Uniform Fiber Distribution Research Articles

Comprehensive structural evaluation of composite materials in 3D-printed shin guards

This study introduces a novel approach to designing and fabricating lightweight football shin guards, leveraging advanced digital anatomical capture of players' shins and 3D printing techniques. Using Polyethylene terephthalate glycol (PETG) and carbon fiber (CF) composites, the 3D-printed shin guards showcased enhanced tensile, compressive, and flexural properties. Impressively, the patterned structure facilitated a 42 % weight reduction compared to its solid counterpart. Mechanical tests confirmed the consistent behavior of the printed samples, independent of their raster orientation. This consistency emphasizes the promise of expanded 3D printing utility in sports gear production. Surface and compositional evaluations were carried out using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), revealing a uniform fiber distribution. Notably, at 70 % and 30 % infill densities, PETG/CF met the predefined criteria; in the solid structure, its compressive strength overshadowed its tensile strength yet remained below its flexural strength. The pattern structure, particularly at 0° orientation, showed marked tensile advantages over the solid format. With the fundamental role of shin guards in preventing football injuries, this research paves the way for optimized protection, as many players presently utilize shin guards made from PETG, CF, or potent PETG/CF combinations.

Prediction of the compressive strength of lightweight concrete containing industrial and waste steel fibers using a multilayer synthetic neural network

The use of waste and industrial steel fibers as part of the materials used in concrete can increase resistance and reduce cost and air pollution. It also saves energy. One of the important measures for technical inspections and assessment of the existing condition of structures, especially bridges, which is the most important communication factor, is to check the compressive strength. Considering that the calculation of compressive strength in the laboratory is done with the intervention of human power and is undoubtedly affected by human error, we decided to use it through.Predicting the mechanical properties of concrete reinforced with steel fibers based on artificial neural network models without the need to conduct any laboratory studies will save money in construction projects. Unlike classical methods in statistical theories, neural networks do not require any specific model or function along with limiting assumptions to linearize problems.For this purpose, this research was done with the aim of compensating this problem and with the aim of building a neural network with high accuracy that can make the desired predictions with the least error. In this research, this modeling was done using artificial neural networks (ANN) and Levenberg algorithm. The data used to train the neural network was collected from 45 different mixing schemes. Then the compressive strength of the sample is determined experimentally. The parameters considered for the ANN inputs are the values of steel fiber, water, water-cement ratio, cement and superlubricant. The objective data of this study included the compressive strength of each of these mixing designs at the ages of 7, 28 and 60 days. Then, to design the neural network, 75% of the data were considered as training data, 15% as target data and 15% as validation data. The compressive strength of concrete samples made from waste steel fibers increases. One of the reasons for this result is the placement and uniform distribution of fibers in the cement matrix, or in other words, the optimal amount of desired fibers in concrete. For experimental information and data, results can be seen with the help of neural network in data analysis. It was observed that the validation is correlated with a correlation coefficient above 99% and the constructed neural network has sufficient accuracy and validity.

Effect of Fiber Dosage On Mechanical Properties Of Geopolymer Mortar Under The Coupling Of Sulfate Erosion And Dry-Wet Alternation

Coastal buildings are susceptible to long-term sulfate erosion and alternating wet-dry cycles, leading to rapid degradation in mechanical properties and durability. Therefore, there is an urgent need to find a construction material that is superior to ordinary silicate concrete. Geopolymer concrete, an innovative environmentally-friendly material, offers advantages like early strength, fire resistance, and durability. Research reveals that even after sulfate erosion, geopolymer concrete outperforms regular silicate concrete in terms of mechanical properties and durability. However, geopolymer concrete suffers from high brittleness. A remedy is found in the incorporation of fibers, which substantially enhances its mechanical properties and durability. This study investigates the influence of carbon fibers and polypropylene fibers on the mechanical traits of metakaolin-geopolymer mortar, exposed to sulfate action and wet-dry cycles for 60 repetitions. Results indicate that the addition of 0.6% carbon fibers yields the highest compressive strength, while a 1:1 combination of carbon and polypropylene fibers produces peak flexural strength. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) confirm uniform fiber distribution within the mortar, reinforcing material bonds and retarding crack propagation. Consequently, mechanical properties and durability are improved.

