Effect Of Hybrid Fibers Research Articles

Experimental study on mechanical properties of fiber reinforced concrete: Effect of cellulose fiber, polyvinyl alcohol fiber and polyolefin fiber

Mechanical properties of concrete reinforced with cellulose fiber (CTF), polyvinyl alcohol fiber (PF) and polyolefin fiber suitable for various spray (VS) are experimentally studied. The individual impact of single fiber as well as synergistic effect of hybrid fiber on axial compressive strength, splitting tensile strength and shear strength of concrete are investigated. Microstructures of fiber reinforced concrete specimen as well as its stress–strain relationship is also observed. The results show that CTF alone enhances axial compressive strength of concrete but weakens splitting tensile strength; VS weakens splitting tensile strength as well but has little impact on the other two strength; PF has a negative effect on all the three mechanical strength. Synergistic effect of hybrid fiber varies with dosage, and only with the appropriate fiber dosage can hybrid fiber has positive synergistic effect on mechanical properties. 1.5 kg/m3 cellulose fiber with 1.0 kg/m3 polyvinyl alcohol fiber is found to be optimal combination of CTF-PF hybrid fiber to achieve the best synergistic effect. Practical implications of CTF, PF and VS are also put forward.

Effect of Hybrid Fibers on Flexural and Tensile Properties of Ultrahigh Performance Fiber-Reinforced Cementitious Composites: Experiments and Calculation

AbstractThis paper addresses effects of hybrid fibers on the flexural and tensile properties of ultrahigh performance fiber-reinforced cementitious composites (UHPFRCC). The workability, compressiv...

Effects of mixing and clustering properties on hybrid carbon/glass fibers polymer/composite for effective applications

The hybrid carbon/glass fiber polymer possesses an interesting balance in properties that the drawbacks of one fiber can be balanced out by the virtues of the other. The mixing and clustering of hybrid fibers have a significant effect on the elastic modulus of materials. In this paper, a new micromechanics model is proposed to study the effective elastic modulus of hybrid composite with agglomerated carbon and glass fibers. Three types of fiber dispersion or aggregation forms are proposed to present new relations for a hybrid composite that contains carbon and glass fibers. The Mori–Tanaka method and Voigt and Reuss theory are modified to analyze the aggregation effect of hybrid fibers. The analytical expressions for the effective elastic modulus of hybrid fiber–reinforced composites are defined, which consider the fiber agglomeration effect. It is found that the effective properties are very sensitive to the dispersion state and agglomeration degree of hybrid fibers.

Effect of hybrid fibres on the mechanical properties of high performance concrete

Fibre reinforcement is a technique used to provide toughness and ductility to brittle cementitious matrices. Reinforcement of concrete using a single type of fibre could improve the properties to a limited level. A hybrid composite refers to two or more types of fibres that are rationally combined to produce a composite that stems benefits from each of the individual fibres and exhibits a synergetic response. This study intends to illustrate and quantify the mechanical properties of Hybrid Fibre Reinforced Concrete. For this purpose, a reference High Performance Concrete (HPC) of grade M65 with water-binder ratio of 0.34 was used. Specimens of plain concrete mix, HPC with silica fume, Steel Fibre Reinforced High Performance Concrete (SFRHPC) containing only steel fibres, and Hybrid Fibre Reinforced High Performance Concrete (HFRHPC) containing steel fibres and carbon fibres were prepared. Optimum amount of silica fume was taken as 12.5%. The crimped steel fibre was added initially at 0.25%, 0.5%, 0.75%, 1% and 1.25% by weight of concrete and its optimum percentage was found out. Once the optimum dosage of crimped steel fibre was obtained, carbon fibre was used to replace the optimum steel fibre dosage at 25%, 50%, 75% and 100% by volume fraction. Thus an optimum hybrid fibre dosage was obtained. The mechanical properties of the HFRHPC like compressive strength, flexural strength, splitting tensile strength, modulus of elasticity and impact resistance were studied and compared with HPC mix. The results revealed that the addition of steel fibre improved all the mechanical properties of concrete.

