Polymer Fibers Research Articles

Numerical study on the flexural and shear behavior of steel fiber and high‐strength steel combination in ultra‐high‐performance fiber‐reinforced concrete beams under cyclic loading

AbstractFiber‐reinforced concrete consists of hydraulic cement, water, aggregate, and discrete fibers, making it a composite material. These fibers, available in different shapes, sizes, and materials such as steel, polymer, glass, and natural fibers, are commonly utilized in structural applications. The tensile strength of conventional concrete tends to decrease as micro‐cracks develop rapidly under applied stresses. However, incorporating closely spaced fibers can hinder the progression of micro‐cracks, leading to a substantial improvement in both tensile and flexural strengths of concrete. Furthermore, fibers can delay the initiation of tensile cracks, effectively enhancing concrete's ability to withstand tensile strains before failure. As a result, fiber‐reinforced concrete exhibits increased durability and enhanced resistance to impacts compared to plain concrete. This study aims to evaluate and compare the cyclic flexural behavior of a cantilever beam constructed from ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) using reinforcing bars made of high‐strength steel (HSS). The beams contain varying relative proportions of longitudinal reinforcement and steel fibers. Various key performance parameters of the cantilever beam were thoroughly examined, such as load capacity, flexural ductility, failure mode, hysteresis response, energy dissipation, and hardness. The study demonstrated that UHPFRC beams with HSS exhibit good cyclic flexural performance prior to failure.

Bisphenol A disrupts the neuronal F-actin cytoskeleton by activating the RhoA/ROCK/LIMK pathway in Neuro-2a cells

Bisphenol A (BPA) is an environmental endocrine disruptor that is widely present in the environment and has been reported to affect neuronal cytoskeleton and neural function. However, the exact molecular mechanisms remain unclear. In the present study, the effects of BPA on cytoskeleton rearrangement were examined, and the associated signaling pathways, which were influenced by the RhoA/ROCK/LIMK pathway in Neuro-2a cells in vitro, were identified. Specifically, Neuro-2a cells were exposed to BPA, and the effects of BPA exposure on the cytoskeleton of neuronal cells and on the activation or nonactivation of the RhoA/ROCK signaling pathway were evaluated using Cell Counting Kit-8 (CCK8), phalloidin staining, western blot, and real-time PCR. A RhoA inhibitor (Rhosin hydrochloride) and a ROCK inhibitor (Y-27632) were then used to elucidate the precise function of the pathway. The results demonstrated that 50–100μM BPA exposure inhibited Neuro-2a cell viability and caused the formation of aberrantly polymerized F-actin and stress fibers. In addition, the RhoA/ROCK pathway was activated, and the expression levels of the pathway-related molecules—RhoA, ROCK2, LIMK1, Cofilin, Profilin, p-MLC2, and F-actin were dramatically elevated. The addition of Rhosin and Y-27632 resulted in a decrease in F-actin polymerization in the Neuro-2a cells, the disassembly of stress fibers, and a noteworthy drop in the levels of molecular proteins related to the RhoA/ROCK pathway affected by BPA. Together, these new findings indicated that BPA exposure thus activated the RhoA/ROCK signaling pathway and caused an abnormal accumulation of F-actin in the Neuro-2a cells, in turn altering the microfilament cytoskeleton. F-actin was restored when the RhoA/ROCK pathway was inhibited, suggesting that the process of BPA-induced neuronal cytoskeletal degradation is linked to the RhoA/ROCK signaling cascade.

