Carbon Fiber Core Research Articles

Mechanical properties of sandwich panels with corrugated carbon fiber cores

Mechanical properties of sandwich panels with corrugated carbon fiber cores

Si/TiO2 carbon fiber core encapsulated in hierarchical multiple MXene@Co-MoS2 shells for constructing a free-standing anode of lithium storage

Si/TiO2 carbon fiber core encapsulated in hierarchical multiple MXene@Co-MoS2 shells for constructing a free-standing anode of lithium storage

The flexural and compressive properties of sandwich composites with different 3D-printed core structures

In this study, different core structures are produced with polylactic acid (PLA) and carbon fiber reinforced PLA (CFR-PLA) filaments using a 3D printer with fused deposition modeling (FDM) technique. An alternative new core structure is proposed to the honeycomb and square core structures commonly used in the literature. Then, sandwich composites are produced by bonding carbon fiber-epoxy plates to the lower and upper surfaces of these core structures. The effect of carbon fiber reinforcement and core types on the mechanical properties of sandwich composites was investigated. The core structures produced with carbon fiber-reinforced PLA showed lower compressive strength but higher compressive modulus than those produced with pure PLA. Among the core structures, the designed structure showed the highest compressive strength with a value of 9.867 MPa, which is 32.18% and 54.36% higher than the honeycomb and square structure. While the flexural strength and flexural stiffness of the sandwich composites increased with carbon fiber reinforcement, the designed sandwich composite showed approximately 1.40 and 3.15 times the flexural strength of the honeycomb and square sandwich composites, respectively.

Fiber optic detection method for intrinsic defects in carbon fiber composite core overhead conductors considering bending performance

Carbon fiber composite core wire in the carbon fiber core rod bending strength is low, easy to break, and thus affects the detection effect. In this regard, it is proposed to consider the bending performance of carbon fiber composite core overhead wire intrinsic defects fiber detection method. The overhead wire is X-ray scanned, and the image is bent compensated by the filtering algorithm. The image is reconstructed using an iterative reconstruction algorithm, and the Tamura texture feature operator is used to extract the roughness feature parameters in the texture feature enhancement map of each conductor to achieve the identification of defects. In the experiments, the proposed method is verified for detection accuracy. The analysis of the experimental results shows that the proposed method has a high correct defect recognition rate and has a more excellent detection accuracy when the proposed method is used to detect the inherent defects of overhead conductors.

An experimental and numerical study on the ballistic performance of a lightweight ceramic composite armor

In this paper, the ballistic limit velocity of 12.7mm armor-piercing incendiary projectile impacting a typical lightweight ceramic composite armor made of boron carbide ceramic and multi-layered composite materials (carbon fiber/aramid fiber/ultra-high molecular weight polyethylene fiber) was obtained experimentally. The process of impact was numerically simulated by the FEM-SPH method, and the results pointed out the characteristics of the penetration and the energy dissipation rule of each component of the ceramic composite armor. On this basis, the influence of thickness changing of the carbon fiber core layer on the ballistic performance of ceramic composite armor was studied with a typical “sandwich” structure, and the results showed that: when the thickness ratio of ceramic tile to the backing panel is about 1.5, the thickness changing of the carbon fiber core layer has the greatest effect on the ballistic performance. Under this thickness ratio, when the ratio of ceramic tile thickness to bullet diameter is greater than 1, the increase of carbon fiber core layer thickness will cause the ballistic performance index (BPI) of the target to decrease while the ratio is less than 1, the BPI increases or holds at first, and then decreases.

Effect of mold and core preheating temperature on corrosion resistance of casting Al-12Si alloy U-shaped cooling channel

Temperature has an important impact on the corrosion resistance of mold with cooling channels prepared by casting method. The effect of preheating temperature of the mold and the carbon fiber core on the roughness and corrosion resistance of U-shaped cooling channels made of Al-12Si alloy was examined in depth. The experimental results suggest that as the preheating temperature increased from 273 K to 573 K, the roughness of the inner wall of the cooling channel reduced from 96.6 µ m to 77.0 µm. When the preheating temperature continued to increase to 723 K, the roughness increased to 85.3 µm. The wetting between the Al melt and the carbon fiber will reduce micro bubbles and waves on the channel wall as the preheating temperature rises, thereby reducing the roughness. However, with the further increase of preheating temperature, it will increase the solidification time of the Al melt. At this time, the carbon fiber and Al melt will take more time to react, which increases the roughness of the channel wall to a certain extent. The results of exfoliation corrosion show that the larger roughness will aggravate exfoliation corrosion. The prolongation of high temperature reaction time between the carbon fiber and the Al melt will lead to the segregation of Si, which is easy to cause intergranular corrosion. Therefore, reasonable preheating temperature has an important impact on the roughness and corrosion resistance of U-shaped cooling channels.