Study on the deformation and cracking characteristics of bamboo fiber reinforced concrete anti-slide pile considering the aspect ratio, fiber dosage and its coupling effect with rebars

In order to avoid cracks in anti-slide piles and thus causing brittle damage, incorporating fibers in anti-slide piles to improve their ductility is an effective way to enhance the crack resistance. Bamboo fiber, as a low carbon fiber material, has good crack resistance and toughening effect, and can be used as a new concrete reinforcement material to enhance the crack resistance of anti-slide piles. In this paper, the load–displacement relationship, deformation and cracking characteristics of 28 bamboo fiber-reinforced concrete anti-slide piles are studied considering the aspect ratio, fiber dosage and its coupling effect with rebars. The main conclusions of the study are as follows: (1) The bamboo fiber used in the anti-slide pile can play the role of crack resistance. The plain anti-slide pile produces one main tension crack and full-section fracture failure, while the anti-slide pile with the coupling effect of bamboo fiber and rebars suffers from diagonal section instability failure with one main diagonal tension crack and several secondary cracks. (2) The anti-slide pile with 1% volume ratio of bamboo fiber can achieve better flexural and crack resistance. The optimal dosage for bamboo fiber with rebars is further reduced, which is 0.5% (3) The optimal aspect ratio of bamboo fiber is between 16.7 and 23.3, which can improve the flexural performance of anti-slide piles, but the aspect ratio of bamboo fiber fails to essentially change the failure mode of anti-slide piles. Fiber dosage has a significant effect on the cracking failure mode of anti-slip piles. The rapid development of microcracks in anti-slide piles can be restrained more effectively by the uniform distribution of bamboo fibers with appropriately small aspect ratio and volume ratio.

In-situ micro-characteristics of fiber at the mortar transition zone in asphalt mixtures

Due to certain differences in physical and chemical properties of fibers used, there will be various defects in the internal structure of the resulted mixture from a microscopic perspective. The establishment of correlation between the microstructure characteristics and road performance of asphalt mixture has certain scientific research value. In this research, the proposed method of Resin Impregnated Mixture Slices was successfully used for the in-situ micromorphology, chemical heterogeneity and micro-mechanical properties investigation of lignin fiber, polypropylene (PP) fiber and polyester (PET) fiber at the mortar transition zone in asphalt mixtures. The box dimension presented by Fluorescence Microscope (FM) images indicates the most uniform distribution of polyester fibers. It is possible to trace methoxy group and ester group as an indicator on lignin fiber and polyester fiber in the thermodynamic distribution images of Attenuated Total internal Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR). And it was found that the fibers mainly concentrated in the inner region of asphalt mortar. In the testing mortar region of lignin, polypropylene and polyester fibers by Atomic Force Microscope-Quantitative Nano Mechanical (AFM-QNM), DMT-modulus in the areas containing fibers is 2.0 ∼ 18GPa, 1.0 ∼ 2.5GPa and 2.5 ∼ 5.0GPa, adhesion ranges from 50 ∼ 75nN, 20 ∼ 35nN, 30 ∼ 60nN, and the Dissipation values are 5.0 ∼ 15KeV, 0.5 ∼ 3.5KeV, 3.5 ∼ 7.0KeV, respectively. The mechanical properties of PP fiber modified asphalt mixture are considerably 0.5 ∼ 1.0 time lower than those of other samples due to the low-density and weak mechanical properties.

Universal displacements in inextensible fiber-reinforced linear elastic solids

For a given class of materials, universal displacements are those displacements that can be maintained for any member of the class by applying only boundary tractions. In this paper, we study universal displacements in compressible anisotropic linear elastic solids reinforced by a family of inextensible fibers. For each symmetry class and for a uniform distribution of straight fibers respecting the corresponding symmetry, we characterize the respective universal displacements. A goal of this paper is to investigate how an internal constraint affects the set of universal displacements. We have observed that other than the triclinic and cubic solids in the other five classes (a fiber-reinforced solid with straight fibers cannot be isotropic), the presence of inextensible fibers enlarges the set of universal displacements.

