High Performance Fiber Research Articles

Superstrong and tough silk fibers cross-linked with functionalized graphene

Natural silkworm silks with an intriguing integration of good strength, modulus, toughness and biocompatibility, have been widely used in textile and medical industry. However, the strength of silkworm silks is inferior to that of spider dragline silks, which are the strongest natural silks but extremely low yield. Herein, we develop a feasible strategy to continuously produce superstrong and tough regenerated silk fibers (RSFs) through the reconstruction of hierarchical and cross-linked architectures. Amine functionalized graphene (NH2-G) has been introduced to improve the content of β-sheet and crystalline orientation, and glutaraldehyde (GA) has been used to bridge NH2-G and silk micro/nanofibrils (SNFs) to form a highly interconnected and closely packed network, resulting in the remarkably improvement of mechanical properties. The resultant fibers exhibit an excellent tensile strength of 1029.6 ± 144.8 MPa, a Young's modulus of 16.8 ± 1.5 GPa, and a toughness of 277.4 ± 17.0 MJ/m3, exceeding those of the natural silkworm silks, spider dragline silks and most other previously reported regenerated silk fibers. We believe that the high-performance silk-based fibers are promising applications in lightweight and advanced structural materials.

Application of carbon fiber composite materials in aircraft

Carbon fiber composite is a material with excellent mechanical properties. Compared with other high-performance fiber materials, carbon fiber composites have the advantages of high strength and high modulus even at ultra-high temperatures. In addition, the carbon fiber composite material also has excellent electrical and thermal conductivity and electromagnetic shielding performance. Carbon fiber composites are widely used in the aircraft manufacturing industry due to their incomparable performance with other composite materials. In recent years, the amount of carbon fiber composite materials in newly developed aircraft products has reached more than 50%. This paper aims to explore the application of carbon fiber in aircraft, and to reflect the importance of carbon fiber composite materials by comparing models that use composite materials and models that do not use composite materials. The study explores the application of carbon fiber composite materials in aircraft through a comprehensive literature analysis and review. Key findings indicate significant advantages of these materials in enhancing aircraft performance, including reduced weight and increased strength. The paper also discusses the challenges in manufacturing and environmental impacts, offering insights into future research directions for sustainable aviation technologies.

Polymer Physics behind the Gel-Spinning of UHMWPE Fibers.

Gel-spinning of ultra-high molecular weight polyethylene (UHMWPE) fibers has attracted great interest in academia and industry since its birth and commercialization in the 1980s, due to unique properties such as high modulus, low density, and excellent chemical resistance. However, the high viscosity and long relaxation time greatly complicate processing. In industry, solvents, like decalin and paraffin oil, usually disentangle the physical networks and promote final drawability. From extruding the polymer solution to post-solid-stretching, many polymer physics problems that accompany high-modulus fiber gel-spinning should be understood and addressed. In this review, by detailed discussions about the effect of entanglements and intracrystalline chain dynamics on the mechanical properties of UHMWPE, theoretical descriptions of the structure formation of disentangled UHMWPE crystals, and the origin of high modulus and strength of final fibers are provided. Several physical intrinsic key factors are also discussed, revealing why UHMWPE is an ideal material for producing high-performance fibers.

The Influence of Utilizing High-performance Fibers on the Breathability of Doctors' Clothing Fabrics (scrubs)

The Influence of Utilizing High-performance Fibers on the Breathability of Doctors' Clothing Fabrics (scrubs)

Design of vibration sensors based on fibre Bragg grating type composites for earthquake detection and early warning application

Composite materials can be rapidly moulded using additive manufacturing processes due to their excellent mechanical and physical properties. Combining fibre Bragg gratings with composites results in high-performance fibre grating vibration sensors that address the limitations of electrical sensors and traditional materials. This study focused on developing a fibre optic acceleration sensor that utilizes a parabolic column made of silica gel. The sensor underwent fabrication, packaging, and calibration using a dedicated test system. Parametric calibrations and vibration detection tests were conducted to evaluate the performance of the system. The experimental results indicate that the sensor exhibits an intrinsic frequency of 70 Hz, a flat response range of 5 to 40 Hz, a linearity coefficient greater than 0.99, effective control of transverse interference, and exceptional low-frequency response, which improves the detection of vibration signals. Therefore, the sensor’s low intrinsic frequency and exceptional low-frequency response make it well-suited for detecting vibrations at low to medium frequencies.

