Isotropic Fiber Research Articles

Increasing softening point of isotropic spinnable asphalt by two-step preparation from ethylene tar residue modified with bio tar residue

Carbon fiber prepared from asphalt may be a critical type of low-weight chemical material of excellent mechanical performances. Here, an isotropic spinnable asphalt (EBA) was prepared from ethylene tar residue (ETR) by a two-step method of bio tar residue (BTR) through co-polymerization-air blowing, and isotropic asphalt carbon fibers were prepared from the product asphalt. The main types of molecules contained in the two feedstocks were determined by 1H NMR and LDI-TOF MS analyses. The co-polymerization behavior and thermal stability of the asphalt blends were analyzed using polarized light microscopy and thermogravimetric analyzer, respectively. Finally, the morphology and mechanical properties of carbon fibers made from EBA were evaluated by scanning electron microscope and universal testing machine. The results show that BTR contains much more oxygen-containing functional groups and unique long-chain sawtooth molecular structure; the former can promote the reactivity of the co-polymerization reaction, and the latter can limit the formation of large-plane cyclic aromatic hydrocarbon polymers due to the spatial resistance effect to greatly reduce the content of the mesophase. The softening point of the product asphalt shows a tendency of increasing and then decreasing with the increase of the proportion of BTR in the raw material mixture, and a reaction mechanism based on linear and bulky molecules is proposed to explain it by analogy with the structure of macromolecules. Consequently, the EBA made from a mixture of ETR and BTR at ideal moderate proportions has excellent performance in terms of softening point and mesophase content than ETRO made from ETR alone, and the carbon fiber made has a high tensile strength of 1.82 GPa with an elastic modulus of 38.9 GPa, which has reached the level of high tensile strength carbon fiber. Therefore, the use of inexpensive renewable energy bio-asphalt in the modification of heavy oil to obtain high softening point isotropic asphalt for preparing isotropic carbon fiber with excellent properties is achievable.

Carbon fibers from bitumen-derived asphaltenes: Strategies for optimizing melt spinnability and improving mechanical properties

The demand for low-cost carbon fibers with exceptional mechanical properties continues to grow across various industries. Bitumen-derived asphaltenes have emerged as a promising alternative to polyacrylonitrile (PAN), yet asphaltenes are a complex mixture of compounds, and the fundamental understanding of which asphaltenes are melt spinnable is not clearly understood. In this study, we utilized three distinct types of asphaltenes, each exhibiting notably distinct thermal softening temperatures (Ts) and aromaticity. The optimal melt processing conditions of asphaltenes were determined by dynamic rheology tests. Moreover, we introduced a novel strategy to facilitate the melt spinning of non-spinnable samples by preparing 100 % asphaltene blends with a low Ts asphaltene at different weight fractions. By this means, we achieved continuous melt spinning of precursor fibers. After careful selection of the stabilization and carbonization conditions, uniform carbon fibers were obtained from asphaltenes, which had the highest tensile strength (∼570 MPa) and modulus (∼60 GPa) values, comparable to isotropic pitch-based carbon fibers. Further post-processing of the as-spun fiber resulted in a significant increase in tensile properties, ∼1.1 GPa for strength and ∼91 GPa for modulus. Overall, this study identified spinnable asphaltene precursor characteristics and fiber post-processing methods for achieving low-cost, high-quality carbon fibers from asphaltenes.

Emulation and evaluation of tumor cell combined chemotherapy in isotropic/anisotropic collagen fiber microenvironments.

