Uniform Fiber Distribution Research Articles

Characterisation of fibre distribution uniformity in steel fibre-reinforced concrete under microwave-induced heating during casting

Traditional active microwave thermography (AMT) tests for hardened steel fibre-reinforced concrete (SFRC). The surface temperature of SFRC derived from AMT cannot fully characterise the distribution of steel fibres in the SFRC. This study proposes a microwave-induced heating method combined with temperature sensors (MI-TS) to estimate the fibre dispersion of an SFRC mixture during casting. The principles and testing process are discussed, and a numerical model is developed to evaluate the temperature distribution of the SFRC mixture following microwave exposure. Through MI-TS and numerical models, the temperature in the SFRC mixture with uniform fibre distribution, fibre clustering and fibre sinking is investigated, and the results are compared with those obtained by AMT and destruction technology to evaluate the feasibility of the proposed method. The results show that in the same specimen, the temperature difference between areas with similar fibre content falls in a very narrow range (e.g., 3.5–4.5 °C for a 100 × 100 × 100 mm specimen exposed to 600 W of microwave irradiation for 180 s). When the fibre content in a given area is more than 0.5 vol%, a large temperature difference forms between this and other areas. When the equivalent fibre content of the specimen is ignored, the temperature difference between the two areas is directly proportional to the difference in fibre content. Therefore, the area that shows differences in fibre clustering and fibre content can be easily determined found based on the temperature difference derived from MI-TS.

Effect of Triton X-100 surfactant concentration on the wettability of polyethylene-based separators used in supercapacitors

Polyethylene-based separators are generally unsuitable for aqueous supercapacitors due to their poor wettability with the electrolyte, which impedes ion transport. However, incorporating Triton X-100 (2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol) into the aqueous sulfuric acid (H2SO4) electrolyte improves the wettability of polyethylene and facilitates ionic movement through its pores. In this study, Triton X-100 was added to 1.0 M H2SO4 at various concentrations (0.122%–1.210% V/V) to evaluate its impact on supercapacitor performance. Supercapacitors were assembled using activated carbon-filled carbon cloth electrodes, each of the above electrolytes and polyethylene sheet separators. Scanning electron microscopy revealed that the carbon cloth exhibited a uniform fiber distribution and high surface area for activated carbon integration. The polyethylene separator displayed a porous structure with an average pore size of 165 ± 35 nm. Triton X-100 significantly reduced the water contact angle from 101.5° (without surfactant) to 30.2° (with 1.21% V/V Triton X-100), enhancing polyethylene’s wettability. This change from hydrophobic to hydrophilic characteristics enabled the formation of an electrical double layer at the separator/electrolyte interface, improving ionic transport. However, higher Triton X-100 concentrations increased the electrolyte's viscosity, which impeded ion movement. The highest specific capacitance of 55.3 F/g (at a scan rate of 0.005 V s−1) was achieved with 0.488% V/V Triton X-100. The specific capacitance varied with surfactant concentration in a complex manner, influenced by micelle formation and precipitation. These findings were corroborated by cyclic voltammetry and AC impedance spectroscopy.

Advanced monitoring of damage behavior and 3D visualization of fiber distribution in assessing crack resistance mechanisms in steel fiber-reinforced concrete

This study presents a novel approach to understanding the reinforcing mechanisms of steel fiber-reinforced concrete, particularly its crack resistance and toughening effects. By integrating dynamic surface strain monitoring with advanced three-dimensional visualization techniques, new insights are provided into how steel fibers enhance concrete's structural performance. X-ray computed tomography (CT) technology enabled detailed 3D visualization and analysis of steel fibers embedded within the concrete matrix, facilitating an in-depth examination of their distribution patterns, orientation, and positioning. Additionally, the Digital Image Correlation (DIC) three-dimensional full-field strain measurement system was utilized to dynamically monitor the loading process during three-point bending tests on semicircular concrete specimens. The findings indicate that the uniform distribution of steel fibers significantly reduces stress concentration and effectively delays crack initiation and propagation. Steel fibers bridge cracks, mitigate local stress concentrations, and substitute for the tensile components of concrete after macro-crack formation, thereby inhibiting further crack propagation. Quantitative analysis of fiber distribution through 3D image reconstruction and coordinate extraction confirmed a strong correlation between fiber orientation and crack resistance. This study contributes to the field by offering a comprehensive analysis of key parameters such as fracture process strain monitoring, 3D visualization, and quantification of fiber distribution, advancing the understanding of crack propagation mechanisms and failure processes in fiber-reinforced concrete.

