Carbon Fiber Bundles Research Articles

Mechanical Properties of Thermoplastic Composites Made of Commingled Carbon Fiber/Nylon Fiber.

Commingled yarns consisting of thermoplastic nylon fibers and carbon fibers can be used to produce superior carbon fiber reinforced thermoplastics (CFRTP) by applying fiber spreading technology after commingling. In this study, we examined whether spread commingled carbon fiber/nylon fiber yarns could reduce the impregnation distance, as there are few reports on this. From this study, the following are revealed. The impregnation speed of the nylon resin on the carbon fiber was very fast, less than 1 min. As the molding time increased, the tensile strength and tensile fracture strain slightly decreased, and the nylon resin deteriorated. The effects of molding time on flexural strength, flexural modulus, and flexural fracture strain were negligible. From the cross-sectional observation conducted to confirm the impregnation state of the matrix resin, no voids were observed in the molded products, regardless of molding time or molding pressure, indicating that resin impregnation into the carbon fiber bundle of the spread commingled yarn fabric was completed at a molding pressure of 5 MPa and a molding time of 5 min.

Electric resistance measurement–based structural health monitoring with multifunctional carbon fibers: Predicting, sensing, and measuring overload

Polymer matrix composites that also contain carbon fiber reinforcement can be given a secondary function in addition to load bearing due to the electrical conductivity of the reinforcing fiber. We investigated how to measure the deformation of a composite by measuring the resistance of the carbon fiber and indicate its current or previous overload. We found that the resistance of the carbon fiber bundle initially increases linearly and then progressively during the testing of the specimens, and finally, when the fiber bundle snaps, the circuit breaks. We have shown by cyclic testing that overload exceeding reversible deformation can be detected and measured by examining the first derivative of the resistance change with respect to deformation. Based on our results, electric measurements of either an only carbon fiber-reinforced composite or a hybrid composite can be used to detect a possible previous overload of a component with an unknown load history.

Mechanical properties and failure mechanism of 3D needle-punched Cf/SiC–Al composites

Tensile behaviour and failure mechanism of 3D needle-punched Cf/SiC–Al composites were studied in detail. Cf/SiC–Al composites were prepared by precursor infiltration pyrolysis (PIP) and vacuum pressure infiltration processes. The bulk density and open porosity of the as-fabricated Cf/SiC–Al composites were tested by drainage method. The as-cut samples were subjected to tensile tests in air at room temperature and the stress-displacement response was analyzed. The cross-section and fracture regions of tested samples were analyzed by SEM in order to understand microstructure-property relationships. It was observed that Al alloy was successfully prepared between carbon fiber bundles which resulted in the low porosity (5.5%). Cf/SiC–Al composites showed higher values of tensile strength (159 ± 10 MPa) and modulus as compared to Cf/SiC composites. Failure mechanism of Cf/SiC–Al composites was analyzed combining the stress-displacement response and fracture morphology. Fracture mode of the 0° fiber bundle, the 90° fiber bundle and the needle fiber bundle were significantly different which had an important influence on the failure mechanism of Cf/SiC–Al composites. Fracture surface of the 0° fiber bundle was relatively flat, and there was no sign of fiber pulled-out which showed the characteristics of brittle fracture. Toughening mechanism such as interface debonding and fiber pulled-out exhibited in the 90° fiber bundle.

Mechanical and ablation properties of a C/C-HfB2-SiC composite prepared by high-solid-loading slurry impregnation combined with precursor infiltration and pyrolysis

An improved high-solid-loading slurry impregnation process was developed to introduce HfB2 particles into a low-density C/C preform efficiently, and precursor infiltration and pyrolysis process was used for densification to obtain a C/C-HfB2-SiC composite. The microstructure characterization revealed that HfB2 particles uniformly filled the pores in the C/C preform, and SiC well densified the interstices between HfB2 particles and the small pores in the carbon fiber bundles. After being tested, the C/C-HfB2-SiC composite had a density of 4.07 g/cm3 and a bending strength of 344.8 MPa, and exhibited a non-brittle fracture behavior. After ablation with oxyacetylene flame at 2500 ℃ for 120 s, the mass ablation rate and linear ablation rate of the C/C-HfB2-SiC composite were 0.5 mg/s and 0.415 μm/s, respectively. The good ablation performance is attributed to the hindering effect of the HfO2 scale on oxygen diffusion at high temperature.