Surfactant-Enabled BM particle-embedded coaxial PVDF/PEI electrospun membranes enhancing Lithium-Ion battery safety

In response to the issue of thermal runaway in lithium-ion batteries, a new battery separator with high safety was developed in this study. By incorporating trace amounts of the surfactant sodium dodecyl sulfate (SDS) into the boehmite (BM) slurry, uniform infiltration of the polyvinylidene fluoride/polyetherimide (PVDF/PEI) coaxial electrospun fiber membrane was successfully achieved, thereby significantly enhancing the membrane’s flame retardancy and thermal stability at high temperatures. This method is straightforward and versatile, facilitating a tight integration of BM with individual fibers. Owing to the synergistic effects of the fiber structure, polymer matrix, BM, and binder, the separator also exhibits excellent electrolyte wettability, thermal conductivity, and toughness. Batteries assembled with this membrane demonstrated an initial discharge capacity of 142.1 mAh/g at a 0.5C charge–discharge rate, with a capacity retention of 97.4 % after 120 cycles. This research provides an innovative solution for the fabrication of high-safety lithium-ion battery separators, holding profound scientific significance and promising application prospects.

Micro-void nucleation at fiber-tips within the microstructure of additively manufactured polymer composites bead

The presence of voids within the microstructure of short carbon fiber polymer composites produced by additive manufacturing (AM) technology are known to alter the expected material behavior that impair part performance. Previous research efforts aimed at understanding the formation mechanisms of these micro-voids during the polymer extrusion/deposition process have not kept up with the advancement of this AM technology. The present study investigates the phenomenon of micro-void nucleation at the fiber/matrix interface, especially those that form at fiber tips, by characterizing the microstructural configuration of a 13 % carbon fiber filled ABS polymer composite print bead specimen using 3D X-ray micro computed tomography image acquisition and analysis. The results reveal a high level of micro-voids segregation at the ends of fibers that are relatively larger in size and less spherical as compared to micro-voids isolated within the ABS matrix. Additionally, by simulating the hydrostatic flow-field pressure distribution surrounding a single rigid ellipsoidal fibre in colloidal suspension using Jeffery’s model equations, we show that the pressure drops to a critical value at the fibre tips where the micro-voids nucleation is experimentally observed to occur. The study helps to improve our understanding of the potential mechanisms that may be responsible for micro-void development within beads printed with extrusion/deposition AM.

High-filler content electrospun fibers from biodegradable polymers and hydroxyapatite: Toward improved scaffolds for tissue engineering.

One of the key challenges in tissue engineering area is the creation of biocompatible scaffolds that support cell growth and mimic the structural and mechanical properties of native tissues. Among various materials used for scaffold fabrication, composite materials based on biodegradable polymers reinforced with bioactive inorganic fillers have attracted significant attention due to their properties. One of the important problems with the preparation of composite electrospun fibers is the low filler content in the fiber. This study aims to select the best composition for electrospun polymer fibers in terms of potential application in tissue engineering. The effect of the viscosity of polymer solution/dispersion and filler content on the structure and properties of the fibers was determined. Morphology and filler content were compared. Series of electrospun composite fibers were fabricated from poly(ĺ-caprolactone) (PCL), poly(L-lactic acid) (PLLA) and hydroxyapatite (HAP), containing from 10 wt% to 40 wt% HAP. The properties of the resulting composites were studied using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and viscosimetry measurements. The addition of HAP to the polymer solution caused a significant increase in viscosity, but the results showed that it is possible to obtain composite electrospun fibers even with 40 wt% filler content. Scanning electron microscopy analysis shows randomly oriented electrospun fibers with an average diameter in the range of 3.8-8.5 ěm for solution and dispersion with high viscosity (1,210-2,000 mPa·s) and significantly larger diameters (approx. 12 ěm) for the PCL solution (326 mPa·s). It is possible to transform the composite dispersion from biopolymers and HAP into nonwoven fabrics at up to 40 wt% filler content. Due to their unique properties, such materials are promising for application in tissue engineering.

Structural-Functional Integrated Graphene-Skinned Aramid Fibers for Electromagnetic Interference Shielding.

