Incorporation Of Carbon Fibers Research Articles

Preparation of a novel foamed concrete modified with carbon fiber and graphite: Mechanical, electro-magnetic and microstructural characteristics based on X-CT

In this paper, foam concrete is modified using graphite and carbon fiber as absorbents. The mechanical properties are analyzed in conjunction with hydration products, pore size distribution based on XCT test. Additionally, the resistivity, complex permittivity and complex permeability are tested. The results demonstrate that carbon fiber enhances the proportion of pores with diameters less than 200 μm in foam concrete, thereby significantly enhancing its flexural strength. Furthermore, incorporating graphite helps offset the initial retardation of sulfoaluminate cement hydration induced by carbon fibers, leading to an increase in the average pore size and a reduction in compressive strength. The incorporation of carbon fibers at a concentration of 0.6 wt% achieves the percolation threshold, akin to scenarios with singular fiber incorporation. Exceeding 2 wt% graphite content results in negligible influence on the conductivity. The synergistic integration of graphite and carbon fibers significantly improves the electromagnetic wave absorption performance of the composite. At a thickness of 6 mm, the material exhibits an effective bandwidth where the reflection loss is less than −10 dB, extending up to 2.5 GHz, which constitutes 52.08 % of the tested frequency spectrum.

Effect of process parameters on the mechanical performance of FDM printed carbon fiber reinforced PETG

Additive manufacturing (AM), shows promising advancements in layer-based modeling displaying its potential for substantial waste reduction. Out of all the AM methods, the most cost-effective and popular choice for prototyping and making customized parts is fused deposition modeling (FDM). This research investigates how various FDM process parameters specifically layer thickness, raster angle, and printing speed affect the mechanical properties of 3D-printed PETG (polyethylene terephthalate glycol) specimens reinforced with carbon fiber (CF). Optimal settings, including a 0° raster angle, 0.2 mm layer thickness, and 40 mm/s printing speed, enhance both tensile and flexural strength due to improvement in material bonding and alignment. Interestingly, lower values for raster angle, layer thickness, and printing speed also lead to notable improvements in mechanical properties. Contour and interaction plots provide valuable insights into the significant impact of these parameters. The study also explores how different printing speeds influence the mechanical characteristics of CF-reinforced PETG specimens. Furthermore, the comparative analysis demonstrated that incorporating carbon fiber into recycled PET waste materials resulted in an approximately 30% increase in tensile strength. These findings imply that using CF with plastic waste in large-scale industries can pave the way for innovative solutions, enhancing performance and sustainability, especially in the automotive, and defence sectors.

Life cycle evaluation of seismic retrofit alternatives for reinforced concrete columns.

The critical earthquakes of the last few years highlight the urgent seismic retrofitting of existing buildings due to their aging or inadequate design. This paper aims to evaluate reinforced concrete column retrofit alternatives in a region of high seismic risk. Significant economic, environmental, and functional factors must be considered when deciding between various building retrofit options. The study uses a cradle-to-grave analysis to examine the economic and environmental impacts through life cycle assessments. Specifically, the life-cycle performance of three classic alternatives for rehabilitating columns lacking adequate confinement is compared: concrete jacketing, steel jacketing, and carbon fiber incorporation. The research adopts a holistic approach using multi-criteria decision-making methods, integrating economic, environmental, and functional criteria. A set of criteria and indicators is presented in a structured hierarchy that facilitates the orderly evaluation of alternatives. The results suggest that steel jacketing is preferred, as it presents a balanced performance in most criteria. The incorporation of carbon fiber is viable due to its low environmental and functional impact, although the high production costs of the raw materials limit it. In contrast, concrete jacketing has the highest environmental and functional impacts, making it the least favorable option. The results of this study will provide relevant information for engineers and decision-makers to select the most suitable options for building retrofit when considering several simultaneous perspectives.