Pore‐scale analysis of a PEM fuel cell cathode including carbon cloth gas diffusion layer by lattice Boltzmann method

AbstractOne of the parameters which can greatly affect (i.e., enhances or diminishes) the performance of a PEM fuel cell cathode is the GDL microstructure. In the present study, the role of carbon cloth GDL microstructure on the performance of a PEM fuel cell cathode is investigated, for the first time. In this regard, three carbon cloth GDLs with three different microstructures are reconstructed via merging bundles of carbon fibers with sinusoidal form; afterward, the passing reactive air through these GDLs is simulated at pore‐scale using lattice Boltzmann approach. The distributions of oxygen and water vapor through the carbon cloths and the distribution of current density on the catalyst layers are presented and analyzed. The results show that when the carbon cloth bundles consist of more fibers (i.e., having larger cross‐sections), the penetration of oxygen toward the catalyst layer is more difficult, and consequently, the average current density is smaller. Besides, the results reveal that the through‐plane compactness of carbon cloth microstructure does not bring a significant effect on the distribution of current density and species.

Synthesis, structure, and properties of carbon/carbon composites artificial rib for chest wall reconstruction

In this work, braided carbon fiber reinforced carbon matrix composites (3D-C/C composites) are prepared by chemical vapor infiltration process. Their composite structure, mechanical properties, biocompatibility, and in vivo experiments are investigated and compared with those of traditional 2.5D-C/C composites and titanium alloys TC4. The results show that 3D-C/C composites are composed of reinforced braided carbon fiber bundles and pyrolytic carbon matrix and provide 51% open pores with a size larger than 100 μm for tissue adhesion and growth. The Young’s modulus of 3D-C/C composites is about 5 GPa, much smaller than those of 2.5D-C/C composites and TC4, while close to the autogenous bone. 3D-C/C composites have a higher tensile strength (167 MPa) and larger elongation (5.0%) than 2.5D-C/C composites (81 MPa and 0.7%), and do not show obvious degradation after 1 × 106 cyclic tensile loading. The 3D-C/C composites display good biocompatibility and have almost no artifacts on CT imaging. The in vivo experiment reveals that 3D-C/C composites artificial ribs implanted in dogs do not show displacement or fracture in 1 year, and there are no obvious proliferation and inflammation in the soft tissues around 3D-C/C composites implant. Our findings demonstrate that 3D-C/C composites are suitable for chest wall reconstruction and present great potentials in artificial bones.

Study on wear characteristics of carbon fiber at needle end in prefabricated composite weaving

Abstract Carbon fiber composites are widely used in aerospace, military and other fields. Their tensile properties are mainly borne by interwoven carbon fibers, wear of carbon fiber seriously affects the mechanical properties of carbon fiber composite material. In the process of prefab weaving, the end of the weaving needles carrying the movement of the carbon fibers causes serious wear on the fibers. In order to study the effect of weaving needle parameters and process parameters on the wear of carbon fiber bundle, a friction and wear experimental device of carbon fiber bundle was made. According to the research results, the corresponding parameters were optimized to reduce the wear of the carbon fiber bundle during weaving. The wear of carbon fiber bundle modified by imidazoline surfactant was also studied. The effects of fiber tension, weaving angle and needle end angle on the wear of carbon fiber bundle were studied by the control variable method. The wear of carbon fiber bundle was characterized by image binarization, SEM scanning and residual fracture strength detection. The residual fracture strength of the optimized weaving needles was increased by 23.92%, the residual fracture strength of the modified carbon fiber bundle increased by 14.57% after needle end wear.

Three-dimensional numerical study of the directional heat transfer in an L-shaped carbon/carbon composite thermal protection system

Designing an accurate and efficient heat protection system for the area around the high-temperature stagnation point on supersonic aircraft is still an important topic of research. In the present study, a three-dimensional high thermal conductivity carbon/carbon (C/C) composite thermal protection system embedded with L-shaped carbon fiber bundles for directional heat transfer is proposed as a high-efficiency thermal protection design. A multi-scale method, which couples the finite volume method (FVM) and lattice Boltzmann method (LBM), is developed to investigate the directional heat transfer in the proposed structure. The FVM is used to calculate the heat radiation information, which is needed to solve the energy equation with the LBM. Further, the failure temperature of the proposed thermal protection structure is defined. The effects of the porosity, carbon fiber bundle and pore diameter on the directional heat transfer of the L-shaped C/C composite thermal protection system are investigated in detail. The results show that the effective thermal conductivity of the proposed thermal protection system increases with increasing temperature and carbon fiber bundle diameter. It decreases with increasing porosity when the temperature is below 1000 °C. There exists the competitive relationship between the pore heat radiation and carbon fiber bundle thermal conductivity. An increased porosity results in a decrease in the failure temperature of the proposed thermal protection structure, while increasing the carbon fiber bundle diameter can increase the failure temperature. These findings can provide some new insights for designing a high-performance C/C composite thermal protection system.

