Twisted Fiber Research Articles

Mechanical characterization and performance evaluation of twisted Jute-Kevlar hybrid composites with varied fiber orientations

Abstract Composite materials play a vital role in developing new materials in engineering and technology. Composites show how the properties of the matrix and reinforcement work together to create more robust, more rigid materials than would be possible from the individual components working alone. They consist of two or more component materials combined with notably dissimilar physical or chemical characteristics. Two categories of composite coupons have been developed in this research work: the first category (C1) is made up of jute twisted-Kevlar twisted jute fiber (0/90 degree), and the second category (C2) is made up of jute twisted-Kevlar twisted jute fiber (0/45 degree). The nano-silica is reinforced with the matrix with a weight percentage of 0%,5%,10% and 15%. The necessary interfacial adhesion and bonding between fiber layers have been accomplished using a 10:1 mixture of epoxy resin (LY556) and hardener (HY951). According to ASTM guidelines, the tensile, flexural, impact, double shear, wear, and hardness tests were carried out. This study uses two natural and synthetic fibers—twisted Jute and Kevlar fibers—as reinforcement. The Jute fibers have a high strength since they are high in cellulose. Efforts have been made to create a composite material with completely different twisted fiber orientations and to assess the mechanical properties of the composites. This involved various mechanical tests, analysis of wear surfaces, as well as DMA, DSC, FEA testing, and ultimately, the machining of the composites studied. The machining parameters used in waterjet machining have been carefully analyzed.

Elastocaloric Heat Pump by Twist Induced Periodical Non-Linear Stress for Low Hysteresis and High Carnot Efficiency.

Elastocaloric cooling is one of the most promising solid-state cooling approaches to address the issues of energy shortage and global warming. However, the cooling efficiency and cycle life of this technology need to be improved, and the required driving force shall be reduced. Here, a novel elastocaloric heat pump by periodic non-linear stress is developed by employing fiber twisting and separated cooling and heating media. The non-linear stress generated by fiber twisting yields a hierarchical, rigid-yet-flexible architecture and a periodic entropy spatial distribution, which result in a low mechanical hysteresis work and a high cooling efficiency (a maximum material coefficient of performance (COP) of 30.8 and a maximum Carnot efficiency of 82%). The torsional non-linear stress inhibits crack propagation and results in a highly extended cycle life (14752 cycles, more than ten times of fiber stretching). The heat pump exhibits a maximum average temperature span of 25.6 K, a maximum specific cooling power of 1850W Kg-1, a maximum device COP of 19.5, and a maximum device power of 5.0W, under each optimal condition.

In-situ twisting of carbon nanotube fiber synthesized by floating catalyst chemical vapour deposition

The carbon nanotube fiber (CNT fiber) represents a remarkable advancement in harnessing nano-level properties akin to those of individual CNTs in macrostructure. The most essential step in achieving this is to densify the CNTs within the fiber. Among various densification techniques, twisting has emerged as one of the prominent methods due to its continuous nature. In this study, we conducted in-situ continuous twisting of CNT fibers synthesized by floating catalyst chemical vapour deposition alongside ex-situ twisting experiments for comparative analysis. Through focused ion beam analysis, we probed the effect of twisting on the densification of CNT fibers, revealing pore elimination and complete fiber densification as outcomes. Intriguingly, in-situ twisting yielded higher density compared to ex-situ twisting despite identical twist levels maintained in both methods. We unraveled the mechanism behind this superior density achieved through in-situ densification. Furthermore, in-situ twisted fibers exhibited superior tensile strength and electrical conductivity when compared to their ex-situ twisted fiber. The in-situ twisting process demonstrated remarkable enhancements, with electrical conductivity increasing by up to 254 % and tensile strength by 125 % compared to untwisted fibers.

