Fiber Pull-out Test Research Articles

Nitric acid-modified amorphous alloy fiber and its effects on mechanical properties of ultra-high performance concrete (UHPC)

The traditional steel fiber UHPC has the phenomenon of low strength and poor durability, which can not give full play to the practical value of UHPC. Nevertheless, amorphous alloy fibres possess notable strength, flexibility and corrosion resistance. The incorporation of amorphous alloy fibres into ultra-high performance concrete (UHPC) has been demonstrated to enhance the strength and toughness of UHPC. However, the surface of amorphous alloy fibres is characterised by a smooth and hydrophobic quality, which presents a challenge in terms of the interface bond with the cement matrix. In order to address this issue, three concentrations of nitric acid (HNO3, 2 mol/L, 4 mol/L and 6 mol/L) were employed to modify the surface of amorphous alloy fibres, and then the amorphous alloy fibres were incorporated into the cement matrix for fiber pull-out test, compression, flexural strength and impact testing. The changes in the physical and chemical properties of the amorphous alloy fibres before and after modification were analysed, and the effects on the interface bond strength and dynamic and static mechanical properties of UHPC were studied by means of SEM. The results demonstrate that the adhesion strength of the modified amorphous alloy fibre with 4 mol/L HNO3 is the most robust, with an increase of 18.7 % in compressive strength, 13.8 % in flexural strength, and 5.4 % in impact resistance. The method has been demonstrated to be effective in strengthening and toughening the cement matrix with HNO3-modified amorphous alloy fibres.

Enhancing mechanical properties and crack resistance of high-strength SHCC/ECC for durable transportation through ethylene-vinyl acetate polymer modification

Strain-hardening cementitious composites (SHCC) possess excellent ductility and toughness, making them suitable for reinforcement and repair projects of transit infrastructures, such as tunnel linings, bridges, and highways. Especially, polyethylene (PE) fiber is admixed to SHCC for fabricating high-strength PE-SHCC. However, the hydrophobic nature of PE fibers results in relatively weak interfacial frictional bond strength with cementitious matrix, ultimately leading to larger crack widths and wider gaps. This poses durability and safety concerns for the practical applications of PE-SHCC in transit infrastructure. In this study, ethylene-vinyl acetate (EVA) dispersible polymer is selected to address this problem. The effect of admixing EVA on mechanical and direct tensile properties of PE-SHCC is investigated. The compressive strength, first crack strength and matrix fracture toughness of PE-SHCC tended to decrease after EVA modification, however, the tensile strength and tensile strain increased significantly with doping. After that, the single fiber pullout test combined with flaw size/distribution analysis is performed to explore the improvement mechanism of PE-SHCC after EVA modification. It was found that the addition of EVA could significantly improve the interfacial transition zone (ITZ), increase the interfacial friction between PE fibers and matrix, and optimise the defect distribution within the matrix. The recommended dosage of EVA is 3–6 % comprehensive consideration of the tensile strength, strain energy, crack width, and mechanical strengths of the EVA-modified PE-SHCC. The enhancement of mechanical strengths and crack resistance in PE-SHCC contributes to the development of transit infrastructure towards greater reliability, durability, and resilience.

Mechanical properties of steel fibre–UHPC interface: Experimental study and numerical simulation

The aim of this study was to investigate the interfacial mechanical attributes between steel fibre (SF) and an ultra-high-performance concrete (UHPC) matrix. Using both experimental testing and numerical simulation, a comprehensive analysis on the pull-out process of SF from the UHPC matrix was conducted. The effects of fibre embedment depth, fibre diameter and fibre embedment angle on the mechanical properties of the SF–UHPC interface were examined. In the fibre pull-out tests, the maximum pull-out force of the group of specimens with different embedment depths showed a trend of rapid rise and then slow development, and the pull-out work increased with an increase in embedment depth. The maximum pull-out force and pull-out work of the group with variable fibre diameters increased with an increase in fibre diameter. The maximum pull-out force and pull-out work of the group with different embedment angles increased first and then decreased with an increase in embedment angle. The maximum pull-out force was 72.5 N when the embedment angle was 45° and the maximum pull-out work was 214.4 N.mm when the embedment angle was 30°. The results of finite-element simulations were found to be in good agreement with the experimental results.