Flexural strength and wear resistance of C/C–SiC brake materials improved by introducing SiC ceramics into carbon fiber bundles

In this work, we adopted PIP technology to introduce SiC ceramics into the carbon fiber bundles of C/C–SiC composites. The obtained C/C–SiC composites containing PIP-SiC exhibited improved flexural strength. Meanwhile, the strength difference was reduced in in-plane and vertical directions. Fracture morphology revealed that the introduction of SiC into the fiber bundles broadened available toughening mechanism of the prepared composites. The braking performance of the materials was tested on an MM-1000 dynamometer. After braking at different speeds, we analyzed wear rates, variations in friction coefficient, and the morphological evolution of the friction surface. The results indicated that the introduction of SiC into the fiber bundles enhanced the abrasive resistance of local C/C regions, which yielded a significant reduction of the wear rates.

All-solid-state wire-shaped asymmetric supercapacitor based on binder-free CuO nanowires on copper wire and PPy on carbon fiber electrodes

Abstract A wire-shaped asymmetric supercapacitor based on CuO and polypyrrole (PPy) is developed in this work. The fiber-shaped positive electrode composed of CuO nanowires (CuO NWs) on Cu wire (Cu wire/CuO NWs) is successfully prepared via anodization of copper wire followed by thermal treatment. Meanwhile, conductive polymer PPy is grown on carbon fiber bundle (CF/PPy) by electrodeposition as a negative electrode. Subsequently, an all-solid-state wire-shaped asymmetric supercapacitor is assembled with Cu wire/CuO NWs, CF/PPy and PVA-KOH gel electrolyte. Benefiting from the efficient pseudocapacitive properties of the binder-free positive electrode with CuO nanowires directly grown on the copper wire surface and the negative electrode with PPy tightly covered on the carbon fibers, the all-solid-state wire-shaped asymmetric supercapacitor assembled exhibits a high energy density (9.31 μWh cm−2) and specific capacitance (39.67 mF cm−2, 24.91 mF cm−1). Moreover, this device also shows an excellent stability of electrochemical performance at different bending conditions, demonstrating its potential to serve as a flexible power source for portable/wearable electronics.

Additive manufacturing of multimaterial and multifunctional structures via ultrasonic embedding of continuous carbon fiber

Multimaterial and multifunctional parts were fabricated using an ultrasonic embedding technology in combination with 3D printing of thermoplastic. Continuous carbon fiber (CF) bundles were impregnated with polycarbonate solution (7 wt.%) prior to use in the embedding process. Using an ultrasonic embedding tool, a single layer of CF bundle was embedded into 3D printed polycarbonate parts containing one of three raster angles (RA): 0°, +45/-45°, and 90° RA. In tensile testing, the highest ultimate tensile stress (UTS) was found in samples printed with +45/-45° RA (75% higher UTS when compared to neat samples having the same RA), followed by those printed with 0° RA (60% UTS increase). Samples printed with 90° RA and containing a single layer (bundle) of embedded CF yielded the least UTS improvement (13%). Statistical t-test results showed that +45/-45° RA samples with embedded CF had superior mechanical strength while exhibiting less variation. Flexural testing of +45/-45° RA specimens with embedded CF showed an average flexural strength increase of 7%, and an average modulus increase of 7% when compared to the neat specimen. In addition to the mechanical reinforcement, multilayer CF embedding using ultrasonic energy was demonstrated. In addition, the change in electrical resistance in embedded CF layers was measured during mechanical loading to demonstrate structural health monitoring functionality.

