Fiber Geometry Research Articles

The impact of thermal treatment parameters on the preservation of carbon fiber mechanical properties after reclamation

Carbon fiber, despite its exceptional properties, remains underutilized due to monetary and environmental concerns. Concurrently, the imminent challenge associated with rising quantities of End-of-Life CFRP (carbon fiber reinforced polymer) demands the further development of recycling strategies. This study focuses on optimizing the recycling process parameters of pyrolysis and oxidation thermal treatment to maximize the retention of mechanical properties in the recycled fibers in the shortest process time. To assess the result of the pyrolysis, single fiber tensile tests were executed to measure strength and stiffness. Additionally, microscopy and spectroscopy studies were carried out to evaluate fiber geometry as well as surface quality. At the laboratory scale, experiments demonstrated that the combination of pyrolysis and oxidation yields clean, reusable fibers with mechanical properties suitable for secondary applications. The influence of various treatment parameters on the strength and stiffness of the recycled fibers was explored, establishing a clear correlation. The outcome is a set of optimized parameters that contribute to mechanical property retention, including a novel recycling method that allows for reduced processing times, as short as 10 min. This work paves the way for a more eco-friendly and cost-effective approach to harnessing the potential of carbon fiber in a wide range of applications while mitigating environmental concerns associated with landfill disposal.

Predictable Local Polarization inside Electrodes By Three-Dimensional Multi-Scale Model in Flow Batteries

Redox flow batteries (RFBs) are regarded as one of the most promising grid-scale energy storage technologies, which can improve the applicability of wind and solar energy by leveling their fluctuating power output. In RFBs, the gas side reactions including hydrogen evolution reaction and oxygen evolution reaction reduce the efficiency and capacity of the batteries and the gas produced may even cause safety problems. Even if the voltage is controlled in practical applications to restrict the gas side reactions, it is still inevitable due to flow dead zones or insufficient reactants locally inside the electrode. Gas side reactions are usually caused by too high local overpotential, i.e., local over polarization. Therefore, in this work, we propose a multi-scale model that allows the rapid prediction of local polarization to limit and manage the gas side reactions. The multi-scale model contains a deep neural network, a pore network model, and a three-dimensional continuum model with the advantages of both accuracy and extensibility. By learning from the sample data provided by the cell-scale model and the pore-scale model, the deep neural network can quickly predict the local polarization under different operating conditions and give the distribution map of the entire electrode. Compared with conventional models, multi-scale models can take into account the geometry of electrode fibers and are suitable for electrode design and modification. Due to the calculation superiority of the pore network model, the multi-scale model can realize three-dimensional local polarization prediction, which enables a more accurate analysis of the internal uniformity of the electrode. Through the developed model, we explore the effects of the interdigitated flow field, flow rate, initial concentration and voltage on local polarization. It is shown that the multi-scale model can accurately predict local polarization. However, the promotion of flow rate cannot completely eliminate the occurrence of local over polarization.

Influence of fibre curvature and orientation on the mechanical properties of injected irregular short hemp fibres reinforced polypropylene

This paper presents a numerical study of the influence of geometry and orientation of fibres on the mechanical behaviour of a hemp fibre reinforced polypropylene, obtained with injection. Tensile tests and multiplexing mode Dynamic Mechanical Analysis (DMA) were carried out in order to determine the mechanical behaviour of the neat and reinforced material. A numerical homogenization was then performed with the elastic hemp fibres for aligned and random orientation as well as a reconstructed microstructure obtained with injection simulation to correlate with tensile tests. The simulations were performed for sphero-cylinder and curved fibres and the results were compared to FFT results obtained directly on micro-tomography images as well as experimental data. The results showed that the complex geometry of the fibres can be approximated with a random 3D orientation of sphero-cylinder shaped fibres, a reasonable hypothesis leading to a simplification of the problem and an easier process of design of parts made with such materials.