Enhanced filtration characteristics of a PTFE foam-coated filter using PTFE nanofibers

Polytetrafluoroethylene (PTFE) is a bag filter material with limited options for fiber production methods because of its high melt viscosity. In this study, a new method for fabricating a PTFE composite filter with high filtration performance was proposed. PTFE nanofibers produced by electrospinning, were coated on the surface of the PTFE foam-coated filter, and heat-treated, resulting in the fabrication of PTFE composite filter. The optimal conditions for preparing PTFE nanofibers with a uniform fiber distribution were determined using a systematic approach. A uniform fiber morphology of the electrospun fibers was prepared by controlling the PTFE-Polyvinyl alcohol (PVA) mixing ratio and the electric field strength, and pure PTFE fibers were obtained by heat-treatment at an optimal temperature based on TGA, DSC, and FT-IR analyses. The filter quality factor of the resultant PTFE composite filter, which represents the filtration performance, was approximately twice that of the PTFE foam-coated filter for all particle sizes. Furthermore, the cleaning cycle and cleaning efficiency of the PTFE composite filter improved by 9% and 3.9–5.4%, respectively, compared to those of the PTFE foam-coated filter, which was closely related to high contact angles of water and oil.

Mechanical properties of a novel UHPC reinforced with macro basalt fibers

Adding fibers in ultra-high performance concrete (UHPC) significantly enhances its mechanical properties. This study investigated the effects of the novel macro basalt fibers (MBF) content and geometric characteristics on flowability and mechanical properties of UHPC, the MBF which was a kind of minibar composited of basalt fiber reinforced polymers (BFRP). Two fiber shapes, including straight and twisted shape, and two aspect ratios with the volume fractions ranging from 0% to 3% were employed. The fiber distribution, interfacial bonding behavior between MBF and UHPC were tested and evaluated. The effects of MBF on the flowability, compressive strength, flexural strength and toughness of UHPC were revealed. The toughness, compressive strength, and flexural strength of UHPC increased with the increase of MBF content, but the flowability decreased. The relatively uniform fiber distribution was observed when the MBF content was lower than 3%. Compared with the straight MBF, the twisted MBF showed higher bonding behavior between fiber and UHPC. It resulted in that the twisted MBF performed more efficient in enhancing mechanical properties of UHPC than the straight MBF. The flexural post-cracking strength of UHPC with various MBF contents and geometric characteristics could be accurately predicted using the quadratic model and the modified model based on the Composited Theory because the values of R2 were more than 0.95.

Large-scale production of the 3D warp knitted terry fabric triboelectric nanogenerators for motion monitoring and energy harvesting

In the coming era of intelligence, the textile-based triboelectric nanogenerator (T-TENG) is considered to be one of the most important development directions to achieve flexible wearable sensing and micro/nano energy harvesting. Among them, due to excellent physical proeprties of nano/micro fibrous structure, fluff/terry /fleece/brush/fur/pile/villus/velvet structure fabrics are gradually being applied to TENG. However, the research on the relationship between the triboelectric properties of TENG and the structural parameters of fluff, as well as the fabrication of large-scale fluff TENG are very lacking. Here, a 3D warp knitted terry fabric TENG (WKTF-TENG) is mass produced by a mature warp knitted technology. The triboelectric properties of contact-separation mode, lateral-sliding mode and single electrode mode are systematically investigated by changing the height and density of the pile loops of the fabric. This study demonstrates that terry fabric is an excellent triboelectric materials for it high output and good wear resistance, especially for ateral-sliding mode. The output of WKTF-TENG even increases with the increase of working cycles due to the more fluffy and uniform distribution of fibers on the surface of the fabric. What’s more, the triboelectric properties of terry fabrics also have a great relationship with the compression properties of the pile loops. As smart textile matertail, WKTF-TENG can be usde as self-powered motion monitoring sensor and energy harvesting device. The research on the output performance of WKTF-TENG through theoretical analysis and experimental testing may provides a promising direction for fluff fabric based TENG.

