Carbon Fiber Content Research Articles

Mechanical Properties of TWILL Carbon Fiber Fabric-Reinforced Single-Layer Thermoplastic Polyamide and Polybutylene Terephthalate-Based Composite Materials Manufactured by Hot Pressing

This study investigates carbon fabric-reinforced thermoplastic composites produced via hot pressing, using Polyamide PA6 and Polybutylene Terephthalate (PBT) as matrix materials. These materials are increasingly utilized in the development of lightweight, high-performance, multilayer structures, such as aluminum-reinforced laminates, for automotive and aerospace applications. The mechanical properties, including tensile strength and stiffness, were systematically evaluated under varying loading conditions. The PBT-CF composite exhibited a 17% higher tensile strength and stiffness compared to the PA6-CF composite, despite the low carbon fiber content. This highlights the critical role of uniform fiber distribution in enhancing material performance. Slower loading speeds (1 mm/min) resulted in higher strength, emphasizing the influence of process parameters on mechanical behavior. Cyclic loading tests showed a gradual reduction in stiffness with increasing strain range, particularly for the CF-45° configuration. The warp and weft arrangement of the carbon fabric contributed to structural inhomogeneity but did not significantly affect the global mechanical properties. These findings demonstrate the suitability of PBT as a matrix material alongside PA6 for carbon fiber-reinforced thermoplastics, offering new possibilities for the design of advanced composite materials with tailored properties.

Finite Element Analysis of Flexural Performance of Cut Carbon Fiber Reinforced Concrete Hollow Slab

As a kind of light wall material installed on the surface of the main structure, hollow hanging wall board is widely used in prefabricated buildings. Ordinary concrete hollow board can no longer meet the needs of actual engineering. In order to study the influence of the length and content of carbon fiber on the bending performance of concrete hollow board, the optimal length and content of fiber in hollow board are determined. ABAQUS finite element software is used to simulate the whole process of concrete hollow slab with different fiber length and dosage, and the load displacement curve is analyzed. The results show that the bending performance of concrete slabs increases and then decreases with the increase of fiber length and content. When the fiber length is 10mm and the content is 0.24%, the bending performance of concrete hollow slabs is the strongest, and the ultimate load is increased by 27.90%, showing better deformation resistance under the same load.

Multifunctional ultra-lightweight engineered cementitious composites (ECC) for electromagnetic interference shielding

This study developed the multifunctional ultra-lightweight engineered cementitious composite (ULW-ECC) by integrating conductive fillers to achieve effective electromagnetic interference (EMI) shielding capabilities, outstanding mechanical properties and thermal insulation. The mechanical performance, electrical conductivity, EMI shielding effectiveness (SE), and microstructure were analysed. Initially, the effects of the carbon fibre (CF) content and the pre-heating temperature of CF on EMI SE of the matrix (named: ULW-CC) without polyethylene (PE) fibre were tested. Then, CFs (0.5 and 1.0 vol%) with seven lengths (1–20 mm) were respectively incorporated into ULW-ECC to study EMI SE. The EMI SE of ULW-ECC incorporating powder calcined petroleum coke (CPC) was compared with that of CF. Experimental results demonstrated that the incorporation of conductive fillers improved the strength, conductivity, and EMI SE. Both the conductivity and EMI SE of ULW-CC and ULW-ECC increased with the dosage of conductive filler. EMI SE was enhanced with increased electrical conductivity, and pre-heating CF at 300 °C further improved the EMI SE. In ULW-ECC, 9-mm CF showed the highest EMI SE and conductivity. The conductivity and EMI SE of ULW-ECC were lower than those of ULW-CC at the same CF dosage due to the negative impact of PE fibre dispersion on the conductive network of CFs. The mixing method of CF in ULW-ECC affected the EMI SE. The EMI SE of ULW-ECC incorporating powder CPC was much lower than that incorporating CF, but hybridization of CPC and CF significantly enhanced EMI SE.