Microstructure generation algorithm and micromechanics of curved fiber composites with random waviness

During multiscale modeling and analysis of composite materials, accurately capturing the distinctive microstructural features of the material is essential. This is achieved by generating a representative volume element (RVE). Fiber reinforcements in composites can exhibit various shapes, including straight, slightly wavy, or complex shapes, depending on the inherent properties or the manufacturing process. Fibers are characterized based on their tortuosity, spread, and orientation distribution. It is crucial to account for these geometrical attributes during the microstructure generation and subsequent micromechanics modelling as they significantly influence the effective properties of the composite. The present work describes a novel algorithm capable of modeling a broad range of 3D periodic microstructures with fibers having random waviness. The effects of various parameters in the algorithm are studied to understand their influence on fiber shapes. This is followed by finite element analysis of the generated RVEs using the embedded element technique to quantify the microstructure- mechanical properties relationships. Finally, guidelines on the usage of the proposed model to generate fibers with desired microstructure is elucidated. A comprehensive framework for modeling and analyzing microstructures with complex fiber geometry is outlined.

Effect of Droplet-Laden Fibers on Aerodynamics of Fog Collection on Vertical Fiber Arrays.

Growing population, along with rapid urbanization, has led to severe water scarcity, necessitating development of novel techniques to mitigate this looming problem. Fog contains water in the form of liquid droplets suspended in air, which can be collected on a porous structure placed in the path of the fog flow. We first develop an artificial fog-generating system using the thermodynamic principle of mixing of air streams followed by condensation, which closely mimics the liquid water content and droplet size distribution of natural fog. We then investigate how collected fog droplets growing on fiber surfaces alter the aerodynamics of fog flow across vertical fiber arrays, called harps, thus affecting their fog collection efficiency. As deposited droplets grow on the fiber surface, they increase the area occluded by droplet-laden fibers, thus increasing the effective shade coefficient (SCact), which increases with time from its initial geometric value (SCgeo), eventually reaching a quasi-steady state, as droplet shedding due to gravity and droplet growth due to fog collection balance each other. We find that this difference in the SCgeo and SCact is governed by local fiber geometry and its physico-chemical morphology; the process dynamics is captured by a nondimensional number, SC*, which increases with the length scale corresponding to the critical volume of droplet shedding relative to the fiber diameter, V*. Thus, there is a significantly greater increase in the effective shade coefficient for thin fibers having larger values of V* as compared to fibers with larger diameters which have lower V* values. On hydrophobic fibers, the quasi-steady state is achieved faster, and the time-averaged SCact is lower as compared to hydrophilic fibers due to the lower critical volume of droplet shedding. The shape of droplets growing on harp fibers affects the aerodynamics of fog flow, its inertial capture mechanism, and efficiency, which can guide design considerations for fog harps toward achieving optimal fog collection performance.

Polyacrylonitrile and polyethersulfone based co-axial electrospun nanofibers for fluoride removal from contaminated stream

Coaxial electrospun polyacrylonitrile (PAN) and polyethersulfone (PES) based nanofibers were prepared and was used for filtration of fluoride from drinking water for the first time. Well defined fiber geometry was obtained at 1 ml/h of core polymer, i.e., PES flow rate, 1.4 ml/h of shell polymer, i.e., PAN flow rate, voltage of 22 kV, while the distance between the needle tip and the collector was 15–17 cm. Increase in bead like structure in fiber strands was observed with higher PAN concentration, while it decreased for lower PES concentration, thereby giving an optimum composition (6 wt% PAN and 10 wt% PES) for uniform fiber morphology. This nanofiber, abbreviated as N2 acted as an ultrafiltration membrane having permeability in the lower range, i.e., 0.5 × 10−11 m/s Pa and its fluoride removal efficacy was 46%. Fibers were also hydrophilic with considerable porous nature. Uptake of fluoride by this N2 nanofibers were evident from binding energy of 685.2 eV during XPS analysis. It is probable that nitrile and sulfone groups present in the core and shell of the nanofibers played an active in fluoride uptake, which was estimated as 110 mg/g at 298 K. Isoelectric point was in alkaline range which promoted negative fluoride ion uptake on positive nanofiber surface. Lead played higher masking effect in the uptake of fluoride in comparison to arsenic as coexisting ion. Dynamic cross flow filtration was also studied with this nanofiber in both synthetic and real life feed solution.

ReeBundle: A Method for Topological Modeling of White Matter Pathways Using Diffusion MRI.