Mechanical Behavior Analysis of Lightweight Concrete Reinforced by Metalized Plastic Waste Fibers

This study evaluates the impact of adding metalized plastic waste (MPW) fibers to lightweight concrete that is used as a filler material in building slopes and bridge ramps. The goal is to open up new opportunities for recycling plastic waste and promote a more sustainable and productive construction industry. This study examined the mechanical behavior of lightweight concrete (LC) at 3, 28, and 90 days, both with and without MPW fiber (1%, 2%, and 3%). Compression tests, 3-point bending tests, and pull-out tests were used to measure the fibers' compressive strength, flexural strength, and maximum load-bearing capacity, respectively. According to the results, the compressive strength (CS) and elasticity modulus (MOE) decreased with increasing fiber content when MPW fiber was added. In the long term, the CS and MOE decrease for the LC containing 3% MPW fiber was 8% and 7%, respectively, lower than for the control concrete. At 90 days, the flexural strength of the LC with 1% MPW fiber was marginally higher than that of the control concrete, rising by 2.40%. After this initial rise, however, the flexural strength declined as the fiber concentration increased, eventually reaching an 8% reduction for LC with 3% MPW fiber.The optimum method for determining maximal load-bearing and comprehending the deformation mechanism is hence the fiber pull-out test. The microstructure study of the LC examined how the pull-out test affected the quality of bonding at fiber-matrix interfaces. The tensile and flexural strength of lightweight concrete are enhanced by MPW fiber's ability to bear significant pulling stress.

Investigation of pull-out and mechanical performance of fibre reinforced concrete with recycled carbon fibres

This paper presents the pull-out bonding behaviour and mechanical performance of recycled carbon fibre (rCF) reinforced concrete based on the recent investigation of fibre reinforced concrete (FRC) with rCF recovered from pyrolysis. Single fibre pull-out tests have been carried out to identify the apparent interfacial shear strength of different types of rCF and virgin carbon fibre (vCF) to identify the fibre matrix connection. Furthermore, a series of tests have been carried out to identify the workability, compressive strength and tensile strength of FRC. Besides rCF, also vCF and steel fibre were used for fabrication of FRC test specimens. rCF have shown the same adhesion behaviour and strength like vCF. Furthermore, the use of unsized or acrylate-based sized rCF creates an adhesion between fibre and matrix material. During the pull-out tests, the failure does not occur as an adhesive crack between fibre and cement matrix, but as a cohesive crack in the cement matrix. The mechanical performance of FRC with rCF was compared with mortar and FRC with vCF and steel fibres. The results of compressive test conducted for FRC with vCF and rCF indicated that the influence of vCF and rCF on the compressive strength of FRC was insignificant. On the other hand, the results of tensile test conducted for FRC with vCF and rCF indicated that the tensile strength of FRC with rCF was at least 14.9% greater than that of FRC with vCF.