САМОУПЛОТНЯЮЩИЙСЯ ТОКОПРОВОДЯЩИЙ БЕТОН НОРМАЛЬНОГО ТВЕРДЕНИЯ НА ОСНОВЕ ПОРТЛАНДЦЕМЕНТА С ТЕХНИЧЕСКИМ УГЛЕРОДОМ И УГЛЕРОДНОЙ ФИБРОЙ

An approach to obtaining self-sealing conductive concrete of normal hardening is presented. The results of a study of the properties of self-sealing concrete of normal hardening based on Portland cement obtained by the joint introduction of carbon black of two grades TU P-803 and TU K-354 with their mass ratio of 4:1 and volume concentration in a mixture equal to 0.25%, as well as carbon fiber with a length of 3mm in an amount of 1% by weight of cement are presented. Con-crete was obtained with a specific electrical resistance equal to 0.25 Ohms * m, which does not increase during the harden-ing process, a strength of 53 MPa at the age of 28 days, frost resistance F200, water resistance W20, tensile strength at bending 8.2 MPa. Resistive heating elements with a capacity of 600 W/m2 or more have been obtained, providing the possi-bility of obtaining coatings with an anti-icing effect. It is shown that drying concrete of the developed composition can in-crease the conductivity by 50%, which is associated with an improvement in the contact between conductive particles caused by their compression during shrinkage, the value of which decreases with an increase in the amount of carbon fiber from 0.25% to 1% by weight of cement. It is noted that with an increase in the applied voltage to the sample, its electrical resis-tivity decreases, the more the carbon fiber content is in the range of 0.25-1% of the cement weight.

Enhancement of friction and wear performance of polytetrafluoroethylene composites through the synergistic effect of hard fillers

AbstractThe Stirling engine is a high‐efficiency externally heating piston engine. The self‐lubricating properties of polytetrafluoroethylene (PTFE) are crucial for the operation of Stirling engines. Three PTFE composites filled with different contents of carbon fiber (CF), polyimide (PI) and nano‐zirconia (nano‐ZrO2) were prepared and their mechanical, friction and wear properties were investigated. The results showed that the density of CF‐containing PTFE composites was significantly reduced by 1.46% to 6.9% compared to neat PTFE. Meanwhile, the incorporation of fillers greatly enhanced the hardness by more than 21.4% over the hardness of neat PTFE. In addition, the friction coefficients of three PTFE composites were lower than those of neat PTFE, and the wear rate of these composites was three orders of magnitude lower than that of neat PTFE. In particular, the wear rate of PTFE filled with CF and PI at high pressure (2 MPa) and high velocity (4 m/s) was only 1.24 × 10–6 mm3/Nm. The wear morphology was also analyzed by scanning electron microscopy and energy‐dispersive x‐ray spectroscopy. It was found that the addition of CF and PI in PTFE has the most pronounced improvement on tribological performances. The synergistic effect of CF's mechanical reinforcement and PI's adhesive properties reduces the wear of the matrix, resulting in excellent wear resistance of PTFE composites.Highlights The compressive strength of PTFE was reinforced by CF and nano‐ZrO2. CF can lower the density and significantly enhance hardness of PTFE. Synergistic CF and PI enhance PTFE composites' friction & wear performance. Adhesive fillers & debris size key to forming uniform continuous transfer films.

Fabrication and tribological behaviors of copper fiber and carbon fiber reinforced phenol‐formaldehyde resin‐based composite for sliding current collector

