Strength Of Carbon Fibers Research Articles

Effectively enhanced interlaminar shear strength of carbon fiber fabric/epoxy composites by oxidized short carbon fibers at an extremely low content

Carbon fiber reinforced epoxy composites have high specific strength and modulus but relatively low interlaminar shear strength (ILSS). Herein treated short carbon fibers (SCFs) with ethanol and concentrated nitric acid are added to epoxy matrix to improve the ILSS of carbon fabric (CF)/epoxy composite. The effects of SCF content and treatment (oxidization) time are systematically examined on the ILSS of the CF/EP composite. An effective enhancement of 13.5% in the ILSS of the CF/EP composite is achieved by oxidized-SCFs at an extremely low content of 0.07 wt% relative to the epoxy matrix. The main mechanisms for enhancing the ILSS of CF/EP composite are explored by the addition of oxidized-SCFs. This strategy is of great practical significance since SCFs are very cheap and also can be easily dispersed in epoxy resins compared with nano-fillers etc. previously used for this purpose.

Mechanical Properties of Fabricated CFRP with Filler

In this paper fabrication of carbon fiber-based hybrid composite was carried using graphene and industrial waste (Fly-ash) as filler material in different percentages. Fly-ash was chosen as it is a major industrial waste. The graphene possesses various functional properties that made good interfaces with epoxy and carbon fibers. Fillers (graphene and fly ash) are considered to improve the reinforced strength, surfacing characteristics, toughness of the reinforced composite plate like structure. Properties like compressive strength, tensile strength, hardness and impact strength of carbon fiber reinforced polymer (CFRP) with fillers are tested. The change in the properties of CFRP composites attributable to mechanical interlocking of graphene and fly-ash with epoxy and fiber was observed.

Fiber-reinforced polymer plates for strengthening web opening in steel I-beams under cyclic loading

This article is interested in finding the most appropriate strengthening scheme for web opening in steel I-beam under cyclic loading. Different opening shapes and locations were strengthened using two different fiber-reinforced polymer plates: carbon fiber–reinforced polymer and basalt fiber–reinforced polymer. A three-dimensional nonlinear finite element model was adopted using ANSYS program. The results showed that the high strength of carbon fiber–reinforced polymer plates helped the steel beam to recover its original strength; however, noticeable reduction was observed in beam ductility and in the number of inelastic excursions that took place before failure. Moreover, remarkable difference in stress concentration existed at the position of the carbon fiber–reinforced polymer plate edges. Under cyclic loading, fiber-reinforced polymer composites with low modulus of elasticity such as basalt fiber–reinforced polymer managed to eliminate these deficiencies using longer strengthening length. The most appropriate strengthening length and scheme for each opening case were outlined.

Experimental investigation for the effect of fiber on the mechanical properties of light-weight concrete under dry and wet conditions

Purpose The purpose of this paper is to investigate the effect of steel and carbon fibers on the mechanical properties of light concrete in terms of tension strength, compressive strength and elastic modulus under completely dry and wet conditions. Design/methodology/approach In this study, the lightweight concrete made of Light Expanded Clay Aggregate (LECA) as coarse aggregate and sand as fine aggregate was used. To achieve a compressive strength of at least 20 MPa, microsilica was used 10 percent by weight of cement. In order to compensate for the reduction of tension strength of concrete, steel and carbon fibers were used with three volume ratio of 0.5, 1 and 1.5 percent in concrete. The results of concrete specimens were studied at the age of 7, 28, 42 and 90 days under controlled dry and wet conditions. Findings The results showed that the addition of steel and carbon fibers to the concrete mixture would reduce the drop in slump. Also, the use of steel and carbon fibers plays a significant role in increasing the tension strength of the specimens. Furthermore, the highest increase in tension strength of steel and carbon fiber samples was 83.3 and 50 percent, respectively, than the non-fibrous specimen when evaluated at 90 days of age. Moreover, the steel and carbon fiber increased the water absorption of the samples. Adding steel and carbon fibers to a lightweight concretes mixture containing LECA aggregates plays a significant role in increasing the modulus of elasticity of the samples. The highest increase in the elastic modulus of steel and carbon fibers was 18.9 and 35.4 percent, respectively, than the non-fibrous specimen at 28 days of age. Originality/value In this paper, the authors investigated the mechanical properties of steel fiber and carbon reinforced concrete. Also, according to the conditions of storage of samples and the age of concrete (day), the experiments were carried out on samples.