Bridging Behavior of Palm Fiber in Cementitious Composite

This study addresses the growing need for sustainable construction materials by investigating the mechanical properties and behavior of palm fiber-reinforced cementitious composite (FRCC), a potential eco-friendly alternative to synthetic fiber reinforcements. Despite the promise of natural fibers in enhancing the mechanical performance of composites, challenges remain in optimizing fiber distribution, fiber–composite bonding mechanism, and its balance to matrix strength. To address these challenges, this study conducted extensive experimental programs using palm fiber as reinforcement, focusing on understanding the fiber–matrix interaction, determining the pullout load–slip relationship, and modeling fiber bridging behavior. The experimental program included density calculations and scanning electron microscope (SEM) analysis to examine the surface morphology and diameter of the fibers. Single fiber pullout tests were performed under varying conditions to assess the pullout load, slip behavior, and failure modes of the palm fiber, and a relationship between the pullout load and slip with the embedded length of the palm fiber was constructed. A trilinear model was developed to describe the pullout load–slip behavior of single fibers, and a corresponding palm-FRCC bridging model was constructed using the results from these tests. Section analysis was conducted to assess the adaptability of the modeled bridging law calculations, and the analysis result of the bending moment–curvature relationship shows a good agreement with the experimental results obtained from the four-point bending test of palm-FRCC. These findings demonstrate the potential of palm fibers in improving the mechanical performance of FRCC and contribute to the broader understanding of natural fiber reinforcement in cementitious composites.

MXene nanosheets magic: Unveiling the dual effect of strength and ductility enhancement in strain hardening cementitious composites

The aim of this study was to modify strain hardening cementitious composite (SHCC) using MXene nanosheets to further enhance its strength and ductility. The results showed that the addition of 0.03 wt% MXene nanosheets increased the compressive strength and tensile strain of SHCC by 18.04 % and 88.18 %, respectively. The mechanism of MXene nanosheets in improving the mechanical properties of SHCC was revealed by single fiber pullout test, micromechanical analysis, microstructure analysis and finite element analysis. Firstly, MXene nanosheets fill the pores inside the matrix, reduce the porosity of the matrix, disperse the stress, and inhibit the crack propagation, thus improving the compressive properties of SHCC. Secondly, when MXene nanosheets adhered to the fiber surface, they modified the interfacial properties between the fiber and the matrix, preventing fiber pullout and consequently improving the tensile ductility of SHCC.

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.

Pullout behavior of polyethylene fiber from cement matrix: Effect of embedment length, matrix strength, and inclination angle

Engineered cementitious composites reinforced with polyethylene fibers (PE-ECC) exhibit the potential for high strength and toughness. To optimize the performance and tailor the properties of PE-ECC, this study focuses on analyzing the pullout behavior of polyethylene (PE) fibers from matrices through single fiber pullout tests and scanning electron microscopy analysis. One fiber type was used throughout the experiment, while three embedment lengths and three inclination angles were considered to investigate the pullout behavior from high-strength matrices. Furthermore, the pullout response from matrices with middle and low strength was examined, considering two embedment lengths. The results indicate that fibers with shorter embedment lengths exhibit lower pullout loads but higher energy absorption capacities. High matrix strength enhances adhesion and friction at the fiber-matrix interface, resulting in plumper pullout load versus slip curves. Owing to snubbing and matrix spalling effects, as the inclination angle increases, both the peak load and slip at the peak load of the inclined fibers exhibit an exponential increasing trend. Additionally, following the peak load, the pullout load of inclined fibers decreases more gradually than that of aligned fibers, and the energy absorption capacity of inclined fibers is significantly improved. Ultimately, general equations are derived for the calculation of pullout work and equivalent bond strength.

Enhancing mechanical properties of cementitious composites by boron nitride nanosheets modified carbon fiber

Carbon fiber (CF) is commonly employed to enhance the mechanical properties, electrical conductivity, and electromagnetic absorption properties of cementitious composites. However, its weak interfacial bonding with the matrix limits its application in such composites. In this study, boron nitride (BN) nanosheets were synthesized via the solid-state reaction and used to modify CF surface. The flexural and compressive strengths of cementitious composites incorporating BN nanosheets coated CF (BN@CF) increased by 18.45 % and 29.38 %, respectively, with CF doping at only 0.2 wt%. Isothermal calorimetry and TGA results revealed that BN nanosheets on CF surface would provide nucleation sites for the formation of C–S–H and CH. The microstructure and bonding properties of BN@CF were characterized using SEM/EDS, FTIR, XPS, finite element analysis, and single fiber pullout test. The results showed that the significant improvement of interfacial properties between the fiber and the matrix contributed to the increase of mechanical properties of cementitious composites. These findings provide an effective strategy for the strength development of CF-reinforced cementitious composites.