Analysis of synergistic effect of bending energy absorption capacity of fiber reinforced concrete based on fiber distribution characteristic

Macro fibers could contribute to absorb energy through fiber sliding, which significantly enhance the energy absorption capacity of concrete beams. In this research, the synergistic effect of macro steel fibers and polypropylene (PP) fibers on the energy absorption capacity of concrete under bending is under investigated. The three-point bending test is adopted to compared the residual flexural strength and energy absorption capacity of fiber reinforced concrete (FRC) beams. Besides traditional Load-deflection curves, the energy absorption-crack mouth opening displacement (CMOD) curves are adopted to reflect the toughness of FRC beams. The synergistic effect of steel fibers and PP fibers on the residual flexural strength and energy absorption capacity is evaluated. A linear function is proposed to describe the relationship between energy absorption and CMOD for FRC beams. In addition, fiber distribution on cracking surface of FRC beams is analyzed through fiber distribution density and fiber spacing to explain the synergistic effect. Experimental results indicate that the behaviors of FRC beams, that is, residual flexural strength and energy absorption, are improved by adding macro fibers, in particular macro steel fibers. Besides, the relationship between energy absorption and CMOD of FRC beams can be fitted very well by the linear function. The slope of the energy absorption and CMOD relationship is adopted to analyze the contribution of macro fibers to energy absorption. The uniformity of fiber distribution is improved by increasing of fiber dosage for SFRC and PFRC beams. The hybrid use of macro steel fibers and PP fibers demonstrates a positive synergistic effect on the energy absorption capacity and flexural strength of concrete. The improved fiber spacing and fiber distribution density of hybrid fiber on cracking surface contribute to the positive synergistic effect observed in hybrid fiber reinforced concrete (HyFRC) beams.

Practicability and fundamental performance of alkali treated raw bamboo fiber reinforced high performance seawater sea sand concrete

In pursuit of sustainable development, there has been an increasing amount of research on plant fiber reinforced concrete and seawater sea sand concrete in recent years. In this study, a new type of alkali treated raw bamboo fiber reinforced high performance seawater sea sand concrete (ABFRHPSSC) was suggested, with its practicability evaluated and its fundamental performance investigated. The practicability was evaluated through fiber tensile test, water absorption test, single fiber pull-out test, and degraded fiber characterization test. The fundamental performance, including flowability, mechanical performance, pore volume distribution and three-dimensional distribution of pores and raw bamboo fibers, were then investigated when fiber content and length were used as two parameters. The results showed that the alkali treatment of raw bamboo fibers could increase their tensile strength and elastic modulus, reduce their water absorption, improve their bond performance, and ensure their degradation stability. The fiber content and length had significant effects on the fundamental performance. A fiber content of 0.5 % and a fiber length of 12 mm resulted in relatively optimal mechanical performance while ensuring satisfactory flowability and uniform fiber distribution. At this point, compared with plain high performance seawater sea sand concrete (HPSSC), the compressive, splitting tensile, and flexural strengths increased by 20.1 %, 33.2 %, and 33.6 %, respectively, and the pores were refined. Therefore, ABFRHPSSC has a promising future as a new environmentally friendly material.

