and further elucidated through a series of comparative reactions. Thedegree of functionalisation was mapped against the reagent reduction potential, degree of electron donation of substituents(Hammett parameter), and energies calculated, ab initio, for dissociation and heterolytic cleavage of the C-Br bond. Incontrast to the previously assumed reduction/homolytic cleavage mechanism, the reaction was shown to consist of a rapidassociation of carbon-halide bond to the reduced nanotube as a complex, displacing surface-condensed countercations,leading to an initial increase in the net nanotube surface negative charge. The complex subsequently slowly degradesthrough charge transfer from the reduced single-walled carbon nanotube to the organobromide, utilizing charge, and thecarbon-halide bond breaks heterolytically. Electron density on the C-Br bond in the initial reagent is the best predictor fordegree of functionalisation, with more electron donating substituents increasing the degree of functionalisation. Both themechanism and the new application of OCV to study such reactions are potentially relevant to wide range of related systems.
Clancy A, Anthony DB, Shaffer M, 2019, Reactive coagulation of single-walled carbon nanotubes for tougher composites – solution processing and assembly, Polymer Processing Society Europe Africa Conference 2017 (PPS 2017) with 7th International Conference on Carbon NanoParticle Based Composites (CNPComp2017), Publisher: AIP Publishing, Pages: 090005-090005, ISSN: 1551-7616
The injection of reduced single-walled carbon nanotubes into a coagulation bath of polyvinyl chloride (PVC) solution leads to the formation of nanocomposite fibres with polymer covalently bound to the nanotubes. The influence of PVC concentration and molecular weight, and the extrusion diameter on the nanocomposite fibre tensile properties and composition have been examined. The nanocomposite fibres produced have strengths as high as 480 MPa and modulus of 15 GPa, making them the strongest and stiffest PVC composites recorded to date.
Liu B, Liu C, De Luca H, et al., 2019, Synthesis of epoxidized poly(ester carbonate)-b-polyimide-b-poly(ester carbonate): reactive single-walled carbon nanotube dispersants enable synergistic reinforcement around multi-walled nanotube-grafted carbon fibers, Polymer Chemistry, Vol: 10, Pages: 1324-1334, ISSN: 1759-9954
Polyimides (PI) generally have a high affinity for single-walled carbon nanotubes (SWNTs), but they suffer from poor solubility in most low boiling point organic solvents and low compatibility with common resins (such as epoxy) used in composites, limiting their suitability as dispersants. PI block copolymer systems containing reactive poly(ester carbonate)s have not yet been reported and are expected to act as effective reactive dispersing agents of SWNTs. Herein, PI-derived block copolymers are synthesized via ring-opening copolymerization of lactide (LA) (a control monomer) and allyl-bearing 2-methyl-2-(allyloxycarbonyl)-propylene carbonate (MAC) from the OH-terminal ends of the PI block to produce PLA-PI-PLA (TB1, a control) and PMAC-PI-PMAC (TB2). The allyl pendant group of TB2 allows further facile functionalization to form a third series of epoxidized (EP) derivatives, i.e. PMACEP-block-PI-block-PMACEP (TB3). TB3 copolymer when mixed with a conventional structural epoxy resin forms blends that do not show inferior tensile properties compared with the epoxy, which is unusual. Furthermore, the mixing solvent tetrahydrofuran (THF) can be readily evaporated off after forming the blends. TB3-dispersed (2 wt%) SWNTs added to epoxy increased the tensile strength, modulus, and elongation at break of the resulting nanocomposite films by 40%, 34%, and 26% respectively, compared to the baseline epoxy resin. Furthermore, when TB3b triblock-dispersed SWNTs in epoxy were combined with fuzzy carbon fibers, i.e. carbon nanotube-grafted-carbon fibers (CNT-g-CF), a synergistic interfacial strength reinforcement was observed, together with shifting of the failure mode from the matrix interphase to the carbon fiber-grafted nanotube interface. The ultimate interfacial shear strength between the TB3-dispersed SWNT-epoxy matrix and the fuzzy carbon fibers (i.e., fibers having carbon nanotubes grown on them) measured via single fiber pull-out tests was 100 MPa, which was ca. 11% imp
Anthony DB, Sui X, Kellersztein I, et al., 2018, Continuous carbon nanotube synthesis on charged carbon fibers, Composites Part A: Applied Science and Manufacturing, Vol: 112, Pages: 525-538, ISSN: 1359-835X
Carbon nanotube grafted carbon fibers (CNT-g-CFs) were prepared continuously, spool to spool, via thermal CVD. The application of an in-situ potential difference (300 V), between the fibers and a cylindrical graphite foil counter electrode, enhanced the growth, producing a uniform coverage of carbon nanotubes with diameter ca. 10 nm and length ca. 125 nm. Single fiber tensile tests show that this approach avoids the significant reduction of the underlying carbon fiber strengths, which is usually associated with CVD grafting processes. Single fiber fragmentation tests in epoxy, with in-situ video fragment detection, demonstrated that the CNT-g-CFs have the highest interfacial shear strength reported for such systems (101 ± 5 MPa), comparable to state–of–the–art sizing controls (103 ± 8 MPa). Single fiber pull-out data show similar trends. The short length of the grafted CNTs is particularly attractive for retaining the volume fraction of the primary fibers in composite applications. The results are compared with a short review of the interfacial data available for related systems.