Development of a novel characterization model for innovative bionic helical carbon fiber tows

The design of bionic helical structures significantly enhances load-bearing capacity and impact resistance, demonstrating great potential for mechanical property improvement. However, there is still a lack of precise characterization models for the helical structures of carbon fibers, which constrains their potential in engineering applications. This paper successfully fabricated helical carbon fiber tows using a carbon fiber twisting technique and introduced a novel intersecting circular cross-section model to thoroughly investigate the influence of the helical structure on the mechanical properties of carbon fiber tows. Tensile test results show that at a twist angle of 5°, the helical structure increases the tensile strength and fracture toughness of carbon fiber tows by 13.6% and 34.3%, respectively. Additionally, the introduction of complex structures such as helices significantly influences the material’s modulus, and precise modulus prediction is crucial for material optimization and practical application. Based on the newly proposed model, a modulus prediction model is developed, demonstrating higher predictive accuracy than traditional models with a prediction error of 2.8%. Finite element simulations further validate the practicality and superiority of the intersecting circular cross-section model. Compared to traditional models, the predictions of the novel model are closer to experimental data, with a prediction error below 2%, emphasizing the significant impact of microstructures on macroscopic properties and offering a new perspective for modeling complex material systems. These findings provide crucial theoretical and methodological support for the design and performance optimization of carbon fiber materials.

Bond performance and constitutive model of steel bar in G-UHPC under cyclic loading

The increasing embrace of the low-carbon and environmentally sustainable construction approach has opened exciting opportunities for using environmentally friendly geopolymer based ultra-high-performance concrete (G-UHPC) in engineering structures, drawing significant attention to its performance. Seismic performance is a crucial factor in structural design, and it is greatly affected by the bond behavior between steel bar and concrete. As a result, a thorough understanding of the bond behavior of steel bars to G-UHPC provides essentially theoretical support for the structural design and nonlinear finite element analysis of G-UHPC structures, which is vital for their widespread implementation in earthquake engineering. This study tested 54 specimens from 18 groups to examine the bond performance of G-UHPC and steel bars under cyclic loading. The influence of concrete and steel bar types, protective layer thickness, bond length, and steel fiber on critical bond performance indicators were evaluated, and the bond stress-slip hysteretic and skeleton curves were analyzed. Subsequently, based on the experimental data, a constitutive model was proposed to predict the bond stress-slip relationship of steel bars and G-UHPC under cyclic loading. The results indicated that the steel bars exhibited superior bond performance with G-UHPC as compared to NSC. The bond and residual strength between steel rebars and G-UHPC was approximately 1.73 times and 3 times greater, respectively, in comparison with that between NSC and steel rebars. Increasing the strength of steel bars only resulted in a limited 2 % improvement in bond strength. The steel bar diameter, protective layer thickness, bond length, and the dosage and length of steel fibers in G-UHPC significantly influenced the bond performance. The addition of irregular-shaped steel fibers to G-UHPC has demonstrated potential in improving energy consumption, with the most remarkable enhancement observed for the inclusion of twisted steel fibers. Specifically, the incorporation of twisted steel fibers signally enhanced the energy consumption to approximately 1.3 times the energy dissipation as compared to straight steel fibers with the same dosage and aspect ratio. In addition, the accuracy of the proposed constitutive model has been validated.

Unveiling the microstructural evolution and interaction mechanisms for twisted structures

Twisting plays an important role in fabricating twisted actuators and energy harvesters, which require excellent microstructural deformation and interaction properties between different layers. However, the cross-layer microstructural evolution and interaction mechanism of helical structures under twisting and stretching are still unclear. Herein, a multi-layer model is established to theoretically investigate the response of the filaments under twisting and stretching. The results quantitatively indicate that the filaments with a higher twist have more structural evolution and less elongation deformation in the tensile process, which contributes to the increase of ductility. The evolution of the helical angle is also verified by in-situ experiments and finite element simulations. Besides, a theoretical method is provided for investigating the mechanical behavior of anisotropic twisted fibers, and the contact pressure is also promoted to understand the twisting-induced densification. The interlayer extrusion reveals that appropriate stretching of twisted fiber is an effective way to densify the loose fibers, and it also provides the theoretical reason for twisting and stretching simultaneously when wringing out a wet towel. We believe that this work would shed light on the interaction mechanism of twisted filaments and provide mechanistic insights into the twisting design of multi-layer helical structures.