Dynamic tensile properties of straw fiber reinforced rubber concrete

Rubber concrete (RC) has received a great deal of attention in the field of construction materials, owing to its outstanding mechanical properties and potential for waste recycling. Despite extensive research on the mechanical behavior of RC, there remains a notable gap in understanding the dynamic characteristics of fiber reinforced rubber concrete. This study specifically focuses on the dynamic characteristics of RC with straw fibers as reinforcement. The investigative methodologies employed scanning electron microscope (SEM) analysis, computed tomography (CT) scans, and split Hopkinson pressure bar (SHPB) with a high-speed camera system for dynamic tension tests. The CT experimental findings reveal a uniform distribution of rubber particles and straw fibers within the concrete matrix. The dynamic tensile strength of straw fiber reinforced rubber concrete (SFRC) demonstrates a linear correlation with increasing loading rates. The results showed that SFRC-1.5 had 4.8 % lower static strength and 15 % lower dynamic strength than RC without straw fibers at the load rate of 110 GPa/s. In terms of energy, the dissipated energy density increased by 5.36 % at this loading rate. In addition, at a straw content of 2.5 %, the initial cracking time reached a maximum value of 220 μs. The highest level of shear resistance was observed at this content. This study emphasizes the heightened capability of SFRC under dynamic loading forces, thereby contributing to its potential application in green civil engineering and other related fields.

Microstructural characteristics and mechanical properties of 3D printed Kevlar fibre reinforced Onyx composite

Abstract The main objective of this study is to develop the Kevlar fibre reinforced Onyx composite (KFRO) material by employing the 3D printing technology and examine the effect of Kevlar fibre reinforcement percentage on microstructural characteristics and mechanical properties of developed composite material. The methodology of continuous fibre reinforced composites (CFRC) was followed and the Kevlar fibre reinforcement % was varied as 10 %, 20 % and 30 % in the composite material fabrication. Results disclosed that the KFRO composite 3D printed using 30 % Kevlar fibre reinforcement in Onyx matrix yielded greater tensile strength of 124 MPa, flexural strength of 105 MPa, impact toughness of 2.4 J and shore hardness of 76 D. The mechanical properties of KFRO composite were significantly improved at 20 % of Kevlar fibre reinforcement compared to 10 % of Kevlar fibre reinforcement. Further increase in Kevlar fibre reinforcement up to 30 % showed slight enhancement in mechanical properties of KFRO composite when compared to 20 % of Kevlar fibre reinforcement. The overall strength improvement is a result of the increased reinforcement, precise alignment of fibres in the loading direction, and the uniform distribution of fibres within the onyx.

Towards Sustainable Packaging Using Microbial Cellulose and Sugarcane (Saccharum officinarum L.) Bagasse.

The high consumption of packaging has led to a massive production of waste, especially in the form of nonbiodegradable polymers that are difficult to recycle. Microbial cellulose is considered a biodegradable, low-cost, useful, ecologically correct polymer that may be joined with other biomaterials to obtain novel characteristics and can, therefore, be used as a raw material to produce packaging. Bagasse, a waste rich in plant cellulose, can be reprocessed and used to produce and reinforce other materials. Based on these concepts, the aim of the current research was to design sustainable packaging material composed of bacterial cellulose (BC) and sugarcane bagasse (SCB), employing an innovative shredding and reconstitution method able to avoid biomass waste. This method enabled creating a uniform structure with a 0.10-cm constant thickness, classified as having high grammage. The developed materials, particularly the 0.7 BC/0.3 SCB [70% (w/w) BC plus 30% (w/w) SCB] composite, had considerable tensile strength (up to 46.22 MPa), which was nearly thrice that of SCB alone (17.43 MPa). Additionally, the sorption index of the 0.7 BC/0.3 SCB composite (235.85 ± 31.29 s) was approximately 300-times higher than that of SCB (0.78 ± 0.09 s). The packaging material was also submitted to other analytical tests to determine its physical and chemical characteristics, which indicated that it has excellent flexibility and can be folded 100 times without tearing. Its surface was explored via scanning electron microscopy, which revealed the presence of fibers measuring 83.18 nm in diameter (BC). Greater adherence after the reconstitution process and even a uniform distribution of SCB fibers in the BC matrix were observed, resulting in greater tear resistance than SCB in its pure form. The results demonstrated that the composite formed by BC and SCB is promising as a raw material for sustainable packaging, due to its resistance and uniformity.