The rapid emergence of anisotropic collagen fibers in the tissue microenvironment is a critical transition point in late-stage breast cancer. Specifically, the fiber orientation facilitates the likelihood of high-speed tumor cell invasion and metastasis, which pose lethal threats to patients. Thus, based on this transition point, one key issue is how to determine and evaluate efficient combination chemotherapy treatments in late-stage cancer. In this study, we designed a collagen microarray chip containing 241 high-throughput microchambers with embedded metastatic breast cancer cell MDA-MB-231-RFP. By utilizing collagen's unique structure and hydromechanical properties, the chip constructed three-dimensional isotropic and anisotropic collagen fiber structures to emulate the tumor cell microenvironment at early and late stages. We injected different chemotherapeutic drugs into its four channels and obtained composite biochemical concentration profiles. Our results demonstrate that anisotropic collagen fibers promote cell proliferation and migration more than isotropic collagen fibers, suggesting that the geometric arrangement of fibers plays an important role in regulating cell behavior. Moreover, the presence of anisotropic collagen fibers may be a potential factor leading to the poor efficacy of combined chemotherapy in late-stage breast cancer. We investigated the efficacy of various chemotherapy drugs using cell proliferation inhibitors paclitaxel and gemcitabine and tumor cell migration inhibitors 7rh and PP2. To ensure the validity of our findings, we followed a systematic approach that involved testing the inhibitory effects of these drugs. According to our results, the drug combinations' effectiveness could be ordered as follows: paclitaxel + gemcitabine > gemcitabine + 7rh > PP2 + paclitaxel > 7rh + PP2. This study shows that the biomimetic chip system not only facilitates the creation of a realistic in vitro model for examining the cell migration mechanism in late-stage breast cancer but also has the potential to function as an effective tool for future chemotherapy assessment and personalized medicine.

Anisotropic auxetic composite laminates: A polar approach

The problem of obtaining anisotropic auxetic composite laminates, i.e. having a negative Poisson’s ratio for at least some directions, is examined in this paper. In particular, the possibility of obtaining auxeticity stacking uni-directional identical plies is considered. It is shown that if the ply is composed by isotropic matrix and fibers, then it is impossible to obtain totally auxetic orthotropic laminates, i.e. auxeticity for each direction, unless at least one among matrix and fibers is auxetic itself. Moreover, it is shown what are the conditions, in terms of the mechanical properties of the constituents and of the volume fraction of the fibers, to fabricate uni-directional plies with which to realize laminates having a negative Poisson’s ratio for some directions. Several existing materials are also examined. All the analysis is done using the polar formalism, very effective for the study of plane anisotropic problems.

Controllable synthesis of naphthalene-derived isotropic pitch with linear molecular structure via Blanc chloromethylation–dechlorination reaction

Isotropic pitches with high softening points were controllably synthesized using naphthalene (NAP) via Blanc chloromethylation–dechlorination. Under mild conditions, chloromethyl was introduced into the NAP ring in the presence of chloromethylation reagent. The chloromethylation products of NAP are mainly composed of 1-chloromethylnaphthalene (1-CMNP) and a small amount of 1,4-dichloromethylnaphthalene (1,4-DCMNP). The results of the thermodynamic and kinetic calculations confirmed that the alpha-hydrogen on the NAP ring was more susceptible to being substituted by chloromethyl during chloromethylation, resulting in the formation of 1-CMNP and 1,4-DCMNP. High-quality isotropic pitches with linear methylene-bridged NAP ring structures, characterized by high purity, a high H/C ratio, 100 % solubility in quinoline, and excellent spinnability, were obtained after thermal dechlorination polymerization. Due to their homogeneous isotropic phase, appropriate viscosity, and outstanding spinnability, the as-synthesized pitches were adopted as precursors to prepare isotropic pitch-based carbon fibers via melt spinning. Additionally, the investigation of the carbonization behavior of the as-synthesized pitches showed that the naphthalene-derived isotropic pitch obtained at a polymerization temperature of 380 °C had a 57 % carbon yield at 800 °C, and its derived semi-cokes displayed an isotropic texture, even when carbonized at 550 °C.

