Carbon Fiber Material Research Articles

Features of strengthening metal structures with composite materials under the influence of an aggressive environment

Introduction. This article is devoted to the issues of reinforcing metal building structures with external reinforcement systems with composite materials. The application of these strengthening methods in domestic literature and in practice has not been fully studied. As a result, it is relevant to study the characteristics of strengthening under the action of an external aggressive environment, namely when exposed to galvanic corrosion, elevated ambient temperatures and extreme temperatures from firing. The purpose of the study is to establish the effectiveness of reinforcing metal structures with composite materials under the influence of various force factors, including cyclic loads, and under the action of an external aggressive environment.
 Materials and methods. The methodological basis of scientific research was the analysis of publications of domestic and foreign scientists on the theoretical and practical experience of using composite materials to strengthen metal structures. During the study, when describing the dependences of physical quantities on external and internal force and non-force factors, scientific methods of induction, deduction, generalization and comparison were used.
 Results. Performed a comprehensive study of the effectiveness of the use of composite materials to enhance the metal structures in hostile environments. The dependence of the increase in strength of reinforced steel samples on the length of the adhesive joint of external reinforcement is analyzed, the possibility of applying reinforcement at fatigue stresses is investigated. Recommendations on the use of protective insulating systems and materials that prevent the reduction of the bearing capacity of structures from external non-force factors are given.
 Conclusions. The effectiveness of reinforcing metal structures using composite carbon fiber materials is revealed. The bearing capacity of reinforced structures may be increased by 59 %. When the glass transition temperature of carbon fiber materials is reached, the increase in the bearing capacity from external amplification systems decreases by 50 %, and when the temperature is increased to 60 °C, the external amplification systems are ineffective and do not increase the bearing capacity. To achieve the required fire resistance of the amplification systems, equal to at least one hour, it is necessary to use external fire insulation.

Interpreting Dynamic Interfacial Changes at Carbon Fiber Microelectrodes Using Electrochemical Impedance Spectroscopy.

Carbon-fiber microelectrodes are instrumental tools in neuroscience used for the electroanalysis of neurochemical dynamics and recordings of neural activity. However, performance is variable and dependent on fabrication strategies, the biological response to implantation, and the physical and chemical composition of the recording environment. This presents an analytical challenge, as electrode performance is difficult to quantitatively assess in situ, especially when electrodes are permanently implanted or cemented in place. We previously reported that electrode impedance directly impacts electrochemical performance for molecular sensing. In this work, we investigate the impacts of individual components of the electrochemical system on impedance. Equivalent circuit models for glass- and silica-insulated carbon-fiber microelectrodes were determined using electrochemical impedance spectroscopy (EIS). The models were validated based on the ability to assign individual circuit elements to physical properties of the electrochemical system. Investigations were performed to evaluate the utility of the models in providing feedback on how changes in ionic strength and carbon fiber material alter impedance properties. Finally, EIS measurements were used to investigate the electrode/solution interface prior to, during, and following implantation in live brain tissue. A significant increase in impedance and decrease in capacitance occur during tissue exposure and persist following implantation. Electrochemical conditioning, which occurs continually during fast-scan cyclic voltammetry recordings, etches and renews the carbon surface, mitigating these effects. Overall, the results establish EIS as a powerful method for characterization of carbon-fiber microelectrodes, providing unprecedented insight into how real-world factors affect the electrode/solution interface.

Nebulized jet-based printing of bio-electrical scaffolds for neural tissue engineering: a feasibility study

In this paper we investigate the application of a direct writing technique for printing conductive patterns onto a biocompatible electrospun-pyrolysed carbon-fibre-based substrate. The result is a first study towards the production of bio-electrical scaffolds that could be used to enhance the promotion of efficient connections among neurons for in vitro studies in the field of neural tissue engineering. An electrospinning process is employed for production of the materials derived from the precursor polyacrylonitrile, in which the embedding of carbon nanotubes (CNTs) is also investigated. Subsequently, the methodology of research into suitable parameters for the printed electronics, using a commercial silver nanoparticle (Øavg,particle size ∼ 100 nm) ink, is described. The results show values of 2 Ω cm for the resistivity of the carbon-fibre materials and conductive printed lines of resistance ∼50 Ω on glass and less than ∼140 Ω on carbon-fibre samples. Biocompatibility results demonstrate the possibility of using electrospun-pyrolysed mats, also with embedded CNTs, as potential neural substrates for spatially localized electrical stimulation across a tissue. In addition, the data concerning the potential toxicity of silver suspensions are in accordance with the literature, showing a dose-dependent behaviour. This work is a pioneering feasibility study of the use of the flexible and versatile printed electronic approach, combined with engineered biocompatible substrates, to realize integrated bio-electrical scaffolds for in vitro neural tissue engineering applications.