Force model of ultrasonic empowered minimum quantity lubrication grinding CFRP

As a weight-reducing material in aerospace applications, carbon fiber reinforced polymer (CFRP) requires precision grinding to ensure the accuracy and assembly of mating positioning surfaces. However, achieving low-damage machining of CFRPs remains challenging. Flood cooling reduces the mechanical properties, while dry grinding deteriorates the surface integrity, making minimum quantity lubrication (MQL) a viable alternative. However, nanolubricants struggle to penetrate the grinding area due to gas barrier obstruction. Consequently, a new CFRP grinding approach using multiangle 2D ultrasonic vibration-empowered nanolubricant MQL was proposed. An analytical force model is crucial for optimizing machining strategies and adjusting parameters. The aim is to reveal grinding mechanics and develop a force model under different ultrasonic and lubrication-cooling conditions. First, a uniform random fiber distribution model and a grinding wheel model were established, and the mechanical properties of the interface were predicted. Then, the intermittent grinding behavior and dynamic stiffnesses of the multiangle 2D ultrasonic vibration-assisted grinding (UVAG) system were investigated based on the geometric kinematics of the grains' trajectory. Furthermore, based on the deformation deflection curve, bending fracture force models for 45°, 90°, and 135° fibers were established with different contact and boundary conditions. The material removal mechanisms of shear and tension-compression buckling in 0° CFRP grinding were revealed, and an elliptical contact normal force model was established. The interlayer shear in 45° CFRPs was analyzed. The longitudinal compressive matrix cracking and fiber shear fracture in the 90° CFRPs were elucidated. Fiber microbuckling and fiber bundle removal of 135° CFRPs were investigated. Finally, grinding force models with different fiber orientation angles (FOAs) were interconnected and experimentally assessed. Experimental assessments demonstrated that the grinding force model has acceptable estimation error and effectively captures the mechanics of CFRPs with different FOAs.

Sustainable mortar reinforced with recycled glass fiber derived from pyrolysis of wind turbine blade waste

Pyrolysis technology has recently made significant progress in recycling millions of tons of wind turbine waste (WTB). Short fibers represent its main product (∼70 wt%), which needs further studies to explore its future applications. In this context, this work aims to the valorization of the recycled glass fiber (rGF) derived from pyrolysis of WTB (at 550 °C) in the production of rGF-reinforced mortar composite (rGF/M) for sustainable building applications. The research began by subjecting the derived rGF to sieving (rGFs), washing (rGFw), and oxidation (rGFo) pretreatments for purification and removing any impurities, organic residues, and char particles. Afterward, the chemical degradation of the treated rGF in a strong alkaline cement solution with pH = 14 was studied for up to 90 days. In parallel, the mortar composite samples were fabricated at 1 wt% of the treated rGF batches (rGFr, rGFw, and rGFo) to study the effect of different pretreatments on their microstructure, dispersion, compressive strength, flexural strength, and water absorption capabilities behavior after different curing periods (28 and 90 days). The results showed that rGFo (7.84%) showed a lower degradation rate versus rGFw (16.41%) and rGFr (30.76%). Meanwhile, the highest curing period (90 days) contributed to improving the properties of the mortar composites in general, especially in the case of using rGFo which led to improved compressive strength (15%) and reduced absorption coefficient (38%) and cumulative water content (32%) with a uniform distribution of short fibers in the matrices and a slight increase in flexural strength compared to control mortar sample (8.6 MPa). While rGFs provides better flexural strength (9.3 MPa) with a 12% improvement. Based on these results it can be concluded that rGFo has high potential in sustainable building materials with high competition with virgin glass fiber.

Ultrarapid soldering Cf/Al by inactive solder by ultrasonic assistance

Ultrasonic vibration was applied when soldering carbon fiber-reinforced aluminum composites (Cf/Al) in this work. The effects of ultrasonic action time on joint formation, carbon fiber distribution, and mechanical properties of the joints were studied. Results show that, with the assistance of ultrasonic vibration, inactive solder can wet the carbon fiber within dozens of seconds at low temperature (250 °C). Short ultrasonic action time leads to minor erosion of aluminum substrate, thereby restricting the movement of carbon fibers into joint. Extensive erosion of the aluminum occurs with prolonged ultrasonic action time. A uniform distribution of carbon fibers in joint is achieved at 60 s. Wetting of carbon fiber is characterized by amorphous-nanocrystalline oxides on its surface, which can be attributed to the elevated temperature and pressure induced by the cavitation of the solder. Extending ultrasonic time enhances the hardness and the shear strength of the joint. The failure cracks propagate through the substrate when ultrasonic time exceeds 15 s. This work provides referential value when soldering materials with low surface energies.