Improvement of fresh and hardened properties of a sustainable HFRSCC using various powders as multi-blended binders

Hybrid fiber-reinforced self-compacting concrete (HFRSCC) has been very popular in recent years due to its high mechanical, durability and flexural performance. HFRSCC properties are also closely related to its workability properties. Therefore, a high proportion of binder material is required to provide a uniform distribution of the fibers in the matrix. The use of mineral admixtures replaced by cement has a vital importance to improve especially the workability of HFRSCC mixtures, resulting in reduction of CO2 emission because the production of 1 ton Portland cement releases about 1 ton of CO2. For this reason, in this study, the effects of multi-blended (binary, ternary and quaternary) binders containing Portland Cement (PC), fly ash (FA), ground granulated blast furnace slag (BS) and limestone powder (LP) on the workability (Slump-flow, T500, J-ring and V-funnel) and hardened (compressive, splitting tensile and flexural tensile strength) properties of HFRSCC as well as flexural performance for 7, 28 and 90 days are investigated. The first of three group mixtures in this study consists of only control mixture (Control) without fiber and mineral admixture blends (MAB), in second group there are four SCC mixtures with only MAB replaced by cement as binary, ternary, quaternary SCC-MAB and the last group also includes four SCC mixtures with both mineral admixtures same as second group and hybrid fiber (HFRSCC-MAB). The total binder amount, water/binder ratio, fine aggregate/all aggregate ratio and fiber hybridization are kept constant while the mineral admixture type and blending system are variable parameters. According to the test results, among the HFRSCC-MAB blends, the quaternary blend system performed the best in terms of workability, followed by the binary blends containing FA. In addition, when it came to ultimate strengths, hybrid fiber-reinforced samples with ternary blends performed best for compressive strength, while hybrid fiber-reinforced samples with binary blends containing FA performed best for splitting tensile and flexural tensile strengths. Finally, it has been seen that the use of various powders as multi-blended binders is a successful solution to obtain high workability for uniform distribution of fibers in HFRSCC as well as high compressive strength and flexural performance, resulting in economical, eco-friendly and sustainable composite.

Electrically-assisted supersonic solution blowing and solution blow spinning of fibrous materials from natural rubber extracted from havea brasilienses

Natural rubber (NR) is one of the most-studied natural polymers in the world due to its inherent characteristics and excellent properties. This renewable polymer has been used in industrial production of a wide range of products, from aircraft tires to medical devices. In the present study two novel methods of NR fibrous mat formation are investigated and compared: the electrically-assisted supersonic solution blow technique (EASBS) and solution blow spinning (SBS). The influence of processing parameters on the formation, morphology, and physical properties of the NR fibers is explored using scanning electron microscopy (SEM), mechanical testing, mechanical dynamic analysis (DMA), and thermal analysis (DSC and TG/DTG). Furthermore, the effect of 10% phenolic resin (PHOH) admixture on the final properties of NR obtained by EASBS, SBS and films formed by casting was investigated. SEM analysis helped to optimize the production conditions for NR and NR-PHOH fibrous mats by both EASBS and SBS with a fiber diameter in the 2–4 µm and 20–40 µm ranges, respectively. As a result of a more uniform distribution of NR fibers forming soldering points, the EASBS specimens appeared to be stiffer than those obtained by SBS and casting, resulting in a lower strain and a higher stress at break. TG/DTG analysis revealed that the thermal profiles were the same for all specimens, with polyisoprene decomposition occurring between 350 and 450 °C, whereas the Raman spectrum revealed that the bands for NR and PHOH resin were superimposed, indicating that there is no chemical interaction between the materials. Overall, NR fibrous mats with and without PHOH formed via EASBS and SBS revealed good mechanical properties as well as thermal stability.

MXene-Functionalized Ferroelectric Nanocomposite Membranes with Modulating Surface Potential Enhance Bone Regeneration.