Activated Carbon Fiber Fabrics in Filtration and Clean Water Resources

Activated carbon fiber has excellent structural characteristics and adsorption performance. It can effectively adsorb various inorganic and organic compounds and has good regeneration performance. Therefore, it is widely used in the market. To study the advantages of activated carbon fiber in purifying water resources, this research use application of activated carbon fiber material in purification and filtration of water filter, and the test of adsorption and filtration effect of different host materials are described. The main body and influencing factors of filtering effect are obtained. In this research, the viscose-based activated carbon fiber mats and acrylic-based activated carbon fabrics are the main research subjects, and other materials were added for coating composite research. Through a comparative study of the two materials, it has been found that carbon fiber has many advantages, such as is more economical, practical, convenient, low cost, and cost-effective, and is worthy of promotion in industry and daily life using.

Structural analysis of hexagonal and solid carbon fibers composite

This paper is showed to explore the relationship between materials and their properties. The elements are defined by their features. It identifies the composition of the pyrolysis products obtained through pyrolysis in the structure of different designs. Two design specimens of carbon fibers structure with different directional load were fabricated, solid carbon fibers and hexagonal carbon fibers structure. The deformation behavior is well-known and has been analyzed. 3D finite element (FE) models were used to investigate both structures. There was some impact on the specimens used, and the behavior of the strain and stress line was captured. These results show that the positive Poisson's ratio of both composites structures obtained when appropriate yarn structure in the 3D material system is adopted in both designs. The main purpose of the experiment was to define and test the structure's use in industries that require carbon fiber material that has excessively excellent mechanical and thermal properties. DMA tests have been conducted, and both the thermal and mechanical properties investigated. The compositions can improve carbon vs the adhesion of the polymer matrix for carbon fibers structure, which allows the use of such fibers for the reinforcement of plastics without extra processing.

Calculation Method Analysis for Structure Strengthening with External Reinforcement

This article describes the main provisions of the calculating method for the gain of reinforced concrete structures by the system of external reinforcement. As an example, the calculation of monolithic reinforced concrete slab with carbon fiber material using the SCAD Office software package was considered and analyzed, which most accurately reflects the geometry and physico-mechanical parameters of the structure. The calculation of reinforced concrete structures includes engineering survey to determine the existing physic-mechanical characteristics of materials, perform calibration calculations and stress calculations in reinforced concrete structures of buildings and structures, taking into account the existing stiffness characteristics, designing reinforcement engineering solutions, the calculation of the forces in the structures and verification of the structures bearing capacity after the reinforcement is completed. During the survey of reinforced concrete structures, it is determined existing loads, deformations, deflections, physico-mechanical characteristics for the subsequent selection of the composite material cross section and taking them into account after the concrete structure’s reinforcement. The external reinforcement systems is used for reinforcing concrete structures and rely on tensile stress perception, taking into account the joint deformations of the composite material used for reinforcement and the concrete structure. The calculation of reinforced concrete structures carried out on the first and second limit state. If the load after reinforcement with a composite material does not increase compared with the loads at the stage of the reinforced concrete structure operation, the calculation for the second group of limit states is not performed. The reinforced concrete structures calculation using an external reinforcement system made of composite materials is carried out from the joint operation conditions of the installed external reinforcement and the concrete base before the limit state onset. The calculation is performed in two stages: at the first stage, the reinforced concrete structure is calculated without reinforcement taking into account the existing loads and deformations, at the second stage, after the work on reinforcement, the design is calculated taking into account the efforts and deformations in the first stage.

Theoretical Assessment Of The Bearing Capacity Of A Steel Beam Reinforced With Carbon Fiber

To reinforce steel beams, modern carbon fiber materials that are attached to the beam from the stretched side using a special two-component adhesive can be effectively used. Compared to traditional methods of cross-section increase by means of additional steel elements attached by welding or on bolts, reinforcing with carbon fiber plastic has a number of advantages. Carbon plastic has a much smaller weight than a steel element that has the same load-bearing capacity; the adhesive layer prevents corrosion of the reinforced element; work on strengthening is carried out in a short time and with less labor expenditures etc. The article presents the results of theoretical studies of beams reinforced with carbon fiber lamellas. For the theoretical assessment of the strength of a reinforced steel beam, deformations and stresses in the section at the elastic, elastic-plastic and plastic stages of steel work are considered. It is established that a significant effect of carbon fiber reinforcement is observed even when the stresses in it are determined by the strength of the adhesive joint. Formulas, taking into account the strength of the adhesive layer determined experimentally, for determining the strength of a reinforced beam are obtained. A theoretical model of the operation of bent steel elements is constructed and theoretical dependencies are obtained that can be used for calculations of steel beams reinforced with carbon plastic.