Tractography can generate millions of complex curvilinear fibers (streamlines) in 3D that exhibit the geometry of white matter pathways in the brain. Common approaches to analyzing white matter connectivity are based on adjacency matrices that quantify connection strength but do not account for any topological information. A critical element in neurological and developmental disorders is the topological deterioration and irregularities in streamlines. In this paper, we propose a novel Reeb graph-based method "ReeBundle" that efficiently encodes the topology and geometry of white matter fibers. Given the trajectories of neuronal fiber pathways (neuroanatomical bundle), we re-bundle the streamlines by modeling their spatial evolution to capture geometrically significant events (akin to a fingerprint). ReeBundle parameters control the granularity of the model and handle the presence of improbable streamlines commonly produced by tractography. Further, we propose a new Reeb graph-based distance metric that quantifies topological differences for automated quality control and bundle comparison. We show the practical usage of our method using two datasets: (1) For International Society for Magnetic Resonance in Medicine (ISMRM) dataset, ReeBundle handles the morphology of the white matter tract configurations due to branching and local ambiguities in complicated bundle tracts like anterior and posterior commissures; (2) For the longitudinal repeated measures in the Cognitive Resilience and Sleep History (CRASH) dataset, repeated scans of a given subject acquired weeks apart lead to provably similar Reeb graphs that differ significantly from other subjects, thus highlighting ReeBundle's potential for clinical fingerprinting of brain regions.

Muscle Fiber Conduction Velocity During Electrically Stimulated Contraction at Various Joint Angles, During Joint Movements, and During Voluntary Contractions.

Muscle fiber conduction velocity (MFCV) can be affected by muscle fiber geometry at different joint angles and during joint movements. This study aimed to investigate MFCV during electrically evoked contraction at different joint angles, during joint movements, and during voluntary contractions. Sixteen healthy young men participated. A stimulation electrode was attached on the innervation zone of the vastus lateralis, and a linear electrode array was attached on the vastus lateralis. Under a static condition, electrically evoked electromyography signals were recorded at knee joint angles set every 15° between 0° and 105°. Under a passive movement condition, signals were recorded during knee extension and flexion passively. Under a voluntary contraction condition, signals were recorded while performing 30% or 60% of maximum voluntary contraction. MFCV was calculated using cross-correlation coefficients. Under the static condition, there were no differences in MFCV among various joint angles. Under the passive movement condition, MFCV was significantly greater during high velocity or shortening. Under the voluntary contraction condition, MFCV was significantly greater during high-intensity voluntary contraction and with a shortened muscle length. Joint angles do not influence MFCV markedly during relaxation, but it is possible to overestimate MFCV during movement or voluntary contraction.

Experimental investigation on the flexural behavior of concrete reinforced by various types of steel fibers

The benefit of steel fiber on the mechanical behaviors of concrete has been well accepted. The flexural behavior of steel fiber reinforced concrete (SFRC) is complicated which depends on many factors, such as matrix properties, fiber material properties, fiber geometries, fiber volume contents, and interface properties. Thus, the investigations on the flexural behavior of SFRC are needed to be expanded. In this study, the effects of fiber type with varying shapes and aspect ratios on the flexural performance of SFRC were investigated. Five steel fibers were adopted in this study: milled fiber (M), corrugated fiber (C) and three hooked fibers with aspect radios of 45 (HA), 55 (HB), and 65 (HC). Two volume fractions (0.4% and 1.0%) of steel fiber and two compressive strengths (normal and high strengths) of matrix were considered. The load-deflection curves, energy absorption capacity and equivalent flexural strength were discussed. The results show that the flexural behavior of SFRC beams reinforced by 1.0% fibers is significantly higher than that of the beams reinforced by 0.4% fibers. Hooked fiber reinforced beams performed the best flexural load-deflection response compared to the beams reinforced by milled fiber and corrugated fiber reinforced, and exhibited an increasing trend of flexural performance as the fiber aspect ratio increased. The differences between specimens with different fibers for high strength matrix are more obvious compared to the normal strength matrix.

