Glass Fiber Reinforced Polymer Hybrid Research Articles

Effectiveness of hybrid textile bars in tensile and bond stresses as an alternative to concrete reinforcement

Development for low and/or middle-income countries is not an option anymore. Therefore, developing Egyptian society must create its own sustainable model based on the ability to leverage the existing resources. Hybrid Textile Fiber Reinforced Polymers (HTFRP) introduce an innovative and/or alternative approach to replace traditional steel bar. Our study aims to introduce HTFRP to overcome the poor elastic modulus of existing FRP bars when utilized as a structural element in reinforced concrete constructions. In the proposed hybrid rebar, the steel core is protected through winding of various textile materials as an out layer. Thus, the relatively cheap cost of steel improves the viability of utilizing HTFRP. In addition, the behavior of HTFRP with varied volume fractions under uniaxial tensile load is investigated. Moreover, the bond stress of various HTFRP texture treatments is assessed. During the experimental investigation of the study, four groups were involved: Group A contains ten samples of natural and synthetic ropes which were used either before treatment or after being immersed in polyester resin to form the matrix. Group B contains five samples of Glass Fiber Reinforced Polymer (GFRP) bars made of glass fiber and matrix with variable volume fractions. Group C contains seven samples of hybrid/core-steel bars. The types of steel include wires steel, threaded steel, and mild steel. Finally, group D contains two samples of hybrid/powder bars. To assess the bond stress, four groups with various surface treatments of hybrid GFRP bars, including rib yarn, rib knotted yarn, braided yarn, and uniform sand-coated, are considered. The results showed that increasing the volume fraction of the GFRP rods increases the number of fibers, which leads to a significant improvement in the properties of the GFRP rods. In addition, the hybridized bars have more balanced tensile behavior that not only enhanced the ultimate tensile strength compared to steel reinforcement but also overcame the limitation of GFRP bars’ low elastic modulus by introducing a 220% improvement. The results showed also that braided yarn treatment has the highest pullout strength of 15.03 MPa, while the rib knitted treatment showed the lowest pullout test of 10.61 MPa. Moreover, the braided, rib yearn, and sand samples showed increased pullout results of 41.65%, 16.68%, and 12.06% respectively, compared to the rib-knotted sample. Finally, the rib-knotted and sand-coated samples illustrated sudden failure, whereas the rib knotted and rib sample had a ductile failure.

Experimental study on seismic performance of squat RC shear walls reinforced with hybrid steel and GFRP rebars

This laboratory study investigates the effect of using steel and glass fiber reinforced polymer (GFRP) rebars in shear walls with aspect ratios less than two. The study evaluates six full-scale shear walls subjected to constant axial load and cyclic lateral loading, with aspect ratios of 1.08 and 1.75. The aim is to analyze how the use of steel and GFRP rebars affects crack patterns, fracture, seismic performance, dissipated energy, and ductility of shear walls. The six specimens consist of two reference ones (SRC1 and SRC2) reinforced with steel rebars, two specimens (GRC1 and GRC2) reinforced with GFRP rebars, and two specimens (S-GRC1 and S-GRC2) reinforced with a hybrid of steel and GFRP rebars. The conclusions drawn suggest that employing a hybrid combination of steel and GFRP rebars resulted in a notable alteration of crack propagation behavior and failure mode, transitioning from flexural compression to flexural tension. Additionally, compared to the specimens reinforced solely with GFRP rebars, there was an observed expansion of the hysteresis curve. Additionally, parameters such as cumulative dissipated energy, ductility, and load modification factor based on ductility increased in the S-GRC1 and S-GRC2 specimens compared to the GRC1 and GRC2.

Dynamic response of concrete beams reinforced with GFRP and steel bars under impact loading

This study explores the dynamic response of concrete beams reinforced with hybrid glass fiber-reinforced polymer (GFRP) and steel bars under impact loading. A detailed three-dimensional nonlinear finite element model of concrete beams is developed, considering the strain rate effects for concrete, GFRP and steel bars. The accuracy of the numerical model is validated against experimental results available in existing literature. Based on the simulation results, the impact responses of hybrid GFRP-steel RC beams are discussed and compared with steel-RC and GFRP-RC beams. The study results reveal that increasing the effective reinforcement ratio of hybrid GFRP-steel RC beams enhances impact performance, with values above 1% found to be crucial for mitigating severe damage and deflection. Hybrid GFRP-steel RC beams with an effective reinforcement ratio ranging from 1.04% to 1.30% demonstrated enhanced impact resistance compared to GFRP-RC and steel-RC beams. Additional parameters affecting the impact response of hybrid GFRP-steel RC beams, such as impact location, configuration of tensile longitudinal bars, impact velocity and drop weight inclination angle, are explored.

