Properties Of Carbon Fibers Research Articles

Effect of oxygen content on the preoxidation structure of polyacrylonitrile fibers

AbstractDuring the preoxidation process of polyacrylonitrile (PAN) fibers, the diffusion behavior of oxygen from skin to core can lead to the formation of radially uneven structure of fibers, which affects the mechanical properties of subsequent PAN carbon fibers. Here we examine the effect of oxygen content on the subsequent structure evolution of fibers with different preoxidation structure, by using13C Solid‐state NMR analysis (13C‐NMR), optical density characterization, differential scanning calorimetry analysis, and thermalgravimetric analysis. The results show that increasing the oxygen content during the subsequent heat treatment can effectively reduce the radial structure difference of fiber, its efficiency is related to the preoxidation degree of fibers. For fibers with lower preoxidation degree, namely less heat treatment work (W), the radial structure difference disappears when the oxygen content reaches 29%. Further study shows that the improvement of radial structure of preoxidized fibers improved fiber thermal stability, its efficiency is also related to theWof fibers; when theWof fibers is 5, the carbonization yield at 800°C increased from 56.79% to 62.61%, which is 10.25% higher; when theWof fibers is 20, under the same oxygen content range, the carbonization yield increased from 68.97% to 69.60%, which is only 0.913% higher.

Effect of the Hybridization of Carbon Fibers with Aramid and UHMWPE Fibers on the Impact Properties of Hybrid Carbon Fiber Reinforced Plastics

Effect of the Hybridization of Carbon Fibers with Aramid and UHMWPE Fibers on the Impact Properties of Hybrid Carbon Fiber Reinforced Plastics

Multifunctional properties of carbon fiber integrated cement composite – A review and insights

This article examines the strength characteristics of carbon fiber-reinforced cement composite (CFRCC). The research explores the residual mechanical characteristics and microstructure of concrete reinforced with carbon fiber. The review also focused on the determination of the effect of CFRCC on the improvement of strength, microstructure, crystalline phase shift, and hydration products of the cement composites. The review indicates that the inclusion of carbon fibers can intensify the flexural and splitting strengths of CFRCC, but the compressive strength is magnified to a lesser extent. In addition to the initial elastic modulus and peak stress of carbon fiber-reinforced cement composite, a discernible strain-rate hardening effect was also observed. This indicates that carbon fiber-reinforced cement composite has a promising future as cement composite reinforcements. The review of the characteristics of the composites also suggests their applicability in tunnel building in the cement composite. It is determined that carbon fiber-reinforced cement composite has a stronger capacity to withstand impact loads, and further information about its features will be supplied. The scanning electron microscopy (SEM) result demonstrates that the single and most significant failure mode under stress is carbon fiber breaking and the pull-out of carbon fibers. Thus, the review reveals that carbon fibers have a limited but positive act on enhancing the mechanical properties of cement composites.

Experimental investigation on workability and mechanical properties of carbon fiber reinforced high-strength concrete (HSC) containing waste bakelite aggregate (WBA)

High-strength concrete (HSC) is a type of concrete that is, due to its improved mechanical and durability properties, most often used in the construction of high-demand structures such as bridges, structural elements in aggressive environments, skyscrapers, and large-span constructions. In order to obtain high-strength concrete, a larger amount of cement is required, which can lead to questionable ecological acceptability of this material. To reduce the ecological footprint of this material, supplementary cementitious materials such as silica fume or metakaolin are often used. By reducing the porosity and increasing the density of the concrete mixture, fine particles of supplementary cementitious materials have a positive effect on the mechanical and durability properties of high-strength concrete. Along with cement and supplementary cementitious materials, another important component of high-strength concrete is aggregate, which is in most cases a fine aggregate. In this research, the natural fine aggregate was partially replaced with bakelite plastic waste, and the influence of this replacement on the fresh and hardened properties of high-strength concrete was presented. Seven mixtures were designed, a reference mixture and six other mixtures in which supplementary cementitious materials, waste bakelite aggregate, and carbon fibers were combined to produce environmentally friendly high-strength concrete. 5 % of the cement mass was replaced with silica fume or metakaolin, 10 % volume of natural fine aggregate was replaced with waste bakelite aggregate (WBA) and carbon fibers were added in the amount of 0.5 % of the cement mass. In a fresh state, the workability of HSC is determined by using a flow table. To determine the influence of waste bakelite aggregate on mechanical properties, flexural and compressive strength tests were carried out on 7- and 28-day-old samples. The test results indicate that the combined effect of waste bakelite aggregate, supplementary cementitious materials, and carbon fibers can be a promising solution not only to improve high-strength concrete mechanical properties but to potentially save millions of tons of natural fine aggregate and preserve natural resources and the environment.