Rapid and effective bone defect repair remains a challenging issue for clinical treatment. Applying biomaterials with endogenous surface potential has been widely studied to enhance bone regeneration, but how to regulate the electric potential and surface morphology of the implanted materials precisely to achieve an optimal bioelectric microenvironment is still a major challenge. The aim of this study is to develop electroactive biomaterials that better mimic the extracellular microenvironment for bone regeneration. Hence, MXene/polyvinylidene fluoride (MXene/PVDF) ferroelectric nanocomposite membranes were prepared by electrospinning. Physicochemical characterization demonstrated that Ti3C2Tx MXene nanosheets were wrapped in PVDF shell layer and the surface morphology and potential were modulated by altering the content of MXene, where uniform distribution of fibers and enhanced electric potential can be obtained and precisely assembled into a natural extracellular matrix (ECM) in bone tissue. Consequently, the MXene/PVDF membranes facilitated cell adhesion, stretching, and growth, showing good biocompatibility; meanwhile, their intrinsic electric potential promoted the recruitment of osteogenic cells and accelerated the differentiation of osteoblast. Furthermore, 1 wt % MXene/PVDF membrane with a suitable surface potential and better topographical structure for bone regeneration qualitatively and quantitatively promoted bone tissue formation in a rat calvarial bone defect after 4 and 8 weeks of healing. The fabricated MXene/PVDF ferroelectric nanocomposite membranes show a biomimetic microenvironment with a sustainable electric potential and optimal 3D topographical structure, providing an innovative and well-suited strategy for application in bone regeneration.

Computational-experimental method for determining the height of steel fiber sedimentation in Ultra-High Performance Self-Compacting Concrete

The uniform distribution of steel fibers in self-compacting Ultra-High Performance Steel Fiber Reinforced Concrete is one of the factors that determine the properties of the hardened material. In self-compacting concrete mixes characterized by low yield stress and plastic viscosity, steel fibers can settle under gravity, which can lead to a decrease in strength. In this study, a computational-experimental method is proposed for determining the height of steel fiber sedimentation, as well as the segregation index of a steel fiber reinforced concrete mixture. Mixtures were tested with a superplasticizer content of 1, 1.3, and 1.6% with a slump flow diameter of 288, 356, and 378 mm. According to the results of calculations performed according to the proposed method, it was found that the height of steel fiber sedimentation is 3.1, 5.9, and 22.8 mm in mixtures with a plasticizer content of 1, 1.3 and 1.6%. The calculated value of the segregation index of the steel fiber reinforced concrete is quite close to the experimental one with a correlation coefficient of 0.998. Based on the results obtained, a criterion was proposed for determining the maximum allowable height of fiber sedimentation, taking into account the actual height of the concreted structure, which can be used in the concrete mix design.

Investigation on tempering process parameters of in-situ consolidation CF/PEEK thermoplastic composites

In this paper, the effect of in-situ consolidation (ISC), hot-press (HP) tempering, and vacuum-bag-only (VBO) tempering process parameters on interlaminar shear strength (ILSS) of CF/PEEK laminates is investigated. Short beam shear (SBS) tests are performed on the prepared samples to characterize the load-displacement response, the ILSS trend, and the microscopic influence mechanism of different preparation processes on the ILSS. The experimental results show that the highest ILSS of the HP tempered samples reached 73.07 MPa, which is 132.04 % higher than the ILSS of the ISC samples. Furthermore, the highest ILSS of the VBO tempered sample is only 66.11 % of the HP tempered sample. Microscopic mechanism analysis revealed that the most direct reasons for the improved ILSS are stronger CF and PEEK binding interfaces, more stable crystal structures, and more uniform fiber distribution. The proposed method provides an important reference for green thermoplastic composites (TPC) for highly reliable and low-cost applications in aerospace skin types.