Properties of Multistranded Twisted Graphene Fibers and Their Application in Flexible Light-Emitting Devices.

As a typical carbon-based material electrode, graphene fiber exhibits many advantages, such as good electrical conductivity, lightweight, and strong structural designability. Its demand is increasing in the wearable display field. With the help of fine denier fiber spinning combined with multistranded graphene fibers prepared via twisting and drafting, their petal-like twisted structure endows the fibers with a high specific surface area, enabling them to complete dye adsorption within 30 min. Simultaneously, compared with that of a single fiber with the same thickness, the volume specific resistance of a multistranded twisted graphene fiber is reduced by 2.4 times. During force sensing, the twisted structure of multistranded fibers exhibits varying simultaneity of fiber fracture with excellent resistance sensitivity reaching up to 55%. The multistranded twisted flexible graphene fibers demonstrate excellent robustness. Electroluminescent flexible devices prepared with graphene fibers and fiber braided fabrics with different organizational structures as electrodes emit highly saturated short-wave blue light during long-term multiple use. Therefore, multistranded twisted graphene fibers exhibit considerable potential for future applications in wearable multicolor smart displays and flexible optical signal electronics.

Twist sensor based on fiber Bragg grating fiber laser frequency splitting effect

AbstractA twist sensor based on the frequency splitting effect of fiber Bragg grating laser is proposed and experimentally demonstrated. Laser longitudinal mode was split into two frequencies under the action of birefringence induced by fiber twist and by monitoring the periodical beat frequency response, the twist angle could be deduced. The experimental results show that the relationship between the fiber twist angle and the beat frequency is linear (linearity is more than 99%) when the twist angle is in the range of 10°–55°. Moreover, the wavelength drift caused by the temperature does not affect this linearity. Since the sensor is based on frequency rather than on the wavelength, its sensitivity is not limited to the resolution of the spectrometer, and has been improved to 31.59 MHz/rad (0.55 M/degree).

Effects of amount and geometrical properties of steel fiber on shear behavior of high-strength concrete beams without shear reinforcement

This study aims to investigate the effects of the geometrical properties and volume content of steel fibers on the shear resistance of reinforced high-strength concrete (HSC) beams without stirrups. Hooked-end and twisted steel fibers with different aspect ratios ranging from 60 to 100 were used at volume fractions of 0.5%–1.0%. The shear strength of HSC beams without stirrups significantly increased due to the addition of steel fibers and by increasing their volume fraction by up to 1.0%, resulting in approximately 1.7 times higher shear resistance. A higher fiber aspect ratio was effective in improving the resistance to shear failure of HSC beams without stirrups and in enhancing beam deformability relative to the increase in shear strength. Using twisted steel fibers led to better shear resistance than hooked-end steel fibers, resulting in 1.11- and 3.34-times higher shear strength and ductility at the same fiber volume fraction on average. The shear strength of steel fiber-reinforced concrete (SFRC) beams was also predicted using eight different models. Narayanan's model most precisely predicted the shear strengths of reinforced SFRC beams without shear reinforcement, with an average vu,exp/vu,pred ratio of 1.16. The shear strength increased with the decrease in shear span-to-depth (a/d) ratio and the increase in the fiber factor. The contribution of steel fibers to shear strength was greater for deep beams than slender beams. The predicted shear strengths of deep beams and high-strength SFRC showed a significant deviation from the actual value and required careful consideration.