Anthony DB, Bacarreza Nogales O, Shaffer M, et al., 2018, Pseudo-ductile failure mechanism introduced into finger jointed thermoplastic PES interleaved CFRC, ECCM18 - 18th European Conference on Composite Materials
Pre-cut unidirectional carbon fibre prepreg composites, with an overlapped finger-joint architecture, were modified through the addition of polyethersulfone (PES) interleaves. The properties arising from these finger-jointed configurations were strongly dependent on the interply overlap region. When the tough thermoplastic interleaves spanned only the central portion of the overlap, a crack arresting failure mechanism was observed in tension. A pronounced plateau region or pseudo-ductile response was shown in conjunction with a strain hardening response after crack arrest. The local strain-to-failure of PES interleaved samples was ~3.2%, an increase of 85% compared to the pre-cut baseline (strain-to-failure 1.6%, pre-cut specimens without interleaves).
De Luca F, Clancy A, Rubio Carrero N, et al., 2018, Increasing carbon fiber composite strength with a nanostructured“brick-and-mortar” interphase, Materials Horizons, Vol: 5, Pages: 668-674, ISSN: 2051-6355
Conventional fiber-reinforced composites suffer from the formation of critical clusters of correlated fiber breaks, leading to sudden composite failure in tension. To mitigate this problem, an optimized “brick-and-mortar” nanostructured interphase was developed, in order to absorb energy at fiber breaks and alleviate local stress concentrations whilst maintaining effective load transfer. The coating was designed to exploit crack bifurcation and platelet interlocking mechanisms known in natural nacre. However, the architecture was scaled down by an order of magnitude to allow a highly ordered conformal coating to be deposited around conventional structural carbon fibers, whilst retaining the characteristic phase proportions and aspect ratios of the natural system. Drawing on this bioinspiration, a Layer-by-Layer assembly method was used to coat multiple fibers simultaneously, providing an efficient and potentially scalable route for production. Single fiber pull out and fragmentation tests showed improved interfacial characteristics for energy absorption and plasticity. Impregnated fiber tow model composites demonstrated increases in absolute tensile strength (+15%) and strain-to-failure (+30%), as compared to composites containing conventionally sized fibers.
Woodward RT, Markoulidis F, De Luca F, et al., 2018, Carbon foams from emulsion-templated reduced graphene oxide polymer composites: electrodes for supercapacitor devices, Journal of Materials Chemistry A, Vol: 6, Pages: 1840-1849, ISSN: 2050-7496
Amphiphilic reduced graphene oxide (rGO) is an efficient emulsifier for water-in-divinylbenzene (DVB) high internal phase emulsions. The polymerisation of the continuous DVB phase of the emulsion template and removal of water results in macroporous poly(divinylbenzene) (polyDVB). Subsequent pyrolysis of the poly(DVB) macroporous polymers yields ‘all-carbon’ foams containing micropores alongside emulsion templated-macropores, resulting in hierarchical porosity. The synthesis of carbon foams, or ‘carboHIPEs’, from poly(DVB) produced by polymerisation of rGO stabilised HIPEs provides both exceptionally high surface areas (up to 1820 m2/g) and excellent electrical conductivities (up to 285 S/m), competing with the highest figures reported for carboHIPEs. The use of a 2D carbon emulsifier results in the elimination of post-carbonisation treatments to remove standard inorganic particulate emulsifiers, such as silica particles. It is demonstrated that rGO containing carboHIPEs are good candidates for supercapacitor electrodes where carboHIPEs derived from more conventional polymerised silica-stabilised HIPEs perform poorly. Supercapacitor devices featured a room-temperature ionic liquid electrolyte and electrodes derived from either rGO- or silica-containing poly(DVB)HIPEs and demonstrated a maximum specific capacitance of 26 F g-1, an energy density of 5.2 Wh kg-1 and a power density of 280 W kg-1.