Design of Experiment to Determine the Effect of the Geometric Variables on Tensile Properties of Carbon Fiber Reinforced Polymer Composites

Carbon fiber reinforced polymers (CFRPs) are increasingly used in the aerospace industry because of their robust mechanical properties and strength to weight ratio. A significant drawback of CFRPs is their resistance to formability when drawing continuous CFRPs into complex shapes as it tends to bridge, resulting in various defects in the final product. However, CFRP made from Stretch Broken Carbon Fiber (SBCF) aims to solve this issue by demonstrating superior formability compared to conventional continuous CFRPs. To study and validate the performance of SBCF, a statistical design of the experiment was conducted using three different types of CFRPs in tow/tape form. Hexcel (Stamford, CT, USA) IM7-G continuous carbon fiber impregnated with Huntsman (The Woodlands, TX, USA) RDM 2019-053 resin system, Hexcel SBCF impregnated with RDM2019-053 resin, and Montana State University manufactured SBCF impregnated with Huntsman RDM 2019-053 resin were tested in a multitude of forming trials and the data were analyzed using a statistical model to evaluate the forming behavior of each fiber type. The results show that for continuous fiber CFRP tows forming, Fmax and Δmax do not show statistical significance based on temperature fluctuations; however, in SBCF CFRP tows forming, Fmax and Δmax is dominated by the temperature and geometry has a low statistical influence on the Fmax. The lower dependence on tool geometry at higher temperatures indicates possibly superior formability of MSU SBCF. Overall findings from this research help define practical testing methods to compare different CFRPs and provide a repeatable approach to creating a statistical model for measuring results from the formability trials.

Optimization of interfacial properties of different high modulus carbon fiber composites by tailored interphase stiffness with MWNT-EP/epoxy sizing

Based on the physicochemical properties of high modulus carbon fibers (HMCF, p-CCM40J, p-CCM50J and p-CCM55J), the interphases of various gradient modulus were designed and constructed via epoxy suspension with epoxide functionalized muti-wall carbon nanotubes (MWNT-EP), and the relations and mechanisms of optimized interfacial properties with different interphase structures of HMCF composites were explored. Due to the increased degree of surface graphitization of pristine HMCFs, a smoother and more inert surface structure was exhibited. As the elevated sizing concentration of MWNT-EP, the HMCF morphology displayed a tendency from sparseness to uniformity then agglomeration with a slackened ascent of chemical activity, which indicated the various thresholds of MWNT-EP on different HMCF surface. Compared to pristine HMCF composites, the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of CCM40J, CCM50J and CCM55J composites at the threshold concentration (0.7 wt%, 0.5 wt%, 0.3 wt%) showed remarkable enhancements by 58.46%, 54.39%, 34.92% and 25.19%, 24.43%, 17.95%, respectively, which was attributed to the modulus transition layer. Schematic models of tailored interfacial reinforcing mechanism were proposed to illustrate the various optimal content of MWNT-EP applied to buffer the exterior load and achieve smooth modulus transition at the interphase, which was ascribed to the corresponding matching of the MWNT-EP threshold with the intrinsic structure and modulus of HMCFs.