Effect of hybrid fibers on shear behaviour of geopolymer concrete beams reinforced by basalt fiber reinforced polymer (BFRP) bars without stirrups

The shear response of thirteen slender geopolymer concrete (GPC) beams reinforced with basalt fiber reinforced polymer (BFRP) bars as longitudinal reinforcements without stirrups was investigated. Different fiber combinations were used to enhance the shear capacity of the beams, including (1) single type of macro-steel fibers (SF) or (2) macro-synthetic polypropylene fibers (PF), (3) hybridization of SF and micro-polyvinyl alcohol fibers (PVF) or (4) PF and micro- carbon fibers (CF). The experimental results indicated that the presence of SF yielded the greatest improvement in the cracking behavior, post-cracked stiffness, and shear capacity of the beams. The addition of 0.5% SF to the GPC and OPC beams increased the normalized shear strength most by 56% and 14%, respectively. The higher contribution of SF to the shear strength of GPC can be attributed to the superior adhesive bonding strength of fiber and GPC matrix. Despite being less effective than SF, adding PF also improves significantly the normalized shear strength up to 33% with 0.5% fiber content. The hybridization of SF and PVF showed a good synergy in enhacing the shear capacity. Meanwhile, the combination of PF and CF did not improve the shear strength but enhanced considerably the ductility of the beams. In addition, three analytical models were proposed to estimate the shear capacity of the SF reinforced concrete beams. The comparison of prediction and experimental results demonstrated the model derived from the modified compression field theory (MCFT) achieved the best correlation.

Dynamic compressive response of high-performance fiber-reinforced cement composites

Composite effect of hybrid fibers with different types containing steel fibers of two different length-diameter ratio, and polymer (PE) fiber was experimentally investigated for high-performance fiber-reinforced cement composites (HPFRCCs). Both of cylindrical cement paste and mortar specimens reinforced with 1.5% vol. hybrid fiber were carried out using a Φ75mm diameter split Hopkinson pressure bar ranged strain rates from 67 s−1 to 219 s−1. A dynamic relationship of compressive stress–strain were tested. Results shows that different fiber reinforcement and strain-rate have a great effect for dynamic behavior of HPFRCCs. The dynamic compressive strength and ultimate strain all generally increase with increasing strain rate. At the similar strain rates, HPFRCCs with larger amount of PE fiber had higher compressive strength. Addition of steel fiber has improved the deformation performance and energy absorption. HPFRCCs with a larger amount of long steel fibers have shown higher dynamic strength.

Experimental and numerical behavior of hybrid-fiber-reinforced concrete compression members under concentric loading

The modern research is aimed to enhance the tensile properties of concrete so that its performance should be made better in various reinforced concrete structures. In the current study, twenty hybrid-fiber-reinforced concrete (HFRC) columns and one plain concrete column were cast to examine the effect of hybrid fibers on the axial capacity, load-deflection response and cracking patterns of columns under axial concentric loading. All specimens were square in cross section having a side length of 150 mm and a height of 1200 mm. Two different types of fibers were used; one is steel fibers (SF) and second is polypropylene fibers (PPF). Four different volumetric ratios of SF (0.7%, 0.8%, 0.9%, 1.0%) and five different ratios of PPF (0.1%, 0.3%, 0.5%, 0.7%, 0.9%) were used in the current study. The results indicate that the combination of 0.8% SF and 0.5% PPF performed well for load-carrying capacity and a combination of 0.9% SF and 0.3% PPF presented the best performance for the ductility of HFRC columns. Moreover, a constitutive finite element model (FEM) was proposed using concrete damaged plastic (CDP) model in ABAQUS for predicting the axial behavior and crack patterns of HFRC columns under concentric loading. A close agreement was observed between the experimental measurements and FE predictions. Finally, a detailed comparison of theoretical axial capacities of HFRC columns was performed using the predictions of various codes and proposed equations.