Investigation on fatigue behavior of GFRP hybrid bonded/bolted joint under shear loading based on nondestructive monitoring test and numerical modeling

The GFRP (Glass Fiber Reinforced Polymer) is prospective in bridge and building engineering for its advantageous material property. The connection configuration of hybrid bonded/bolted joint of GFRP is thought superior in mechanical performance compared with the traditional bonded and bolted joints. However, the fatigue issue of this type of joint remains unclear which impedes its engineering applications. The presented work experimentally and numerically investigated the fatigue behavior of the GFRP hybrid bonded/bolted single-lap joints under shear loading. High-cycle fatigue tests on single-bolt, four-bolt, and nine-bolt specimens were conducted to study the failure process, rigidity degradation, failure mode, and fatigue life of the hybrid joints, where the nondestructive monitoring techniques of AE (Acoustic Emission) and 3D-DIC (Three-Dimensional Digital Image Correlation) were adopted, respectively to detect the material damages and overall deformation of specimens. Finite element modelling was further carried out to reveal the fatigue failure mechanism of hybrid joints, in which the property degradation of GFRP plates and adhesive layer were considered. Results showed that the failure process of GFRP hybrid single-lap joints under fatigue shear loading can be divided into four stages: (1) steady and (2) rapid development of adhesive damage, (3) steady and (4) rapid development of GFRP damage, of which the (2) and (4) stages account for less than 3% of the total fatigue life of joint, respectively. Stiffness degradation of 14–35% were read for the tested joints before final failure, and the joints with more bolts performed a superior degradation resistance compared to the less ones. Besides debonding and bolt inclination, the single-bolt joints failed with bearing failure of GFRP material, while the failure mode of multi-bolt joints were dominated by shear failure in GFRP plate with Y-shaped zone. The simulation results well supported the observations in experimental test. Based on the experimental results, the S-N curve of the GFRP hybrid single-lap joints is proposed, which can provide support for the engineering design of this type of joints.

Experimental and numerical investigation on failure behavior of hybrid bonded/bolted GFRP single-lap joints under static shear loading

The mechanical performance of the GFRP (Glass Fiber Reinforced Polymer) hybrid bonded/bolted single-lap joints under static shear loading is investigated. Static loading tests considering the hybrid joints with one bolt, four bolts, and nine bolts were first conducted to study the failure mechanism of hybrid joints, where failure process, rigidity, failure load, and failure modes were focused. Finite element (FE) analysis involving the material degradation and failure laws was also carried out for exploring the internal mechanism of joints’ failure. Based on the verified FE model, the effects of plate thickness and bolt edge distance on the failure capacity and strength of the hybrid joints were further investigated by performing a numerical parametric analysis. Results show that, the failure process of the hybrid joints can be divided into two stages which correspond to the failures of adhesive layer and GFRP plates, respectively. The joint rigidity of joints increases by 98.9 %∼133.1 % comparing the second loading stage to the first stage, and it is found that the rigidity in the first stage is hardly affected by the number of fasten bolts, while it decreases with more bolts in the second stage due to the severe incompleteness of GFRP plates. The failure patterns of the hybrid joints mainly include the slippage between connected plates, the compressive failure and shear failure of GFRP material, and the inclination of bolts. A proper arrangement of bolts can lead to shear failure of GFRP which makes full use of the material property. The final failure loads of four-bolt and nine-bolt joints are respectively 14.5 % and 22.9 % higher than the single-bolt specimen. As the plate thickness getting greater, the shear bearing capacity of hybrid joint increases almost linearly, while it would increase first and then descend with increasing bolt edge distance. In general, the achievement of this work can provide references for the design and further study of the GFRP hybrid joints.

Effect of graphene nano-additives on the fatigue limit of fiber-reinforced polymer hybrid composites—A micromechanical modeling procedure

In this article, the effect of graphene nanoadditives on the fatigue limit of unidirectional glass fiber-reinforced polymer (GFRP) composites has been investigated. A micromechanical model based on the crack growth has been used to analyze the fatigue limit response of unidirectional GFRP hybrid composite containing nanoadditives. The influence of different percentages of graphene nanosheets (GNS) and different types of nanofiller dispersion has been investigated by the micromechanical model. The fatigue limit of unidirectional GFRP hybrid composites has been plotted in terms of glass fiber volume fraction, interfacial friction shear stress, interfacial fracture energy and reference length. The fatigue limit of unidirectional composites can be improved by addition of GNS into the polymer matrix of such composite systems. The obtained results on the GNS dispersion type demonstrate that the uniform dispersion of GNS into the polymer matrix increases the fatigue limit of unidirectional GFRP hybrid composites. As the agglomeration density of GNS is low, the fatigue limit of GFRP hybrid composites will be improved more than when the density of agglomeration is high.