Tuning damping and dynamic response of smart MR cylindrical composite panels based on a higher-order shear deformation theory

This study delves into the dynamic analysis of magnetorheological elastomer composite (MREC) cylindrical panels with laminated construction. Magnetorheological elastomers (MREs) are viscoelastic materials that exhibit tunable properties when subjected to magnetic fields. By incorporating reinforcing fibers, a new class of materials, MRE Composites (MRECs), is formed, which not only inherits MRE properties but also enhances rigidity. The novelty of the present study resides in its comprehensive exploration of the vibration and damping characteristics inherent in deep laminated cylindrical shells composed of MRECs. The homogenization of this composite media is performed by employing the modified rule of mixture and Halpin-Tsai micromechanical rule. To achieve this, the Mechab theory, utilizing a high-order hyperbolic function, approximates the displacement field. The study employs the generalized Maxwell's constitutive model to describe the viscoelastic behavior of MRECs, and Hamilton's principle is used to derive the partial differential form of vastly coupled equations of motion. The 2-dimensional Chebyshev collocation method, a discretization method, is applied to solve these equations, allowing the determination of natural frequencies and loss factors. The investigation covers various parameters, including magnetic field strength, volume fraction of reinforcers, layering, and fiber angles, geometry, and boundary conditions, to understand their influence on the dynamic response of MREC cylindrical panels. The results provide valuable insights into the potential applications of these tunable materials in adjustable dynamic and damping systems, contributing to advancements in solid mechanics and materials engineering. Such knowledge opens up new possibilities for utilizing MRECs in diverse technological applications.

High power pulse delivery over a short distance through an all-solid anti-resonant microstructured optical fiber at [formula omitted] wavelength

We propose an all-solid silica-based, large mode area (LMA) anti-resonant microstructured optical fiber through which optical pulses of high-power can be delivered at the near mid-infrared wavelength range. Anti-resonant guidance of light has been achieved in the silica-based microstructured geometry by embedding 15 high-index solid cylinders in a low-index background matrix that essentially creates a node-less negative curvature cladding region surrounding the low-index core. The fiber geometry has been optimized in such a way that a large mode area of ∼2000μm2 is achieved for the fundamental mode with a loss in the order of 0.04 dB/m at 2μm wavelength. Moreover, the higher-order modes are at least one order of magnitude lossy than the fundamental mode at the operating wavelength. The optimized fiber structure has exhibited that a pulse of peak power as high as 1 kW and width of 2.2 ps can be sustained without any alteration in shape and degradation of power when the pulse is delivered through the fundamental mode over the proposed fiber length of 25 m. Hence, this proposed unique silica-based all-solid anti-resonant fiber structure is suitable for short-distance delivery of high-power pulses at 2μm wavelength with effective single mode separation.

Pullout behavior of recycled macro fibers in the cementitious matrix: Analytical model and experimental validation

A novel mechanical recycling method has been recently developed in the authors’ group for processing waste glass fiber-reinforced polymer (GFRP) composites into macro fibers, which are then incorporated into concrete to produce green fiber-reinforced concrete (FRC). The present study has been conducted for facilitating the characterization of the tensile properties of macro fiber reinforced concrete (MFRC). A trilinear bond-slip model based on the shear-lag theory has first been refined by introducing a slip coefficient to consider different slip behaviors at the final pullout stages. Such a refined trilinear bond-slip model is suitable for describing the bond-slip behavior of the recycled macro fibers embedded in the cementitious matrix. The bond parameters are obtained through an inverse analysis, in which an improved particle swarm optimization algorithm (PSO) is used. The predicted force-end slip curves are compared with the pullout test results, and a good agreement is observed counterparts with the integral absolute error (IAE) ranging from 3.05% to 5.52%, demonstrating the feasibility of the proposed analytical model. A parametric study is finally conducted to examine the sensitivity of different parameters including the fiber geometries and bond properties on the pullout behavior of the macro fibers.

Integrated FRET Polymers Spatially Reveal Micro- to Nanostructure and Irregularities in Electrospun Microfibers.