In-situ forming ultra-mechanically sensitive materials for high-sensitivity stretchable fiber strain sensors.

Fiber electronics with flexible and weavable features can be easily integrated into textiles for wearable applications. However, due to small sizes and curved surfaces of fiber materials, it remains challenging to load robust active layers, thus hindering production of high-sensitivity fiber strain sensors. Herein, functional sensing materials are firmly anchored on the fiber surface in-situ through a hydrolytic condensation process. The anchoring sensing layer with robust interfacial adhesion is ultra-mechanically sensitive, which significantly improves the sensitivity of strain sensors due to the easy generation of microcracks during stretching. The resulting stretchable fiber sensors simultaneously possess an ultra-low strain detection limit of 0.05%, a high stretchability of 100%, and a high gauge factor of 433.6, giving 254-folds enhancement in sensitivity. Additionally, these fiber sensors are soft and lightweight, enabling them to be attached onto skin or woven into clothes for recording physiological signals, e.g. pulse wave velocity has been effectively obtained by them. As a demonstration, a fiber sensor-based wearable smart healthcare system is designed to monitor and transmit health status for timely intervention. This work presents an effective strategy for developing high-performance fiber strain sensors as well as other stretchable electronic devices.

Mechanical behavior of nacre-inspired CFRP composites by 3D printing

High-performance carbon fiber reinforced polymer (CFRP) composites are essential for many structural applications, however, properties such as strength and toughness are often considered mutually exclusive in CFRP composites. Inspired by the biological structure of nacre, this study offers a new 3D printing strategy for manufacturing nacre-inspired CFRP composites, aiming to overcome the limitations of traditional materials. The geometric parameters of the nacre-inspired brick composites, including waviness angle and aspect ratio were considered to systematically investigate their respective roles in achieving both strength and toughness and reveal the failure and deformation mechanisms through tensile and three-point bending tests. The results indicated the interlocking and appropriate aspect ratio nacre-inspired CFRP composites provides distinct advantages in enhancing both the overall strength and toughness of the structure under tensile loading. It is further shown that the bending property exhibited a significant sensitivity to the waviness angle. As the waviness angle gradually increases from negative to positive, the bending resistance of the sample decreases. The findings regarding deformation, failure modes, and toughening mechanisms shed light on how geometric parameters affect the mechanical performance of the nacre-inspired CFRP composites.

Spider silk-inspired heterogeneous interphase featuring hybrid interaction for simultaneously improving the interfacial strength and fracture toughness between carbon fiber and epoxy by regulating hydrogen bond density

Designing advanced fiber-reinforced polymer composites through biological inspiration proved to be a crucial strategy for overcoming limitations in simultaneously enhancing the strength and toughness of composites. To achieve simultaneous improvement in the interfacial strength and toughness between carbon fiber (CF) and epoxy, a spider silk-inspired interphase featuring hybrid interaction was constructed by introducing hyperbranched polyamide-amine (HPAA) and graphene oxide (GO) onto the surface of CF. The results suggested that manipulating the feed ratio to adjust the branching degree of HPAA allowed for the attainment of various hydrogen bond densities. The fiber surface with high hydrogen bond density provided more hydrogen bond interaction sites to promote the deposition of GO. Benefitting from the ameliorative interfacial adhesion force, surface energy and interface thickness, impressive improvements of 94.5 % and 110.0 % in respective interfacial strength and fracture toughness over those of untreated CF/EP composites were achieved for functionalized CF/EP composites. The enhancement mechanism of interfacial performance was attributed to the formation of a “nano-fishnet” structure, which improved the stress transformation efficiency and consumption of external energy absorbed by hydrogen bonds. The method of regulating the branching degree of hyperbranched polymers and hydrogen bond density has opened an advanced way for surface modification of high-performance fibers.