Effect of Graphite Defect Type and Heterogeneous Atomic Doping Structure on the Electromagnetic Wave Absorption Properties of Sulfur-Doped Carbon Fibers

The heterogeneous atom-doped structure breaks the atomic-level symmetry of the local microstructure, and it and the defect design are considered to be an efficient way to fabricate microwave absorbers with a wide effective bandwidth and strong absorption capability. Herein, we have successfully designed and synthesized sulfur-doped carbon fibers by combining a strategy of introducing heterogeneous atoms with defect engineering. The analysis of Raman spectroscopy and transmission electron microscopy data reveals the correspondence between the type of graphite defects in sulfur-doped carbon fibers and their microwave absorption properties. The heterostructure formed by graphite and amorphous carbon can be considered a boundary-type defect, which is beneficial for microwave absorption. The introduction of vacancy defects and sulfur atom doping in graphite crystals breaks the symmetry of the graphite structure and leads to changes in dipole polarization. The ratio of the two sulfur-doped structures, C═S and C–S–C, is controlled to achieve the microwave absorption properties of the material in the high-frequency region. The three-dimensional structure formed by the cross-linking of one-dimensional fibers is more conducive to the formation of macroscopic eddy current losses. The strong absorption of microwaves at extremely thin thicknesses has been achieved with S-doped carbon fibers due to the synergy of multiple loss mechanisms. When the absorber thickness is only 0.98 mm, the optimized S-doped carbon fiber can reach a minimum reflection loss (RL) of −69.232 dB, and when the thickness is 1.04 mm, the widest effective bandwidth reaches 3.9 GHz (14.1–18 GHz), demonstrating a strong electromagnetic wave absorption capability.

The hierarchical layer with dynamic imine bonds on carbon fiber surface to simultaneously improve interface and electromagnetic shielding properties of carbon fiber reinforced thermoplastic composites

Constructing surface hierarchical layer is regarded as an effective surface modification of carbon fibers (CFs) to enhance their composites mechanical properties. However, this method usually deteriorates the intrinsic properties of CF and the hierarchical layer is not fully compatible with thermal processing of the polymer. Here, a novel hierarchical layer consisting of polydopamine, polyethyleneimine and multi-walled carbon nanotubes without damages to CF was successfully decorated on CF surface (CNT@PP-CF) for simultaneously enhancing the mechanical and the electromagnetic interference (EMI) shielding properties of CF reinforced polyamide 66 (PA66) composite. The CNT@PP hierarchical layer with dynamic imine bonds enhanced the interfacial wettability and bonding between CF and PA66 during thermal processing. Compared with that of untreated-CF, the interfacial shear strength and tensile strength of CNT@PP-CF/PA66 composite were increased by 52.3% and 19.2%, respectively. Meanwhile, the EMI shielding performance was enhanced by 89.6%. This improvement would be ascribed to the dynamic imine polar groups and heterogeneous interfaces in the hierarchical layers which enhanced the conductive and dielectric losses of composites. Our research provided a novel approach based on dynamic covalent bond exchanges to achieve the functional and structural integration of CF reinforced thermoplastic resin composites.

Preparation and interfacial properties of functionalised graphene oxide modified carbon fibre/epoxy resin matrix composites

ABSTRACT The interfacial properties of carbon fibre (CF) reinforced epoxy resin composites are the key factors affecting the mechanical properties of the materials. To improve the interfacial adhesion between CF and epoxy resin, an effective CF surface modification method is proposed in this paper. The surface of graphene oxide (GO) was functionalised with 3-aminopropyltriethoxysilane (APTES), and then the functionalised graphene oxide (FGO) was grafted on the surface of CF. The surface roughness of modified CF was significantly improved by the SEM experiment. The effectiveness of grafting was verified by FTIR and XPS, and the chemical functional groups on the surface of modified CF were increased. The microstructure of the failure interface of the composites was observed, the modification did not reduce the tensile strength of CF, and the interlaminar shear strength (ILSS) of modified CF/ epoxy resin composite was increased by 39.91%. It was found that the CF modified by FGO was beneficial to the improvement of the interface properties of CF/epoxy resin composite. This has positive academic significance for improving the interfacial and mechanical properties of CF composites.

The effect of the molecular structure of naphthalene-based mesophase pitch on the properties of carbon fibers derived from it

The effect of the molecular structure of naphthalene-based mesophase pitch on the properties of carbon fibers derived from it

Preparation and properties of carbon fiber reinforced bio‐based degradable acetal‐linkage‐containing epoxy resin composites by RTM process