An experimental investigation on freeze-thaw resistance of fiber-reinforced red mud-slag based geopolymer

This study aims to investigate the influence of different fiber types, lengths, and contents on their performance in freeze-thaw environments. Indoor freeze-thaw tests were conducted to evaluate the flexural strength, compressive strength, and mass loss of fiber-reinforced geopolymer materials. Additionally, SEM and XRD analyses were performed to examine the internal structure of the geopolymer composites. The results demonstrated that the incorporation of different fibers significantly improved various properties, particularly the flexural strength of the specimens. With an increasing number of freeze-thaw cycles, surface cracks became more prominent in the geopolymer specimens, leading to a gradual decrease in frost resistance. However, the addition of an appropriate amount of fiber effectively enhanced frost resistance. Following freeze-thaw exposure, an increase in fiber content initially resulted in a decrease and subsequently an increase in relative flexural strength, compressive strength, and mass loss. Notably, studies revealed that polypropylene fibers with a length of 9 mm and a content of 0.9 % exhibited minimal mass and strength loss. SEM analysis indicated uniform distribution of fibers within the geopolymer matrix, contributing to improved flexural strength and enhanced frost resistance in fiber-reinforced structures. XRD results indicate that red mud-slag based geopolymers produce high-strength hydrated calcium (aluminosilicate) silicate and hematite phases, which enhances the mechanical properties and durability of the specimens. In conclusion, this study highlights that incorporating suitable fibers can enhance the durability and performance of red mud-slag based geopolymers under freeze-thaw conditions. The findings provide valuable insights for optimizing fiber type, length, and content to achieve superior mechanical properties and frost resistance in geopolymer composites.

Designing Multifunctional Multiferroic Composites for Advanced Electronic Applications

This paper presents a novel approach for the fabrication of magnetoelectric composites aimed at enhancing cross-coupling between electrical and magnetic phases for potential applications in intelligent sensors and electronic components. Unlike previous methodologies known for their complexity and expense, our method offers a simple and cost-effective assembly process conducted at room temperature, preserving the original properties of the components and avoiding undesired phases. The composites, composed of PZT fibers, cobalt (CoFe2O4), and a polymeric resin, demonstrate the uniform distribution of PZT-5A fibers within the cobalt matrix, as demonstrated by scanning electron microscopy. Detailed morphological analyses reveal the interface characteristics crucial for determining overall performance. Dielectric measurements indicate stable behaviors, particularly when PZT-5A fibers are properly poled, showcasing potential applications in sensors or medical devices. Furthermore, H-dependence studies illustrate strong magnetoelectric interactions, suggesting promising avenues for enhancing coupling efficiency. Overall, this study lays the basic work for future optimization of composite composition and exploration of its long-term stability, offering valuable insights into the potential applications of magnetoelectric composites in various technological domains.

Design and economic implications of using steel fibers in elevated slabs of multi‐story buildings

AbstractThis paper presents a comprehensive comparison between conventional reinforced concrete (RC) and steel fiber‐reinforced concrete (SFRC) slabs. Twenty‐two‐way rectangular RC and SFRC slabs are designed with varying dimensions, aspect ratios, and boundary conditions, following verified international standards to compare the steel quantities in a unique study. SFRC slabs with larger aspect ratios and discontinuous edges required significantly higher steel percentages than square slabs, as the random three‐dimensional distribution of steel fibers suited the load distribution pattern of square slabs. To further conduct a detailed design and economic feasibility case study on a realistic building model, two 12‐story buildings are computationally designed with RC and SFRC alternatives. The results indicate that SFRC slabs required approximately 25% more steel than RC slabs due to the uniform distribution of steel fibers throughout the section. Project cost and time estimates were conducted based on standard productivity manuals and cost databases in two distinct economies, India and the USA. Despite the higher steel requirements, the 12‐story SFRC building showed time savings of 34.1 days (5.44%) and cost savings of 4.88% and 1.27% when constructed in the USA and India, respectively. The results are compared with limited available data in literature. In conclusion, the study suggests that SFRC slabs in multi‐story buildings could be more economically favorable in countries with higher labor costs.