Construction of a flexible, integrated rechargeable Li battery based on a coaxial anode with a carbon fiber core encapsulated in FeNiMnO4 and a nitrogen-doped carbon sheath

Construction of a flexible, integrated rechargeable Li battery based on a coaxial anode with a carbon fiber core encapsulated in FeNiMnO4 and a nitrogen-doped carbon sheath

Construction of a flexible, integrated rechargeable Li battery based on a coaxial anode with a carbon fiber core encapsulated in FeNiMnO4 and a nitrogen-doped carbon sheath

A coaxial anode with a carbon fiber core encapsulated in nanocrystalline FeNiMnO4 with a nitrogen-doped carbon sheath was prepared using carbon fiber cloth as the core, FeNiMnO4 nanocrystallite arrays as the first coating layer and nitrogen-doped carbon derived from F127 (a kind of triblock copolymer)-resorcinol-melamine gel as the outer layer. After annealing at 600 °C it was used as the anode material of an all solid flexible lithium ion battery using LiFePO4 as the cathode material and boron nitride modified polyethylene oxide as the electrolyte. The battery had a large areal capacity of ∼1.40 mAh cm−2 and satisfactory cycling stability under different bending and strain states. Annealing below 600 °C leads to incomplete carbonization of the nitrogen-doped carbon and thus a low electrical conductivity while above 600 °C aggregation of FeNiMnO4 nanocrystallites and their detachment during cycling are observed under bending and strain.

Fiber-shaped dynamic thermal radiation-regulated device based on carbon fiber and polyaniline

Electrochromic devices for effective infrared (IR) modulation are receiving increasing attention in engineering. However, the majority of the devices for IR modulations possess planar sandwich structures, restricting their implantation into fabrics and limiting their comfortable wearability due to the bad air permeability. Herein, a fiber-shaped dynamic thermal radiation-regulated device with a novel integrative core-shell structure, based on carbon fiber and polyaniline has been developed. The device with high performance can realize dynamic thermal radiation regulation with the IR emissivity (△ε) as high as 0.4 at 7.5–14 μm. Furthermore, the device can reversibly change color between dark green (in the oxidized state) and golden yellow (in the reduced state) as a response to low applied potentials (−0.5 V and 0.6 V) with fast response time (1.7 s). In addition, the device demonstrates high cycling stability as evident from the current-time (i-t) curve of the reduced and oxidized states as well as stable Δε after 500 cycles. The performances, including △ε and cyclic voltammetry curve (CV) of the device demonstrate no apparent degradation after 500 bending cycles, indicating high durability. This study provides new insights into fiber-shaped dynamic thermal radiation-regulated devices and highlights their applications in personal thermal management, adaptive thermal camouflage, and intelligent wearable devices. • The fiber-shaped dynamic thermal radiation-regulated device based on carbon fiber (core) and polyaniline (electrochromic functional layer) was fabricated. • The device demonstrates an integration of the structure and function design to make the carbon fiber as the substrate and electrode simultaneously, which contributes to an uncomplicated structure. • Under low external voltages, the device can be reversibly transformed from the reduced state with low emittance to the oxidized state with high emittance in fast response time (1.7 s). • The device displays outstanding dynamic thermal radiation regulation (Δε = 0.4 at 7.5–14 μm) and can realize the color transformation between dark green and golden yellow to integrate with the environment. • The device possesses excellent structural stability, mechanical flexibility, cycling stability and durability.

Symmetric and asymmetric intercalation effect on the low-velocity impact behavior of carbon/Kevlar hybrid woven laminates

Hybrid fiber composite laminates with the same materials, manufacturing methods and molding processes may present different mechanical behaviors. In this paper, the effect of intercalation sequence on the mechanical performance of carbon/Kevlar plain laminates were studied. According to different intercalation methods, the hybrid layout was divided into symmetric and asymmetric configurations. It is found that the symmetric intercalation structures (KCCK and CKKC) possess better load-bearing and resilience capacity compared with asymmetric structures (CCKK and CKCK), even better than pure carbon structure (CCCC) under high energy impact. The impact damage volume of symmetric specimens was significantly smaller than that of asymmetric specimens by quantitative micro-CT analysis. The apparent damage index (df and dr) can be used to estimate the internal damage data (dCT, H and V). KCCK, a typical symmetric sandwich-like structure, presented the most slight damage among all symmetric and asymmetric configurations, with shear cracks observed at the brittle carbon fiber core layers, while the delamination cracks between Kevlar-carbon interlayers were away from the central damaged region. In CKCK, interlaminar cracks were formed at each carbon-Kevlar interlayers, which shared and relieved the primary interlaminar crack at the core layers compared with CCKK.