탄소섬유 및 무기질 소재를 충전한 하이브리드 고분자개질 방수아스팔트

본 연구에서는 하이브리드 방수 개질아스팔트에 충전되는 충전재와 적정조성을 도출하였다. 탄소섬유(2.5%)와 스테아릭산-코팅 탄산칼슘(2.5%)의 적정조성비를 가진 하이브리드 충전재가 첨가된 하이브리드 방수 개질아스팔트의 경우에, 하이브리드 충전재가 없는 기본조성 또는 기본조성과 기존 충전재인 탄산칼슘의 5% 조성비를 가지는 방수 개질아스팔트와 다르게, KS F 3211의 인장강도, 신장률 및 인열강도의 요구조건을 만족하였다. 또한 기본조성과 방수 개질아스팔트의 기존 충전재인 탄산칼슘의 5% 조성비를 가지는 방수 개질아스팔트의 경우에는 수압이 0.3 N/mm² 경우에 투수되어서 KS F 4935의 투수저항성능 시험의 요구조건을 만족시키지 못하였으나, 적정조성비를 가진 하이브리드 방수 개질아스팔트 시편에 대한 투수저항성능 시험에서는 0.4 N/mm²의 수압에서 투수가 되었음에도 불구하고, 수압이 0.3 N/mm² 경우에 투수되지 않아서 투수저항성능에서 KS F 4935를 만족시켰다.

Nanoscale Oxidation Behavior of Carbon Fibers Revealed with <i>in situ</i> Gas Cell STEM

Thermal protection systems are used to protect spacecraft payloads during the extreme conditions of atmospheric entry. The backbone of the composite material often used for NASA mission is carbon fiber, which oxidizes at these conditions. This study presents the direct observation of carbon oxidation using in situ Scanning Transmission Electron Microscopy (STEM). A thin section of a commercially-available carbon fiber material containing multiple structures was examined by STEM in a closed-environmental cell in which temperature was raised from 25 to 1050°C under a steady flow of air. Results show that the random polycrystalline carbon structure oxidized more uniformly and rapidly than the single crystallite region, which oxidized more anisotropically. These findings are the first to directly observe the structural dependence of carbon oxidation rates at these length-scales while also giving important insight into the onset of pitting at various active surface sites, important pieces in fundamentally understanding of carbon oxidation.

Numerical analysis of mechanical behavior of unidirectional thermoplastic-based carbon fiber composite for 3D-printing

The paper is dedicated to the simulation of mechanical behavior of a unidirectional thermoplastic-based composite material reinforced with carbon fibers. The influence of microstructure imperfections on mechanical characteristics of the composite material has been studied, and numerical parameters that ensure a good correlation between nonlinear two-scale simulation of progressive damage and experimental data have been identified. Results of the study revealed limited importance of accounting for such imperfections of composite microstructure as deviation in fiber laying direction and fiber curvature. The two-scale simulation approach based on submodeling technique was proved to describe the nonlinear behavior of the thermoplastic-based carbon fiber material with a reasonable accuracy.

Application of Adhesive Compositions Based on a Silicon Sealant and an Acrylic Adhesive as Binders in the Technology of Flexible Conductors

An adhesive composition based on acrylic acid and a silicon sealant is developed for impregnating carbon-fiber materials to obtain composites that can be used as flexible conductors. The physicomechanical and dynamic characteristics of the developed adhesive are investigated, and optimal impregnation conditions are determined. It is demonstrated that using this composite makes it possible to increase the operation life of a flexible conductor due by preserving high strength under alternating bending strains over a long period of time.

Deposition of Metal Nanoclusters from Colloidal Solutions on the Surfaces of Porous Roll Materials by Means of Electrophoresis

The technology for producing metallized coatings on superporous carbon fiber materials from colloidal solutions by means of electrophoresis is studied. Technologies and equipment for the deposition of silver nanoparticles and other metal nanoparticles on rolled carbon materials are considered. The carbon materials consist of fibers 6 μm thick and are used as an electrode materials for current sources.