Fluorescent modification and performance study of carbon quantum dots on twisted bamboo fiber bundles

ABSTRACT In recent years, carbon quantum dots (CQDs) have been employed in the functionalization research of fiber-based materials due to their distinctive physicochemical properties. We used citric acid and urea as precursors and combined with hydrothermal method to prepare green and non-toxic carbon quantum dots (NCQDs), which were loaded into four-color twisted bamboo fiber bundles and possessed photoluminescence effect by simple impregnation method. Based on the verification of the structure and fluorescence properties of NCQDs, the fluorescent twisted bamboo fiber tows were comparatively analyzed for their chemical composition, microscopic morphology, mechanical properties, color difference, and thermal stability. The results showed that the four groups of fluorescent twisted bamboo fiber tows emitted uniform and bright blue fluorescent effects under UV light irradiation, and increased the tensile strength by 19.77% ~ 39.27% and the sexual modulus by 66.11% ~ 88.78% compared with the original twisted bamboo fiber tows. The impregnated carbon quantum dot solution enhances the functionality of the fiber bundle while enriching the color expression. It is expected to be a potential application material in the fields of smart marking, fluorescent anti-counterfeiting, interior decoration, and home textile industry.

Development of a dual point humidity sensor using POF based on twisted fiber structure

The humidity has often been measured through a single point sensor. Where, the humidity could be varied at different locations as well as depending on environmental conditions. The present paper developed the dual point humidity measuring sensor by using a polymer optical fiber (POF) based on a single illuminating fiber. The sensor’s basic structure is to twist two fibers and bend them at a certain radius. However, the dual point sensor is developed through the cascading of twisted micro bend (TMB-1 and TMB-2). The twisting of fibers couples the light from one fiber to another fiber through the side coupling method. An increase in the humidity level leads to a change in the reflective index, which helps to get variation in coupled light intensity. To measure the humidity, the dual point sensors are placed into the control humidity chamber at two random positions. The power reading variation is significantly linear when the humidity level increases from 30 to 80%. The sensor has a fast response of about 1 s and a recovery time of about 4 s. Furthermore, the chemical coating is applied to improve the sensor’s sensitivity. Between 30 and 80% range of humidity, the both sensors of dual point TMB-1 and TMB-2 have appropriate sensitivity and detection limits, which is about 680.8 nW/% and 763.9 nW/% and 1.37% and 1.98%, respectively. To measure the humidity at variable positions, the present dual points humidity sensor is well-stable, easy, and straightforward, which uses a less expensive method.

The characteristics of vortex modes in twisted fiber with dielectrically chiral ring core

A novel twisted ring core fiber incorporating chiral material into the ring core is proposed, which supports orbital angular momentum (OAM) modes. Results show that between chirality and twist rate there exist a cooperative effect in birefringence and a competitive effect in mode index bifurcation between OAM modes with different helicity. The cooperative effect between chirality and twist rate also breaks the degeneracy within OAM modes of the same or opposite helicity while preserving the vectorial nature of the modes. The OAM modes generated by twisted dielectrically chiral fiber are less likely to have crosstalk. The dependences of OAM modes birefringence on chirality and twist rate are investigated. Additionally, the mode effective index bifurcation as a function of wavelength is also discussed under both kind of chirality. Owing to high birefringence, good refractive index bifurcation, we believe that this kind of fiber can find applications in new kind of OAM mode generators, OAM mode filters, optical communication, and sensing.

Sonographic observation of the paradoxical masseteric bulging and clinical implication of functional compartment.

Masseter are commonly botulinum neurotoxin targeted muscle for facial contouring in aesthetic field. However, paradoxical masseteric bulging is common adverse effect that has not been discussed with ultrasonographic observations. Retrospective study has been conducted from October, 2021 to January, 2023, out of 324 patients have done blinded botulinum neurotoxin injection in the masseter at the middle and lower portion of the masseter with each side of 25 units (letibotulinum neurotoxin type A), 3 patients demonstrated paradoxical masseteric bulging has been reported and the image observed by ultrasonography by physician. Based on the observations made, we can infer that the function of the moving muscle involves twisting of the muscle fibers during contraction, along with the twisting of the deep inferior tendon, which causes the muscle to be divided into anterior and posterior compartments rather than into superficial and deep compartments of masseter. In ultrasonographic observe the skin surface of a patient with paradoxical masseteric bulging, it is observable that either the anterior or posterior part contracts significantly. The functional units of anterior and posterior compartment are observable as muscular contraction of inward movement of the muscle from either the anterior or posterior functional unit.