AbstractTo achieve new current collector (pantograph strip, electric brush) with easy industrialization and high strength‐toughness, carbon fiber and copper fiber reinforced phenol‐formaldehyde (Cuf/Cf/PF) composite is fabricated by over‐lapping and hot‐pressing processes. Cuf/Cf/PF composite has compact structure and good interfacial bonding between fibers and resin matrix. Cuf/Cf/PF composite is superior to carbon skateboard in terms of electrical conductivity, mechanical strength, and friction behavior. As the carbon fiber content increases, fracture failure mechanism of Cuf/Cf/PF composite transforms from plastic failure into brittle fracture. Wear mechanism is studied by combining electrical contacting and sliding friction, and appropriate arc discharge (2.48%) is benefit for the resin‐based composite to form a smooth tribolayer, but high arc discharge rate (4.83%) rapidly deteriorates wear condition on the worn surface.Highlights Carbon fiber and copper fiber mixing reinforce resin‐based composite. Cuf/Cf/PF composite has high strength‐toughness and low friction. Fracture failure mode changes to brittle fracture with increasing carbon fiber. Wear mechanism includes electrical contacting and sliding friction. Appropriate arc discharge improve friction performance of resin‐based composite.

Fabrication of dense Cf/SiC ceramic matrix composites using 3D printing and PIP with short carbon fibre as a toughening material

ABSTRACT To achieve weight reduction, toughness enhancement, and the fabrication of complex structures in SiC composites, a combination of SLS and PIP processes was used. Silicon carbide powder served as the matrix material, while short carbon fibres were used for toughening, resulting in dense Cf/SiC ceramic matrix composites. The effects of varying carbon fibre sizes and contents on the microstructure and mechanical properties of Cf/SiC composites were examined. Results indicated that adding 8% carbon fibre increased the fracture toughness of Cf/SiC composites by 33.33%. Further increases in carbon fibre content showed minimal effects on fracture toughness. Based on experimental results and finite element simulations, toughening mechanisms, including fibre pull-out, fibre debonding, and crack deflection, were further elucidated. Consequently, Cf/SiC composites with complex structures, such as turbine specimens and lattice structures, were successfully fabricated.

Mechanical properties and vibration characteristics of multiaxial carbon/glass hybrid fiber composites

AbstractIn this paper, the mechanical properties and vibration characteristics of Carbon‐Glass Hybrid Fiber Composites (CGHFC) are experimentally investigated with varying axial directions and blending ratios. The experimental results demonstrate a significant increase in the tensile strength of the CGHFC with an increasing content of carbon fibers. The biaxially CGHFC exhibits a maximum static tensile strength of 413.27 MPa in the 0° direction and 466.33 MPa in the 90° direction, surpassing both the quadratic and uniaxial directions. Notably, compared to biaxially oriented glass fiber material, the tensile strength of CGHFC is enhanced by 44.36%, thereby significantly improving its overall performance, making them particularly suitable for blade structures subjected to simultaneous tensile and vibratory loads. By optimizing the fiber orientation and blend ratio, the CGHFC provides good vibration control and fatigue resistance while ensuring high strength, thus maximizing the overall performance and service life of the blades. The results of this paper provide important data and theoretical support for the selection and design of wind turbine blade materials and help to promote the development of composite materials in wind turbine blade structure and design.Highlights CGHFCs show enhanced tensile strength with more carbon fibers. Biaxial CGHFCs have max tensile strength at 0° and 90° directions. CGHFCs' strength improves by 44.36% over glass fiber materials. Optimized CGHFCs offer superior vibration control and fatigue resistance. Research supports wind turbine blade material innovation.

Sensitivity analysis of carbon fiber reinforced asphalt pavements: Experimental study and data driven predictive model using machine learning