Structural-functional integrated polymer fibers with exciting properties are increasingly important for next-generation technologies. Herein, we report the structural-functional integrated graphene-skinned aramid fiber (GRAF) featuring high conductivity, high strength, and light weight, which is weaved for efficient electromagnetic interference (EMI) shielding. Graphene was self-assembled onto the surface of aramid fibers through a dip-coating strategy using an aramid polyanion (APA) as the binder and the etchant. The molecular dynamics (MD) simulation results show that the binding energy of the APA-modified aramid chain and graphene (1.3 J/m2) is superior to that of the aramid chain and graphene (0.2 J/m2). The APA has a higher surface energy (55.2 mJ/m2) and can etch the fiber surface, forming grooves, which enables effective adsorption and self-assembly of graphene onto the fiber surface. The GRAF exhibits a high conductivity of 1062.04 ± 116.78 S/m, along with excellent strength (4.66 ± 0.16 GPa) and modulus (106.33 ± 8.21 GPa), outperforming most reported conductive composite fibers (e.g., natural fibers, polymer-based fibers, inorganic fibers, etc.). The weaved functional fabric using the structural-functional integrated GRAF shows an EMI shielding efficiency (SE) of up to 67.86 dB in the X-band and can rapidly heat up to 200 °C within 40 s at 12 V voltage. In addition, the GRAF fabric can maintain its electrical conductivity after a long-term washing, showing excellent washing resistance. This study demonstrates an effective method to fabricate structural-functional integrated materials and shows the promise of carbonene fibers for EMI shielding.

Development and characterization of glass fiber composites impregnated with limestone powder and bagasse fiber

Abstract Materials development is essential for all industries to meet the current demands Limestone powder (LS), coconut shell fiber (CSF) and sugarcane bagasse fiber (SBF) were impregnated in a laminated glass fiber polymer matrix. The fiber to matrix ratio is 50 %, while SBF and CSF start replacing natural fibers at a rate of 5–15 %, and LS is always 5 %. The proposed fiber-reinforced composites were manufactured by compression molding (CMM) and the test samples were cut according to the ASTM for tensile, impact, moisture, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric (TGA) tests. The results showed that the strength of the materials is influenced by the impregnation of the fibers into the matrix phase. Impregnation of natural fibers in glass fiber composite structures at 10–15 % loading demonstrated a weight saving of 7–8 %, tensile strength ranging from 330 to 350 MPa, maximum moisture absorption of 3.4 g, and thermal stability around 300 °C. Addition of limestone powder resulted in improved bonding ability, better surface finish, and reduced porosity, as demonstrated by SEM analysis.

Characterization and modelling of the microstructural and mechanical properties of additively manufactured continuous fiber polymer composites

The additive manufacturing of continuous fiber reinforced polymer composites is a technology showing great potential for the production of end-use functional and structural components. The reasons for its still limited use are primarily related to an insufficient knowledge of the mechanical behavior of these composites, especially when considering the features that distinguish the printed components from conventional composite parts. Among these peculiar features, their bead-based architecture has been experimentally and analytically investigated in this study. Following an analysis of the process-morphology correlation, carbon fiber (CF)/polyamide 12 (PA12) specimens were tested to characterize the in-plane quasi-static material properties. Then, a modelling framework has been proposed for assessing the composite elastic properties and average bead stresses. This framework holds the potential to scale up to a structural level, accommodating various fiber trajectories.

Polymer Fibers Based on Dynamic Covalent Chemistry

Polymer Fibers Based on Dynamic Covalent Chemistry

Laser-Assisted Micropatterned 3D Printed Scaffolds with Customizable Surface Topography and Porosity for Modulation of Cell Function.

The dynamic interaction between cells and their substrate is a cornerstone of biomaterial-based tissue regeneration focused on unraveling the complex factors that govern this crucial relationship. A key challenge is translating physical cues from 2D to 3D due to limitations in current biofabrication techniques. In response, this study introduces an innovative approach that combines additive and subtractive manufacturing for precise surface patterning of 3D printed scaffolds. Using poly(𝜀-caprolactone) as the scaffold material, polymeric fibers are 3D printed and subsequently laser-engraved with femtosecond laser to precisely create controlled microtopographies, including microgrooves (10 and 80µm in width) and micropits (25µm in diameter). Testing shows that the process does not compromise the mechanical properties of the fibers, which is critical for structural applications in tissue engineering. Human mesenchymal stem cells are used to investigate the effects of these topographical features on cell behavior. The 10 µm wide microgrooves notably enhance cell attachment, with cells aligning in elongated forms along the grooves, while micropits and unpatterned surfaces promote polygonal cell shapes. This combined approach demonstrates that precisely engineered microtopographies on 3D printed scaffolds can better mimic the natural extracellular matrix, improving cellular responses and offering a promising strategy for advancing tissue regeneration.