Mn–Zn ferrite foam concrete: Enhanced electromagnetic wave absorption and pore structure by incorporating carbon fibers

In this study, an absorbent composite of carbon-fibre-reinforced Mn–Zn ferrite foam concrete was fabricated. The influence of carbon fibre (CF) concentration on the mechanical and electromagnetic wave (EMW) absorption characteristics of Mn–Zn ferrite foam concrete within the 0.2–5GHz were investigated. Key performance indicators, such as compressive and flexural strengths, electromagnetic parameters, reflection loss, and absorption bandwidth were thoroughly analysed. The pore size and distribution were examined by X-ray computed tomography (CT) to reveal the EMW absorption mechanism. The findings indicate that CF effectively mitigates agglomeration in Mn–Zn ferrites, enhancing dielectric and magnetic losses synergistically, which improves not only the mechanical properties but also the EMW absorption capacity of Mn–Zn ferrite foam concrete. The optimal wave absorption performance was observed at a CF content of 0.3 wt%, yielding an impressive absorption bandwidth of 1.46 GHz and a minimum reflection loss (RLmin) of −28.75 dB. A noteworthy observation was the inverse correlation between the CF doping level and resistivity. The attenuation constant peaked at 108.13. When the CF content reached 1.2 wt %, the composite attained its percolation threshold, manifesting a resistivity of 145.4 Ω·m.

A novel thermal-tailored strategy to mitigate thermal cracking of cement-based materials by carbon fibers and liquid-metal-based microencapsulated phase change materials

Massive concrete structures are susceptible to thermal cracking due to the large surface-to-internal temperature gradients induced by the exothermic cement hydration, threatening their durability and safety. This study explored a novel thermal-tailored strategy to mitigate thermal cracking of cement-based materials by incorporating carbon fibers (CF) and liquid-metal-based microencapsulated phase change materials (MEPCM). Specifically, spherical MEPCM composed of In-Bi-Sn alloy cores coated by polyvinyl alcohol shells was prepared through a high-speed liquid-phase dispersion method, with average diameters of 36.26 μm and a high volumetric latent heat of 214 MJ/m3. The synergistic effect of CF and MEPCM on the microstructure, mechanical and thermal properties of cement mortars was further investigated. Upon adding 0.3 wt% of CF and 3.2 vol.% of MEPCM, the flexural strength of cement mortars exhibited a significant increase of 30.3 %. Microanalysis revealed that the molten MEPCM could flow to fill the pores and microcracks within its surrounding matrix and form a network skeleton with well-dispersed CF, imparting flexibility to the typically rigid cement hydrates. By this way, the thermal conductivity of cement mortars was increased by 21.7 % and internal temperature rise was decreased by 12 ℃ by adding 4.8 vol.% of MEPCM, contributing to the mitigation of risks associated with thermal cracking. The research outcomes will provide valuable insights into the development of thermal cracking-resistant cement-based materials in a highly efficient way.

Short carbon fiber-reinforced PLA composites: influence of 3D-printing parameters on the mechanical and structural properties

3D printing, particularly “fused filament fabrication” (FFF), plays a crucial role in Industry 4. FFF is widely used for creating complex structures and multi-material parts across various industries such as food industry, fashion industry, and manufacturing sectors. The properties of FFF-produced objects are remarkably affected by printing parameters. This study explores the impact of printing parameters and the addition of short carbon fibers on the strength of polylactic acid (PLA) printed samples. The lowering layer height, increasing feed rate and extrusion temperature boost impact strength, while a smaller raster angle enhances it. Meanwhile, an improved flexural strength is achieved by adjusting layer height, extrusion temperature, and raster angle. Higher extrusion temperatures enhance tensile strength, microstructure, and reduce porosity. Lower layer height improves flexural and impact strength (28.05% increase in 0.1 mm layer height), higher feed rate boosts strengths (12.56% improvement in 7 mm3/s feed rate), and elevated extrusion temperatures enhance impact strength (14.49% increase in 230 °C extrusion temperature) but reduce flexural strength (14.44% decrease). Incorporating carbon fibers in PLA negatively affects the microstructure but increases crystallinity, raising the melting temperature and lowering cold-crystallization temperature. The introduction of carbon fibers into PLA results in a complex interplay of mechanical and thermal properties.Graphical abstract

Preparation of high-performance materials based on carbon nanofibers and analysis of mechanical properties at room and high temperatures