Microstructural evolution effects on the density of carbon nanotube fibers

In this study, we investigate structural change in wet-spun carbon nanotube (CNT) fibers and explore the resulting changes in density and tensile strength. Given the presence of chlorosulfonic acid (CSA) inside the fiber and the evolution of tubular shape, the difference between the experimental density of CNT fibers and the theoretical density of individual CNTs can be reasonably approximated. During the heat treatment of pristine CNT fibers at 1400 °C, the capillary force induced by removal of CSA between or inside CNTs leads to the polygonization of the circumference of individual nanotubes. This morphological transformation results in the improved tensile strength and increased density by enlarging the contact area between CNTs and reducing the occupied volume. The demonstration of correlation between CNT structure and density can offer insights into the manufacturing and applications of high-performance CNT fibers.

High-Performance Thermoelectric Fibers from Metal-Backboned Polymers for Body-Temperature Wearable Power Devices.

Metal-backboned polymers (MBPs), with a unique backbone consisting of bonded metal atoms, are promising for optic, electric, magnetic, and thermoelectric fields. However, the application of MBP remains relatively understudied. Here, we develop a shear-induced orientation method to construct a flexible nickel-backboned polymer/carbon nanotube (NBP/CNT) thermoelectric composite fiber. It demonstrated a power factor of 719.48 μW ⋅m-1 K-2, which is ca. 3.5 times as high as the bare CNT fiber. Remarkably, with the regulation of carrier mobility and carrier concentration of NBP, the composite fiber further showed simultaneous increases in electrical conductivity and Seebeck coefficient in comparison to the bare CNT fiber. The NBP/CNT fiber can be integrated into fabrics to harvest thermal energy of human body to generate an output voltage of 3.09 mV at a temperature difference of 8 K. This research opens a new avenue for the development of MBPs in power supply.

Establishing superfine nanofibrils for robust polyelectrolyte artificial spider silk and powerful artificial muscles

Spider silk exhibits an excellent combination of high strength and toughness, which originates from the hierarchical self-assembled structure of spidroin during fiber spinning. In this work, superfine nanofibrils are established in polyelectrolyte artificial spider silk by optimizing the flexibility of polymer chains, which exhibits combination of breaking strength and toughness ranging from 1.83 GPa and 238 MJ m−3 to 0.53 GPa and 700 MJ m−3, respectively. This is achieved by introducing ions to control the dissociation of polymer chains and evaporation-induced self-assembly under external stress. In addition, the artificial spider silk possesses thermally-driven supercontraction ability. This work provides inspiration for the design of high-performance fiber materials.

High-performance fibre battery with polymer gel electrolyte.

Replacement of liquid electrolytes with polymer gel electrolytes is recognized as a general and effective way of solving safety problems and achieving high flexibility in wearable batteries1-6. However, the poor interface between polymer gel electrolyte and electrode, caused by insufficient wetting, produces much poorer electrochemical properties, especially during the deformation of the battery7-9. Here we report a strategy for designing channel structures in electrodes to incorporate polymer gel electrolytes and to form intimate and stable interfaces for high-performance wearable batteries. As a demonstration, multiple electrode fibres were rotated together to form aligned channels, whilethe surface of each electrode fibre was designed with networked channels. The monomer solution was effectively infiltrated first along the aligned channels and then into the networked channels. The monomers were then polymerized to produce a gel electrolyte and form intimate and stable interfaces with the electrodes. The resulting fibre lithium-ion battery (FLB) showed high electrochemical performances (for example, an energy density of about 128 Wh kg-1). This strategy also enabled the production of FLBs with a high rate of 3,600 m h-1 per winding unit. The continuous FLBs were woven into a 50 cm × 30 cm textile to provide an output capacity of 2,975 mAh. The FLB textiles worked safely under extreme conditions, such as temperatures of -40 °C and 80 °C and a vacuum of -0.08 MPa. The FLBs show promise for applications in firefighting and space exploration.

