Interfacial Charge Dynamics
In article number 2306104, Xiaolong Jia and co‐workers clarified the charge dynamics mediated by the work function within the heterointerface. This understanding guides ...the proposal of a surface chemistry‐tailored strategy aimed at sparking hetero‐interfacial polarization between carbon fibers and ZnO nanowires. Consequently, the microwave attenuation ability is synergistically aligned with interfacial bonding, bestowing polymer‐based composites with remarkable microwave absorption efficiency and mechanical robustness.
The strength and deformation properties of carbon fiber reinforced concrete under different fiber volume loadings under impact loading were studied by using the ɸ100 mm split Hopkinson pressure bar ...(SHPB) test system. The results show that after the carbon fiber is added, the stress-strain curve of the specimen shows the platform section at the peak stress. The strength and peak strain of the concrete under the impact load increase first and then decrease with the increase of the carbon fiber volume. Trend, when the carbon fiber volume is 0.2%, the impact mechanical properties of concrete are significantly improved.
High-speed penetration into carbon fiber composites is of fundamental importance to materials science and impact engineering, but research along this line suffers considerably from the lack of direct ...experimental observations. Here we investigate such penetration dynamics of a unidirectional carbon fiber reinforced epoxy (UCFRE) composite, with a combination of in situ, ultrafast, synchrotron phase contrast imaging and finite element (FE) analysis. The experiments yield the first direct observation on projectile trajectories and fiber-scale deformation and damage in the UCFRE composites during supersonic microprojectile penetration, for different fiber orientations (0∘−90∘ from the impact direction) and projectile velocities 600−850m.s-1, at unprecedented temporal (∼100 ps) and spatial (5 μm) resolutions. The maximum penetration depth decreases with increasing fiber orientation angles, as a result of anisotropic damage evolution in the composite sample. Strain localizations are prone to develop along a direction perpendicular to the fiber orientation, while the damage or cavity region, along the fiber direction. FE modeling with a three-dimensional Hashin criterion yields consistent projectile trajectory and cavity morphology with the experimental results. With increasing fiber orientation angles, damage analyses show a transition in the damage mode from fiber compression to matrix compression damage, in line with the increasing maximum penetration depth.
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In this study, the graphene nanoplates (GnPs) and carbon nanotubes (CNTs) are simultaneous deposited on carbon fiber (CF) surface by fiber sizing method. The synergistic effect between GnPs and CNTs ...in increasing the interfacial and mechanical properties of carbon fiber reinforcement epoxy composites (CFRP) is investigated. The fracture surfaces of the CFRP composites indicated that GnPs/CNTs hybrid coating exhibited the best interfacial and mechanical performance in all coating sample. The interlaminar shear strength of GnPs/CNTs hybrid coated CFRP composites was 90% higher than non-coated CF composites. The flexural and tensile strength of CFRP composites with GnPs/CNTs hybrid coating have an improvement of 52% and 70%, respectively, compared to non-coated CF.
To meet the lightweight production requirements of automobiles and achieve high strength, reinforced thermoplastic composite materials are gradually replacing metal materials. Injection molding is ...the preferred manufacturing method to enable the production of complex‐shaped parts, facilitate production, and reduce costs. In this study, carbon fiber (CF) was added to the commonly used resin‐reinforcing material, polyamide (nylon) PA6, to create a CF‐reinforced thermoplastic composite (polyamide 6 PA6/CF) that was welded using injection molding. This study not only investigates the impact of different welding conditions on shear strength but also discusses the sequence of welding. Achieving 85% of the shear strength of the PA6 base material under ideal circumstances. The CF distribution and reinforcement mechanism were analyzed by observing the connection interface and cross section using a polarizing microscope and a scanning electron microscope. When PA6/CF was used as the secondary molded body, the welding results were better. The addition of CF had a significant strengthening effect on the strength of the PA6 injection welding.
Highlights
Carbon fiber‐reinforced thermoplastic composite materials were prepared, and welding with PA6 was achieved using the injection molding method.
The optimal welding parameters were determined by varying the mold, injection speed, injection temperature, and order of injection. The maximum welding shear strength reached 85% of the base material shear strength.