High Strength Anhydrite Cement Based on Lime Mud From Water Treatment Process: One Step Synthesis in Water Environment, Characterization and Technological Parameters

ABSTRACTIn the process of water treatment from surface water sources, lime mud as waste is formed. This waste contains CaO, Ca(OH)2, and CaCO3. The article proposes a comprehensive method for processing lime mud into high‐strength anhydrite cement. The method involves the interaction of lime mud with waste sulfuric acid from the production of polymer fibers using a structure‐controlled method in the (CaO·Ca(OH)2·CaCO3)—H2SO4—H2O system at a temperature of 40°C. X‐ray diffraction analysis showed the presence of CaSO4 and CaSO4·0.62H2O phases with a purity of 99.8%. The structure‐controlled method makes it possible to control the formation and growth of calcium sulfate crystals of the required shape and size, due to which it is possible to obtain anhydrite cement with desired properties. Combined grinding of synthetic anhydrite with activator additives makes it possible to obtain anhydrite cement with a strength of up to 28.5 MPa.

Exploring synergies between GnP and fiber orientation in enhancing mechanical, thermomechanical, and shape memory properties of carbon fiber polymer composites

Abstract This research investigates the mechanical, thermomechanical, and shape memory properties across 12 configurations of shape memory hybrid composites, varying in carbon fiber orientation: uni-directional (UD), bi-directional-Twill (BDT), and bi-directional-Plain (BDP), and multi-walled carbon nanotube weight percentages of 0.4%, 0.6%, and 0.8% elucidate the synergistic effects of fiber architecture and nanomaterial reinforcement. The fabrication process involves initially preparing GnP-modified epoxy nanocomposites through ultrasonication followed by hand layup techniques to fabricate three-phase shape memory hybrid composites. Optimal tensile performance is observed in GnP-modified UD composites at a 0.6 wt% concentration, achieving a tensile strength of 728.32 MPa and a modulus of 71.29 GPa. Furthermore, enhancements in thermomechanical and shape memory properties are noted in GnP-modified BDT composites and are further improved in GnP-modified BDP composites configurations. These improvements are attributed to enhanced interfacial bonding between the polymer and fiber, with the maximum effect observed at the 0.6 wt% BDP composite, validated by morphological analysis using FESEM. The study demonstrates that despite polymer modification, all configurations maintain high shape recovery ratios, particularly notable at 97.54% for 0.6 wt% GnP modified BDP composite, exceeding 90% across all configurations, indicating robust performance in shape memory capabilities.

Electrospinning of LaB6/PEDOT:PSS/PEO Fiber Composites of Unique Morphologies.

We present a direct electrospinning fabrication technique for the manufacture of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(ethylene oxide) (PEDOT:PSS/PEO) polymer fibers containing embedded cubic lanthanum hexaboride (LaB6) particles. We focus on the impact of relative humidity on the formation of uniform polymer fibers and show that a relative humidity of 5% is optimal, resulting in an average fiber thickness of 266 ± 88 nm. As the relative humidity is increased, the fibers contain beads as a consequence of Rayleigh instabilities. The addition of lanthanum hexaboride cubic particles to the polymer solution before electrospinning results in the encapsulation of the LaB6 particles inside the fibers. We investigate the effect of LaB6 particle size on morphology and observe that particles of ∼500 nm yield a fiber-cube-fiber morphology, while 2 μm particles result in fewer embedded cubes along the length of the polymer fibers. This phenomenon likely arises from electrodynamic interactions between the LaB6 particles in the polymer solution and the electric field lines generated during electrospinning between the spinneret and the collector. Our results display the versatility of the electrospinning technique in the fabrication of unique polymer/hexaboride composite fibers.