AbstractThe recycling of carbon fiber (CF) reinforced bio‐based degradable epoxy resin composites is of great significance for resource saving, environment protection and sustainable development of economy and society. Resin transfer molding (RTM) has been recognized as one of the most promising processes to manufacture CF Reinforced polymeric composites cost‐effectively. The bio‐based diglycidyl ether pentaerythritol vanillin diacetal (DEPVD) epoxy resin used in this study is an epoxy resin that can be degradable under mild conditions. And its CF composites were prepared by the RTM process using DDS as a curing agent and low viscosity bisphenol A‐E51 epoxy resin as a diluent. The chemical rheological properties, curing behavior, thermal stability, dynamic viscoelasticity and mechanical properties of DDS‐E51‐DDS epoxy resin were investigated. It is found that the increase of DEPVD content is beneficial to improve the mechanical properties, Tg and solid residue after thermal degradation of DEPVD‐E51‐DDS epoxy resin. Moreover, the effects of DEPVD content in epoxy resin on the mechanical properties of CF/DEPVD‐E51‐DDS composites were evaluated. When the DEPVD content is 70%, the tensile and flexural strength of CF/EPVD‐E51‐DDS composites are 1649.4 MPa and 1207.4 MPa, respectively. The degradability and mechanism of CF/DEPVD‐E51‐DDS composites were further investigated. CF/DEPVD‐E51‐DDS composites containing 70% DEPVD have excellent degradability, and the recycled CFs exhibit comparable mechanical properties to the virgin CFs, which demonstrates a novel way to recover the high‐quality of used CFs.

Experimental investigation of mechanical properties of bamboo/carbon fiber reinforced hybrid polymer matrix composites

Natural fiber composites are gaining popularity in various fields such as aerospace, automotive, and interior design due to their biodegradability, cost-effectiveness, and wide availability. Hybrid composites, which utilize both natural and synthetic fibers as reinforcement, are becoming more prevalent due to the desirable properties of each. Natural fibers possess strong damping properties and are biodegradable, while synthetic fibers have good elastic modulus. This research aimed to investigate the mechanical properties of bamboo and carbon fiber reinforced hybrid composites through tensile, flexural, and Izod tests. Hybrid composites exhibited 74.53% higher tensile strengths, 41.47% higher flexural strengths, and 182.24% higher impact strength than bamboo fiber reinforced composites. Carbon fiber reinforced composites had superior mechanical properties compared to hybrid and bamboo fiber reinforced composites, especially in terms of tensile and flexural characteristics. The study concludes that combining natural and synthetic fibers leads to composite materials with acceptable mechanical performance.

Buckling and Post-buckling Analysis of Composite Hat Stiffened Panels under Axial Compression Loads

Owing to their unique material design-ability and excellent weight reduction properties of carbon fibre reinforced polymers(CFRP), commercial aircraft OEMs have been innovating design and manufacturing approaches to wider the application of advanced composites. In this paper, the bearing capacity of composite hat-stiffened panels is determined by an improved engineering calculation method and numerical analysis method. The effectiveness of both methods is verified by the test. The advantage of the engineering estimation method is simple and fast, which is suitable for the parametric analysis of the structure in the preliminary design phase. The finite element method can better simulate the test process and is suitable for the comprehensive evaluation of structural strength. The combination of the two methods has a high reference value for rapid design and selection.

Novel preparation of nano-SiO2 core-shell hybrid inorganic-organic sizing agents for enhanced interfacial and mechanical properties of carbon fibers/epoxy composites

The interfacial properties of carbon fibers (CFs) composites were improved by modifying the self-emulsifying amphiphilic epoxy sizing agent with nano-SiO2 particles. Herein, a series of inorganic–organic nano-SiO2 core-cationic epoxy shell hybrid sizing agents (referred to as nano-SiO2 core–shell hybrid sizing agents) with various nano-SiO2 contents were synthesized and used to enhance the mechanical properties of CF/EP. The study indicated that the nano-SiO2 core–shell hybrid sizing agents had the characteristics of the perfect core–shell structure, single dispersion, particle sizes controllable, good storage and high heat resistance. Nano-SiO2 core–shell hybrid sizing agents significantly increased the surface roughness and the surface energy of CFs compared to the unmodified sizing agent. Nano-SiO2 core–shell hybrid sizing agents (7.2% SiO2) increased ILSS, IFSS by 16.92%, 21% and nano-SiO2 core–shell hybrid sizing agents (5.8% SiO2) increased tensile force of monofilament CF by 23.78%, respectively, compared with the unmodified agent. These reinforcements may have been caused by the enhancement of the stress transference of nano-particles in the interface between CFs and EP through an interlocking mechanism. As a result, the nano-SiO2 core–shell sizing agent overcomes the lack of adhesion of traditional nano modification methods and shows remarkable adhesion properties.