Study of the structure of fibrous carbon materials using X-ray diffractometry

New possibilities for diagnosing the structure of carbon materials by X-ray diffraction analysis are described. The studies were performed on an X-ray diffractometer D8 ADVANCE (filtered Cu K α radiation) using carbon fibers (CF) differed in the mode of heat treatment (~2300 to ~3000°C). It is shown that when studying the structure of fibrous carbon materials characterized by a large depth of X-rays penetration, it is necessary to limit the thickness of the object under study to ~0.1 mm to provide the self-focusing condition for the entire sample volume engaged in formation of the diffracted beam. The material of high modulus carbon fibers can be heterogeneous and contain coherent scattering regions wherein the crystal structure parameters are somewhat different and experimentally observed diffraction peaks 002, 004, and 006 become asymmetric and are not described by the Gauss, Lorentz, or Voigt functions. Thus, the standard method used for determination of the average value of the interplanar spacing and the size of coherent scattering regions does provide reliable information on the real structure of the material. The profile of the asymmetric diffraction peak 002 was analyzed using the Origin program thus providing information about fine (heterogeneous) structure of the carbon fiber material which largely determines the physicomechanical properties. The data on 002 diffraction peak profiles of carbon fibers before and after removal of the Cu K α 2 component are presented. The data on decomposition of the experimentally observed asymmetric 002 diffraction peaks into symmetric peaks described by the Gaussian, Lorentz, and Voigt functions are compared. The most preferable is the decomposition into the components described by the Gaussian or Voigt functions.

The dimensional stability assessment of the composite honeycomb panel for the conditions of thermal and gravitational loading in a Near-Earth Orbit

The results of the numerical determination of the stress-strain state of the composite honeycomb panel under gravitational and thermal loads of varying intensity in a near-earth orbit are presented. As a simulation model of the structure under study, a typical structure of a composite cell panel with a known type of cell arrangement of honeycomb aluminum filler and reinforcement schemes for layers of carbon fiber material for upper and lower plates with known thermomechanical properties was chosen. To solve the problems of thermoelasticity, we used the finite element method in mathematical formulations for stationary thermal and quasistatic thermomechanical analysis. The distribution of the values of von Mises equivalent stresses in the structural elements of the honeycomb panel under thermal loads in the temperature range from -80 to +80 is determined. The longitudinal and transverse deflections of the honeycomb from the action of thermal loads of various intensities in the near-earth orbit are found. The limiting value of the temperature difference between the outer surfaces of the plates, which ensures the thermal stability of the composite honeycomb panel, has been established. The maximum deflections of the honeycomb have been found out from gravitational and thermal stresses in the near-Earth orbit.

Vibration modal experiments and modal interactions of a large space deployable antenna with carbon fiber material and ring-truss structure

This paper investigates the vibration modal experiments and the modal interactions for a large space deployable antenna with the ring-truss structure. The reduced scale model of the large deployable ring-truss antenna is firstly introduced briefly. The reduced experimental scale model of the ring-truss structure is designed and is manufactured. The experimental measurements of the vibration modals are carried out for reduced scale model of the ring-truss structure. The natural frequencies and the corresponding modal shapes are obtained for the reduced scale model of the ring-truss structure. The forced vibration experiments of the reduced scale model are also finished for the ring-truss structure. The displacements of the joint point under different excitation frequencies are obtained and are analyzed. A finite element (FE) analysis is finished for the reduced scale model of the ring-truss structure through applying Nastran. The results of the finite element method (FEM) verify the dynamic behaviors of the experimental model. The modal results of the vibration experiments are compared with those of the theoretical analysis and are indicated to be at a good agreement. The phenomena of the energy transfer are observed from the low frequency modal vibration to the high frequency modal vibration in the forced vibration experiments. We also find these phenomena in the process of studying the theoretical model for the ring truss antenna. It is demonstrated that there exist the phenomena of the energy transfer from the low frequency mode vibration to the high frequency mode vibration for the ring truss antenna when the excitation frequency is consistent with the lower order frequency of the vibration.

Characterization of Wood-based Industrial Biorefinery Lignosulfonates and Supercritical Water Hydrolysis Lignin

Understanding the properties of any particular biorefinery or pulping residue lignin is crucial when choosing the right lignin for the right end use. In this paper, three different residual lignin types [supercritical water hydrolysis lignin (SCWH), ammonium lignosulfonate (A-LS), and sodium lignosulfonate (S-LS)] were evaluated for their chemical structure, thermal properties and water vapor adsorption behavior. SCWH lignin was found to have a high amount of phenolic hydroxyl groups and the highest amount of β-O-4 linkages. Combined with a low ash content, it shows potential to be used for conversion into aromatic or platform chemicals. A-LS and S-LS had more aliphatic hydroxyl groups, aliphatic double bonds and C=O structures. All lignins had available C3/C5 positions, which can increase reactivity towards adhesive precursors. The glass transition temperature (Tg) data indicated that the SCWH and S-LS lignin types can be suitable for production of carbon fibers. Lignosulfonates exhibited considerable higher water vapor adsorption as compared to the SCWH lignin. In conclusion, this study demonstrated that the SCWH differed greatly from the lignosulfonates in purity, chemical structure, thermal stability and water sorption behavior. SCWH lignin showed great potential as raw material for aromatic compounds, carbon fibers, adhesives or polymers. Lignosulfonates are less suited for conversion into chemicals or carbon fibers, but due to the high amount of aliphatic hydroxyl groups, they can potentially be modified or used as adhesives, dispersants, or reinforcement material in polymers. For most value-adding applications, energy-intensive purification of the lignosulfonates would be required.Graphic