A spatial view of macroscopic polymer material properties, in terms of nanostructure and irregularities, can help to better understand engineering processes such as when materials may fail. However, bridging the gap between the molecular-scale arrangement of polymer chains and the spatially resolved macroscopic properties of a material poses numerous difficulties. Herein, an integrated messenger material that can report on the material micro- to nanostructure and its processes is introduced. It is based on polymer chains labeled with fluorescent dyes that feature Förster resonance energy transfer (FRET) dependent on chain conformation and concentration within a host polymer material. These FRET materials are integrated within electrospun polystyrene microfibers, and the FRET is analyzed by confocal laser scanning microscopy (CLSM). Importantly, the use of CLSM allows a spatial view of material nanostructure and irregularities within the microfibers, where changes in FRET are significant when differences in fiber geometries and regularities exist. Furthermore, changes in FRET observed in damaged regions of the fibers indicate changes in polymer conformation and/or concentration as the material changes during compression. The system promises high utility for applications where nano-to-macro communication is needed for a better understanding of material processes.

Axial strength of fibrous reactive powder concrete circular columns

In this paper, a formula is proposed to calculate the nominal axial strength (Po) of fibrous reactive powder concrete (RPC) columns reinforced with steel fibres of different geometries and volume contents. The formula takes into account the effects of concrete, longitudinal reinforcement, transverse constraints, geometry of steel fibres and their volume content. A comparison is made with existing formulations that consider only for concrete and steel reinforcement. The proposed formula has been verified and validated by the experimental results of different types of steel fibre reinforced concrete (SFRC) columns in the literature. The results show that the current formulation considering only concrete and reinforcement significantly underestimatesPo of fibrous RPC columns. Furthermore, it is found that the proposed formula well predicts the nominal axial strength for fibrous RPC columns with an accuracy of 97–99%.

Mechanical properties of alkali-activated slag based SIFCON incorporating waste steel fibers and waste glass

This experimental study focuses on sustainable slurry infiltrated fiber concretes (SIFCONs) by utilizing alkali-activated ground granulated blast furnace slag (GGBS) and waste fibers. The waste fibers were high-strength steel fibers recovered from scrap tires. Additionally, waste glass was employed as a substitute for commercial sodium silicate activator, contributing to the reutilization of a waste material. Such an approach stands out for its use of various waste materials to achieve a high-performance concrete primarily composed of recycled materials. Literature survey indicate that there are no studies available on concrete primarily composed of waste or recycled materials. In this study, the molarities of the activators were selected as 8 M and 14 M based on a prior research. Due to the fiber geometry and the associated bulking effect, a maximum waste fiber content of 5 % was adopted, with increments of 1 %. Load–deflection curves of the specimens were obtained in the bending test. Various mechanical properties, including compressive strength, splitting tensile strength, flexural strength, and fracture energy, were determined for the mixtures. The mechanical properties of the alkali-activated mixtures were improved compared to those of the reference concretes. Based on the mixture proportions and materials employed, alkali-activated mixtures in the study achieved compressive strengths exceeding 120 MPa and flexural strengths approaching 30 MPa. Furthermore, significant enhancements in fracture energies were observed. The strengths of the mixtures with waste glass, however, were lower compared to the other mixtures. Nonetheless, in summary, the study shows the promising potential of waste steel fibers and waste glass for the production of alkali-activated slag SIFCON. This approach not only enhances cost-effectiveness, sustainability, and mechanical properties but also reflects a significant step towards achieving a concrete composition that relies solely on waste materials.

Micro-computed tomography imaging and segmentation of the archaeological textiles from Valmarinniemi

ObjectiveArchaeological textiles represent a variety of structures and materials, often subject to post-depositional effects such as dirt and decay. In this study, we examined textiles in 3D with high-resolution micro-computed tomography (μCT) imaging and studied the internal structures and patterns of textiles. In addition, nanoscale CT was used to identify fibre material. DesignTwo tablet-woven textile fragments and a plain-woven textile were excavated from a late medieval burial site in Valmarinniemi, Finland. Two textiles were scanned with μCT imaging and one with nanoscale CT imaging. Image segmentation was performed to study the internal structural components of the fabrics, yarns, and fibres. ResultsThe tablet-woven ribbon and plain-woven textile were imaged and visualised in 3D using high-resolution μCT and nanoscale CT imaging. 3D μCT images together with segmenting showed the structure of the woven textiles and how warp and weft intertwine. Nanoscale CT imaging of plain-woven fragment showed individual fibres and provided information in identifying the fibres as cotton. ConclusionsHigh-resolution μCT and nanoscale CT enabled the examination and identification of archaeological textiles in 3D. Thus, μCT imaging brings added value to the study of archaeological textiles with a precise method to study internal structures that otherwise would be invisible or difficult to examine and evaluate yarn and individual fibre geometry in a way that is less laborious and time-consuming than conventional methods.