The Investigation of General Properties of Carbon Fiber (CF) Composites - Preliminary Study

The most commonly used materials in the production of high-performance CFs are cellulose, polyacrylonitrile, and pitch. Polyacrylonitrile (PAN)-based fibers dominate the market (representing nearly 90% of total CF production), with some companies producing more than 10,000 tons per year. However, the current technique's high cost (the combined cost of the precursors and stabilization accounts for 70% of total CF synthesis cost) limits the technology's applicability. Carbon fiber manufacturing is characterized by a high energy demand due to long processing times and energy intensive thermal processes. PAN-based CFs are difficult to commercialize due to the time-consuming pre-oxidation step, which significantly raises the manufacturing cost. As a result, advanced processing technologies aimed at reducing CF production costs should be developed. They were consisting of a thin but strong crystalline filament of carbon. This experimental study was to learn the mechanical properties of carbon fiber using Universal Testing Machine (UTM). There was a section where we made a phone case out of Polyacrylonitrile (PAN) carbon fiber and compared it to other materials for phone cases. The phone cases of carbon fiber composites as the one examples of consumer product was made from the woven carbon fiber then was hardened by hard epoxy mixed with resin epoxy. Then, the phone cases were tested with UTM machine to compare the tensile strength and high modulus. Other than that, there were few samples with different composition of PAN powder mixed with different composition of sodium thiocyanate. The results of the testing shows that the carbon fiber had the high tensile strength than the other materials of phone cases which were silicone and thermoplastic polyurethanes (TPU). The microstructure of carbon fiber has a significant impact on its mechanical properties.

Structural and Tribological Characterization of Carbon and Glass Fabrics Reinforced Epoxy for Bushing Applications Safety.

This article investigates the effect of geometrical alternatives for fiber directions on the structural and tribological properties of glass and carbon fibers when molded with epoxy as polymeric composite fabrics for the safety and quality of bushing applications. To confirm the best composite fabric direction, scanning electron microscope and tribological analyses were carried out for the glass and carbon fabrics at horizontal and vertical geometrical alternative orientations. The tribological test was applied using a pin-on-disk tribometer at constant bark velocity of 0.520 m/s against different loads, beginning with 5, 10, 15, and 20 N for the investigated composite samples. The structural measurements demonstrated that the carbon fiber had a high ability to merge with the resin epoxy when compared with the glass fiber. The tribological analysis elucidated that the lower wear volume loss and friction coefficient were obtained when molding the resin epoxy horizontally to the fiber-stacking direction compared with the other vertical direction. Accordingly, the study deduced that the carbon fiber composite material achieves superior wear resistance when molded by resin epoxy horizontally to the direction of tribological wear, which is suitable for several advanced bushing applications.

Self-assembly of carbon nanomaterials onto carbon fiber to improve the interfacial properties of epoxy composites

The interfacial property of carbon fiber (CF) reinforced composites is crucial to facilitate the application of high-strength composites. Utilizing the electrostatic and hydrogen bond properties of diazo resin, carbon nanotubes (CNTs) and graphene oxide (GO) could be quickly grafted onto the surface of the CF via the layer-by-layer self-assembly technique. The results showed that CNTs and GO were uniformly coated onto the CF surface, and the chemical activity and roughness of the modified CF surface were improved significantly. The modified CF surface can significantly augment the interaction between the epoxy resin and the fiber. Remarkably, due to the good interfacial property, the impact performance of the composites reinforced with the nanomaterial-modified CF was improved obviously. In addition, the interface properties of the composites are studied in depth. This method is expected to achieve rapid surface modification of carbon fiber.