Dispersion of optical vortices in twisted elliptical-core optical fibers with torsional stresses

In this paper, the dispersion of optical vortices (OVs) with a topological charge l >= 1 in twisted elliptical fibers (TEF) with torsional stresses (TS) is studied. Analytical expressions for polarization, topological, and hybrid dispersion are derived from the spectra of vortex modes in step- and gradient-index TEFs with TS. It is shown that in strongly twisted fibers with a gradient refractive index profile, new types of dispersion appear in comparison with the case of a step-index profile. The dependence of the dispersion of OVs on the material and geometrical parameters of the fiber is studied numerically. It is established that in step-index TEFs with TS, there is a spectral region near which all types of dispersion for OVs with l >= 1 take a near zero value. It is also demonstrated that for TEFs with a gradient profile, this regime is realized for strongly twisted strongly elliptical fibers.

Twisted fiber microfluidics: a cutting-edge approach to 3D spiral devices.

The development of 3D spiral microfluidics has opened new avenues for leveraging inertial focusing to analyze small fluid volumes, thereby advancing research across chemical, physical, and biological disciplines. While traditional straight microchannels rely solely on inertial lift forces, the novel spiral geometry generates Dean drag forces, eliminating the necessity for external fields in fluid manipulation. Nevertheless, fabricating 3D spiral microfluidics remains a labor-intensive and costly endeavor, hindering its widespread adoption. Moreover, conventional lithographic methods primarily yield 2D planar devices, thereby limiting the selection of materials and geometrical configurations. To address these challenges, this work introduces a streamlined fabrication method for 3D spiral microfluidic devices, employing rotational force within a miniaturized thermal drawing process, termed as mini-rTDP. This innovation allows for rapid prototyping of twisted fiber-based microfluidics featuring versatility in material selection and heightened geometric intricacy. To validate the performance of these devices, we combined computational modeling with microtomographic particle image velocimetry (μTPIV) to comprehensively characterize the 3D flow dynamics. Our results corroborate the presence of a steady secondary flow, underscoring the effectiveness of our approach. Our 3D spiral microfluidics platform paves the way for exploring intricate microflow dynamics, with promising applications in areas such as drug delivery, diagnostics, and lab-on-a-chip systems.

Mechanical properties of twisted galvanized iron fiber reinforced concrete with different contents and pitches

Utilizing galvanized iron (GI) instead of expensive steel fiber has become a new technique in concrete construction to improve the mechanical properties of concrete. Tensile strength tests confirm that twisted GI fibers could serve as a viable alternative to steel fibers. Using deformed fiber instead of straight fiber increases the strength parameters of concrete significantly. As such, twisted GI fibers were employed in this study to improve the quality of the concrete. The GI fibers were mechanically twisted with varying twisting pitches (4, 6, and 8 turns per inch) to create rope-like fibers. Thirteen different concrete mixtures were prepared using three different fiber contents (1.0%, 1.5%, and 2.0% by weight), maintaining a constant 25.4 mm fiber length. Compressive strength, split tensile strength, flexural strength, toughness indices, and residual strength of GI fiber reinforced concrete (GIFRC) were determined. Employing GI fibers increased the compressive strength to a range from 13.4% to 28.9%, the split tensile strength from 18.8% to 42.5%, and the flexural strength from 11.5% to 46.0% compared to the control specimen. Besides, twisted GI fiber increased compressive strength from 1% to 7%, split tensile strength from 2% to 11%, and flexural strength from 3% to 13% than those of plain GIFRC. Toughness indices and residual strengths were significantly higher for GIFRC beams compared to the control specimen, which indicated greater energy absorption capacity of GIFRC. Additionally, strength prediction models were established to estimate different strength parameters with varying twisting pitch of GIFRC. Experimental results resembled the proposed strength models. Therefore, using twisted GI fibers in concrete can be an excellent choice to improve the mechanical properties of concrete.