It is well known that the impact of fibers on reinforcing asphalt pavement (AP) has been extensively investigated. However, the optimal fiber length and content considering various temperatures is still an unresolved issue in this field. To reach this goal, this research aims to study the impact of carbon fiber (CF) reinforcement on the fracture energy and toughness of AP under varying environmental conditions. Several mix designs considering different CF length (10–30 mm) and content (1–3.5 %) at 5 °C and ambient temperatures were evaluated to determine the optimal values. The results demonstrated that while increasing CF length and content generally improves fracture energy and toughness, there is an optimal threshold beyond which additional CF content yields diminishing returns. Notably, the sample with a 1.5 % replacement ratio and 15 mm CF length exhibited superior performance, significantly enhancing the AP’s resistance to fracture due to effective stress distribution and crack bridging. Conversely, samples with the higher fiber content and length showed decreased fracture toughness, due to fiber clustering and reduced workability. Additionally, experimental results indicated higher values at 5 °C for fracture energy and toughness. Advanced machine learning techniques were also utilized to develop predictive models to accurately simulate the fracture behavior of CF-reinforced AP mixtures. Among all models, Gaussian process regression demonstrated superior performance and exhibited lower error in predicting experimental data. Moreover, a sensitivity analysis of this model was conducted to determine how the length and content of CF, as well as temperature, influence fracture energy and toughness, guiding the optimization of CF integration in AP design. These findings provide valuable insights for engineering durable and resilient asphalt pavements capable of withstanding diverse climatic stresses, ultimately contributing to more sustainable and cost-effective infrastructuresolutions.

Development of Electrically Conductive Wood-Based Panels for Sensor Applications.

This study investigates the development of electrically conductive panels for application as emergency detection sensors in smart house systems. These panels, composed of wood chips coated with polymeric methylene diphenyl isocyanate, were modified with carbon black and carbon fibers to enable detection of moisture, temperature, and pressure variations. Manufactured via hot pressing, the panels retained standard mechanical properties and exhibited stable performance under diverse environmental conditions. Carbon black-filled panels achieved electrical percolation at a lower filler concentration (5%) compared to carbon fiber-filled panels. The incorporation of carbon black reduced the electrical resistivity to 8.6 ohm·cm, while the addition of carbon fibers further decreased it to 7.7 ohm·cm. In terms of sensor capabilities, panels containing carbon fibers demonstrated superior sensitivity to moisture and pressure changes. However, carbon black was ineffective for temperature sensing. Among the carbon fiber-filled panels, those with 20 wt.% concentration exhibited the best performance for moisture and pressure detection, whereas panels with 40 wt.% carbon fiber content displayed the most reliable and consistent temperature-sensing properties.

Study on tribological properties of carbon fiber surface-enhanced 7075 Al alloy

In this study, carbon fiber was used to improve the wear resistance of the 7075 Al alloy surface. The tribological properties of carbon fiber reinforced 7075 Al alloy were evaluated on a reciprocating friction tester in water as the environmental medium. The effects of carbon fiber additions and speed on the wear characteristics were explored at 10N and 50N load, respectively. The abraded composite surfaces were analyzed using scanning electron microscopy (SEM). It was found that at 10 N load, the higher the content of carbon fibers in the sample, the lower the coefficient of friction of the sample; at 50 N load, some of the carbon fibers were broken and lost their lubricating effect, which resulted in that the addition of 15 vol% carbon fibers could not reduce the coefficient of friction of the 7075 Al alloy very well, but the sample with 30 vol% still maintained a low coefficient of friction. For 7075 Al alloy, the speed affects the coverage area of aluminum oxide on the friction surface, which in turn affects the coefficient of friction of the samples. The addition of carbon fiber can also effectively reduce the wear rate of 7075 Al alloy.

Scratch load and indenter type dependent scratch evaluation of milled carbon fiber filled basalt fiber/epoxy composites with factorial design

AbstractThis work investigates the addition of milled carbon fiber reinforcement and its effect on scratch resistance and mechanical durability for basalt fiber/epoxy composites, assessed under varied loading conditions with the aid of different indenter types according to a factorial design. Composites with MCF content from 0 to 10 wt% were prepared. Scratch behaviors under Vickers and Rockwell indenters were studied for loads of 5, 10, and 15 N. The addition of 10 wt% MCF has resulted in scratch hardness increase from 13.255 N/mm2 up to 47.952 N/mm2, depending on the type of indenter used. Precisely, in conditions of a 5 N load and when a Rockwell‐type indenter was used, a scratch hardness maximum of 47.952 N/mm2 was achieved, while for a Vickers‐type indenter under the same conditions, the maximum value of its equivalent was 23.327 N/mm2. Profilometric and SEM analyses evidence that matrix cracks and surface deformation have been reduced with higher MCF content, at least for the application of lower scratch test loads. The mechanical and surface performances of the basalt fiber composites were found to be considerably improved by the reinforcement with MCF.Highlights Scratch resistance for milled carbon fibers increases and peaks at 10 wt% reinforcement. The Rockwell indenter indicates a steady increase in hardness up to 47,952 N/mm2. Peak hardness of 10 wt% is observed under the Vickers indenter for the 5 N load. Higher milled carbon fiber content reduces matrix cracking and surface deformation. There is a clear correlation between scratch performance, milled carbon fiber content, and indenter type.