The shortcomings of conventional building materials, such as inadequate tensile strength and fire resistance, have been significantly exacerbated with the emergence of complex and diverse engineering practices. However, the current research on high-performance building materials is still in its nascent stage. Therefore, our study aims to investigate the potential improvements in the mechanical properties of building materials through the incorporation of carbon fiber and nano silica. Specifically, we focus on assessing the mechanical properties of these modified materials at both room and elevated temperatures. Our experimental results demonstrate a notable enhancement in compressive strength. At room temperature, the H2 group exhibited a 15.1% increase in compressive strength, while the H5 group experienced a 7.3% increase. Notably, the compressive strength of the H7 group reached its highest value at 47.13 MPa. Additionally, the H2 group displayed the highest bending strength at 5.18 MPa. Our electron scanning microscopy analysis revealed the uniform dispersion of carbon fibers within the building materials, without any clumping. This suggests that when the dosage of Carbon Fiber reaches 0.6% of the mass of building materials, it can be uniformly dispersed within the mixture. We have also evaluated the performance of the modified materials under high temperatures. It was observed that the prefabricated building materials group experienced a 65% reduction in compressive strength when subjected to 800 °C. Conversely, the carbon fiber building materials exhibited a compressive strength loss of over 62%. Overall, the carbon fiber building materials outperformed the standard building materials under high temperature conditions, with significantly higher compressive strength. Moreover, the modified materials demonstrated an improvement in the residual splitting strength, ranging from 26% to 37% when exposed to temperatures over 800 °C. These findings indicate a substantial enhancement in the mechanical properties of the proposed modified materials. In conclusion, the incorporation of carbon fiber and nano silica into the building materials resulted in substantial improvements in their mechanical properties. These modified materials hold great potential for practical construction projects, offering higher performance and enhanced durability.

Self-sensing properties of cementless ultra-high performance concrete (UHPC) with slag aggregates

This research addresses the environmental impact of traditional cement-based construction materials and explores sustainable alternatives. The study aims to explore the mechanical properties, flowability, setting time, and self-sensing performance of cementless ultra-high performance concrete (UHPC) by utilizing the electrical properties of electric arc furnace slag (EAF slag) as a replacement for natural aggregates, along with alkali-activated slag as the binding material. Comparative analyses are conducted between cementless UHPC with EAF slag and silica sands, as well as the impact of incorporating carbon fiber. The study reveals that cementless UHPC with EAF slag exhibits improved fluidity and slightly increased setting time compared to UHPC with silica sands, attributed to the spherical shape and ball bearing effect of EAF slag. While the compressive and tensile strength of cementless UHPC with EAF slag is slightly lower than that of UHPC with silica sands, it still meets UHPC standards with strengths of 150 MPa and 8 MPa, respectively. Nonlinear curve fitting accurately quantifies the self-sensing performance, yielding precise simulation results. Importantly, EAF slag-based UHPC exhibits superior self-sensing capabilities, outperforming carbon fiber incorporation. Unlike UHPC with silica sands, which generates substantial noise even with carbon fiber, EAF slag-based UHPC demonstrates effective self-sensing with minimal noise, even in the absence of carbon fiber. This study expands the understanding of self-sensing performance in cementless UHPC by effectively utilizing EAF slag as a replacement for natural aggregates. The results suggest that the valorization of EAF slag has the potential to enhance sustainability and the self-sensing capabilities of cementless UHPC.

Investigating the synergistic effects of carbon fiber and silica fume on concrete strength and eco-efficiency

The present study endeavors to quantitatively evaluate the performance of concrete by incorporating carbon fiber reinforcement and micro silica addition. A comprehensive experimental investigation is conducted to examine the effects of these two additives on the concrete properties. Additionally, an eco-efficiency analysis is performed to assess the environmental impact of the modified concrete. Furthermore, a response surface optimization technique is employed to optimize the concrete mix design based on desired performance criteria. The findings of this study provide valuable insights into enhancing the performance and eco-efficiency of concrete by utilizing carbon fiber reinforcement and micro silica addition. To accomplish this objective, varying percentages of CF (ranging from 0% to 0.80%) and different densities of micro silica (ranging from 0 kg/m3 to 50 kg/m3) were incorporated into the concrete mixtures. Subsequent tests were conducted to evaluate the mechanical properties, including compressive strength, split tensile strength, and flexural strength, at least 3 specimens for each mix were tested. Furthermore, the eco-strength efficiency of the concrete mixtures was assessed by determining the ratios of embodied carbon. The results demonstrate that the inclusion of 0.60% CF and 26.5 kg/m3 of micro silica in the concrete mixture yields the optimal proportion, leading to a significant enhancement in compressive strength (CS), split tensile strength (STS), and flexural strength (FS) by 54.11%, 80%, and 36.6%, respectively, compared to a control sample devoid of CF and micro silica. Through thorough experimentation, a response surface methodology (RSM) was employed to develop an optimized model. Consequently, the derived equations enable the calculation of the impact of adding carbon fiber to concrete.