Quantitative and deep learning based fourier transform infrared radiation and tensile characteristics study on chemically treated hibiscus rosa-sinensis plant fibers

Incorporation of natural fibers with Fiber Reinforced Polymers (FRPs) is a promising avenue for sustainable and high-performance composite materials. The fibers, derived from outer bark portion of plants, offer significant merits such as renewability, low cost, and eco-friendly. Unique mechanical and physical properties, and widespread availability of Hibiscus Rosa-sinensis have made them subject of intense research interest. The present study investigated the chemically treatment of HRS Fibers using Sodium Hydroxide (NaOH), Potassium Permanganate (KMnO4), and Acetic Acid (CH3COOH) bat varying weight percentages (3, 4, 5 Wt%) and solutionizing times (1, 2, 3 h) based on Taguchi’s L27 orthogonal array. Fourier Transform Infrared (FT-IR) analysis revealed significant changes in O–H, C–H stretching, C=O moiety, aromatic ring, and C–O/C–C stretching. Potassium Permanganate treatment at 4 Wt% and 3 h of solutionizing time has yielded the best results. Multi-Layer Perceptron Artificial Neural Network (MLP-ANN) has been successfully applied to accurately predict the output physical characteristics of chemically treated HRS fibers using experimental data. Further Single Fiber Pull-out test results in Potassium Permanganate at 4 Wt% and 3 h solutionizing time as best sample with highest Tensile Strength and Modulus. This research underscores the effectiveness of the chemical treatment process in enhancing the properties of HRS plant fibers for potential composite applications.

Influence of electrophoretic deposition of micro- or nanosized silica particles on the microstructure of carbon fibers and their bond behavior with cementitious matrices

The application of carbon fiber (CF) reinforced cementitious composites is often restricted by the poor load transfer between the components. In this study, two reactive coating materials—nano-silica and micro-silica—are utilized to modify the CF surfaces via an electrophoretic deposition approach. These negatively charged particles are able to be electrosorbed onto the fiber surfaces under a constant electrical field according to the zeta and cyclic voltammetry measurements. After surface treatment, XRD analysis of CFs showed an increase in graphite crystallite thickness and decrement in interlayer spacing d002\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${d}_{002}$$\\end{document}, significantly affecting the fiber diameters. Additionally, the lengths of crystallites were reduced, which can impair the fiber strength and their temperature stability. Single fiber pullout tests exhibited that the interfacial bonding can be clearly enhanced by both reactive coatings. Microscopic observation revealed that C–S–H gel and calcite structures can be formed near the fiber surfaces after immersion in cement pore solution owing to pozzolanic reaction and nucleation effect, tremendously heightening both chemical and mechanical interaction between fiber and cement. Finally, based on a detailed micromechanical analysis, the reinforcing mechanisms between the differently modified fibers and the cementitious matrix were elaborated and discussed.Graphical abstract

Assessing the desiccation crack propagation performance of cemented soil reinforced by modified polyvinyl alcohol fiber

The increasing application of fiber reinforcement to mitigate desiccation cracks induced by evaporation during backfill curing addresses the dispersion challenge associated with high fiber addition. This study aims to enhance the interfacial strength between fibers and cement-soil mixtures through chemical modification methods (NaOH, HCl, and Silane Coupling Agent). By conducting a single fiber pull-out test and microstructures observation, the outcomes reveal that modified PVA fibers exhibit a notable increase in shear strength and pull-out energy compared to unmodified ones, thereby necessitating a reduced fiber dosage for desiccation crack reduction. Furthermore, this investigation delves into the Digital Image Correlation (DIC) feasibility of employing the Digital Image Correlation (DIC) method to monitor the desiccation crack pattern of cement-soil slurry during the initial hydration stages. The findings indicate that NaOH and HCl treatment notably diminishes stress concentration under drying conditions, consequently reducing crack width and area.