Buckley DJ, Hodge SA, De Marco M, et al., 2017, Trajectory of the Selective Dissolution of Charged Single-Walled Carbon Nanotubes, Journal of Physical Chemistry C, Vol: 121, Pages: 21703-21712, ISSN: 1932-7447
Single-Walled Carbon Nanotubes (SWCNTs) are materials with an array of remarkable physical properties determined by their geometries, however, SWCNTs are typically produced as a mixture of different lengths and electronic types. Consequently, many methods have been developed to sort the as-produced SWCNT samples by their physical cha-racteristics, often requiring aggressive and unscalable techniques to overcome the strong bundling forces between the nanotubes. Previously, it has been shown that negatively charging SWCNTs can lead to their thermodynamically-driven dissolution in polar solvents, and moreover that this process can selectively dissolve different SWNCT species, albeit with contrasting claims of selectivity. Here we carefully investigate dissolution as a function of charge added to the SWCNT starting material, using a range of complementary techniques. We uncover a far richer dependence on charge of SWCNT dissolution than previously reported. At low charge added, amorphous carbons preferentially dissolve, followed sequentially by metallic, larger diameter semiconducting SWCNTs, and finally smaller diameter semiconducting SWCNTs. At an optimal value, the dissolution yield is maximized across all species, however at higher charge than this we find the larger diameter and metallic SWCNTs are so charged they are no longer soluble, leaving smaller diameter SWCNTs in solution. Our results therefore clearly demonstrate two interconnected mechanisms for dissolution: on one hand charging of the SWNCTs based on their respective electron affinities on the other the solution thermodynamics. This work reconciles contrasting reports in the literature, provides a blueprint for scalable SWCNT separation and more generally demonstrates the..
Anthony DB, Bacarreza Nogales OR, Shaffer MSP, et al., 2017, Crack arrest in finger jointed thermoplastic interleaved CFRC, 21st International Conference on Composite Materials, Publisher: Chinese Society for Composite Materials
Pre-cut unidirectional carbon fibre prepreg (M21/194/34%/T800S) composites were tested in tension with a 20 mm overlapped finger joint architectures. In between the overlapping finger jointed region the effect of introducing polyethersulfone (PES) interleaves is investigated. Samples with the addition of a thick PES interleave arrested the initial crack which formed at the pre-cut site. The strain-to-failure of the thick PES interleaved samples was over 3.2%, an increase of 85% compared to the baseline samples, and catastrophic failure was delayed in the majority of instances.
De Luca, Anthony DB, Greenhalgh ES, et al., 2017, Continuous production of carbon nanotube-grafted quartz fibres: Effect of carbon nanotube length on fibre/matrix adhesion, 21st International Conference on Composite Materials, Publisher: Chinese Society for Composite Materials
Here, the continuous production of carbon nanotube-grafted-quartz-fibres was performed in an open chemical vapour deposition reactor with continuous in line catalyst deposition. Highly graphitic carbon nanotubes (CNTs) with controllable lengths ranging from 0.1 μm to 20 μm were grown on the quartz fibre surface by adjusting the reduction and growth times, with shorter fibres growing homogeneously and longer CNTs growing in a splayed “Mohawk” manner. The effect of CNTs length (and thus microstructure) upon the mechanical properties of CNT-grafted-quartz-fibre/epoxy composites was investigated through single fibre pull-out test. The presence of a uniform coverage of sub-micron long CNTs led to an increase in interfacial shear strength of 11% and 29% when compared to sized and de-sized quartz fibres, respectively.
Anthony DB, Qian H, Clancy AJ, et al., 2017, Applying a potential difference to minimise damage to carbon fibres during carbon nanotube grafting by chemical vapour deposition, Nanotechnology, Vol: 28, ISSN: 1361-6528
The application of an in-situ potential difference between carbon fibres and a graphite foil counter electrode (300 V, generating an electric field ca. 0.3 V μm-1 to 0.7 V μm-1) during the chemical vapour deposition synthesis of carbon nanotube (CNT) grafted carbon fibres, significantly improves the uniformity of growth without reducing the tensile properties of the underlying carbon fibres. Grafted carbon nanotubes with diameters around 55 nm and lengths around 10 μm were well attached to the carbon fibre surface, and were grown without the requirement for protective barrier coatings. The grafted CNTs increased the surface area to 185 m2 g-1 compared to the as-received sized carbon fibre 0.24 m2 g-1. The approach is not restricted to batch systems and has the potential to improve carbon nanotube grafted carbon fibre production for continuous processing.
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