Study of Full Composite Pole-Aluminum Conductor Composite Core System Ice-Shedding Response

Full composite pole-aluminum conductor composite core system is gradually used in the 10kV distribution network. In order to study the different ice-shedding forms of the dynamic response of this distribution system, the author established a conductor-insulator and pole-conductor system with two finite element models to study the linear section and corner section of the line in different forms of ice-shedding and ice-shedding rate under the influence of the line ice-shedding response degree. The results show that the pole-conductor model is a good model for the design of distribution lines with carbon fiber cores. The results also show that the ice jump height of the pole-conductor model is smaller than that of the conductor-insulator model, which is related to the coupling relationship between the composite pole and aluminum conductor composite core. The stay wire of the corner pole will absorb most of the energy generated by ice-shedding. In addition, when non-uniform ice-shedding, the line vibration is more violent, the jump height is higher, and the maximum axial force generated after ice-shedding is greater, which has certain safety risks.

Microwave-assisted synthesis of hybrid supercapacitors consisting of Ni, Co-layered double hydroxide shell assembled around wood-derived activated carbon fiber core

Activated carbon fibers (ACFs) are prepared from the discarded fir wood using two-step melt-spinning and CO2 activation post-treatment. Then, composites composed of these ACFs and Ni, Co-layered double hydroxides (NiCo-LDH@ACF) are synthesized by a microwave-assistant hydrothermal strategy. NiCo-LDHs agglomerated around ACFs, forming core-shell structures with sheet- or microsphere-like morphologies, which provide large surface area, hierarchical porosity, and numerous active sites for efficient charge and mass transfer. The NiCo-LDH@ACFs are used as an active material to construct the supercapacitors, the highest of capacitance and the corresponding rate performance of which are equal to 1453.3 F/g at 1 A/g and 78% at 10 A/g by microwave-assistant hydrothermal at 120 °C, respectively. We also use this material to assemble an asymmetric supercapacitor using activated carbon derived from fir bark as a negative electrode. The resulting device demonstrates excellent capacitance (equal to 146.9 F/g at 1.6 V), very high energy density (equal to 52.2 Wh/kg at 800 W/kg), and cycle life (judging by the 79.8% capacitance retention after 10000 cycles).

Flexural and compressive residual strength of composite bars subjected to harsh environments

This work aims to evaluate the degradation mechanisms of selected composite bars subjected to exposure to various chemical environments. Sets of three different groups of bars, such as glass fiber reinforced epoxy pultruded at Wroclaw University of Science and Technology (WUST), commercial glass fiber reinforced epoxy overwrapped with carbon fiber, and hybrid bars (H-bar) manufactured by a combination of pultrusion and filament winding methods. The hybrid bar is a composition of a pultruded carbon fiber reinforced epoxy core and the filament-wound glass overwrap. The research included a macro and microscopic evaluation of bars before and after 50 days of degradation in three types of chemical solutions, that is, 5% NaCl, 5% H2SO4, NaOH with pH = 12 and a comparative analysis of bar damage mechanisms under the influence of compressive and tensile forces. These loading conditions are provided by an out-of-plane compression test, which allows one to assess the quality of the matrix, especially in unidirectional bars, where the applied force is carried only by the matrix. Furthermore, the four-point bending test is performed to assess the flexural behavior of the investigated bars. Research has shown that the most degrading solution is 5% H2SO4 causing the greatest drop in the maximum force concerning the exemplified specimens. Moreover, the most resistant to aggressive environments and mechanical degradation appears to be the “H” hybrid bar; its greater resistance may be affected by the additional filament-wound glass layer, which protects the carbon fiber core.