The positive effect of specific fiber distribution on welding strength was analyzed by observing the interface using a scanning electron microscope and a polarizing microscope.
This study provides valuable insights into the optimization of welding processes for carbon fiber thermoplastic composite materials, offering possibilities for connecting dissimilar materials with poor compatibility.
The addition of short carbon fibers effectively enhances the interfacial strength of polyamide resin after injection welding and analyzes the fiber distribution at the interface.
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•Development of isotropic and mesophase pitch by controlled heat treatment of parent coal tar pitch leads to increase in softening point of the precursor.•Stabilisation time, ...temperature and rate should be finely tuned as the radial variation in oxygen content in the fiber causes defects in further processing.•Pyrolysis of stabilized fiber determines the structural properties of the final carbon fiber product. Beyond 1200 °C, the graphitic structure gets formed along the fiber axis. Therefore, tensile, thermal and electrical properties increase with increase in pyrolysis temperature.•GPCF has a typical tensile strength in the range of 3500-4500 MPa and tensile modulus of 230-270 GPa. This are suitable for automotive applications.•Carbon fiber finds its major application in carbon composites manufacturing. Apart from that, activated carbon fiber is used in water treatment and many other areas. Some high end applications like medical material, energy storage material has also been explored.
This review focuses on recent development of technologies used for producing coal tar pitch-based carbon fiber along with its applications. In the first part, modification of coal tar pitch by different methods for obtaining the carbon fiber precursor was presented. In the second part, melt spinning process for producing the green fiber and subsequent post spinning stabilisation and pyrolysis process was described. The present review article shows that an extensive research on pitch modification has been done through heat treatment process. Development of isotropic and mesophase pitch by controlled low temperature pyrolysis of parent coal tar pitch leads to increase in softening point of the precursor, which is a vital parameter. This article is also evident that the stabilisation time, temperature and rate should be finely tuned to obtain fiber of desired properties. Carbonisation beyond 1200 °C seems to be sufficient for obtaining an ordered structure. All the possible applications of carbon fiber have been portrayed in the current review article. It was observed that the main application of carbon fiber is in the composite manufacturing sector. Starting from carbon-carbon composite to metal composites, carbon fiber found its major applications. Apart from that, activated carbon fiber had also been a topic of interest in the research domain.
A practical method for growing generation 1–3 melamine-based dendrimers onto carbon fibers (CFs) surface was proposed. The microstructures and interfacial properties of CFs before and after ...modification were investigated. X-ray photoelectron spectroscopy (XPS) confirmed the successful growth of different generation dendrimers. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images showed that melamine-based dendrimers grafting enhanced surface roughness, and this effect was more pronounced with increasing generation. The results of dynamic contact angle (DCA) demonstrated that the surface energy and the wettability of the grafted CFs were increased with generation. After generation 3 dendrimers grafting, the interfacial shear strength (IFSS) and impact strength of CF/epoxy composites were enhanced by 61.8% and 39.9%, respectively. The tensile strength of the composites were enhanced as the generation increased. Moreover, the reinforcing and toughening mechanisms were also discussed.
Abstract
Carbon fiber‐reinforced composites (CFRPs) offer numerous benefits due to their exceptional strength and modulus, making them extensively utilized in various applications. However, the ...disadvantage of poor impact resistance also limits their application in some aspects. In this study, silk fabric is used to hybridize CFRPs, and the silk/carbon fiber‐reinforced polybutylene succinate (PBS) composites were fabricated by combining the film stacking technique with the hot‐pressing method. The mechanical, thermal, and thermodynamic properties of the composites were assessed using various techniques, including tensile testing, scanning electron microscope, flexural testing, Charpy impact test, low‐velocity impact test, differential scanning calorimetry, and dynamic mechanical thermal analysis, and the optimal preparation process conditions (140°C/15 min) for the composites were obtained. Additionally, the mechanical properties of silk fiber/PBS, carbon fiber/PBS, and hybrid composite materials are comprehensively compared and evaluated. This work indicates that the synergistic toughening of silk and PBS significantly improves the impact resistance of CFRPs, and the impact strength of sample 5 (140°C/15 min) (54.97 kJ/m
2
) is higher than many reported values for CFRPs.