Synergy effect of hybrid steel-polyvinyl alcohol fibers in engineered cementitious composites: Fiber distribution and mechanical performance

The fiber distribution is a crucial factor governing the superb strain-hardening and multiple cracking behavior of engineered cementitious composites (ECC). However, the desired uniform distribution of fibers is challenging in ECC with large amounts of binders and fibers, especially for hybrid fiber system. In the present study, we employed image analysis to investigate the fiber distribution characteristics in hybrid steel-polyvinyl alcohol (PVA) fiber ECC and its influence on the mechanical performance. Special attention was paid to the impact of additional steel fiber content and its size. The results show that the dispersion coefficient of PVA fibers in hybrid fiber system was at most 50% higher than that of mono fiber system. Fiber hybridization rendered more fibers distributed in smaller angles of 0°–40°, which helped to enhance the fiber bridging capacity. The addition of steel fibers significantly improved the flexural properties of ECC, with maximized strength at steel fiber content of 1.0% and maximized deformability at 0.6% dosage. The incorporation of steel fibers greatly enhanced the crack control ability of hybrid fiber ECC. The average crack width was reduced to 36.1 μm when the volume fraction of steel fiber gone to 1.0%. Furthermore, larger sized steel fibers played a more pronounced role in improving the fiber dispersion, fiber orientation and mechanical properties than that with smaller size. Synergy effect of hybrid steel-PVA fiber on fiber distribution and mechanical properties was revealed. The findings are expected to contribute to the blending ratio design of hybrid fibers and the selection of fiber size in preparing ECC. And the obtained robust ECC can provide strong support for performance enhancement and maintenance of building engineering.

Effect of Hydrothermal Environment on Mechanical Properties and Electrical Response Behavior of Continuous Carbon Fiber/Epoxy Composite Plates.

In this work, the effect of a hydrothermal environment on mechanical properties and the electrical response behavior of continuous carbon fiber/epoxy (CFRE) composite produced by the pultrusion method were investigated. Due to the relatively uniform distribution of fibers and lack of resin-rich interlayer area, this effect for the pultruded CFRE composite plates is different from the common CFRE laminated composites. Firstly, its hygroscopicity behavior was studied. The absorption ratio increases rapidly to 1.02% within 3 days before reaching a relatively stable state. A three-point bending test, a Vickers hardness test, a thermogravimetric analysis (TGA), and a scanning electron microscope (SEM) analysis were performed to investigate the effect of the hydrothermal environment on the mechanical properties and thermal stability of the CFRE composite. The results indicated that the bending strength decreased quickly within 3 days of hydrothermal treatment, followed by a stable trend, which coincided with that of the hygroscopicity behavior of the composites. The fracture surface analysis indicated that the interfacial properties of carbon fibers in the epoxy matrix were decreased after the hydrothermal treatment, and more carbon fibers could be pulled out from the CFRE in the hygroscopic state. After the hydrothermal treatment, the micro-hardness of the composites was reduced by 25%. TGA confirmed the decreased thermal stability of the CFRE composites after the hydrothermal treatment as well. Moreover, the hydrothermally treated CFRE composites could a reach stable resistance response more readily. The revealing of the effect of moisture and hot environment on the mechanical properties and electrical response behavior of pultruded CFRE composites prepares the ground for their design and practical application in the corresponding environment.

Unravelling the Influence of Surface Modification on the Ultimate Performance of Carbon Fiber/Epoxy Composites.

The overall performance of polymer composites depends on not only the intrinsic properties of the polymer matrix and inorganic filler but also the quality of interfacial adhesion. Although many reported approaches have been focused on the chemical treatment for improving interfacial adhesion, the examination of ultimate mechanical performance and long-term properties of polymer composites has been rarely investigated. Herein, we report carbon fiber (CF)/epoxy composites with improved interfacial adhesion by covalent bonding between CFs and the epoxy matrix. This leads to the improved ultimate mechanical properties and enhanced thermal aging performance. Raman mapping demonstrates the formation of an interphase region derived from the covalent bonding between CFs and the epoxy matrix, which enables the uniform fiber distribution and eliminates phase separation during thermal cycling. The covalent attachment of the CF to the epoxy matrix suppresses its migration during temperature fluctuations, preserving the mechanical performance of resulting composites under the thermal aging process. Furthermore, the finite elemental analysis reveals the effectiveness of the chemical treatment of CFs in improving the interfacial strength and toughness of silane-treated CF/epoxy composites. The insight into the mechanical improvement of CF/epoxy composites suggests the high potential of surface modification of inorganic fillers toward polymer composites with tunable properties for different applications.