Post-fire flexural performance of hybrid-fibre-reinforced SCC symmetric inclination beams

Twelve post-fire self-consolidating concrete (SCC) symmetric inclination beams containing steel fibre, macroscopic polypropylene fibre, microscopic polypropylene fibre and their hybridisations were studied under the combined loading of flexure and axial compression to evaluate the effect of hybrid fibres on the flexural performance of tunnel segments. The effect of different fibres on the temperature field of the midspan cross-section was analysed. The load–deflection behaviour, crack patterns and crack width of post-fire flexural SCC symmetric inclination beams were investigated. A model for calculating the ultimate bearing capacity of flexural SCC symmetric inclination beams after fire exposure was proposed by considering the contribution of hybrid fibres to SCC in a tension zone. The results of the proposed model were found to agree well with the experimental data in this study. The proposed model can be employed to estimate the ultimate flexural bearing capacity of SCC symmetric inclination beams containing hybrid fibres after exposure to fire.

Hybrid Cellulose-Glass Fiber Composites for Automotive Applications.

In the recent years, automakers have been striving to improve the carbon footprint of their vehicles. Sustainable composites, consisting of natural fibers, and/or recycled polymers have been developed as a way to increase the “green content” and reduce the weight of a vehicle. In addition, recent studies have found that the introduction of synthetic fibers to a traditional fiber composite such as glass filled plastics, producing a composite with multiple fillers (hybrid fibers), can result in superior mechanical properties. The objective of this work was to investigate the effect of hybrid fibers on characterization and material properties of polyamide-6 (PA6)/polypropylene (PP) blends. Cellulose and glass fibers were used as fillers and the mechanical, water absorption, and morphological properties of composites were evaluated. The addition of hybrid fibers increased the stiffness (tensile and flexural modulus) of the composites. Glass fibers reduced composite water absorption while the addition of cellulose fibers resulted in higher composite stiffness. The mechanical properties of glass and cellulose filled PA6/PP composites were optimized at loading levels of 15 wt% glass and 10 wt% cellulose, respectively.

Effect of Hybrid Polypropylene - Carbon Fiber on Self-Compacting Mortar

The present work, aims to improve the properties of fresh and hardened self-compact mortar (SCM) containing hybrid Polypropylene-carbon fiber. The hybrid fiber added as a percentage 0.1%, 0.5% and 1% by volume of self-compact mortar, five different mixture of 100-0%, 70-30%, 50-50%, 30-70% and 0-100% for every fibers ratios (Polypropylene to carbon). The effect of hybrid fiber on some physical and mechanical properties of (SCM) was also investigated as a compressive strength and modulus of rupture, which was examined at ages of 28 days. Results showed that the best added of hybrid fiber (50 P.P-50 C.F) % increased compressive strength with ratio 32%, so increased modulus of rupture for self-compact mortar with ratio 130% at hybrid fiber (0 P.P-100 C.F) %, also indicated that the added improve hard characteristic and decrease of fresh characteristic as a flow time, mini slump flow and specific gravity, when the volume fraction 0.5% and 1% for all hybrid fiber exceeded the limits of the standard because the largest flow time is 11 seconds.

Effects of hybrid fibers on the development of high volume fly ash cement composite

Abstract High volume fly ash (HVFA) is used as cement substitute in many cementitious materials. In recent years, hybrid fibers such as steel and polypropylene have been added to improve the mechanical characteristics. The usage of three fibers combinations is relatively a new concept in HVFA concrete. In this paper, silane coated basalt fiber has been combined with steel and polypropylene due its availability and low costs. Varied hybrid fiber combinations (both two types and three types) were tested on cement mortar specimens to identify the optimal fiber percentages. Based on the experimental results, equations to predict the compressive and flexural strength were developed. Optimal percentages identified from the experimental data were then used to test concrete specimens. It was found that the compressive strengths of three types hybrid fiber concrete showed appreciable increase by 5.44% and the splitting tensile strength increase was 6.77% in comparison with two type hybrid. Furthermore, the long-term durability issue of the selected basalt fiber was examined using the Scanning Electron Microscopy (SEM) and Computed Tomography (CT) X-ray scan. These two techniques confirmed the reduction in porosity and hence the durability of concrete, suggesting the benefit of the added silane coated basalt fiber.