Effect of isopropyl chloride addition in AlCl3 catalytic system on the formation of coal tar pitch-based mesophases

Mesophase pitch is a high-quality precursor for the synthesis of high-performance pitch-based carbon fibers. The mesophase content, texture and softening point are the most important factors for the structure, properties and spinnability of mesophase pitch (MP). Herein, we report a novel approach for the preparation of mesophase pitch with high anisotropic content and low softening point by AlCl3 catalytic pyrolysis in the presence of isopropyl chloride (PrCl). The variation of anisotropic content and mesophase texture under different PrCl additions and the effect of the introduction of isopropyl on the molecular stacking of aromatic lamellar molecules were investigated. The results confirmed that, except for their role in improving catalytic activity, carbocation co-catalysts can improve the structure and molecular assembly of aromatic molecules through the introduction of alkyl groups. The reaction of isopropyl chloride (PrCl) as a co-catalyst catalyzed pyrolysis of medium-temperature coal pitch at 370 ℃ for 8 h produced a bulk mesophase with a content close to 100 %. Compared to the AlCl3 system (without PrCl), the AlCl3-PrCl system can catalyze the preparation of mesophases at lower temperatures. In addition, it is logical that the introduction of isopropyl group significantly increases the stacking spacing of the mesophase pitch layer molecules, which can effectively improve the mobility of the aromatic layer molecules resulting in the growth of mesophase. The fusion texture and anisotropic content of mesophase pitch were significantly improved by replacing the nucleophilic reagent of the AlCl3-catalyzed system. This work provides feasible ideas for the preparation of high-performance coal tar based mesophase pitch.

Hydrophobic Silk Fibroin-Agarose Composite Aerogel Fibers with Elasticity for Thermal Insulation Applications.

Aerogel fibers, characterized by their ultra-low density and ultra-low thermal conductivity, are an ideal candidate for personal thermal management as they hold the potential to effectively reduce the energy consumption of room heating and significantly contribute to energy conservation. However, most aerogel fibers have weak mechanical properties or require complex manufacturing processes. In this study, simple continuous silk fibroin-agarose composite aerogel fibers (SCAFs) were prepared by mixing agarose with silk fibroin through wet spinning and rapid gelation, followed by solvent replacement and supercritical carbon dioxide treatment. Among them, the rapid gelation of the SCAFs was achieved using agarose physical methods with heat-reversible gel properties, simplifying the preparation process. Hydrophobic silk fibroin-agarose composite aerogel fibers (HSCAFs) were prepared using a simple chemical vapor deposition (CVD) method. After CVD, the HSCAFs' gel skeletons were uniformly coated with a silica layer containing methyl groups, endowing them with outstanding radial elasticity. Moreover, the HSCAFs exhibited low density (≤0.153 g/cm3), a large specific surface area (≥254.0 m2/g), high porosity (91.1-94.7%), and excellent hydrophobicity (a water contact angle of 136.8°). More importantly, they showed excellent thermal insulation performance in low-temperature (-60 °C) or high-temperature (140 °C) environments. The designed HSCAFs may provide a new approach for the preparation of high-performance aerogel fibers for personal thermal management.

Comprehensive Analysis of Mechanical, Economic, and Environmental Characteristics of Hybrid PE/PP Fiber-Reinforced Engineered Geopolymer Composites

Engineered Geopolymer Composites (EGCs), known for their excellent tensile properties and lower carbon emissions, have gained widespread attention in the field of fiber-reinforced concrete. However, the high cost of high-performance synthetic fibers, a crucial component of EGCs, limits their practical engineering applications. In this study, by using low-cost PP fibers hybridized with PE fibers and adjusting the fly ash/ground granulated blast furnace slag (FA/GGBS) ratio, cost-effective, high-performing hybrid PE/PP-reinforced engineered geopolymer composites (H-EGCs) were developed. This study conducted axial compressive and tensile tests on H-EGCs with different FA/GGBS ratios (7:3, 6:4, and 5:5) and PP fiber replacement ratios (0%, 25%, 50%, 75%, and 100%), investigated the influence of FA/GGBS and PP fiber replacement ratio on static mechanical behavior, and evaluated the economic and environmental benefits based on mechanical performance indicators. The result indicated that the compressive strength of H-EGCs can reach 120 MPa when the FA/GGBS ratio is 5:5; however, an increase in FA/GGBS and PP fiber replacement ratio leads to a loss in compressive strength and elastic modulus. The incorporation of PP fibers in moderate amounts enhances ultimate tensile strain by reducing crack control ability, and the maximum tensile deformation capacity (7.82–9.66%) was obtained for H-EGCs with a PP fiber replacement ratio of 50%. The optimal economic and environmental benefits of H-EGCs are observed when the FA/GGBS ratio is 5:5 and the PP fiber replacement ratio is set at 50%.