Highlights
High strength, high modulus carbon fiber, and high toughness silk were rarely combined as reinforcing phases for PBS composites.
A hybrid composite material with a balanced combination of stiffness, strength, and toughness was prepared.
Compared with similar studies, it was found that the hybrid composite prepared by this work exhibited relatively balanced mechanical properties, especially, its impact strength higher than many reported values.
Radially aligned titanium dioxide (TiO2) nanowires were synthetized on nitrogen plasma-treated carbon fibers (CF) using a two-step microwave-assisted solvothermal method. The TiO2 synthesis consisted ...in seeding TiO2 nuclei on CF followed by TiO2 nanowire growth. To assess the role of the nitrogen plasma surface treatment and TiO2 seeding, CF and CF-TiO2 hybrids were analyzed by Raman spectroscopy, X-ray diffraction, scanning electron and atomic force microscopies, after each step of the TiO2 synthesis. In addition, X-ray photoelectron spectroscopy was used to analyze the CF chemical composition upon the plasma treatment and TiO2 seeding. Single fiber tensile tests were conducted on CF and CF-TiO2 hybrids to track the mechanical changes induced by the surface treatment and TiO2 synthesis. It was found that both, the nitrogen plasma surface treatment and TiO2 nuclei seeding were essential to homogeneously synthesize radially aligned TiO2 nanowires onto CF. No significant changes in the CF surface roughness after plasma treatment and TiO2 seeding were found; however, upon TiO2 nanowire growth, the surface roughness increased by about twelve times with respect to the pristine ones. The plasma surface treatment generates oxygen- and nitrogen-containing functional groups that promote TiO2 nucleation onto CF. In addition, the CF internal heating due to microwave irradiation triggers a preferential nucleation of TiO2 on the fibers rather than in the reaction medium. The tensile strength of CF remained without significative changes after the surface treatment and TiO2 nanowire growth. The CF-TiO2 hybrid materials developed in this work could be exploited in the development of multifunctional structural composites.
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•Radially aligned TiO2 nanowires were grown on plasma-treated carbon fibers.•A novel TiO2 nanowire microwave-assisted synthesis is explored.•The role of the surface treatment and TiO2 nuclei seeding is investigated.•The surface treatment and TiO2 are crucial to radially grow TiO2 on carbon fibers.•Oxygen and nitrogen species on the fibers promotes preferential TiO2 nucleation.
Reinforced concrete (RC) beams strengthened in shear with carbon fiber reinforced polymer (CFRP) laminates as externally bonded reinforcement (EBR) usually fail due to debonding. This paper presents ...an experimental and analytical investigation on the use of groove-epoxy as an anchorage system for CFRP plates and sheets bonded on both sides of shear deficient RC beams. The aim of this study is to assess the effectiveness of using groove-epoxy in enhancing the shear capacity of RC beams. Nine rectangular RC beams were strengthened with CFRP plates and sheets with groove-epoxy anchorage systems of different groove widths and tested under four point bending. It is observed that the RC beams strengthened with the groove-epoxy anchorage system showed an increase in the shear-strength over the unstrengthened control beam up to 112 and 141% for plates and sheets, respectively. Also, the increase of shear-strength contribution of the groove-epoxy system to that of CFRP without grooves ranged between 30–190% for CFRP plates and between 40–100% for CFRP sheets. Generally, the contributions of groove-epoxy on shear-strength decreased with the increase of groove width. Moreover, shear strength prediction models, based on modifications of the ACI440.2R-17 shear model, were developed by incorporating groove factors as a modifier to the FRP shear-strength contribution. The developed models predicted the experimental shear-strength of the tested RC beams with a good level of accuracy, with an average mean absolute percent error (MAPE) = 3.31% and 6.68%, normalized mean square error (NMSE) = 0.072, 0.523, and coefficient of determination R2 = 0.964, 0.691, for plates and sheets, respectively.
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