Influence of Hybrid Fibers on the Fresh and Hardened Properties of Structural Light Weight Self-Compacting Concrete

The scope of this research is certainly to provide some experimental data on the effect of hybrid fiber on fresh and hardened properties of structural pumice lightweight aggregates self-compacting concrete (SLWSCC). Addition of hybrid fibers to concrete properties has changed the state of concrete from brittle to ductile. Slump flow test, L-box test, and V-funnel test were leading to find the (SLWSCC) workability of fresh properties. The mechanical properties of hardened (SLWSCC), including compressive, and splitting tensile, strengths, and moduli of rupture. Eleven concrete mixtures of (SLWSCC) with different mono and hybrid fibers contents of steel fibers (SF) and polypropylene (PP) fibers with a ratio (0%, 0.3%, 0.6%, and 1.2%) of volume fractions were prepared to study the change in its fresh and hardened characteristics. Test results were showed that the fibers whereas used in a hybrid form with (SLWSCC) be able to have as a result of high composite performance compared to their single thing fiber-reinforced concretes. The optimum properties of (SLWSCC) can get form mix (HF8) with 0.6% (SF) content and 0.3% (PP) fibers exhibit higher flexural strength behavior by 206%, and tensile strength of increased by 129%.

Experimental Study on Mechanical Properties and Fractal Dimension of Pore Structure of Basalt–Polypropylene Fiber-Reinforced Concrete

This study investigates the effects of basalt–polypropylene fibers on the compressive strength and splitting tensile strength of concrete and calculates the fractal dimension of the pore structure of concrete by using a fractal model based on the optical method. Test results reveal that hybrid fibers can improve the compressive strength and splitting tensile strength of concrete, and the synergistic effect of the hybrid fibers is strongest when the contents of basalt fiber (BF) and polypropylene fiber (PF) are 0.05% each, and that the maximum increments in compressive strength and splitting tensile strength are 5.06% and 9.56%, respectively. The effect of hybrid fibers on splitting tensile strength is greater than on compressive strength. However, hybrid fibers have adverse effects on mechanical properties when the fiber content is too high. The pore structure of basalt–polypropylene fiber-reinforced concrete (BPFRC) exhibits obvious fractal characteristics, and the fractal dimension is calculated to be in the range of 2.297–2.482. The fractal dimension has a strong correlation with the air content and spacing factor: the air content decreases significantly whereas the spacing factor increases with increasing fractal dimension. In addition, the fractal dimension also has a strong positive correlation with compressive strength and splitting tensile strength. Therefore, the fractal dimension of the pore structure can be used to evaluate the microscopic pore structure of concrete and can also reflect the influence of the complexity of the pore structure on the macroscopic mechanical properties of concrete.

A novel damage model based on micromechanics for hybrid fiber reinforced cementitious composites under uniaxial compression

A novel damage model based on micromechanics is proposed for hybrid fiber reinforced cementitious composites under uniaxial compression. In this model, a multilevel homogenization method is presented to predict the overall elastic properties of hybrid fiber reinforced cementitious composites. To account for the contribution of microcracks on its macrocompliance under compression, hybrid fiber reinforced cementitious composite is considered equivalent to the microcrack-weakened solid, whose overall compliance consists of the compliance of the matrix and the additional compliance by sliding, propagating and kinking cracks. The bridging effects of hybrid fibers on restraining crack growth are simplified based on the reality that the average sliding displacement of microcracks is much less than the length of reinforcing fibers. The evolutional domains of microcrack growth under loads where the microcracks are sliding, propagating and kinking are discussed in detail. In addition, the weakening effects of fibers upon compressive behavior are captured by introducing two functions, which consider the influences of fiber geometrical parameters, the microcrack density and the distance between two nearest microcracks with the same oriented angle. Simulation results by our evolutionary damage model render reasonable agreements with available experimental data of fiber reinforced cementitious composites and hybrid fiber reinforced cementitious composites with various fiber contents. The new micromechanical damage model would be beneficial to elucidating the strengthening and weakening mechanisms of hybrid fiber reinforcement.