Integrating tough Antheraea pernyi silk and strong carbon fibres for impact-critical structural composites

High stiffness and strength carbon fibres are commonly used to reinforce epoxy-resin composites. While wild Antheraea pernyi silk fibres exhibit high toughness originating from their α-helix/random coil conformation structures and their micro-fibre morphology, their insufficient strength and stiffness hinders them from being used in similar structural composites. In this work, we use interply hybridization of silk and carbon fibres to reinforce epoxy-matrix composites. With increased carbon fibre content, the quasi-static tensile/flexural stiffness and strength increases following the rule of mixtures while more silk fibre acts to increase ductility and impact strength. This results in a composite comprising equal volumes of carbon and silk fibres achieving an impact strength of 98 kJ m−2, which is twice that of purely carbon-fibre reinforced composites (44 kJ m−2). This work shows tough natural silk fibres and strong synthetic fibres can be successfully integrated into epoxy-resin composites for tailored mechanical properties.

Promising hybrid fabrics based on carbon and aramid fibers as a reinforcing filler for polymer composites

The paper considers possibilities of using a hybrid fabric made of high-modulus carbon yarn brand ZhGV and high-strength aramid yarns brand Rusar-NT for polymer composites reinforcement. The results of studies of the physical and mechanical characteristics of hybrid composite material and values of the implementation of the strength and elasticity carbon fibers and aramid module for composite material are presented.

The Influence of Mechanical Recycling on Properties in Injection Molding of Fiber-Reinforced Polypropylene

Abstract Due to higher mechanical demands on technical parts, the application of short fiber reinforced thermoplastics for injection molding is strongly increasing. Therefore, more attention needs to be paid to the optimization of their recycling processes. Mechanical shredding of thermoplastics into granules is a common recycling method within polymer industries. The breaking of polymer chains and reinforcing fibers during this process may affect the material properties. This study presents the effect of ten recycling sequences on four different materials: polypropylene, glass fiber filled polypropylene, carbon fiber filled polypropylene and flax fiber filled polypropylene. Tests indicate that recycling has a negative influence on most of the mechanical properties. Polypropylene without fibers forms an exception as it does not exhibit any significant change in material properties. Glass fiber and carbon fiber reinforced polypropylene show a decrease in stiffness and tensile strength during the recycling steps. The impact strength of carbon and flax fiber reinforced polypropylene increases whereas that of glass fiber reinforced polypropylene decreases.

The effect of carbon fabrics modification on the strength of carbon fiber reinforced plastic

This article reviews the study of influence of carbon fabrics modification on the strength of carbon fiber reinforced plastic. Two types of epoxy compound Etal Inject SLM of “cold curing” and Etal Inject-T of “heat curing”, nitric acid HNO3 of concentration 60 %, carbon fabric of Toho Tenax/Aksa 3k-1200-200 were used in the study. Comparisons of the strength properties of carbon plastic on these compounds were given. The best result was obtained on Etal Inject-T with tensile strength – 1000 MPa and in compression – 425 MPa. Carbon fabric modification was carried out by grafting carboxylated groups treated with HNO3 to the carbon fiber surface. The treatment time in acid varied from 0.5 to 6 minutes. The compressive strength by 17 % from 425 MPa to 497 MPa has been established to increase when carbon fiber by HNO3 is modified for from 0.5 min to 2 min, then the strength decreases enlarging the treatment time. The decrease in strength is associated with supersaturation of the surface of the fibers with carboxyl groups, which were destroyed during heat treatment. Thus, the surface oxidating of carbon fabric is the most effective method of increasing its adhesion to epoxy resin and the strength of carbon fiber. The functional groups formed during the oxidation process allow for a tight cross-linking of the epoxy matrix with carbon fiber. It was previously found that the strength of carbon fiber increases with the modification of epoxy resin with oxidized carbon nanotubes. An assumption is made about a uniform mechanism for strengthening carbon-fiber reinforced plastic due to chemically active functional groups, both on the surface of carbon fiber and on the surface of carbon nanotubes.