Mechanical properties of CFRP bar with different elevated-temperature experiences

Material properties of carbon fiber reinforced polymer (CFRP) at elevated temperatures are of great importance to promote its application in civil engineering. Previous literatures focused mainly on steady-state temperature tests, neglecting the thermal experiences that CFRP may undergo in real fire scenarios. To address this gap, it conducted four types of tensile tests on CFRP bars to simulate different elevated-temperature experiences ranging from 25 to 300 °C. This study investigated properties of CFRP under tensile tests at room temperature and steady-state tests, as well as properties at elevated temperatures with sustained load and after exposure to elevated temperatures. The tests showed that CFRP bars without sustained load remain about 85%, 75%, and 52% of their original strength at 100 °C, 150 °C and 300 °C, after 0.5 h thermal experience, respectively. In addition, the ultimate stress decreased by 11% when heating duration increased from 0.5 h to an hour and thereafter remained stable at 300 °C. Meanwhile, the CFRP bars with sustained load (stress level of 0.3) at 300 °C presented a 7% reduction of tensile strength compared to those without sustained load. For the CFRP bars exposed to 300 °C for an hour and cooled naturally to room temperature, the tensile strength and modulus decreased by 17% and 5%, respectively, but remained higher than those tested at 300 °C due to the solidification of softened resin. This investigation provides insights into the behavior at elevated temperature of CFRP.

Effects of multiple post cure cycles on properties of composite carbon fibre and epoxy materials

Post-curing cycles have an effective impact on the thermal and mechanical properties of thermoset composite materials. Typically, post-cure cycles use heat to expose cured resin parts to high temperatures in an attempt to maximize their final properties. In most cases, these processes allow composite parts to achieve the highest possible strength and become stable. In industrial practice, however, it has been found that there are potential consequences of performing localized repairs on composite parts in an autoclave where the localized repair undergoes a normal curing process while the parent part undergoes an additional curing process. Thus, for the parent part, prolonged exposure to high temperatures can trigger a process of decomposition of the resin matrix, as could be the aging phenomena of composites in service. In such a scenario, two practical questions are worth asking: (1) to what extent can a resin matrix be post cured without risking degrading its thermal properties? (2) what are the residual mechanical and physical properties resulting from prolonged exposure of composite parts to elevated temperatures? In this work, an analysis was carried out to estimate the potential adverse effects on thermoset composite parts made of carbon fibre and epoxy resin materials commonly used in aerospace, in terms of thermal, physical and mechanical properties after a long exposure to high temperatures caused by multiple post cure cycles. Two types of prepreg laminates were used to make monolithic test panels using twill and plain weave architectures for the M21 and 8552 test panels respectively. Thermal tests were conducted to evaluate the evolution of the degree of cure, the glass transition temperature and the inter-laminar shear strength of post-cured panels, which were subjected to a different number of post cure cycles. The study found that multiple post cure cycles alter thermal properties, which in turn have adverse effects on physical and mechanical properties. The results demonstrated that the two types of composite materials respond differently to changes in properties. Twill weave panels quickly reach full cure after three stages while plain weave panels have undergone gradual curing. This difference in the curing process of the resin matrix clearly influenced the changes in the measurements of shear, surface hardness and compressive strengths.

Thermo-mechanical properties of a novel carbon fiber modified self-encapsulated PEG/sulphoaluminate cement-based thermal energy storage composite

In order to synergistically enhance the thermo-mechanical properties of cement-based thermal energy storage composites (TESC), a novel carbon fiber modified self-encapsulated PEG/sulphoaluminate cement-based thermal energy storage composite (CF-PSTESC) was developed using polyethylene glycol (PEG), sulphoaluminate (SAC) and carbon fiber (CF) as the phase change material (PCM), matrix material and modified material separately in this study. The thermal and mechanical performances of CF-PSTESC and their coupling effects were investigated and analyzed using differential scanning calorimetry, mechanical strength test, transient planar heat source method and microstructural analysis. The results show that PEG can be effectively encapsulated in the hydration products of SAC, but it will change the phase change temperature of PEG somewhat. Moreover, the thermal conductivity of CF-PSTESC improved as the CF content grew, which improved by 4.1% and 15.1% at 10 °C and 30 °C, separately, at a CF content of 1.00 wt%. Furthermore, the introduction of CF showed a remarkable influence on the mechanical strength enhancement of CF-PSTESC as confirmed by the experimental results. The compressive strength and flexural strength of CF-PSTESC were increased by 64.9% and 65.7%, separately, when the CF content was 1.00 wt%. Based on the above research results, the CF-PSTESC prepared in this study is a promising TESC.