Experimental investigation on the flexural behavior of steel-polypropylene hybrid fiber reinforced concrete

This paper presents an experimental study on the flexural behavior of steel-polypropylene hybrid fiber reinforced concrete (HFRC) using four-point bending tests on 51 samples. Three types of steel fibers, i.e., straight, hooked-end and corrugated fiber, and a type of monofilament polypropylene fiber are considered. The flexural behavior in terms of load-deflection curves, load and deflection characteristics, toughness, cracking properties as well as the synergetic effect of hybrid fibers is studied. The results show that synergetic effect is observed for all the three types of steel fiber with the combination of polypropylene fiber on improving the flexural behavior of HFRC. Specimens with hooked-end fibers show the best flexural performance. However, the combination of straight steel and polypropylene fibers presents the most obvious synergy. Moreover, an increase in volume fractions of both steel and polypropylene fibers leads to an increase in the compressive, splitting tensile and flexural strengths of concrete. The post-peak ductility of concrete is improved and the strength degradation is alleviated with increasing fiber volume fraction and steel fiber aspect ratio. In addition, specimens with corrugated and hooked-end fibers exhibit a better failure behavior than specimens with straight fibers, with multiply micro-cracks induced by mechanical interlocks of deformed steel fibers observed at the main cracks. Finally, based on a comprehensive fiber reinforcing index, analytical equations for flexural loads, deflections, and toughness of HFRC are developed with varying fiber parameters taken into consideration.

The pull-out behavior of straight and hooked-end steel fiber from hybrid fiber reinforced cementitious composite: Experimental study and analytical modelling

This paper deals with the interfacial bonding performance of the steel fiber in the steel-polypropylene hybrid fiber reinforced cementitious composite. 42 groups of straight and hooked-end steel fiber specimens are investigated by the single-sided pull-out tests. The whole pull-out load-slip responses are captured, and the effects of hybrid fiber dosage, matrix strength and fiber embedded length are analyzed. Furthermore, the interfacial bonding mechanism and fiber reinforcing mechanism are revealed based on SEM images. Results show that the addition of hybrid fibers in the matrix contributes significantly to increasing the maximum and residual pull-out load as well as improving the pull-out energy dissipation capacity. The polypropylene fiber content is found to be the dominant factor for the variation of interfacial properties. For straight steel fiber, the enhancing effect of hybrid fiber on the chemical adhesion force is more pronounced than that on the sliding frictional force. For hooked-end steel fiber, the contribution of hybrid fiber is not significant on the hook mechanical interlocking. Finally, a theoretical model is developed to predict the pull-out behavior with the hybrid fiber effect taken into account. The predictions provide satisfactory correlation to the experimental results from both the current study and previous work.

Hybridization effect of fibers on mechanical properties of PA66/PP blend-based thermoplastic composites

The effect of hybrid fibers on mechanical behavior of thermoplastic composites is most important for structural applications. This article deals with the effect of hybrid short fibers i.e., short glass fiber (SGF), short carbon fiber (SCF), and short basalt fibers (SBF) on 80/20 wt% of polyamide 66/polypropylene (PA66/PP) blend. The glass-carbon hybrid composites (CG) and glass-basalt hybrid composites (BG) were prepared by using melt mix twin screw extruder. The mechanical properties such as tensile, flexure, and impact strength of hybrid composites were studied as per ASTM methods. Further, hardness and density of hybrid composites were also discussed. The experimental results revealed that hybrid fibers effect greatly enhanced mechanical behavior of PA66/PP blend. The CG composites exhibited improvement in tensile strength by 76.7%, flexural strength by 104.12 and 20.82% reduction in elongation whereas BG composites by 77.22, 109, and 12.92% reduction in elongation, respectively. Significant enhancement in strength of composites was observed due to hybrid fibers effect. The synergistic effect between hybrid fibers and matrix helped in improving mechanical behavior. The impact strength of hybrid composites was reduced due to brittle nature of fibers. Fiber fracture, fiber pull out and fiber misalignment are some of the mechanisms observed through scanning electron microscopy (SEM) photographs.