Comparative study of geometry effect for magnetic field sensor based on multi-mode optical fiber

Experimentally and numerically, measurements have been presented for new type of magnetic field sensor based on combining multimode optical fiber and magnetic ferrofluid. The ferrofluid was filled in a capillary tube around a 15 mm uncladded region of optical fiber. Three uncladded geometries cylindrical, D-shaped and 2D-shaped, have been investigated to study the effect of geometry on sensing performance. Results illustrate that the geometry of the optical fiber has a significant impact on the evanescent waves which propagate from the sensing region into the ferrofluid tube. The obtained results expressed that among all studied cases, the D-shaped configuration has the best performance designing an optical fiber-based magnetic field sensor, since the best measured sensor features such as linearity, sensitivity, response time and recovery time for this case are R2 = 0.9865, 0.01795 μW/mT, 3.15 s and 0.26 s, respectively.

Limits of Coupling Efficiency Into Hollow-Core Antiresonant Fibres

We theoretically explore the fundamental limits on the efficiency of coupling light into hollow-core antiresonant fibres. We study in particular the coupling of a free-space Gaussian beam to the guided modes of one of the most successful antiresonant fibre (ARF) geometries, the the nested antiresonant nodeless fibre (NANF). Through finite element simulations, we study the effect of the geometrical parameters of the fibre on the coupling efficiency, showing that coupling into the fundamental LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> -like mode is typically maximized around 96-98 % when the incident beam waist is about 70 % of the core diameter. We find that due to the nature of antiresonance guidance, higher coupling efficiencies are achieved for fibres operating in the second antiresonant window (or generally even-numbered windows) than in those operating in the fundamental antiresonant window (or generally odd numbered windows), although the difference between even and odd decreases with the order of the window. We verify this theoretical finding experimentally with precise measurements of coupling efficiency into two NANFs operating in first and second windows, respectively. Our results which consistently show a steady 1.4 percentage point higher coupling efficiency for the second window fibre imply that such fibers may be the most suitable candidates for applications such as laser delivery which require up to a few hundred meters of fiber.

Transverse curvature characterization of rectangular bistable CFRP laminates with a satellite capturing continuum robotic application

The geometry of a bistable unsymmetric cross-ply carbon fiber reinforced polymer (CFRP) laminate impacts the observed stable configuration curvature. Continuum robotic systems can leverage the multi-stable nature of bistable CFRPs to contort to resemble continuous-bodied appendages observed in nature. The compliance of continuum robots facilitates grasping and manipulating objects such as non-cooperative, tumbling targets encountered in an on-orbit servicing operation. This work investigates large-scale bistable CFRP rectangular laminates previously unexplored in the literature to demonstrate the feasibility of scaling the laminates to meet the needs of potential applications. A numerical parametric study explored the relationship between aspect ratio, thickness, and stable configuration curvature. Non-dimensional parameters enabled the creation of a bifurcation diagram to characterize the stable shapes and bistability. Polynomial regression and machine learning delivered curvature prediction tools. Experiments using an air-bearing zero gravity spacecraft simulator evaluated the feasibility of incorporating rectangular bistable CFRP laminates in an on-orbit servicing continuum robotic system. The initial system resembled a crab claw to grasp target boxes, and the orientation and size of the target significantly contributed to the capture success rate. Future investigations of bistable CFRPs, especially from an application perspective, can benefit from predictive tools like ML to quantify the bistable characteristics.

The Impact of Fiber Geometry on the Mechanical Characteristics of SIFCON Slabs Under Static and Dynamic Loading

The Impact of Fiber Geometry on the Mechanical Characteristics of SIFCON Slabs Under Static and Dynamic Loading