Effect of Low-Temperature Plasma-Modified Carbon Fibers on Impact Load Damage of Low-Density Oil-Well Cement.

After large-scale exploitation of conventional oil and gas resources, most remaining resources are in highly depleted zones, where the fracture pressure of the formations is greatly reduced. Low-density oil-well cement prevents wellbore and formation fractures by reducing annular liquid column pressure and is one of the most commonly used cements in the oil and gas industry. However, cement sheaths made of low-density oil-well cement can be easily damaged due to the impact load generated during the well completion process. Incorporating carbon fibers into the cement matrix can effectively enhance the performance of cement sheaths. To ensure that carbon fibers can be closely combined with the cement matrix, low-temperature plasma modification technology was used in this study to pretreat the fibers. The mechanical properties of low-density oil-well cement incorporated with unmodified or modified carbon fibers were studied in detail under an impact load. The results of X-ray photoelectron spectroscopy revealed that the content of hydrophilic groups on the surface increased from 18.3 to 60.3% after the plasma treatment. The impact test results showed that the peak strengths of the cements cured at 60 °C for 14 days with 0.3% unmodified and modified carbon fibers could reach 37.01 ± 1.7 and 62.27 ± 1.7 MPa, respectively, under the impact load, i.e., an increase of 68.25% after the carbon fibers were treated with low-temperature plasma. Similarly, the absorbed energy increased from 15.59 to 44.31 J, and the energy absorption rate increased from 25.98 to 73.85%. Low-temperature plasma modification provided hydrophilic functional groups on the surface, significantly improving the interfacial bonding between the carbon fibers and cement matrix. The strengthened interaction was beneficial to extending the bearing time under the impact load and demonstrated a positive influence on the mechanical properties related to the impact resistance.

Interface enhancement and distribution of carbon fibers in injection welding

AbstractInjection welding is an excellent adhesive‐free bonding method for thermoplastic resins, demonstrating outstanding connection effectiveness. The incorporation of carbon fibers (CFs) significantly enhances the weld shear strength at the injection interface. This study aims to investigate the reinforcement effect of CF‐reinforced thermoplastic composites (CFRTP) during the injection welding process. And explore the influence of the amount of added CFs on the weld shear strength. Polyamide 6 (PA6)/CF composites with CF contents of 10 wt% and 30 wt% were subjected to injection welding for the first and second molding cycles, respectively. It was observed that the reinforcement effects varied considerably depending on the combinations studied. Under the optimal combination and process parameters, the weld shear strength of PA6/CF composites reached 63 MPa, equivalent to 90% of the shear strength (70 MPa) of the original PA6/CF material. Polarized light microscopy and scanning electron microscopy were utilized to analyze the distribution of CFs at the interface and the reinforcing mechanism during tensile fracture. The significance of maintaining uniform CF content during the welding process of PA6/CF composites was emphasized.Highlights Preparation of PA6 composite materials with different carbon fiber contents. Achieving high welding shear strength of composite materials through injection welding. Identified the optimal injection welding conditions to achieve the highest strength. The positive effect of specific fiber distribution on welding strength was analyzed.