Pseudo-ductile behaviour of fibrous composite Z-pins

This paper describes the development and characterisation of a novel type of composite Z-pin able to accommodate large deformation without exhibiting fibre failure. Three types of pseudo-ductile Z-pins are fabricated by means of micro-pultrusion of polybenzoxazole (PBO) fibres. Namely, unidirectional PBO fibre (uPBO) Z-pins in combination with a ductile (uPBO/DCT) and a brittle (uPBO/BT) matrix system are developed, together with a twisted PBO fibre Z-pin in combination with a ductile matrix (tPBO/DCT). Single pin bridging tests are carried out across the full mode mixity range from mode I (Φ = 0) to mode II (Φ = 1). The tests reveal that uPBO-based pins are able to pull out throughout the full mode mixity range, regardless of the ductility of the pin matrix. uPBO/DCT pins exhibit a 20-fold increase in energy dissipation per pin than traditional carbon fibre/bismaleimide (CF/BMI) pins at load mode mixities higher than Φ = 0.9. The mode I behaviour of all pins considered is comparable. All PBO pins exhibit an apparent delamination toughness enhancement superior to CF/BMI at mode mixities above Φ = 0.2, with a ductile matrix increasing the average energy dissipated per pin by a further 2–8 %.

Test results of a universal woody green separator

The paper presents the test results of the universal woody green separator “Sibirika 21”, which uses a replaceable knife and brush type drum as a working element. The separator was tested at an active clearcutting area of mature and overmature stands at the following coordinates: By. region, Krapivinsky district, Krapivinsky forestry, Ivanovskoye tract, block No. 16, section No. 17. During testing, it was found that for deciduous trees it is preferable to use a brush drum. In this case, for example, for birch, it was possible to obtain woody greens with 100% purity. As a brush material, it is preferable to use twisted nylon fibers with a square cross-section and a side of 3 mm. When harvesting coniferous foot, the best productivity (up to 600 kg person/hour) and cleanliness (82%) is ensured when using a knife drum.

Controllable Circularly Polarized Vortex Beam in a Twisted Few-Mode Polarization-Maintaining Fiber

Controllable Circularly Polarized Vortex Beam in a Twisted Few-Mode Polarization-Maintaining Fiber

Assessment of Mechanically Induced Changes in Helical Fiber Microstructure Using Diffusion Tensor Imaging.

Noninvasive methods to detect microstructural changes in collagen-based fibrous tissues are necessary to differentiate healthy from damaged tissues in vivo but are sparse. Diffusion Tensor Imaging (DTI) is a noninvasive imaging technique used to quantitatively infer tissue microstructure with previous work primarily focused in neuroimaging applications. Yet, it is still unclear how DTI metrics relate to fiber microstructure and function in musculoskeletal tissues such as ligament and tendon, in part because of the high heterogeneity inherent to such tissues. To address this limitation, we assessed the ability of DTI to detect microstructural changes caused by mechanical loading in tissue-mimicking helical fiber constructs of known structure. Using high-resolution optical and micro-computed tomography imaging, we found that static and fatigue loading resulted in decreased sample diameter and a re-alignment of the macro-scale fiber twist angle similar with the direction of loading. However, DTI and micro-computed tomography measurements suggest microstructural differences in the effect of static versus fatigue loading that were not apparent at the bulk level. Specifically, static load resulted in an increase in diffusion anisotropy and a decrease in radial diffusivity suggesting radially uniform fiber compaction. In contrast, fatigue loads resulted in increased diffusivity in all directions and a change in the alignment of the principal diffusion direction away from the constructs' main axis suggesting fiber compaction and microstructural disruptions in fiber architecture. These results provide quantitative evidence of the ability of DTI to detect mechanically induced changes in tissue microstructure that are not apparent at the bulk level, thus confirming its potential as a noninvasive measure of microstructure in helically architected collagen-based tissues, such as ligaments and tendons.