Mechanical Behaviour of As-Manufactured and Repaired Aligned Discontinuous Basalt Fibre-Reinforced Vitrimer Composites.

The aim of this research is to investigate basalt as a natural mineral-based fibre together with a vitrimeric resin as a sustainable alternative to standard composite materials. Vitrimers combine the properties of thermoset and thermoplastic polymers, enabling the repair of specimens and hence prolonging the lifetime of the composite material. The micro-mechanical characteristics between the basalt fibres and the vitrimer resin are reported and shown to match those of a standard Skyflex K51 epoxy resin. Discontinuous (4 mm) basalt fibres were employed to produce aligned discontinuous fibre-reinforced composites (ADFRCs) using the high-performance discontinuous fibre (HiPerDiF) technology. The mechanical characteristics of the laminates were investigated through tensile testing and the fracture zones were analysed under a scanning electron microscope. By normalising the results by their respective fibre volume fraction, it was discovered that the vitrimer-basalt ADFRCs exhibited, on average, a 4% higher strength and a 25% higher stiffness compared to their basalt epoxy counterparts. The repair potential of the vitrimer ADFRC specimens was explored during low-temperature compression repair. Two approaches were tested using double-sided local- and full-patch repair. Both successfully recovered a significant amount of their prime strength. In conclusion, the potential of the sustainable vitrimer-basalt composite is shown by its competitive mechanical performance. Combining this with the manufacturing flexibility, repair potential, and recyclability of the material, the vitrimer-basalt composite seems to be a competitive alternative to standard glass epoxies.

A multiscale experimental study of CFRP-UHPFRC interfacial bond behaviour: Failure mechanisms and a fibre volume dependent bond-slip law

Carbon fiber reinforced polymer (CFRP) materials are being increasingly used with ultra high performance fiber reinforced concrete (UHPFRC) to construct composite structural members making use of their unique properties. As the interfacial bond behaviour between CFRP and UHPFRC plays a key role in the design of such members, it was investigated in detail by multiscale experiments of single shear pull-off tests of 26 CFRP-UHPFRC bonded joints with different bond lengths and widths of CFRP laminates and 0.5–4% volume fraction (Vsf) of straight high-strength steel fibers (length = 13 mm, diameter = 0.2 mm). 12 CFRP-normal strength concrete (NSC) bonded joints were also tested for comparison. The surface strain evolution and the interfacial debonding process were captured and analysed by the digital image correlation (DIC). The complex microscale failure mechanisms, such as the mortar cracking, the CFRP-UHPFRC interfacial debonding, and the steel fibers’ slipping and pulling out of the mortar, were visualised and analysed by the 3D micro X-ray Computed Tomography (μXCT) scanning. It was found that the debonded layer of mortar under the laminates was much thinner than that in the CFRP-NSC bonded joints, due to the lack of coarse aggregates in UHPFRC. The peak pulling forces for the specimens with Vsf = 0.5%, 1%, 2%, and 4% were 9%, 21%, 28%, and 29% higher than those without steel fibers, respectively. An empirical bond strength model and an interfacial bond-slip model were proposed based on the test results, accounting for Vsf, the material properties, and the laminate to UHPFRC width ratio. Finally, the proposed bond-slip model was applied in finite element modelling to simulate the flexural behaviour of an FRP-UHPFRC composite deck in the literature, with the interfacial debonding failure and the ultimate loads successfully predicted.