Huo Cao: a unique collectively utilized natural textile material and its structure and properties

Huo Cao, scientifically known as Gerbera delavayi Franch, is a perennial herb that exhibits the spontaneous growth of fibers, which intricately interweave to form a white network on the underside of its leaf. The Huo Cao fiber network demonstrated distinctiveness by being able to be twisted straight into yarns. The textiles made by Huo Cao also have their own unique characteristics. The structure and characteristics of the Huo Cao fiber and its network were examined in this study using surface morphology, SEM, chemical composition, TGA, FTIR, wettability, XRD, and chemical resistance tests. The outcomes were compared with those of cotton. The Huo Cao fiber naturally forms an isotropic fiber network. When comparing fiber to cotton, it is evident that they have a comparable physical structure. However, there are significant differences in terms of cellulose content and crystallinity. Huo Cao fiber is rich in flavonoids, which possess antibacterial properties. The Huo Cao network exhibits an average contact angle of 140°. Huo Cao fiber is susceptible only to powerful acids and is compatible with the skin.

Toward understanding the damage behavior during orthogonal cutting of 2.5D C/SiC composite based on multi-scale modeling and high-speed photography

2.5D C/SiC composite has been a critical high temperature material for aerospace filed due to its excellent wear, high temperature and oxidation resistance. Understanding the cutting damage behavior is crucial for achieving the high reliability application. This paper presents an in-depth study on damage behavior and material removal mechanism during orthogonal cutting of 2.5D C/SiC composite based on multi-scale modeling and high-speed photography. A three-dimensional numerical micro-macro multi-scale model is established considering the characteristics of the brittle SiC matrix, the isotropic carbon fiber reinforcement, and the pyrolytic carbon (PyC) layer. The orthogonal cutting experiments of 2.5D C/SiC composite with high-speed photography technology is carried out. The results show that the proposed model can accurately predict the microscopic deformation and fracture of the fiber. Meanwhile, surface fiber spring-back phenomenon is found based on high-speed photography, and its mechanism is first explanation based on the stress evolution analysis of the multi-scale model. In addition, it indicates that the increase of the depth of cut has a significant impact on the chip shape evolution, transitioning from powdery, needle-like, to block-like or strip-like shape. The paper covers some new sights for low-damage cutting of 2.5D C/SiC composite materials.

Micromechanics of fibrous scaffolds and their stiffness sensing by cells

Mechanical properties of the tissue engineering scaffolds are known to play a crucial role in cell response. Therefore, an understanding of the cell-scaffold interactions is of high importance. Here, we have utilized discrete fiber network model to quantitatively study the micromechanics of fibrous scaffolds with different fiber arrangements and cross-linking densities. We observe that localized forces on the scaffold result in its anisotropic deformation even for isotropic fiber arrangements. We also see an exponential decay of the displacement field with distance from the location of applied force. This nature of the decay allows us to estimate the characteristic length for force transmission in fibrous scaffolds. Furthermore, we also looked at the stiffness sensing of fibrous scaffolds by individual cells and its dependence on the cellular sensing mechanism. For this, we considered two conditions- stress-controlled, and strain-controlled application of forces by a cell. With fixed strain, we find that the stiffness sensed by a cell is proportional to the scaffold’s ‘macroscopic’ elastic modulus. However, under fixed stress application by the cell, the stiffness sensed by the cell also depends on the cell’s own stiffness. In fact, the stiffness values for the same scaffold sensed by the stiff and soft cells can differ from each other by an order of magnitude. The insights from this work will help in designing tissue engineering scaffolds for applications where mechanical stimuli are a critical factor.