Silane treatment for sisal fibers to improve the degradation resistance and interface with cement matrix

In order to improve the degradation resistance of sisal fibers in the alkaline cement matrix and enhance the fiber-matrix interface adhesion, silane treatment on fiber was studied. Four kinds of commonly used silane coupling agents were selected to modify the sisal fibers via the simple dip-coating method. Contact angle, water retention, and semi-immersion tests were performed on the sisal fibers to determine the influence of silane treatment on their hydrophilicity and barrier property. The interfacial bonding between the sisal fibers and cement matrix was studied by a self-designed fiber pull-out test. Furthermore, the degradation of sisal fibers embedded in cement matrix and sisal fiber reinforced cementitious composites (SFRCC) was evaluated based on the changes of mechanical properties with accelerated aging. The results indicate that silane treatment is an efficient approach to mitigate the degradation of SFRCC.

Measurement of tensile and shear strength of interfacial bonding in fiber reinforced soft composites combining experiments and simulation

Interfacial bonding strength plays a key role in the mechanical performance of fiber reinforced polymers. However, measurement of interfacial bonding strength in fiber reinforced soft composites (FRSCs) becomes a challenging issue, because the large deformation capability of soft matrix invalidates most of current testing methods. This paper demonstrates an advanced method combining experiments and simulation, which provides a convenient and reliable means to measure both tensile strength and shear strength of interfacial bonding for FRSCs. The specimen is made by embedding a fiber bundle in a soft plate for transverse tensile test. Various stress states along the fiber–matrix interface can be realized by controlling the inclination angle of fiber bundle to the stretching direction. Tensile strength and shear strength of interfacial bonding in FRSCs can be estimated based on the analysis of critical stress states. The comparison with the widely adopted fiber pull-out test indicates that the nominal shear strength obtained in pull-out test is severely underestimated.

Influence of rapid high-temperature processing on the interface of CF/PEEK, a quick and effective method for enhancing the IFSS

This study explores the effect of rapid high-temperature processing on the interface of carbon fibre (CF) reinforced poly-ether-ether-ketone (PEEK). Specimens that have been thermally treated at slower and faster heating rates and specimens that have not been post-manufacturing treated (virgin) are examined with single fibre pull-out tests. A comparison between their interfacial shear strength (IFSS) and their failure modes takes place. Scanning electron microscopy is used to assess the surface morphology of the thermally treated specimens, and partly cross-polarised microscopy is employed to investigate the development of transcrystallinity. Furthermore, to identify the extent of thermal degradation the specimens are examined with attenuated total reflection Fourier transform infrared spectroscopy. At faster heating rates, an improved interfacial adhesion up to 25% is found at temperatures where a low-level thermal damage is induced. At higher temperatures and despite the increased thermal damage, an IFSS increase of up to 10% is still identified. This is due to the beneficial formation of thermal residual stresses upon high-temperature processing, and overall, especially rapid high-temperature processing could effectively serve for enhancing the interface properties of CF/PEEK.

The effect of imperfect bonding on stress distribution in fibrous composites

An attempt was made to map the distribution of stress in fibrous composites with imperfect bonding. Two analytical micro-mechanics models were developed. In the first model, the composite was subjected to axial tensile loading, parallel to the fiber direction, and the assumption of iso-strain was employed to derive the control equations. In the second model, the composite was loaded in the direction transverse to the fiber. An iso-stress condition was employed, and Airy stress function was utilized to articulate the stress and displacement equations. An assumption of how the stress is transferred between the matrix and the fiber was introduced in both models. To investigate and validate the models, specimens were fabricated using a carbon plain weave fabric and a geopolymer matrix. Single fiber pullout and three-point bending tests were carried out. The maximum average tensile stress obtained from the three-point bending tests, as well as the mechanical properties of the fiber and geopolymer, served as input for the models. Results indicate that the effect of the level of bonding is very high in the transverse direction while almost negligible in the axial direction. The difference in the maximum value of the axial tensile stress at the fiber-matrix interface was used to calculate the numerical value of the interfacial shear strength, and the numerical result matched the data obtained from the single fiber pullout test.