Laboratory Tests Analysis of Reinforced Concrete Structures Strengthened with CRFP

Modern construction industry is constantly evolving and improving. Therefore, new opportunities are used to solve the constantly emerging new problems. One of the modern innovations in these areas is the use of carbon-fiber nonwoven fabric for strengthening structures and composite materials. Carbon fibers have several advantages in increasing the bearing capacity of the structure: high modulus of elasticity (240-640 GPa) and tensile strength (2500-4000 MPa), minimal coefficient of thermal expansion (approximately 50 times less than steel), high fatigue characteristics, excellent resistance to aggressive environments, withstands many cycles of «freeze-thaw». One of the promising areas for the development for strengthening concrete structures with carbon fiber materials is prestressed carbon fiber reinforced plastic system. This area has a great potential for use in reinforced concrete structures, most often in pavements: to reinforce overloaded elements, external reinforcement of structures with corroded pre-stressed reinforcement, repair of structural nodes. The article reviews and analyzes the laboratory tests result of reinforced concrete structures (slabs and beams), reinforced with prestressed carbon, as well as non-stressed laminates.

Preparation and Heat Transfer Mechanism of ZrO2 Fiber Flexible Heat-Insulating Materials

The high temperature insulation material of zirconia fiber and carbon fiber (CZ) was prepared by wet molding process using chopped carbon fiber and zirconia fiber as raw materials. The thermal conductivity of the block was measured by high temperature flat plate thermal conductivity instrument. The effects of content of zirconia fiber, diameter of zirconia fiber and material density on CZ thermal conductivity were studied. The heat transfer mechanism of CZ was also studied. The results showed that the heat conductivity of CZ insulation material could be reduced with the reducing the diameter of zirconia fiber. The heat conductivity of CZ insulation material also could be reduced with increasing the content of zirconia fiber.

Selectively Enhanced 3D Printing Process and Performance Analysis of Continuous Carbon Fiber Composite Material.

Aiming at the limited mechanical properties of general thermoplastic 3D printed models, a 3D printing process method for selective enhancement of continuous carbon fiber composite material is proposed. Firstly, the selective enhanced double nozzle working mechanism and crafts planning process are put forward. Then, based on the double nozzle carbon fiber 3D printing device, test samples are printed by polylactic acid (PLA) and carbon fiber material, and the test samples are enhanced by inserting layers of continuous carbon fiber material. The performance test of the samples is carried out. Experiment results show that when the volume fraction of continuous carbon fiber material increases gradually from 5% to 40%, the tensile strength increases from 51.22 MPa to 143.11 MPa. The performance improvement curve is fitted through experimental data. Finally, field scanning electron microscopy is used to observe the microscopic distribution of continuous fibers in the samples. The results of the research lay the foundation for the performance planning of 3D printed models.

Fiber with Butterfly Wings: Creating Colored Carbon Fibers with Increased Strength, Adhesion, and Reversible Malleability.

Colored and color-changing materials are central to perception and interaction in nature and have been exploited in an array of modern technologies such as sensors, visual displays, and smart materials. Attempts to introduce color into carbon fiber materials have been limited by deleterious impacts on fiber properties, and the extension of colored fibers toward "smart composites" remains in its infancy. We present carbon fibers incorporating structural color, similar to that observed on the surface of soap bubbles and various insects and birds, by modifying the fiber surface through in situ polymerization grafting. When dry, the treated fibers exhibit a striking blue color, but when exposed to a volatile solvent, a cascade of colors across the visible light region is observed as the film first swells and then shrinks as the solvent evaporates. The treated fibers not only possess a unique color and color-changing ability but also can be reversibly formed into complex shapes and bear significant loads even without being encased in a supporting polymer. The tensile strength of treated fibers shows a statistically significant increase (+12%), and evaluation of the fiber-to-matrix adhesion of these polymers to an epoxy resin shows more than 300% improvement over control fibers. This approach creates a new platform for the multifaceted advance of smart composites.