Co‑carbonization of coal tar pitch and brominated industrial methylnaphthalene for the production of isotropic pitch-based carbon fibers with enhanced tensile strength

The co‑carbonization of refined coal tar pitch (RCTP) and brominated industrial methyl naphthalene (BIMNP) employing benzoyl chloride (BC) as a catalyst has been explored to create an isotropic spinnable pitch for carbon fibers with notable tensile strength. BIMNP is derived from industrial methyl naphthalene (IMNP) via photo-bromination assisted by visible light using N-bromosuccinimide (NBS) as a brominating agent. This research investigates the impact of the mass ratio of RCTP and BIMNP on the composition, molecular structure, and thermophysical characteristics of the co‑carbonized pitch. A tentative elucidation of the co‑carbonization mechanism involving RCTP, BIMNP, and BC is presented. Adjusting the NBS-to-IMNP mass ratio leads to the complete conversion of 1-methylnaphthalene (1-MNP) and 2-methylnaphthalene (2-MNP) in IMNP into 1-bromomethylnaphthalene (1-BMNP) and 2-bromomethylnaphthalene (2-BMNP), respectively. The co‑carbonized pitch exhibits enhanced pitch production, increased thermal stability, and improved spinnability compared to pitch synthesized via thermal polycondensation. The resulting carbon fibers experience a rise in tensile strength by 947 MPa and an increase in Young's modulus by 41.3 GPa as BIMNP content varies from 10% to 30%. Using BIMNP as a co‑carbonization agent offers a promising avenue for producing pitch-based carbon fibers meeting automotive industry requirements.

Numerical Investigation of Stress-Strain State Effects on Strain Measurements with Fiber Bragg Grating Sensors

This study investigates the behaviour of resonant wavelengths of Fiber Bragg Gratings (FBG) inscribed within optically isotropic fibers under transverse loading, both in free and embedded conditions. A numerical-analytical approach is employed, utilizing the finite element method to calculate strain tensor components in the optical fiber core, followed by an analytical determination of resonant wavelengths and reflected FBG spectrum shape. The research demonstrates the influence of the ratio of host material and optical fiber elastic moduli on the birefringence level in FBG area under transversal loading. Based on analytical model of FBG spectrum simulation the discrepancy between analytically calculated and experimentally recorded resonant wavelength shifts in FBG embedded within isotropic material under varying transverse load levels is demonstrated.

Manufacturing of automotive mat using recycled carbon fiber: Obtaining strong physical properties through isotropic fiber orientation and improved adhesion of epoxy resin

Manufacturing of automotive mat using recycled carbon fiber: Obtaining strong physical properties through isotropic fiber orientation and improved adhesion of epoxy resin

Double-clad ytterbium-doped tapered fiber with circular birefringence as a gain medium for structured light.

Amplifying radially and azimuthally polarized beams is a significant challenge due to the instability of the complex beam shape and polarization in inhomogeneous environment. In this Letter, we demonstrated experimentally an efficient approach to directly amplify cylindrical-vector beams with axially symmetric polarization and doughnut-shaped intensity profile in a picosecond MOPA system based on a double-clad ytterbium-doped tapered fiber. To prevent polarization and beam shape distortion during amplification, for the first time to the best of our knowledge, we proposed using the spun architecture of the tapered fiber. In contrast to an isotropic fiber architecture, a spun configuration possessing nearly circular polarization eigenstates supports stable wavefront propagation. Applying this technique, we amplified the cylindrical-vector beam with 10 ps pulses up to 22 W of the average power at a central wavelength of 1030 nm and a repetition rate of 15 MHz, maintaining both mode and polarization stability.

Energy release rate for steady-state fiber debonding in structural battery composites

Structural battery composites are multifunctional materials intended to provide energy storage capacity while maintaining their strength and load bearing capacity under significant mechanical loads. In this study, we investigate the mechanics of carbon fiber debonding, a critical failure mechanism in structural battery composites. The carbon fibers are intended to serve both as an electrochemically active material and to bear mechanical load in the composite system. We derive an analytical solution to the energy release rate for steady-state fiber debonding for different electrochemical and mechanical loading cases with the aid of the classical solution for the Eshelby inclusion problem. The analytical solutions are validated with finite element simulations. We find a higher energy release rate and thus a greater driving force for fiber debonding is caused either by a lower lithium concentration in the fiber and/or by greater transverse mechanical loads such as biaxial tension or shear applied at the far field in the matrix. We find that the model is predictive even for transversely isotropic fibers despite the assumption that the fiber is elastically isotropic in the model. This work can provide guidance for the design of mechanically robust structural batteries.