Water uptake and interfacial shear strength of carbon/glass fiber hybrid composite rods under hygrothermal environments: effects of hybrid modes

The hygrothermal aging of fiber reinforced polymer (FRP) composite rod served as bridge cables played a key role on the long-term service performances. In the present paper, two types of pultruded carbon/glass fiber reinforced epoxy hybrid composite rods, one with uniformly dispersed carbon and glass fibers, and the other with glass fiber shell and carbon fiber core, were investigated on the water uptake and interface shear strength. The aging condition was immersion in deionized water at 40 °C, 60 °C and 80 °C. Interface shear strength degradation mechanism was revealed by thermal analysis and microstructure analysis. It was found that the water absorption of two types of hybrid rods represented the two-stage behavior. For the rod of uniform fiber dispersion, more water uptake in the second stage occurred compared to that of the shell/core rod, which was attributed to the resin rich area and interface debonding of fiber/resin. Long-term hygrothermal exposure led to a remarkable degradation in the interfacial shear strength of the rods, up to 17.5% ∼ 42.1%. The resin plasticization and interface debonding were the main factors contributed to the strength degradation. Based on the Arrhenius equation, the long-term life prediction of the interfacial shear strength under two typical bridge service environments was conducted to the design guideline of hybrid rods in the bridge engineering.

Characterization of hybrid biocomposite Poly-Butyl-Succinate/Carbon fibers/Flax fibers

The investigation of renewable and recyclable materials becomes more critical every day due to the high levels of waste and carbon emissions and their impact on the environment. The use of eco-friendly materials, such as natural fibers and bioplastics, is increasingly important, and their use is always more popular. The aim of this research is to evaluate the changes in properties of composite materials made of Poly-Butyl-Succinate (PBS), a biodegradable thermoplastic matrix, and carbon fiber when some layers of carbon fiber are replaced by some layers of flax fiber to create a hybrid composite; in order to obtain a material more environmentally friendly with similar mechanical properties. To modify the flax fiber's surface energy and improve the wettability with the PBS matrix, an Atmospheric Pressure Plasma Torch (APPT) treatment was performed. The fibers' surfaces were characterized by measuring the contact angle; the contact angle values confirmed the wettability and accordingly, adhesion increased after plasma treatment. Different experiments were performed after substituting carbon fibers to evaluate the changes in the composite material's mechanical and thermal properties: tensile test, three-point bending test, impact tests and differential scanning calorimetry. Replacing the carbon fiber core layer with one or two flax fiber layers did not compromise the thermal stability. It led to the manufacturing of a hybrid composite with improved mechanical properties and higher impact resistance.

Composite helical spring with skin‐core structure: Structural design and compression property evaluation

AbstractThe helical spring is an essential mechanical component of automobile and machinery and has been widely used in industrial application. The weight reduction is the requirement of current material design and also the research trend for material development. In this study, a novel composite helical spring with “skin‐core” structure was designed and fabricated with an integrated formation process based on the vacuum‐assisted resin infusion technology. Based on the different function of skin and core, the skin structure was weft knitting tube made of aramid and ultra‐high molecular weight polyethylene fiber, and the core structure was unidirectional carbon fiber. By selecting material for knitting tube and adjusting the volume content of carbon fiber core, the static and fatigue compression properties of composite helical spring were investigated. It has been found that the spring torsion and bending performance can be improved by wrapping the core with the knitting tube as the spring wire. Moreover, the finite element method was applied to further analyze the stress evolution of the “skin‐core” composite helical spring during compression and fatigue. The results of compression test and simulation show that the spring stiffness can be effectively improved by using knitting tube and increasing the content of carbon fiber. The stress of the spring cross section is concentrated in the internal radial region of 180°, and the distribution of the corresponding cross sections is relatively uniform. The “skin‐core” structure with aramid knitting tube as the outer skin and carbon fiber as the spring core significantly improves the load‐carrying capacity and stability of the composite spring. The proposed lightweight helical composite could provide a replacement strategy of existing metal or unidirectional filament reinforced springs used in the engineering applications.

Core–shell carbon fiber@Co1.5Mn1.5O4 mesoporous spinel electrode for high performance symmetrical supercapacitors

We report a mesoporous composite system consisting of carbon fiber cores surrounded with Co1.5Mn1.5O4 spinel nanocrystal shells, synthesized by a simple two–step process involving single–nozzle co–electrospinning and subsequent calcination. Benefiting from the obtained core–shell structure, this composite has exhibited high specific capacitance in the two–electrode configuration, up to 384 F g−1 at 0.28 A g−1, with no capacitance loss after 2000 cycles at 50 mV s−1. The incorporation of spinel nanocrystals improved the capacitive performances of composite fibers due to a synergistic effect of redox–active shells and the conductive cores, making this novel material promising for symmetrical supercapacitors.