Modeling uniform random distributions of nonwoven fibers for computational analysis of composite materials

This paper considers the random placement of fibers on a square to achieve a desired homogeneous uniform distribution, as required in production of digital twin geometry for computational analysis of composite materials. Six methods of random fiber placement were demonstrated. Bertrand’s paradox for placement of random chords on a circle provided the framework to compare, contrast, and evaluate similar methods for placing fibers on a square. Simulations were performed with chord placement on a circle and fiber placement on a square. Results were evaluated using uniformity of areal line density and fragment size distributions. A combined approach for placement of fibers on a square was developed that achieved homogeneous uniform distribution. A proposed exact solution to achieve the desired uniform distribution was demonstrated. A statistical analysis and data regression demonstrated the homogeneous results achieved by the combined approach and the proposed exact solution. The objectives of this paper were achieved through demonstration of both a combined approach and a proposed exact solution to random fiber placement on a square to achieve homogeneous, uniform distribution of fibers for use in digital twin geometry for computational testing of composite materials.

Carbon nanotube‐polybutadiene‐poly(ethylene oxide)‐based composite fibers: Role of cryogenic treatment on intrinsic properties

AbstractThe low‐temperature response and the notion of crystallization kinetics are critical for developing elastomeric composite fibers, thus the crystallization and mechanical properties are essential for the application of composites of polybutadiene at low temperatures. Despite the high amount of fiber joining and entanglement due to polymers' low glass transition, a defect‐free micro‐scale electrospun carbon nanotube (CNT)‐containing poly(ethylene oxide) (PEO) and polybutadiene (PBu) composite elastomeric fibers with uniform fiber diameter and distribution are successfully fabricated. Thermomechanical behavior analyzed via frequency‐dependent dynamic mechanical analysis under cryogenic conditions shows a remarkable increase in decomposition temperatures (Tend) and storage and loss modulus at cryogenic temperatures, particularly when small amounts of CNTs are present. Dynamic mechanical treatment from 120 K to elevated temperatures yields a pronounced logarithmic increase in Tend by an increase of PEO content (from BEC1 to BEC4) compared to the treatment from 300 K. Through X‐ray diffraction, large shifts toward larger 2θ and formation of new crystals are observed, particularly for the BEC4 sample with high PEO content. Nanoparticles after cryo‐treatment linked with crystallinity are registered by ultra‐high resolution scanning electron microscopy. Improving the thermal and mechanical properties is critical in developing high‐performance composite fibers for cryogenic engineering applications, especially for future research to facilitate them in aerospace and low‐temperature medical and surgical treatments.

МЕХАНИЧЕСКАЯ ТЕХНОЛОГИЯ СОЗДАНИЯ ПЛИТНЫХ ФИБРОБЕТОННЫХ И ФИБРОЖЕЛЕЗОБЕТОННЫХ ЭЛЕМЕНТОВ С НАПРАВЛЕННОЙ ОРИЕНТАЦИЕЙ ФИБР В ДВУХ НАПРАВЛЕНИЯХ

A modified mobile installation has been developed for creating slab fiber-reinforced concrete and fiber-reinforced concrete elements with a directional orientation of the fibers in two directions according to the proposed mechanical technology. The presented mechanical technology for creating slab fiber-reinforced concrete and fiber-reinforced concrete elements will make it possible to provide a mutually perpendicular orientation of the fibers in various layers of the structure, which will allow for the most complete inclusion of each fiber fiber into the work of the element. Also, due to the use of a mobile installation for laying fiber-reinforced concrete mix, specially designed and modified to work with slab elements, a uniform distribution of fibers in the body of concrete will be mechanically ensured.