Effect of carbonization conditions on microstructural properties of isotropic coal tar pitch-based general-purpose carbon fibers

The microstructures of carbon fibers can be significantly modified by understanding the carbonization conditions which improves the properties of fibers. The carbonization is a complex process of converting pitch fibers into carbon fibers through the evolution of gases and arrangement of molecules by polymerization reactions. Hence, the present study focuses on the synthesis of isotropic pitch-based carbon fibers and the investigation of microstructural properties with varying carbonization conditions at 1000 °C. The isotropic pitch is derived from coal-tar pitch through the utilization of a vacuum distillation technique. Various properties of isotropic pitch are studied to determine the flowability and optimum temperature range for melt-spinning into fibers. Subsequently, the stabilization process is conducted in an open atmosphere to retain fibers shape by introducing oxygen-containing functional groups. Time-dependent carbonization parameters such as heating rate and holding/soaking periods are used to optimize the conditions that yield superior microstructural properties. This research reveals that slower heating rates enhance the crystallite sizes while reducing defects. Conversely, longer holding times at carbonization temperature showed adverse effects on the microstructural properties. To assess microstructural, thermal and physical properties of the pitch and fibers, various characterizations are performed, including DSC, TGA, rheology, FTIR, XPS, Raman, XRD, and SEM.

Multi-scale optimization of selectively magnetized isotropic carbon fiber fabrics for microwave absorption using machine learning

A synergistic collaboration between microscopic analysis and macroscopic engineering is essential to attain optimal scientific properties. Traditional material design methods are ineffective in navigating the vast and infinite design space of cross-scale systems. Fortunately, machine learning provides an efficient and time-saving scientific solution for exploring the boundless possibilities offered by multi-component and structural materials systems. Crucially, the development of theoretical predictions, supported by theoretical calculations and finite element simulations, will facilitate the global optimization of materials. In this study, the structure and component of selective magnetic surface @ CF fabric are screened and balanced simultaneously using target-driven optimization frame. In order to achieve dynamic adjustment of micro surface and macro structure parameters, the relative factors are translated into codes and introduced into the design. And simulation, experimental feedback and corrections are established. The flexible CCGF shows a broad effective absorption bandwidth with 8.2 GHz with a thickness of only 1.76 mm and a density of 8.8 × 10−4 kg cm−3. Step-by-step optimizations and summaries are performed for data analysis, together with finite element simulation-based electromagnetic and loss field analysis and theoretical analysis to accelerate understanding, paving the way for development of novel materials for both functional and structural applications.

Isotropic coal tar pitch-based carbon fibers: Effect of nitric acid towards elimination of air-stabilization step

The remarkable properties exhibited by carbon fibers have generated considerable interest in seeking alternative approaches to replace time-consuming, energy-intensive, and multi-step procedures for their synthesis. Among the various stages involved in carbon fiber synthesis, the stabilization step plays a crucial role as it necessitates an extended duration to transform thermoplastic pitch-fibers into thermosetting fibers, thus preventing them from melting during high-temperature treatments. In this study, isotropic coal tar pitch (ICTP) was transformed into pitch fibers through melt-spinning process and subsequently subjected to chemical treatment for stabilization using varying concentrations (ranging from 5% to 50% v/v) of aqueous nitric acid (HNO3) solutions. The objective was to determine the optimal concentration for effective stabilization. Consequently, this research eliminates the conventional, time-consuming air-stabilization process by treating the pitch fibers with nitric acid prior to carbonization. To produce carbon fibers, all chemically stabilized pitch fibers were directly carbonized at 1000 °C. Comprehensive characterizations including Rheology, Elemental analysis, FTIR, TGA, FE-SEM, XRD, Raman, and XPS were conducted to investigate the chemical and structural transformations occurring during the fiber processing. It was observed that aqueous nitric acid solutions ranging from 15% to 30% (v/v) exhibited superior structural, morphological, and mechanical properties compared to other concentrations of HNO3.