Effects of elevated temperature, hydraulic pressure and fatigue loading on the property evolution of a carbon/glass fiber hybrid rod

A carbon fiber core (CFC) and glass fiber shell (GFS) hybrid rod (HFRP) with the diameter of 22 mm was developed to replace the steel rod in the application of underground oil extraction. In the present study, the variation in the properties of the hybrid rod served for 553 days was investigated subjected to the coupling conditions of elevated temperature (T), hydraulic pressure (P) and fatigue load (L)/stress level peak (S), one exposure condition, closed to the ground (T = 25 °C, P = 0.5 MPa, Lmax/S = 70 kN/11.1%) and another in the underground oil-well up to 2600 m (T = 90 °C, P = 18 MPa, Lmax/S = 50 kN/7.9%). Exposed in the deep oil-well condition led to an extra degradation of interface shear strength (ISS) compared to the ground exposure. The degradation mechanism of ISS was attributed to the hydrolysis and plasticization of resin owing to formed multiple hydrogen bonds between the water molecule and chain structures of resin. The removal of free water from the hybrid rod brought about an average increase percentage of ISS, ~10.0% for the upper rod and ~7.4% for the bottom rod. Furthermore, the maximum recovery of ISS was observed for the removal of bound water for the drying at 100 °C for 14 days. The fatigue performance evaluation of hybrid rod exposed in underground oil-well condition showed the optimal rod diameter for the present fatigue load condition (Lmax/S = 70 kN/11.1%) was 19 mm with the service life of ~50 years. Furthermore, the applied maximum fatigue load was obtained to be 114.3 kN with the fatigue life of 22.6 years for the present hybrid rod.

LineSpyX: A Power Line Inspection Robot Based on Digital Radiography

Most of the current power line inspection robots use cameras and LiDARs to inspect the power line surfaces and the surrounding environment. But it is still difficult to detect the internal defects of the power lines. In this letter, the design and implementation of LineSpyX, a novel power line inspection robot based on digital radiography (DR), is introduced to solve the problem of non-destructive testing (NDT) of the overhead Aluminum Conductor Composite Core (ACCC) wires. The proposed robot has a stable wrapped mechanical structure with a moving system, a live work system, and a NDT system. The wheeled moving system enables the robot to move on the wires and cross obstacles such as vibration dampers. The NDT system consists of a portable X-ray generator and a DR detection panel. When the robot performs the inspection task, the X-ray goes up through the ACCC wire to the panel, where the X-ray images of the internal carbon fiber cores are recorded. A deep learning based defect diagnosis method combined with manual diagnosis is proposed to detect potential defects. The main functionalities of the developed robot are verified by lab experiments and field tests.

Mechanical property evolution and service life prediction of pultruded carbon/glass hybrid rod exposed in harsh oil-well condition

A glass fiber shell (GFS) and carbon fiber core (CFC) hybrid rod (HFRP) was produced through pultrusion technology for an alternative to traditional steel sucker rod for petroleum production. The mechanical properties of a really used HFRP rod closed to the ground (25 °C exposed temperature, 0.5 MPa hydraulic pressure and ~70 kN cyclic loading) and in the deep oil-well up to 2600 m (90 °C exposed temperature, 18 MPa hydraulic pressure and ~50 kN cyclic loading) were investigated as a function of service time as long as 553 days. The mechanical, thermal properties and microanalysis tests of HFRP rods were conducted to obtain the long-term evolution of HFRP rods under the above service environments. Exposure closed to the ground caused a maximum degradation rate of short beam shear strength (SBSS) up to 18.92%. Meanwhile, the maximum degradation rates of interface shear strength (ISS) were 28.24% for carbon fiber/resin, 16.88% for glass fiber/resin and 36.07% for CFC/GFS interface. In comparison, exposure in the deep oil-well brought in an extra degradation rate from 4.34% to 11.11% for ISS, and the higher cyclic loading (~70 kN) played an insignificant effect on the degradation. The degradation mechanism of mechanical properties for HFRP rods was attributed to plenty of bound water combined with the resin through the hydrogen bond and brought about the hydrolysis of resin and the increase of pore volume content (~5%), leading to the debonding of fiber/resin. The long-term prediction of interface shear strength shows the degradations of CFC and CFC/GFS were more sensitive to the cyclic load (70 kN) compared to no cyclic load (0 kN), and an extra degradation rate up to 31.3% was observed compared to the no load condition, and the accelerated degradation was weakened with the increase of service temperature and hydraulic pressure. In addition, the exposure at the increased service temperature and hydraulic pressure in the deep oil-well led to an additional degradation rate of ISS in comparison to the ground exposure: 10.70% (CFC), 13.25% (CFC/GFS) and 4.81% (GFS).