Effect of steel slag on the mechanical properties and self-sensing capability of ultra-high performance concrete (UHPC)

This study investigates the self-sensing capability and mechanical properties of ultra-high performance concrete (UHPC) incorporating steel slag aggregates. The experimental findings underscore the potential of steel slag as a promising industrial by-product capable of fully replacing the natural fine aggregates within UHPC. In addition, the incorporation of steel slag is shown to reduce CO2 emissions by approximately 40 kg/m3, as determined through life cycle assessment software, while simultaneously enhancing flowability when compared to UHPC incorporating natural aggregate. Although the compressive and tensile strength of UHPC with steel slag is slightly lower than that of UHPC with natural aggregates, it still demonstrates impressive performance, with compressive and tensile strengths reaching approximately 207 MPa and 14 MPa, respectively. To assess the mechanical properties and self-sensing capacity of steel slag, this study incorporates carbon fiber and multi-walled carbon nanotubes (MWCNT) into the UHPC series. The self-sensing capacity results emphasize the advantage of incorporating steel slag due to its high iron content that leads to superior conductivity compared to silica sand. Furthermore, comparisons are made with UHPC series incorporating carbon fiber and MWCNT. UHPC with steel slag demonstrates superior self-sensing capabilities compared to the silica sand series with carbon fibers, and it is comparable to UHPC with MWCNT. To quantify the self-sensing capability of UHPC with steel slag, nonlinear curve fitting is employed, resulting in highly accurate simulation outcomes. These experiments collectively highlight the multifaceted benefits of utilizing steel slag aggregate in UHPC, encompassing environmental advantages, enhanced flowability, and impressive self-sensing capabilities.

Design and performance evaluation of an electrically heated concrete panel for sustainable winter maintenance

This study focuses on developing an electrically heated concrete panel system incorporating carbon fiber (CF) and carbon nanotube (CNT) as electrical media. Properties of 8 different electrically conductive concrete mixtures, such as workability, air content, compressive strength, and electrical resistivity, were experimentally evaluated to find optimum mixture proportions. Subsequently, three laboratory specimens with different geometric designs were fabricated using a two-lift concrete placement scheme: a normal concrete (NC) layer at the bottom and a conductive concrete (CC) layer at the top. Conventional ribbed rebars were embedded as electrodes to supply electrical power. The electrical heating performance of the specimens was evaluated based on the temperature rise and thermal strain changes during the imposed heating cycles. The findings demonstrated the potential use of the developed electrical HPS for sustainable winter maintenance, which will contribute to advancing heated pavement technologies and minimize the environmental impact caused by traditional snow removal practices.

Optimizing the thermal properties of fiber reinforced phthalonitrile composites

AbstractThe development of lightweight composites with desirable thermo‐mechanical properties is progressively increasing. Phthalonitrile (PN) based composites have shown great potential in this regard. However, the basic thermal properties of PN composites required for engineering design are not yet fully understood. In this work, we investigated the thermal stability, thermal expansion behavior and thermal conductivity of PN composites reinforced with carbon fiber (CF) and high silicon fiberglass (HSF) via combined experimental studies and numerical simulations. The results indicated that CF/PN performs better in thermostability than HSF/PN at temperatures below 500°C. Moreover, the incorporation of CF and HSF lowered the coefficient of thermal expansion (CTE) and thermal insulation of PN. At room temperature, the in‐plane CTE of CF/PN and HSF/PN were 1.97E‐6 and 9.24E‐6°C−1, respectively, while the out‐plane thermal conductivities of CF/PN and HSF/PN were 0.65 and 0.34 W/(m K). It is worth noting that an excessively high fiber volume fraction would lead to poor thermal insulation and lightweight properties of the PN composites, while a low fiber volume fraction would result in poor stiffness and thermal dimensional stability. Determined via TOPSIS model, a fiber volume fraction range of 50%–60% was ideal for both composites with comprehensive optimal properties, respectively.

Solid particle erosion and scratch behavior of novel scrap carbon fiber/glass fabric/polyamide 6.6 hybrid composites

AbstractThis study investigated the tribological performance of hybrid composites composed of scrap carbon fiber (CF), glass fabric (GF), and polyamide 6.6 (PA6.6) through an innovative approach for reusing scrap CFs in high‐value composite structures. The experimental setup included CF/GF/PA6.6 hybrid composite laminates with varying CF contents and surface‐modified GFs, as well as PA6.6 sheets and GF/PA6.6 composite laminates. Solid particle erosion and scratch tests were conducted to assess the influence of scrap CF hybridization and GF surface modification on the tribological properties of the composites. The results demonstrated that neat PA6.6 sheets exhibited the lowest erosion rate, while the incorporation of CF and GF reinforcements had a detrimental effect on erosion resistance. The highest erosion rate was observed within the impact angle range of 15°–30° for pure PA6.6 sheets, whereas for composite laminates, it occurred within the range of 30°–45°. In contrast, CFs positively affected scratch hardness despite their negative impact on erosion resistance. Additionally, the silane treatment of GFs, which enhanced interfacial strength, improved the erosion resistance and scratch hardness of GF/PA6.6 composite laminates without CF. Profilometer‐based topographic analysis revealed a correlation between the average surface roughness of the eroded surfaces and the weight loss resulting from solid particle erosion.