The Influence of the Amount of Technological Waste on the Performance Properties of Fibrous Polymer Composites

The objective of the experimental analysis was to assess the impact of the reuse of technological waste (recyclate) on the selected performance properties of the fibrous polymer composite used to produce components for the automotive industry by injection molding technology. Polyphthalamide (PPA), which belongs to a group of high-tech polymers, was chosen as the analyzed material. In accordance with the set goals, the rheological, mechanical, and structural properties of the material were evaluated using ANOVA analysis in the experimental part of the work, depending on the mass ratio of the recycled material added to the virgin material. The influence of the proportion of recycled material on the lifetime of moldings by the method of their exposure at an elevated temperature for a defined time was also assessed. During the research, it was found that at a concentration of up to 40 wt. % of recyclate, its mechanical properties do not change significantly. At a concentration of 50 wt. %, there is a rapid decrease in mechanical properties. In the long term, it can also be said that the addition of recyclate significantly affects the service life of the components. No significant changes in morphology were observed during the analysis of structural properties.

Utilization of Alternative Fibres Manufactured from Recycled PET Bottles in Concrete Technology for the Improvement of Fire Resistance.

This article addresses the potential use of secondary polymer fibres in the field of structural concrete as a replacement for primary polymer fibres (mainly polypropylene/PP/), which are used in concrete to enhance its resistance when exposed to high temperatures (especially in the case of fire). Research has shown that, in addition to PP fibres, polyethylene terephthalate/PET/fibres, produced by recycling packaging materials (mainly PET bottles), can also be used as an alternative. These fibres are industrially produced in similar dimensions as PP fibres and exhibit similar behaviour when added to fresh and hardened concrete. In terms of their effect on increasing resistance to extreme heat loads, it has been found that despite a higher melting point (Tm), concrete with these fibres demonstrates comparable fire resistance. Therefore, it can be concluded that secondary PET fibres represent an interesting alternative to primary PP fibres from the perspective of a circular economy, and their use in construction represents a potentially valuable application for PET obtained through the collection and recycling of PET packaging materials.

High detail resolution cellulose structures through electroprinting

Electrospinning is a technique used to fabricate polymer fibers in micro- and nanoscales. Due to the large distance between the nozzle and collector, there is a limited positioning accuracy of electrospun fibers. To enhance the possibility of fabricating structures with micrometer placement, an electroprinting technique has been developed. By reducing the distance between the nozzle and the collector it is demonstrated that it is possible to get an improved control over fiber positioning which gives a possibility to fabricate designed 3D structures at the micron scale. In this study, cellulose acetate (CA) has been selected as a biomaterial to advance the 3D printing of membranes with possible use in separation applications. Various parameters, such as CA concentration and molecular weight, printing speed, printing pattern, applied voltage, etc. are evaluated with respect to printing control. Results indicate that by optimizing the printing parameters it is possible to print structures with inter- fiber distances down to 3 µm and fiber diameters at a sub-µm scale. This electroprinting development is promising for the fabrication of customized separation membranes. However, printing speed still remains a challenge.

Melt Spinnability Comparison of Mechanically and Chemically Recycled Polyamide 6 for Plastic Waste Reuse.

With the increasing volume of synthetic fiber waste, interest in plastic reuse technologies has grown. To address this issue, physical and chemical recycling techniques for polyamide, a major component of textile waste, have been developed. This study investigates the remelting and reforming properties of four types of pristine and recycled polyamide 6, focusing on how the microstructural arrangement of recycled polyamides affects polymer fiber formation. DSC and FT-IR were used to determine the thermal properties and chemical composition of the reformed thin films. Differences in the elongation behavior of molten fibers during the spinning process were also observed, and the morphology of the resulting fibers was examined via SEM. Birefringence analysis revealed that the uniformity of the molecular structure greatly influenced differences in the re-fiberization process, suggesting that chemically recycled polyamide is the most suitable material for re-fiberization with its high structural similarity to pristine polyamide.