Upcycling end-of-life carbon fiber in high-performance CFRP composites by the material extrusion additive manufacturing process

Each year, a significant amount of waste is produced from carbon fiber polymer composites at the end of its lifecycle due to extensive use across various applications. Utilizing regenerative carbon fiber as a feedstock material offers a promising and sustainable approach to additive manufacturing based on materials. This study proposes the additive manufacturing of recycled carbon fiber with a polyamide-12 polymer composite. Filaments of recycled carbon fiber-reinforced polyamide-12 (rCF-PA12) with different recycled carbon fiber contents (0%, 10%, and 15% by weight) in the polyamide-12 matrix are developed. These filaments are utilized for 3D printing of specimens by using various infill density parameters (80% and 100%) on a fused deposition modeling 3D printer. The study examined how the fiber content and infill densities influenced the flexural performance of the printed specimens. Notably, the part containing 15 wt% recycled carbon fiber (rCF) composites showed a significant improvement in flexural performance due to enhanced interface bonding and effective fiber alignment. The results indicated that reinforcing the printed part with 10% and 15 wt% recycled carbon fiber (rCF) improved the flexural properties by 49.86% and 91.75%, respectively, compared to the unreinforced printed part under the same infill density and printing parameters. The investigation demonstrates that the additive manufacturing-based technique presents a potential approach to use carbon fiber-reinforced polymers waste and manufacture high-performance engineering, economic, and environmentally friendly industrial applications with the complicated design using different polymer matrices.

Study the Effect of Adding Malic Anhydride and Carbon Fibers to the Mechanical and Morphology Properties of Polypropylene

Adding reinforcement materials like carbon fibers with maleic anhydride improves the strength of polypropylene. The present work aimed to study the effect of adding maleic anhydride and carbon fibers on the mechanical properties of polypropylene enhanced by presenting carbon fibers. Carbon fibers added at different ratios (0, 2, 4, 6, and 8) % and 1% of maleic anhydride were added to pure polypropylene. Standard tensile and impact test specimens were prepared per ASTM standards using an extruder technique. It was observed that increasing the carbon fiber content enhanced the tensile strength, modulus of elasticity, and hardness of polypropylene while the elongation decreased, but it enhanced after MAH addition. SEM and FTIR indicated good adhesion between fibers and polypropylene after adding maleic anhydride (MAH). UV tests showed that carbon fibers protect the composite material from the UV sunlight.

Preparation and Properties of Carbon Fiber/Flexible Graphite Composite Grounding Material

In this paper, flexible conductive composite materials were prepared from flexible graphite and carbon fiber by mould pressing, and their micromorphology was studied by SEM. The influence of carbon fiber content on the mechanical properties and electrical conductivity of the flexible conductive composite material was studied, and the corrosion rate of the flexible conductive composite material coupling with galvanized steel in soil with different SO42− concentrations was studied. The results showed that the tensile strength reached 5.82 MPa when the mass ratio of carbon fiber to flexible graphite was 1:20, and the volume resistivity achieved 4.76 × 10−5 Ω·m when the mass ratio of carbon fiber to flexible graphite was 1:30. With the increase in molding pressure, tensile strength and electrical conductivity had a slight increase. When the flexible conductive composite material was coupled with galvanized steel, sulfate could accelerate the galvanic cell corrosion between the flexible graphite grounding material and galvanized steel. The increase in the sulfate concentration led to more corrosion acceleration. With the increase in corrosion time, the corrosion potential of the flexible graphite grounding material and galvanized steel coupling body decreased to its lowest at 30 days, and then increased gradually. The corrosion current was the highest at 30 days, and then decreased gradually.