Effect of carbon fiber and thermoplastic resin on laminates under lightning and dielectric strength tests

AbstractThe incorporation of carbon fiber (CF) and thermoplastic resin in wind turbine rotor‐blade represents a challenge for lightning events because CF conducts electricity and the behavior of thermoplastic resins is not well known. A comparative study with laminates with epoxy or thermoplastic resins was performed, using lightning and dielectric strength tests. Lightning tests revealed that resins behaved similarly; the current preferentially flowed in fiber direction and in zones with high contact between fibers (e.g., criss‐crossed fibers at panel edges); the level of through‐thickness damage was inversely related to panel thickness; current flow did not affect the tensile properties in fiber direction, but produced a drop in bending strength; the adequate integration of earth terminals in CF laminates was critical for a proper lightning discharge. In dielectric tests, it was concluded that panels with glass fiber covering CF laminates behaved as through‐thickness insulators; the thermoplastic reduced the laminate's dielectric strength, while the incorporation of CF, or laminate aging in a salt spray chamber showed no difference. Electrical resistance tests showed that the results were not dependent on the type of resin, but on the level of fiber‐to‐fiber and fiber‐to‐terminal contact. The lowest linear resistance was obtained in the longitudinal fiber direction, followed by the transverse and through‐thickness ones.

Research on a sustainable concrete synergistic reinforced with carbon fiber and carbon nanofiber: Mechanical properties, durability and environmental evaluation

A sustainable concrete was developed by incorporating carbon fiber (CF) and carbon nanofiber (CNF), where the synergistic modification effect of micro-scale and nano-scale of fibers was exploited and the mechanical properties and durability of concrete were improved. The mechanical test, shrinkage test, freeze-thaw cycle test, water permeability test and carbonation test were conducted on carbon fiber/carbon nanofiber reinforced concrete (CF/CNFRC) with different mix proportions. The results show that, when the content ratio of CF to CNF is 1:3, the compressive strength, splitting tensile strength and flexural strength are increased by 14.12%, 21.46% and 18.05% compared with plain concrete (PC). At the same time, the shrinkage rate at 180-day age, relative permeability coefficient, compressive strength loss rate at 200 freeze-thaw cycles and carbonation depth at carbonation age of 28 days are reduced by 30.57%, 66.56%, 37.72% and 34.09% respectively, at which time CF and CNF have the best synergistic modification effect. Durability value was further introduced to quantitatively evaluate the durability of CF/CNFRC, showing that the durability value of CF/CNFRC01 was the largest and increases by 57% compared with PC. Through MIP and SEM tests, the microstructure of CF/CNFRC was analyzed, and the multiscale synergistic modification mechanism of CF and CNF was further explored. Compared with the single CNF, appropriate amounts of CF and CNF can exert a positive multiscale synergistic effect, which further optimizes the pore structure through fiber bridging and filling, inhibits crack propagation, improves the compactness and integrity, and thus improves the mechanical properties and durability of concrete. In addition, the economic and environmental benefits of CN/CNFRC were discussed by calculating the cost-benefit ratio and CE-benefit ratio (the ratio of CO2 emissions to durability benefits). The calculation results show that CN/CNFRC has the best economic and environmental benefits when the content ratio of CF to CNF is 1:3, where the environmental benefits are 31% higher than that of PC.