LOAD-CARRYING CAPACITY INCREASE OF ARCH-TYPE TIMBER ROOF

Possibility to increase load-carrying capacity of arch-type timber roof of multifunctional public building with the span equal to 60 m was analysed. Three-hinged segment arches with the rectangular glued cross-sections are considered as the main load-carrying structures in the transversal direction. Freely supported purlins with the massive rectangular cross-sections are considered as the main load-carrying structures in the longitudinal direction. The dependences between height of the arches, it bays and distances between the bracing members strengthening top and bottom zone of the arches cross-sections so as relative materials consumption and specific load-carrying capacity of the arches were obtained as the second power polynomial equations. Height of the arches and it bay changes within the limits from 10 to 30 and from 2 to 9 m, correspondingly. The distances between the bracing members strengthening top and bottom zone of the arches changes within the limits from 2 till 10 and from 4 till 16 m, correspondingly. The arch-type timber roof was considered under the action of the load combination which include structural dead weight, drifted and undrifted snow loads and wind loads. The relative materials consumption of the arches was determined as a relation between the dead weight of the arch to it span and changes within the limits from 24 till 114 kg/m. Glued and solid timber with strength classes GL24h and C24 are considered as materials of arches and purlins, correspondingly. The specific load-carrying capacity of the arches was determined as a relation between load –carrying capacity of the arche and volume of structural materials. Specific load-carrying capacity of the arches changes within the limits from 0.23 till 0.83 kN/m/t in the case, if purlins are taken into account. It was shown, that the rational from the point of view of materials consumption and specific load-carrying capacity height of the arche, it bays so as the distances between the bracing members strengthening top and bottom zone of the arches are equal to 15, 7.5, 5 and 15 m, correspondingly. Corresponding values of relative materials consumption and specific load-carrying capacity are equal to 24 and 0.23 kN/m/t. The depth and width of the arche cross-section were equal to 1617 and 318 mm, correspondingly. It was shown, that strengthening of the arches cross-section by the steel bars of strength class B500 and carbon fibre reinforced plastic tape Sika Crbo Dur S512 enables to increase load-carrying capacity of the arche by 10.20 and 9.48%, correspondingly. But common use of the steel bars together with the carbon fibre reinforced plastic tapes enables to increase load-carrying capacity of the arche by 18.89%.

Kinetics of Recycling CF/EP Composites by Thermal Excitation of Cr2O3

Recycling high performance carbon fibers (CFs) by thermal excitation of Cr2O3 semiconductor was proposed. The kinetic model of decomposition of epoxy resin was established and the method for solving kinetic parameters was proposed. The influences of temperature and treatment time on the decomposition rate of epoxy resin were investigated. The kinetic equation was established and the accuracy was verified experimentally. The morphology of the recycled CF was observed and monofilament tensile strength was determined. Results indicated that temperature and treatment time had positive correlation with decomposition rate of the epoxy resin. The reaction order n was 1.5, with excitation energy E of 85.03 kJ·mol−1 and pre-exponential factor k0 of 1.26 × 106 min−1. The established kinetic equation could be used to estimate the temperature and treatment time. Prolongation of treatment time could improve the monofilament tensile strength. The monofilament tensile strength of the recycled CF at 480 °C for 30 min was 102.72% of that of the original CF, indicating that surface heat treatment was performed on CF during the recycling process.

Factorial design approach to assess the effect of fiber–matrix adhesion on the IFSS and work of adhesion of carbon fiber/polysulfone-modified epoxy composites

A two-level full factorial design 22 with three replications was employed to assess the effect of the incorporation of PSF into the epoxy matrix and the surface treatment of carbon fibers on the work of adhesion (WA) and the interfacial shear strength (IFSS) of carbon fiber–epoxy composites. The IFSS was determined using the microbond (or microdrop) micromechanical test, and the work of adhesion was estimated using two different procedures: (1) using the Owens and Wendt method, and (2) from the Dupre–Young expression using the contact angle θ of a cured epoxy resin on a single carbon fiber and the surface energy of the cured epoxy resin. It was found that the treatment of the carbon fiber with the silane-coupling agent appreciably increases its polar component because of the nitric acid oxidation and the chemisorption of the silane-coupling agent onto the carbon fiber surface. Also, the O=S=O group present in the polysulfone chain resin fairly increases the polar component of the epoxy–PSF blend. The results show that the wetting of the silane-treated carbon fiber by the thermoplastic-modified epoxy resin is better, thus increasing the fiber–matrix adhesion. It was also found that there is a similarity between the trends of both, the IFSS and the WA results. Also, from the ANOVA results it was also seen that both the incorporation of the PSF to the epoxy matrix and the surface treatment of the carbon fibers and their interaction were statistically significant to the IFSS and the WA.