Tailoring the additional content of short carbon fiber in the reduced graphene oxide-Cu self-lubricating composites for enhanced mechanical and tribological performance

The reduced graphene oxide-Cu self-lubricating composites with short carbon fiber fillers were fabricated by powders wet-mixing combined with hot-pressed sintering process. The impacts of short carbon fiber content on microstructure, mechanical and tribological performance of reduced graphene oxide-Cu composites were characterized. The reduced graphene oxide/carbon fiber hybrid fillers were randomly distributed in the sintered bulk compacts. The hybrid filled composites achieved enhancement in mechanical and tribological properties. With increasing carbon fiber content, hardness and compressive yield strength of the prepared composites were increased, and both friction coefficient and wear rate showed a constant decrease trend under different loads. Owing to the synergy effect of reduced graphene oxide/carbon fiber hybrid lubricant fillers during sliding together with the greatly enhanced hardness and yield strength, up to 0.6 wt% carbon fiber incorporation resulted a lowest friction coefficient and decreased wear rate. Randomly distributed reduced graphene oxide/carbon fiber hybrid fillers provided the lubrication to reduce friction and wear for Cu matrix.

Mechanical properties and cross-scale synergistic modification mechanism of micro-nano carbon fiber modified concrete

In order to explore the cross-scale synergistic modification effect of carbon fiber (CF) and carbon nanofiber (CNF) on the mechanical properties of concrete, based on CNF modified concrete (NCFC, with CNF volume content of 0.3 %), four kinds of micro-nano carbon fiber modified concrete (MNCFMC, with CNF volume content of 0.3 % and CF volume content of 0.1∼0.4 %) are prepared. For comparison, four kinds of CF modified concrete (CFMC, with CF volume content of 0.1∼0.4 %) are also prepared. The compressive, flexural and splitting tensile strength of concrete are tested, and the cross-scale synergistic modification mechanism is analyzed by SEM and MIP tests. The results show that CF and CNF have cross-scale synergistic improvement effect on the mechanical properties of concrete. The mechanical properties of concrete can be further improved by adding CF with appropriate content on the basis of the addition of CNF. With the increase of CF content, the compressive, flexural and splitting tensile strength of MNCFMC first increase and then decrease. The mechanical properties of MNCFMC are the best when the CF content is 0.2 %, the compressive, flexural and splitting tensile strength of MNCFMC increase by 14.12 %, 19.69 % and 30.32 %, respectively. Compared with CFMC, the mechanical properties of MNCFMC with the same CF content are better. The physical bond between CF and concrete matrix is poor, CNF can enhance the physical bond between CF and concrete matrix by attracting the deposition of cement hydration product crystals. When CF and CNF are added together, the pore size refinement and pore structure optimization effects of fiber on concrete are the best. When the CF content is 0.2 %, the average pore size and total pore volume of MNCFMC decrease by 30.66 % and 16.86 % compared with CFMC, respectively.

A recyclable dispersant based on carbomer utilizing controllable viscosity for high-efficiency dispersion of carbon fibers

Good dispersion of carbon fibers is important for the carbon paper production, which is usually achieved using low carbon fiber concentrations and disposable dispersants. In this study, we developed carbomer as a recyclable and high-efficiency dispersant for carbon fibers. When the carbon fiber concentration was 0.1 wt%, carbon fiber suspension showed improved dispersion performance as increasing the carbomer dosage. It exhibited low Turbiscan Stability Index (TSI) of 0.41 and small change of delta backscattering between −0.5 to 0.8 % when using 0.5 wt% carbomer. However, the good dispersibility fade away when increasing the concentration of carbon fibers. Subsequently, the pH of the carbon fiber suspension was adjusted to 7.0 to improve the dispersibility by increasing the viscosity, but causing a worse flowability. Then the pH was further adjusted to 13.0 to ensure good flowability in the wet-forming process and good dispersibility at carbon fiber concentration of 0.5 wt%. More importantly, the dispersant was successfully recycled and still exhibited excellent dispersion effects for carbon fibers after 5 cycles. Notably, the high-efficiency dispersion of carbon fibers and the recyclability of dispersant were achieved simultaneously for the first time, which is suitable for the eco-friendly and sustainable production of carbon paper.