A novel carbon‐fiber geopolymer composite‐coated electrodes for photoelectrocatalysis: Fabrication and application

AbstractThe photoelectrocatalysis is an efficient and sustainable degradation method for organic contaminant, where the photoanode material plays a critical role. Development of novel, inexpensive, and high‐performance photoanode materials is significant to enhance the degradation performance of anodes catalysis. Herein, a novel carbon‐fiber geopolymer composite‐coated electrode with low cost and facile production was prepared by incorporating carbon fibers in a geopolymer matrix. The as‐developed photoelectrocatalyst coupled with persulfate could effectively degrade more than 98 % of rhodamine B within 6 min, which demonstrated superior catalytic activity compared with various catalysts reported in the literature. Moreover, the composite electrodes exhibited excellent reusability. The endogenous Fe2O3 and TiO2 in the geopolymer matrix were the main active materials, providing photoelectron‐hole pairs for dye molecule degradation. Significantly, the carbon fibers in the matrix effectively connected the scattered oxide species and prompted the separation and migration of photoinduced carriers while enhancing the stability of the catalysts and improving the conductivity of the matrix. When the carbon content was increased from 0 to 6 wt%, the conductivity of the composite increased by 17.75 times. This study offers a cost‐effective and eco‐friendly photoelectrocatalyst, which shows significant potential for further development.

A Comparative Study on Electrical Resistivity and Compressive Strength Properties of Cement Composites Incorporating Conductive Materials

Conductive cement composites have attracted high attention in recent years due to the possibility of achieving multifunctional materials. The usual approach has been to incorporate steel fiber, carbon fiber, graphite, and carbon nanotube/or carbon nanofiber into the cement matrix. In this article, an experimental comparative study was conducted on the electrical resistivity and compressive strength properties of cement composites incorporating carbon fiber (CF) and steel fiber (SF), which are conductive materials. The electrical resistivity of the conductive fiber-reinforced cement composites (FRCCs) was measured using the four-probe method, and compressive strength was conducted based on the KS L ISO 679 and ASTMC109/C109M test methods. Their performance was compared and analyzed with plain cement composites (PCCs). Afterwards, the fracture surfaces of the conductive SFRCCs (steel fiber-reinforced cement composites) and CFRCCs (carbon fiber-reinforced cement composites) were also analyzed using a scanning electron microscope (SEM). The experimental results showed that, in all specimens, the electrical resistivity gradually increased as the curing ages elapsed, while the electrical resistivity decreased significantly as the fiber volume fractions increased. Overall, the addition of SF up to a fiber volume fraction of 1.25% did not significantly affect the electrical resistivity of cement composites. In contrast, however, the electrical resistivity of CF decreased slightly even at a low dosage (i.e., 0.1–0.3%), and thereafter, it was significantly decreased. The percolation threshold of the conductive CFRCC incorporating CF used in this experiment was 0.4%, and this seemed to be the optimal CF dosage that can greatly improve the conductive cement composites while maintaining the maximum performance of compressive strength. In addition, the compressive strength of conductive SFRCC was higher than that of PCC, whereas in the case of conductive CFRCC, it showed a greater tendency to decrease significantly as the fiber volume fractions increased. We expect the results of SEM image analysis to be useful as basic data for establishing microstructure mechanisms of reinforcement fibers in the cement matrix.

High‐performance hierarchical composites based on polyamide 6, carbon fiber and graphene oxide

AbstractThis study reports the effect of graphene oxide (GO) coating on carbon fiber (CF) surface on the mechanical and thermal properties and morphology of CF‐reinforced polyamide 6 (PA6) composites containing 7.5 wt% of short CFs. GO was coated on the CF surface by a physical absorption method with concentrations ranging from 0.05 to 0.5 wt% GO. The PA6/CF composites were prepared by extrusion, and the specimens were obtained by injection molding. Their morphology (SEM, XRD tests), mechanical (tensile, flexural, impact, and fatigue tests), and thermal properties (DSC, TG and HDT tests) were analyzed. A significant change in the preferential (growth) crystal planes of PA6 was observed upon the incorporation of CFs containing GO, favoring the formation of α crystals in PA6. GO coating on CFs was effective and provided an increase in tensile strength and Young's modulus up to 12% and 24%, flexural strength and flexural modulus up to 22% and 25%, and a decrease in impact strength and fatigue life up to 30% and 23%, respectively, when compared to unmodified PA6/CF composites. Fracture micrographs indicated an increase in the PA6/CF interaction and the effectiveness of GO as a coupling agent for the composite.