A novel mesoscale modelling method for steel fibre-reinforced concrete with the combined finite-discrete element method

This paper proposes a novel mesoscale modelling method to study the effect of steel fibres on the fracture properties of steel fibre reinforced concrete (SFRC) based on an integrated finite-discrete element method (FDEM) framework. The present method models the steel fibre of SFRC as multiple bar elements, while simulating the cement matrix using triangle elements. A comprehensive bond-slip model is also introduced between the triangle element and bar element, enabling accurate reproduction of the interaction behaviour between the concrete matrix and steel fibre. Additionally, the progressive failure process of cohesive elements in FDEM is considered as crack propagation, confirming the superiority of FDEM from continuum to discontinuum. The results of the Brazilian split test and uniaxial compression test validate the capability of the FDEM framework for mode Ι and mode II fractures, while single fibre pull-out tests and 3-point-bending beam tests provide validation of the effectiveness of the integrated FDEM framework for the mesoscale modelling of SFRC. The discussion also covers employing the mesoscale modelling method to investigate the effect of steel fibre on the fracture properties of SFRC. Owing to its merits in quantitative analysis, the present method can serve as a feasible potential tool for mesoscale modelling analysis and SFRC design.

Dynamic enhancement induced by interface for additively manufactured continuous carbon fiber reinforced composites

Additive manufacturing (AM) has become one advanced manufacturing method for continuous carbon fiber reinforced polymer (CCFRP) composites, which is promising to work as aerospace materials. To promote their efficient design and extensive application, series of tensile and fiber-pullout tests were implemented to investigate the rate-dependent mechanical behavior and fracture mechanism. Both tensile strength and fracture strain significantly increase with the increase of strain rate in the studied range of 0.0001–1600 s−1. Fiber-pullout test also confirms that the interfacial shear strength of composites increases with the increasing loading rate. Dynamic enhancement is analyzed quantitatively, and it is mainly contributed by the rate-dependent behavior of fiber-matrix interface. Fracture analysis indicates the stronger interfacial bonding under dynamic loading, which is attributed to the impeded interfacial crack propagation by high strain rate. A constitutive model is built to predict the rate-dependent strength of CCFRP composites, and it fits well with the experimental results.

Micromechanical behavior of single fiber-asphalt mastic interface: Experimental studies by self-designed innovative pullout test

Micromechanical behavior of the interface between fiber and asphalt is a crucial factor in the performance of fiber reinforced asphalt concrete, and a thorough understanding of this behavior is essential for the design and optimization of these materials. To evaluate the micromechanical behavior of the interface, an innovative single fiber pullout test platform was designed, and the experimental parameter conditions were systematically studied. Three types of fibers including basalt fiber (BF), glass fiber (GF) and polyester fiber (PF) were adopted, and the pullout test was performed at 60 ℃, 25 ℃ and −10 ℃, respectively, where the micromechanical behavior at the interface under different experimental conditions was obtained. The results showed that the recommended loading rate of the fiber pullout test is 1–3 mm/min, and the measurement of variability is satisfactory. The single fiber pullout behavior was observed and the load-displacement curve was recorded real-time. Three failure modes (fiber pullout, fiber fracture and matrix failure) at the interface between the single fiber and asphalt mastic were observed. Furthermore, a bond-slip model which can accurately characterize the bonding-debonding behavior of the interface between the single fiber and asphalt mastic was established. It was found from the study that micromechanical behavior of the interface between the single fiber and asphalt mastic is influenced by the type of fiber and temperature, the peak load and displacement are significantly different. These findings presented in this study can play a significant role in revealing the reinforcement mechanism of fiber and providing a guidance for the efficient application and development of fiber reinforced asphalt mixture.