Effect of polyurethane sizing agent on interface properties of carbon fiber reinforced polycarbonate composites

ABSTRACTThis work is aimed at investigating how molecule structure of polyurethanes (PUs) as sizing agents influence the interface properties of carbon fiber (CF) reinforced polycarbonate (PC) composites. Effects of four PUs as sizing agents for CF on the interlaminar shear strength (ILSS) of CF reinforced PC composites are investigated. It is found that the three PUs except PC–PU as sizing agents on oxidized CF (OCF) made the ILSS of their reinforced PC composites increase up to 62.9 MPa by more than 24.8%. The chemical interaction between PU sizing agents and CF are attributed to high reactivity of isocyanate, but carbonate groups on PC–PU may have a chain unzipping reaction due to active groups on the surface of OCF. The chemical interaction between PU sizing agents and PC are attributed to transesterification. As a result, PUs containing isocyanate or polyester groups are ideal sizing agents for CF reinforced PC composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47982.

Experimental investigation on the ball burnishing of carbon fiber reinforced polymer

ABSTRACTThe polymer-based materials are generally used in all industrial applications. Even if polymer bars can be machined easily, they need surface finishing treatment after the machining process. The ductile properties make coarse roughness on the surface that causes the elastic structure of polymer materials. The carbon fiber reinforced composite materials differ from polymer-based materials by high strength and stiffness. Its structure exhibits similar performances such as metallic materials. The effect of ball burnishing on the surface quality of rod workpiece was investigated in this study. To enhance the surface quality of high strength carbon fiber reinforced polymer rod workpiece, burnishing process was performed in three different parameters (force, feed rate, number of passes) and under four different mediums (dry, wet, boron oil, and mineral oil) conditions. The results of the experiments were analyzed, and optimum burnishing parameters were determined and discussed in detail. The best surface roughness value of the CFRP material used in the experiments was obtained as burnishing force: 250 N, feed rate: 0.05 mm/rev, four passes and wet medium. According to the results of variance analysis, it was found that the CFRP workpiece is the important leading factor for surface roughness with a contribution ratio of 62.47%.

High Strength and High Modulus Carbon Fibers “TORAYCA<sup>Ⓡ </sup>MX Series”

High Strength and High Modulus Carbon Fibers “TORAYCA<sup>Ⓡ </sup>MX Series”

Design of Pseudoductile Unidirectional Hybrid Composites Based on the Model of a Dry Bundle

An analytical method for designing layered high-modulus and high-strength fibrous hybrid composite materials with a highly nonlinear mechanical behavior is put forward. The elastic and strength characteristics of unidirectional layers of the composites were determined experimentally. Then, the parameters of Weibull distribution of the strength of carbon and glass fibers were estimated using test results for specimens of hybrid structure with a preliminary calculated number of carbon plastic layers in the composite. Using the criterion of maximum structural strength with a restricted elastic modulus and proportionality limit, the structure of a hybrid composite with thin CFRP and GFRP layers is optimized. A kinematic loading of a hybrid composite in which all layers deform together without stratification is considered. The Daniels model of dry bundle, with account of Weibull distribution of fiber strength, is employed to consider the decrease in the stiffness of composite layers and of the composite as a whole caused by microdefects. The approach offered was used in the design of a $$ \left[{0}_m^{\mathrm{c}}/{0}_{1-m}^{\mathrm{g}}\right] $$ pseudoductile hybrid carbon/glass plastic with the highest structural strength. It was found that m ≈ 0.30, which agreed with experimental data.

Influence of fibre content on the strength of carbon fibre reinforced HfC/SiC composites up to 2100 °C

The influence of carbon fibre content on the mechanical behaviour of HfC/SiC composites was investigated up to 2100 °C for specimens containing 40 or 55 vol% fibres. Silicon carbide was added as a sintering aid during hot pressing. Increasing the fibre content made infiltration more difficult, which resulted in higher porosity in the specimen with 55 vol% fibres. The room temperature flexural strength ranged from 340 to 380 MPa, and it increased to more than 400 MPa at 1800 °C due to stress relaxation. Increasing temperature was accompanied by a decrease in the slope of the load-displacement curve, indicating a decrease in elastic modulus, but plastic deformation was not observed below 2100 °C. At 2100 °C, the specimen containing a higher fibre content underwent significant deformation due to low interfacial strength between the fibre plies, retaining a strength at the proportional limit of 290 MPa and an ultimate strength of 520 MPa.