Microwave-Assisted Fabrication and Characterization of Carbon Fiber-Sodium Bismuth Titanate Composites

Lead-based piezoelectric materials cause many environmental problems, regardless of their exceptional performance. To overcome this issue, a lead-free piezoelectric composite material was developed by incorporating different percentages of carbon fiber (CF) into the ceramic matrix of Bismuth Sodium Titanate (BNT) by employing the microwave sintering technique. The aim of this study was also to evaluate the impact of microwave sintering on the microstructure and the electrical behavior of the carbon-fiber-reinforced Bi0.5Na0.5TiO3 composite (BNT-CF). A uniform distribution of the CF and increased densification of the BNT-CF was achieved, leading to improved piezoelectric properties. X-ray diffraction (XRD) showed the formation of a phase-pure crystalline perovskite structure consisting of CF and BNT. A Field Emission Scanning electron microscope (FESEM) revealed that utilizing microwave sintering at lower temperatures and shorter dwell times results in a superior densification of the BNT-CF. Raman Spectroscopy confirmed the perovskite structure of the BNT-CF and the presence of a Morphotropic Phase Boundary (MPB). An analysis of nanohardness indicated that the hardness of the BNT-CF increases with the increasing amount of CF. It is also revealed that the electrical conductivity of the BNT-CF at a low frequency is significantly influenced by the amount of CF and the temperature. Moreover, an increase in the carbon fiber concentration resulted in a decrease in dielectric properties. Finally, a lead-free piezoelectric BNT-CF showing dense and uniform microstructure was developed by the microwave sintering process. The promising properties of the BNT-CF make it attractive for many industrial applications.

Intrinsic self-sensing piezoresistive behaviors of ultra-high strength alkali-activated concrete

In this work, the self-sensing piezoresistive behaviors of carbon fiber (CF)-reinforced ultra-high strength concrete (UHSC) are investigated using alternating current impedance spectroscopy (ACIS) technique. The effects of different fiber contents, fiber lengths, and curing ages are considered. The electrical behaviors of alkali-activated slag (AAS)-based UHSC (AAS-UHSC) and ordinary Portland cement (OPC)-based UHSC (OPC-UHSC) at similar strength from 80 to 110 MPa are compared. The findings reveal that the intrinsic electrical resistivity of AAS-UHSC is significantly lower than that of OPC-UHSC, approximately 1/30 of the latter. The addition of CF results in a substantial reduction in electrical resistivity for both UHSC types, with reductions of up to 96 %, and shows better compatibility with the AAS-UHSC matrix. The piezoresistive properties of CF-reinforced UHSC are investigated using ACIS at a fixed frequency and further evaluated by parameters including sensitivity, linearity, repeatability, and hysteresis. The results indicate that plain OPC-UHSC does not exhibit piezoresistivity, whereas the addition of CF enhances both the sensitivity and linearity of piezoresistivity. In contrast, AAS-UHSC demonstrates inherent piezoresistive behaviors even without CF. The introduction of 0.5 wt% CF improves the sensitivity (by up to 50 %) and linearity (R2 increased from 0.76 to above 0.90) of piezoresistivity in AAS-UHSC. However, increasing the CF content to 1.0 wt% diminishes the sensitivity (by up to 62.5 %) due to decreased fiber dispersion uniformity. Moreover, the addition of 1.0 wt% 8-mm CF reduces the hysteresis of UHSC regardless of the binder type, with the maximum reduction reaching 62.2 %.