Post-bifurcation of inflated fibrous cylindrical membranes under different fiber configurations

We consider a cylindrical membrane that consists of an isotropic ground substance and fibers symmetrically arranged in two helically distributed families which are mechanically equivalent. Pressurized and axially stretched cylinders will undergo a stable inflation period that may be followed, for example, by the initiation of bulging. The pressure and deformation associated with bulging and post-bifurcation depend on various factors such as geometry and material characteristics. While the initiation of bulging has been well-studied, the post-bifurcation process has received less attention. In the post-bifurcation period, the bulge may propagate axially nucleating new configurations in equilibrium as the pressure of inflation increases. This article studies the effect of the material properties, fiber pre-stretch, fiber dispersion, and loading on both the initiation and post-bifurcation behavior of the cylinder. The results show that fiber pre-stretch may stabilize the material against bulging, whereas fiber dispersion may result in the opposite effect. A large axial stretch of the cylinder and a high fiber stiffness may result in a switch from bulging to necking in the post-bifurcation behavior.

Методика определения свойств компонентов композиционного материала на основе миграционных алгоритмов глобальной оптимизации

<p>A mathematical model has been formed for calculating the elastic characteristics of a generalized material based on the properties of a transversely isotropic fiber and an isotropic matrix. The problem of choosing the parameters of materials is formulated as the problem of minimizing the objective function on a parallelepiped set of admissible solutions. To solve it, classical and modified self-organizing migration algorithms of global optimization belonging to the group of metaheuristic are applied. Recommendations on the selection of the best parameter values are obtained.</p>

Investigation of the Tendency of Carbon Fibers to Disintegrate into Respirable Fiber-Shaped Fragments

Recent reports of the release of large numbers of respirable and critically long fiber-shaped fragments from mesophase pitch-based carbon fiber polymer composites during machining and tensile testing have raised inhalation toxicological concerns. As carbon fibers and their fragments are to be considered as inherently biodurable, the fiber pathogenicity paradigm motivated the development of a laboratory test method to assess the propensity of different types of carbon fibers to form such fragments. It uses spallation testing of carbon fibers by impact grinding in an oscillating ball mill. The resulting fragments were dispersed on track-etched membrane filters and morphologically analyzed by scanning electron microscopy. The method was applied to nine different carbon fiber types synthesized from polyacrylonitrile, mesophase or isotropic pitch, covering a broad range of material properties. Significant differences in the morphology of formed fragments were observed between the materials studied. These were statistically analyzed to relate disintegration characteristics to material properties and to rank the carbon fiber types according to their propensity to form respirable fiber fragments. This tendency was found to be lower for polyacrylonitrile-based and isotropic pitch-based carbon fibers than for mesophase pitch-based carbon fibers, but still significant. Although there are currently only few reports in the literature of increased respirable fiber dust concentrations during the machining of polyacrylonitrile-based carbon fiber composites, we conclude that such materials have the potential to form critical fiber morphologies of WHO dimensions. For safe-and-sustainable carbon fiber-reinforced composites, a better understanding of the material properties that control the carbon fiber fragmentation is imperative.

Investigation of the Dimensions of Making Brillouin Laser in Optical Fiber

Optical fiber is a transparent material such as glass (silica) with plastic that can expel light from one end to the other, it has a much higher bandwidth than conventional cables which can be used for image data. It has the capacity to easily transmission of audio and other data with high bandwidth of up to 10 Gbps and above Nowadays optical telecommunications are the most important tools of data transmission due to their wider bandwidth, compared to copper cable, and less latency coppered to satellite telecommunications. In this paper, a fiber optic at speed of (6m)/min is made of an isotropic optical fiber (with similar physical properties on all sides) prefabricated with alight-sensitive core Geo2-B-Sio2.