A two-step carbon fiber surface treatment and its effect on the interfacial properties of CF/EP composites: The electrochemical oxidation followed by grafting of silane coupling agent

A two-step surface treatment was applied on the surfaces of polyacrylonitrile(PAN)-based carbon fibers (CFs) including the electrochemical oxidation process followed by grafting of silane coupling agent KH550. The evolution of the physiochemical structure of the fiber surface during the surface treatment was investigated using Infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and surface tension/dynamic contact angle measurements. The results showed that the CF surface exhibited a significant increase in the relative content of oxygen-containing functional groups after surface treatment while its crystal structure had little change after the grafting of KH550 agents. Effects of surface treatment on the mechanical properties of CFs and the interfacial properties, including the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of carbon fiber reinforced epoxy (CF/EP) composites were evaluated in detail. Both the electrochemical oxidation and the introduction of KH550 agents onto CF surfaces improved the IFSS and ILSS values of CF/EP composites by comparison with untreated fibers. In particular, the maximum interfacial properties of CF/EP composites were obtained by the electrochemical oxidation together with the grafting of KH550 agents onto CF surfaces.

Amorphous Carbon-Induced Surface Defect Repair for Reinforcing the Mechanical Properties of Carbon Fiber.

Graphene oxide (GO) was prepared using metal-catalyzed crystallization of amorphous carbon on a carbon fiber surface to improve the mechanical properties of the carbon fiber (CF). The deposited GO was used for repairing of surface structure defects on CF, thereby improving the tensile strength and interfacial strength force of CF. The grown morphology of GO and the changes in CF surface microstructure before and after remediation were investigated in detail by scanning tunneling microscopy and Raman spectroscopy. The effects of surface repair on the mechanical properties of the CF and the resulting composites were investigated systematically. The results of scanning tunneling microscopy show that the graphene oxide formed on the surface of carbon fiber present uniform dispersion. Raman spectroscopy curves indicate that CF successfully remediated the defects in the CF surface. The results of mechanical properties testing show that such a remediation method could significantly enhance the tensile strength of CF and increase the interfacial strength versus raw fibers; that is, the tensile strength of CF was enhanced by 42% and the interfacial strength by 33.7%.

Improved tensile strength of carbon nanotube-grafted carbon fiber reinforced composites

Increased tensile strength of carbon nanotube (CNT)-grafted carbon fiber (CF) composites has been reported, but the mechanism of this increase is not yet clear. In this study, CNT-grafted CF unidirectional (UD) and woven composites were fabricated using a low-temperature chemical vapor deposition (CVD) and resin transfer molding. Two types of CNTs (short and thin, long and thick) were successfully grown and grafted to CFs without degrading the CFs in the preforms. The CNT-grafted CFs exhibited increased interfacial shear strength (IFSS) similarly regardless of the CNT type. Interestingly, however, long and thick CNT-grafted CF UD and woven composites exhibited significant increases in tensile strength (about 20% and 30%), suggesting other mechanisms besides increased IFSS. The splitting crack initiation under the mixed mode condition was quantitatively characterized for the CNT-grafted CF UD composites, demonstrating that long and thick CNTs delayed the splitting crack initiation. Delayed fiber splitting and increased IFSS were concluded to be the main sources of increased tensile strength of CNT-grafted CF composites.

Time Dependent Structure and Property Evolution in Fibres during Continuous Carbon Fibre Manufacturing.

Here we report on how residence time influences the evolution of the structure and properties through each stage of the carbon fibre manufacturing process. The chemical structural transformations and density variations in stabilized fibres were monitored by Fourier Transform Infrared Spectroscopy and density column studies. The microstructural evolution and property variation in subsequent carbon fibres were studied by X-ray diffraction and monofilament tensile testing methods, which indicated that the fibres thermally stabilized at longer residence times showed higher degrees of structural conversion and attained higher densities. Overall, the density of stabilized fibres was maintained in the optimal range of 1.33 to 1.37 g/cm3. Interestingly, carbon fibres manufactured from higher density stabilized fibres possessed lower apparent crystallite size (1.599 nm). Moreover, the tensile strength of carbon fibres obtained from stabilized fibres at the high end of the observed range (density: 1.37 g/cm3) was at least 20% higher than the carbon fibres manufactured from low density (1.33 g/cm3) stabilized fibres. Conversely, the tensile modulus of carbon fibres produced from low density stabilized fibres was at least 17 GPa higher than those from high density stabilized fibres. Finally, it was shown that there is potential to customize the required properties of resultant carbon fibres suiting specific applications via careful control of residence time during the stabilization stage.