Novel approach for optimizing mechanical and damping performance of MABS composites reinforced with basalt fibers: An experimental study

The purpose of this research is to explore how basalt fibers, when compounded in specific proportions, impact the mechanical and damping attributes of methyl methacrylate acrylonitrile butadiene styrene (MABS). The fabrication process involved compounding basalt fibers in a twin-screw extruder at four distinct weight percentages: 5%, 10%, 15%, and 20%, with an MABS matrix. This study uniquely employs a comprehensive suite of characterization techniques including dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), X-ray microcomputed tomography (micro-CT), scanning electron microscopy (SEM), tensile tests, and density measurements to evaluate the composite's performance. The research significantly reveals that the integration of basalt fibers enhances the damping characteristics of MABS composites, as confirmed by DMA. Additionally, micro-CT scans provide unprecedented insights into the uniform distribution of basalt fibers within the MABS matrix, thereby elucidating the underlying mechanisms for the observed improvements. TGA data further bolsters the composite's thermal resilience, revealing its aptitude for high-temperature applications. Our findings establish a novel correlation between the basalt fiber weight percentage and the damping properties, revealing a non-monotonic relationship. This study thus not only augments the understanding of MABS based composites but also opens new avenues for the exploitation of basalt fibers in advanced composite materials, particularly in terms of their damping capabilities.

Composite materials using recycled high-density polyethylene plastic for railway sleepers

Given the substantial increase in railway load, speed and traffic, there is a notable demand for materials with high durability, long life and good damping. Such materials can be realized through composite materials that contain recycled high-density polyethylene, polypropylene (PP), mica, glass fiber and compatibilizers. In this study, extruded pellets containing the aforementioned materials and produced using a twin-screw extruder were utilized to assess their mechanical performances and microstructures. Composite materials containing 62.5% glass fiber and 20% PP demonstrated remarkable performance for manufacturing sleepers. The addition of 62.5% glass fiber in composite materials containing PP enhanced the flexural strength, flexural modulus, tensile strength and compressive strength by 315, 623, 296 and 40%, respectively, as compared with those of the original composite materials containing PP without glass fiber. Furthermore, the incorporation of glass fiber and the subsequent improvements met the requirements stipulated by the Ministry of Housing and Urban–Rural Development of the People’s Republic of China and International Organization for Standardization standards. This favorable result can be attributed to the good compatibility between the matrix and the glass fiber, as noted from the uniform distribution of glass fiber in the resin matrix in scanning electron microscopy images. The findings of this study highlight the potential of utilizing recycled materials in rail-track-manufacturing applications.

Sustainable energy harvesting and breath sensing with electrospun triboelectric nylon-6

A high-performance triboelectric nanogenerator (TENG) has been developed for breath sensing applications, utilizing tribopositive electrospun nylon-6 nanofibers and tribonegative fluorinated ethylene propylene (FEP). The optimization toward the development of electrospun nylon-6-based TENG includes a range of factors such as the applied force and frequency on tribo responses, the thickness of the fiber mat, the concentration of nylon-6 in the fiber mats, and the selection of the tribonegative material for pairing with nylon-6 nanofiber. Among these parameters, the nanofiber prepared with 18 wt% nylon-6, characterized by a uniform fiber distribution, the highest surface area of 55.69 m2 g−1, and an optimal thickness of 0.169 mm, demonstrated excellent TENG performance, among others. The TENG module constructed using nanofiber in a 4 cm2 area showed the TENG responses of more than 30 μA short-circuit current, 200 V open-circuit voltage, and 90 nC charge when hand-pressed. It achieved a substantial power density of 890 mW m−2 at 20 MΩ by applying a constant force of 10 N at a 10 Hz frequency. Charging a 1 μF capacitor to approximately 30.1 V in just 30 s highlights the potential of electrospun nylon-6 as a promising material for nanogenerator energy harvesting and sensing applications. The TENG device was found to be sufficient to power small, portable electronics such as LEDs and digital watch displays. A wearable belt was fabricated to showcase its breath-sensing capabilities by pairing it with FEP. The microcontroller connected to the TENG in the wearable belt is used to analyze the output produced through breathing patterns, subsequently activating a buzzer and LED by the nature of the breathing.