Flexural Properties of Carbon/Glass Hybrid Thermoplastic Epoxy Composite Rods Under Static and Fatigue Loadings

Cables are primarily used in structures as tensile elements, but they are also subjected to compressive, flexural, and shear loadings. Therefore, in addition to the hybrid rods’ tensile properties, the other corresponding mechanical properties must also be characterized. This study is an investigation of the flexural behavior of carbon/glass hybrid thermoplastic epoxy composite rods. Test results indicated that an increase in the void content to a decrease in the flexural strength, and consequently the Weibull modulus as well. The flexural fatigue performance (in terms of maximum stress) increases with the static flexural strength. The intercept for power law model increased with increasing carbon fiber volume fraction, and decreasing matrix content and void content. The absolute values of slope for power law model decreased with increasing carbon fiber volume fraction, and increasing matrix content and void content. The fatigue strength at 1 × 107 cycles for the hybrid rods was less than 20–30% of the ultimate flexural strength. The static and fatigue flexural properties for the hybrid rods were strongly influenced by kinking, buckling, and delamination behaviors of unidirectional carbon fiber bundle composites.

Prediction of Effective Thermal Conductivities of Four-Directional Carbon/Carbon Composites by Unit Cells with Different Sizes

Two-unit cells developed to predict the effective thermal conductivities of four-directional carbon/carbon composites with the finite element method are proposed in this paper. The smaller-size unit cell is formulated from the larger-size unit cell by two 180° rotational transformations. The temperature boundary conditions corresponding to the two-unit cells are derived, and the validity is verified by the temperature and heat flux distributions at specific positions of the larger-size unit cell and the smaller-size unit cell. The thermal conductivities of the carbon fiber bundles and carbon fiber rods are measured firstly. Then, combined with the properties of the matrix, the effective thermal conductivities of the four-directional carbon/carbon composites are numerically predicted. The results in transverse direction predicted by the larger-size unit cell and the smaller-size unit cell are both higher than experimental values, which are 5.8 to 6.2% and 7.3 to 8.2%, respectively. In longitudinal direction, the calculated thermal conductivities of the larger-size unit cell and the smaller-size unit cell are 6.8% and 6.2% higher than the experimental results, respectively. In addition, carbon fiber rods with different diameters are set to clarify the influence on the effective thermal conductivities of the four-directional carbon/carbon composites.

Effect of plasma surface modification on pullout characteristics of carbon fiber-reinforced cement composites

Light but strong carbon fibers have been utilized as effective reinforcing lattices for cement matrices. However, to explore the intrinsic properties of carbon fibers within the cement matrix, the interfacial behavior between the fiber and matrix must be understood in terms of the bond strength as well as the interfacial failure mode. In the present work, we evaluated the pullout properties of carbon fiber bundles from a cementitious matrix after the fibers were modified via one of three plasma treatments using argon, nitrogen, or oxygen. The plasma-treated carbon fibers were characterized using Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning tunneling microscopy. The treatments introduced hydrophilic functional groups on the carbon fibers’ surfaces and increased their surface roughness. With an appropriate amount of hydrophilic groups on the carbon fiber surface, the rate of hydration was accelerated, which led to a denser cement structure surrounding the carbon fibers. In addition, the fibers’ surface roughness was critical toward improving mechanical interlocking between the fibers and cement matrix. The highest interfacial shear strength for the argon plasma-treated sample can be explained by the improvement in surface roughness without degrading the mechanical strength of the carbon fiber, as well as the modification of the surface from hydrophobic to hydrophilic.

Multifunctional Carbon Fiber Sensors: The Effect of Anisotropic Electrical Conductivity

The multifunctional application of carbon fiber reinforced polymer composites (CFRP) can be affected by the anisotropic electrical conductivity of the carbon fiber because it differs in the longitudinal and the transverse direction of the fiber. In our article, we measured the transverse resistivity of the reinforcing carbon fiber bundle in different conditions: when the fibers were dry, when they were impregnated with non-crosslinked resin, and in a crosslinked matrix. We have shown that in the case of dry and impregnated fibers, a compressive force acting on the fiber bundle has a significant effect on the transverse resistance, while when crosslinked, this effect is negligible. We developed a finite element model (FEM) to investigate the area around the electrodes and the current distribution in the fiber bundles. We have shown that due to the pressure dependence of the transverse resistance and the significant difference in length and transverse conductivity, the current density distribution in the cross-section around the current electrode will not be homogeneous, leading to inaccuracies in sensory applications. We have shown by finite element simulation that the current electrode and voltage measurement electrode can be optimized, which was verified experimentally.