Effect of hybrid fibers on flexural performance of reinforced SCC symmetric inclination beams

In order to evaluate the effect of hybrid fibers on the flexural performance of tunnel segment at room temperature, twelve reinforced self-consolidating concrete (SCC) symmetric inclination beams containing steel fiber, macro polypropylene fiber, micro polypropylene fiber, and their hybridizations were studied under combined loading of flexure and axial compression. The results indicate that the addition of mono steel fiber and hybrid fibers can enhance the ultimate bearing capacity and cracking behavior of tested beams. These improvements can be further enhanced along with increasing the content of steel fiber and macro PP fiber, but reduced with the increase of the reinforcement ratio of beams. The hybrid effect of steel fiber and macro PP fiber was the most obvious. However, the addition of micro PP fibers led to a degradation to the flexural performance of reinforced beams at room temperature. Meanwhile, the hybrid use of steel fiber and micro polypropylene fiber didn\'t present an obvious improvement to SCC beams. Compared to micro polypropylene fiber, the macro polypropylene fiber plays a more prominent role on affecting the structural behavior of SCC beams. A calculation method for ultimate bearing capacity of flexural SCC symmetric inclination beams at room temperature by taking appropriate effect of hybrid fibers into consideration was proposed. The prediction results using the proposed model are compared with the experimental data in this study and other literature. The results indicate that the proposed model can estimate the ultimate bearing capacity of SCC symmetric inclination beams containing hybrid fibers subjected to combined action of flexure and axial compression at room temperature.

Effect of hybrid fibers, calcium carbonate whisker and coarse sand on mechanical properties of cement-based composites

Nowadays researchers are developing a new hybrid fiber reinforced cement-based composites (HyFRCC). The new HyFRCC can restrain micro-cracking, improves compressive and flexural performance of beams by addition of calcium carbonate (CaCO3) whisker, polyvinyl alcohol (PVA) fiber and steel fiber. In this work, a mix optimization procedure is shown for multi-scale HyFRCC, with steel, PVA fiber and CaCO3 whisker. The new HyFRCC is explored with addition of coarse sand to further improve its mechanical properties. Additionally, the flexural performance of beam and slabs has been investigated to optimize sand gradation and fiber combination in new HyFRCC. The compressive strength, flexural strength, flexural behavior, flexural toughness, equivalent flexural strength and deflection-hardening behavior of beams and slabs are improved with optimized content of sand gradation, fibers and CaCO3 whisker. The HyFRCC slab with 1.5% steel fiber, 0.4% PVA fiber, 1% CaCO3 whisker and optimized coarse sand showed overall best properties.

Flexural performance of reinforced self-consolidating concrete beams containing hybrid fibers

Flexural performances of twelve reinforced self-consolidating concrete (SCC) beams containing steel fiber, macro polypropylene fiber, micro polypropylene fiber, and their combinations were studied at room temperature. The major test variables were fiber types, fiber contents and longitudinal reinforcement ratios. Cracking load, yielding load, ultimate load, mid-span deflection, longitudinal reinforcement strain and crack pattern of the reinforced SCC beams were investigated. It was found that the addition of mono steel fiber and hybrid fibers enhanced the ultimate bearing capacity but reduced the mid-span deflection of reinforced SCC beams. With the increase in fiber content, the longitudinal reinforcement strain, crack width and crack spacing decreased significantly. The hybrid use of steel fiber and micro polypropylene fiber did not have a further beneficial effect on the flexural performance of SCC beams at room temperature. Compared to micro polypropylene fiber, the macro polypropylene fiber displayed a more significant effect on the structural behavior of SCC beams. A calculation method for ultimate bearing capacity of flexural SCC beams at room temperature was proposed, which takes into consideration the effects of hybrid fibers. Comparisons were drawn between the predicted results of this proposed model and other previous models with experimental data in this study and previous literature. The results indicate that the proposed model can reasonably estimate the ultimate bearing capacity of SCC beams containing hybrid fibers subjected to flexural loading at room temperature.