Parameter design of continuous carbon fiber-reinforced phenolic resin composites via in situ-curing 3D printing technology

To improve the print quality and mechanical properties, the process parameters of the continuous carbon fiber-reinforced phenolic resin (CF/PF) composites were systematically investigated based on the in situ-curing 3D printing technology. The printing spacing and printing thickness affected the bonding between fiber bundles. Under the optimized parameters, the surface of the CF/PF composites was smooth and flat, without obvious gaps between the adjacent prepregs and printing layers. Especially, we optimized the resin impregnation temperature ( T i) and analyzed the influence mechanism on mechanical properties. With the increasing impregnation temperature, the resin content and the squeezing force applied to fiber bundles decrease, while the wettability between fiber and resin increases. The resin contents and the squeezing force play more important role on the mechanical properties of the CF/PF composites. With the combined influence of the above effects, the flexural strength of CF/PF composites reaches maximum value of 471.1 MPa under the impregnation temperature of 30°C, printing spacing of 0.80 mm, and printing thickness of 0.10 mm, with minimum defect volume, uniform distribution of fiber and resin, and appropriate fiber/resin interaction.

Development and Characterization of Flax–Gypsum Composites

Flax–gypsum composites are an emerging class of environmentally friendly materials that combine the mechanical properties of gypsum with the advantageous characteristics of flax fibers. The production of flax–gypsum composites involve the incorporation of flax fibers, derived from the flax plant, into gypsum matrix systems. In order to create a uniform distribution of fibers within the gypsum matrix, the hand lay-up approach has been used to produce the specimens. The fiber content and orientation significantly influence the resulting mechanical and physical properties of the composites. Various tests were conducted on the samples, such as a flexural test, a compression test, a density test, a water absorption test, and a microscopy test. The addition of flax fibers imparts several desirable properties to the gypsum matrix. When combined with gypsum, these fibers enhanced the composite’s mechanical properties, such as flexural strength and compressive strength. The results indicated improved compression and flexural strengths due to effective load transfer within the matrix, for up to 10% of fiber loading. A decrease in composite density upon flax fiber addition results in a lighter material, enabling insights for various applications.

Enhanced impact properties of functionally graded preplaced aggregate fibrous concrete slabs comprising alkali-activated slag and carbon nanotube grout

Nowadays, cement manufacturing stands as the third most significant contributor to anthropogenic CO2 emissions. Alkali-activated techniques are emerging as a potentially more environmentally friendly alternate binder to mitigate the risks related to climate change. The current investigation utilizes the notion of preplaced aggregate concrete (PAC) and alkali-activated slag grouts comprising multi-walled carbon nanotubes (MWCNT) of 0.1 % dosage to implement functionally graded preplaced aggregate fibrous concrete slabs (FGPAFC). The optimum efflux time of alkali-activated slag grouts was determined through trials with various superplasticizer dosages and water-to-binder ratios. However, as it has not been investigated previously, the effect of alkali-activated grout made up of MWCNT on the impact strength of the FGPAFC slab deserves special focus. For this, seven different slabs were prepared, in which five three-layered FGPAFC slabs containing a steel fibre at a dosage of 3.5–4.5 % at a 0.25 % increment were provided at the upper and lower layers. At the same time, the middle layer contains 0–2 % fibres at 0.5 % increment. Using the same amount of fibre as in FGPAFC, a PAC slab with uniform fibre distribution is made to examine how effectively the three-layer arrangement performs. The slab underwent an impact test in accordance with the guidelines set forth by ACI Committee 544. The cracking and failure impact number, crack resistance at service and ultimate stages, impact ductility, the ratio of crack resistance, failure pattern, and its mechanism were examined. Findings reveal that the cracking and failure impact energies were enhanced by roughly 3–12 % and 15–53 %, respectively, by lowering the fibre content at the middle layer and raising it at the upper and lower layers of the FGPAFC slab from 3.0 progressively to 4.5 %. The contribution of steel fibre is more significant than MWCNT for enriching the impact resistance of FGPAFC. The findings derived from this study offer foundational data for subsequent comprehensive scientific examination of FPAFC subjected to impact.