Improved Plating Adhesion of Polyarylate Fibers via Supercritical CO2 and Impregnation of Slightly Soluble Oil on the Fiber Surface

There is a growing demand for conductive fibers with high bending resistance, particularly for applications, such as smart textiles and robot arms. The amount of fiber for such applications can be reduced using high-performance fibers with high tensile properties, such as polyaramid and polyarylate Vectran®). However, because such fibers are crystalline with rigid molecular structures, they poorly adhere to plated films; thus, the plated fibers exhibit poor bending fatigue resistance. To solve this problem, in this study, we expanded polyarylate fiber using supercritical CO2 (ScCO2) and impregnated it with a metal complex (palladium acetate), which acts as a catalyst for electroless plating to induce an anchoring effect. However, because polyarylate fiber has an extremely low polarity, it is difficult to uniformly impregnate it with many metal complexes, even with ScCO2. Generally, an organic solvent is added to tune the polarity of supercritical CO2; however, the metal complex penetrates the fiber, thereby reducing the amount of metal complex near the fiber surface. Therefore, we tuned the polarity of the surface by applying various oils to the fiber surface. The sample electroplated in ScCO2 with oil applied to its surface showed the highest bending fatigue resistance, followed by that treated in ScCO2 without oil, and the sample treated in an aqueous solution showed the lowest. Furthermore, we measured the interfacial adhesion strength of the samples using the microdroplet method, and the same trend was observed.

Kinetic Modulation of Carbon Nanotube Growth in Direct Spinning for High-Strength Carbon Nanotube Fibers.

With impressive individual properties, carbon nanotubes (CNTs) show great potential in constructing high-performance fibers. However, the tensile strength of as-prepared carbon nanotube fibers (CNTFs) by floating catalyst chemical vapor deposition (FCCVD) is plagued by the weak intertube interaction between the essential CNTs. Here, we developed a chlorine (Cl)/water (H2O)-assisted length furtherance FCCVD (CALF-FCCVD) method to modulate the intertube interaction of CNTs and enhance the mechanical strength of macroscopic fibers. The CNTs acquired by the CALF-FCCVD method show an improvement of 731% in length compared to that by the conventional iron-based FCCVD system. Moreover, CNTFs prepared by CALF-FCCVD spinning exhibit a high tensile strength of 5.27 ± 0.27 GPa (4.62 ± 0.24 N/tex) and reach up to 5.61 GPa (4.92 N/tex), which outperforms most previously reported results. Experimental measurements and density functional theory calculations show that Cl and H2O play a crucial role in the furtherance of CNT growth. Cl released from the decomposition of methylene dichloride greatly accelerates the growth of the CNTs; H2O can remove amorphous carbon on the floating catalysts to extend their lifetime, which further modulates the growth kinetics and improves the purity of the as-prepared fibers. Our design of the CALF-FCCVD platform offers a powerful way to tune CNT growth kinetics in direct spinning toward high-strength CNTFs.

Effect of Bonding Type on the Failure of Reinforced Concrete Beam Strengthened with In-Situ High Performance Fibre Reinforced Concrete Layer

High performance fibre reinforced concrete (HPFRC) materials with tensile hardening behaviour can effectively be used for strengthening reinforced concrete beams. A perfect bond between the original and the reinforcing layer cannot be formed, the load-bearing capacity and ductility of the strengthened beam can significantly be affected by the interfacial bond strength between the contacting surfaces. In this paper, beam retrofitting with cast in-situ strengthening type is examined. The purpose of this experimental study is to investigate the impact of the different bond types on the load-bearing capacity, ductility, and failure mode of the strengthened beams in the case of cast in-situ strengthening. Twenty-four beam tests were performed with untreated and rough surfaced beams, with or without connecting elements. The effect of the bond type proved to be significant regarding the failure mode in the case of compression side strengthening, stronger bond resulted in higher load bearing capacity and ductility, too. When tensile side reinforcement was investigated no average increment was experienced in the maximal force and ductility due to the stronger bond. Based on the results, it can be concluded that the generally applied analytical models that assume perfect connection may lead to exaggerated results in the case of a compressed side HPC-strengthened beam. Therefore, it is necessary to develop a model that considers the effect of the imperfect bond.