Determination of Carbon Fiber Strength Distribution Using Bundle Fiber Tensile Test: Correction of Measurement System Elongation and Kinetic Friction Between Fibers in the Fiber Bundle

In this study, we investigated the improvement in carbon fiber (CF) bundle tensile tests. To effectively evaluate the mechanical properties of CF using the fiber bundle tensile test, measurement of system elongation correction considering nonlinear behavior and Weibull analysis using fitting of stress–strain curves was conducted. Shear-lag theory analysis revealed that the elongation in the nonlinear measurement system was largely governed by the adhesive layer deformation within the tabs. A nonlinear measurement elongation correction method was proposed that can be applied to specimens of different widths. Weibull parameters were extracted by fitting the stress–strain curves, while considering the effect of the kinetic frictional force. The obtained parameters from the fiber bundle tensile test corresponded to those obtained from the SFTT. Thus, the proposed fiber bundle test can be a simple method for evaluating fiber strength distribution.

Shear Strengthening with Carbon Fiber Grid Plate Fixed by Carbon Fiber Bundle and PCM

炭素繊維格子板（CFG板）の端部を炭素繊維束で固定し，ポリマーセメントモルタル（PCM）を乾式で吹き付ける定着方法でせん断補強されたRCはり部材の単調載荷試験を行い，炭素繊維束を用いたCFG板の定着方法の可能性を示すとともに定着性能に及ぼす炭素繊維束の繊維量の影響およびPCMの圧縮強度の影響に関して検討した。その結果，提案工法はCFG板端部の定着方法として効果的であり，定着に必要な炭素繊維束の繊維量は，CFG板縦筋の引張耐力に相当する引張耐力を有する繊維量で十分であることが明らかになった。また，PCMの圧縮強度は50N/mm2程度で十分であることを示した。さらに，提案する定着方法によってせん断補強されたRC棒部材の斜め引張破壊耐力は，既存の式にCFG板縦筋が負担するせん断耐力を加えた式で評価できることが確認された。

Evaluation Through SEM Image Processing of the Volumetric Fiber Content in Continuos Fiber-Reinforced Additive Manufacturing Composites

This work shows the estimation of the volumetric fiber content (Vf) using image processing techniques. The Vf is needed to establish mechanical properties of composites using the rule of mixtures or other more advanced prediction models for the mechanical properties. The proposed method is tested with images acquired for carbon, Kevlar, and fiberglass fiber bundles used in the fiber deposition modeling (FDM) in the additive manufacturing process. The fiber bundles are provided by Markforged ® and are used in the Markforged Two ® printer. Then, different gray threshold and segregation algorithms are convolved with the digitized images to to isolate matrix from fibers such that a separate fiber and matrix area counting can be done and an appropriate Vf can be established. Results obtained with image analysis are close to values reported using technical standards, hence validating the proposed method.

Manufacturing of 3D Printed Laminated Carbon Fibre Reinforced Nylon Composites: Impact Mechanics

This paper presents the manufacturing development of laminated Carbon Fibre Reinforced Thermoplastics Polymer (CFRTP) specimens, which show significant improvement of mechanical properties in comparison with existing thermoplastic composites. There is a need to improve structural performance of thermoplastic composites by using a fully integrated chopped and continuous carbon fibre bundle into a thermoplastic resin matrix in a laminated shape with various stacking sequences. The developed manufacturing technique is capable to print components with various fibre orientations, which is spotted as the novelty of this research. The CFRTP specimens were tested under quasi-static tensile and low-velocity impact loading to proof the improvement of mechanical performance in both static and dynamic applications. Our results indicate a significant improvement in impact resistance and energy absorption capability of CFRTP composites in comparison with existing thermoplastic composites.

Microstructure and properties evolution of C/Mullite composites during fabrication process

Carbon fiber reinforced mullite (C/Mullite) composites with favorable mechanical properties have been fabricated through sol-impregnation-drying-heating (SIDH) route in our previous work. For the further optimization of fabrication technology, it is very necessary to elucidate the evolution of microstructure and properties of C/Mullite composites during SIDH process. For this purpose, C/Mullite composites were fabricated at different cycles through SIDH route in present paper, and the effect of fabrication cycles on microstructure, mechanical properties and oxidation resistance of the composites were investigated. The results show that mullite matrix grew on the surface of single carbon fiber firstly, then grew from inside to outside of carbon fiber bundle during fabrication. Finally, it grew completely on the surface of the composites and formed a “mullite coating”. Porosity of the composites decreased gradually and pores of the composites transformed from connected ones into isolated ones as the fabrication cycles increased. When the fabrication cycles reached 24, the porosity of the composites was unchanged basically. At the same time, the composites possessed the optimal mechanical properties and oxidation resistance.