Numerical modeling and experimental validation of low velocity impact of woven GFRP/CFRP composites

Low-velocity impact of 2D woven glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) composite laminates was studied experimentally and numerically. Hybrid laminates containing blocked layers of GFRP/CFRP/GFRP with all plies oriented at 0° were investigated. Relatively high impact energies were used to obtain full perforation of the laminate in a low-velocity impact setup. Numerical simulations were carried out using the in-house transient dynamics finite element code, Sierra/SM, developed at Sandia National Laboratories. A three-dimensional continuum damage model was used to describe the response of a woven composite ply. Two methods for handling delamination were considered and compared: (1) cohesive zone modeling and (2) continuum damage mechanics. The reduced model size achieved by omission of the cohesive zone elements produced acceptable results at reduced computational cost. The comparison between different modeling techniques can be used to inform modeling decisions relevant to low velocity impact scenarios. The modeling was validated by comparing with the experimental results and showed good agreement in terms of predicted damage mechanisms and impactor velocity and force histories.

Bagworm Silk‐Mimetic Protein Fibers with Extraordinary Stiffness via In Vivo Polymerization and Hierarchical Self‐Assembly

AbstractBagworm silk proteins, which contain crystalline structures with large β‐nanocrystal sizes, are ideal candidates for biosynthetic high‐performance fibers. However, the extremely high glycine content and greater molecular weight limit their heterologous expression efficiency and further application exploration. Here, a multi‐module assembly strategy is developed to engineer novel chimeric structural proteins by incorporating the mechanical functional domains of bagworm silk proteins with the C‐terminal self‐assembly domains of spider silk proteins. By selecting a single repetitive unit of the functional region of bagworm silk proteins, the challenge of low heterologous expression efficiency is successfully addressed. Furthermore, the content and ordering of β‐sheet structure are enhanced in the chimeric proteins through the alignment mediated by the spider silk C‐terminal domain and ligation facilitated by split inteins, resulting in a remarkable Young's modulus of ≈15 GPa. This surpasses many artificial protein fibers, synthetic polymer fibers, and even natural spider silk. Notably, these protein fibers are drawn into surgical sutures and demonstrate superior wound healing effects compared to clinical suture in a skin wound model. This research presents a novel strategy for developing high‐performance protein fibers, which will expand the scope of their mechanically demanding applications.

Comparison of uranium complexes with methyl-glutarimidedioxime vs. glutarimidedioxime: A methyl change generates different consequences in thermodynamic equilibria and coordination modes

Nuclear power serves as an important source of alternative energy. However, land uranium resources are limited. In contrast, seawater contains an estimated total of 4.5 billion metric tons of uranium, which is more than a thousand times as much as that found in terrestrial ores. Therefore, developing techniques for uranium extraction from seawater is attracting research attention. Amidoxime-functionalized polymer fibers are the most widely utilized sorbents for this purpose. On the surface of amidoxime-based sorbents, cyclic glutarimidedioxime (H2A) is the preferred configuration for sequestration of uranium from seawater. Methyl-glutarimidedioxime (H2Q) forms if a methyl group attaches to the piperidine ring of H2A. The binding strength of uranyl complexes with H2Q and the enthalpy of complexation were investigated via potentiometry and microcalorimetry, respectively. The coordination mode was further revealed by single-crystal X-ray diffraction. It was expected that H2A and H2Q should be identical in terms of coordination as tridentate ligands. However, our investigation revealed that a methyl group attached to the piperidine ring not only altered the chelating mode but also lowered the binding strength of oxime groups. These findings show that developing a mechanism for optimizing molecules that would be formed on fiber surfaces remains challenging, even a methyl structural change would result in major consequences.