Axial bearing capacity and ductility of seawater sea sand coral aggregate concrete (SSCC) columns reinforced with hybrid GFRP and corrosion resistant rebars

The shortage of fresh water and river sand resources and steel corrosion are becoming increasingly prominent in engineering construction. Seawater sea sand coral aggregate concrete (SSCC) and corrosion resistant reinforcement are promising materials in replacement of conventional concrete and steel in building structures in island and reef construction. This study investigated the axial compression performance of GFRP (glass fiber reinforced polymer) and corrosion resistant rebars hybrid reinforced seawater sea sand coral aggregate concrete columns. A total of eighteen short columns were tested for axial compression performance, including three reinforcement ratios (1.01%, 1.56%, 2.26%) and 5 reinforcement types (pure GFRP reinforcement or G, pure stainless steel reinforcement or S, pure epoxy coated steel rebar (ECSB) reinforcement or E, GFRP-stainless steel reinforcement or GS and GFRP-ECSB or GE). The failure modes of the column are recorded and analyzed, and the axial bearing capacity and ductility are calculated and analyzed. Results show that the bearing capacity of columns is positively correlated with the reinforcement ratio. Generally, the bearing capacity of S-SSCC column and E-SSCC column are not significant different, but both are larger than that of G-SSCC column. The bearing capacity of hybrid reinforcement GS-SSCC and GE-SSCC column is between S-SSCC column and G-SSCC column. Meanwhile, it indicates that the theoretical calculation results of bearing capacity agree well with the experimental results. The ductility analytical results exhibit that the studied column specimens have the highest ductility when the reinforcement ratio is 1.56%. Among different reinforcement types, the ductility of G-SSCC is the smallest and the GE-SSCC and GS-SSCC column show improved ductility compared with G-SSCC columns.

Strengthening of RC columns under eccentric loads using NSM steel and GFRP bars

The behavior of eccentrically loaded RC columns strengthened by NSM steel and glass fiber reinforced polymer (GFRP) rebars is investigated in this study. A total of six RC column specimens have been cast in this study with dimensions of (150×150×1200) mm (width × height × length). Two column specimens are unstrengthened and considered as controls, while the other specimens are strengthened by the NSM method using steel bars and hybrid steel and GFRP rebars. All column specimens have been tested under concentric and eccentric loads with an eccentricity of 75mm up to failure. Experimental results in terms of crack patterns, modes of failure, and load-displacement curves are all monitored, recorded, and assessed. The experimental results have shown an improvement in the ultimate load capacity for all strengthened column specimens. Further, results have demonstrated that, under concentric load, the almost similar enhancement in the strength of NSM-strengthened RC column specimens using steel bars only and hybrid steel and GFRP bars. However, at eccentric load, the ultimate load capacity of the strengthened RC column was increased by 62% and 79.45% compared to the control column using NSM steel and hybrid steel, and GFRP, respectively. Finally, this study found that at e/h = 0.5 using GFRP in the tension zone increased the ultimate load by about 11% when compared to steel.

EXPERIMENTAL FLEXURAL STRENGTH OF GLASS FIBER REINFORCED POLYMER (GFRP) HYBRID REINFORCED CONCRETE BEAMS

Materials technology is an excellent opportunity to be developed industrially and on a needs scale according to the demands of society, namely supporting the environment, low maintenance, and long-term use. Using composite materials with reinforced polymers is a hot topic of discussion in civil engineering as new materials, strength/stiffness enhancers, or applications in building rehabilitation or renovation. Fiber Reinforced Polymer (FRP) is excellent as a new material because, in addition to being lightweight, corrosion resistant, and easy to work with, it also has high flexural strength, so it is a consideration to replace and or strengthen steel materials that are high in cost value. However, until now there has not been found the correct pattern or variant and volume of fibre so that it can be an alternative to the use of steel. The purpose of the study was to experimentally determine the flexural strength of Glass Fiber Reinforced Polymer (GFRP) hybrid beams either with steel reinforcement, with GFRP reinforcement, or with steel and GFRP combination reinforcement and different GFRP ratios (variants) through two-point load bending tests.The designed model is a development of a previous study that used one layer of 4 mm and produced a flexural strength smaller than the targeted flexural strength, so in this study, two layers of 8 mm were used. In addition, other experimental data that has been carried out from the literature is also used where the results of parametric studies provide evidence of the positive effect of hybrid steel and GFRP reinforcement ratios when obtaining GFRP models and volumes.The materials used to manufacture concrete beam test specimens 53x15x15 cm3 with quality of fc'35MPa have been tested according to SNI standards and meet both the minimum and maximum requirements specified. Based on the results of the material test, it is planned that the characteristic concrete quality fcr'=40.31 MPa, and based on the compressive strength test, the quality fcr'=41.68MPa is produced.The hybrid designed material with concrete or concrete and steel has been tensile tested with a maximum arcing load for the two layers = 8 mm variant; the tensile strength of the GFRP woven roving type with two layers 2 x 4 mm is 92.66 MPa. While plain steel reinforcement Diameter 8mm quality 280 MPa has a minimum tensile strength of 350 MPa (3.8 times the tensile strength of GFRP 8 mm).The results of testing and calculating the effect of GFRP as a substitute for steel reinforcement contributed to the flexural strength of concrete beams on average by 47.52%. In comparison, the contribution of flexural strength produced by concrete with steel reinforcement was 107.09%. The concrete variant of hybrid steel reinforcement and GFRP contributes to an increase in the average flexural strength of 117.02% > 4.8% compared to steel-reinforced concrete beams alone.

Effect of lamina orientation, crack severity, and fillers on dynamic parameters of hybrid composite cantilever beam with double transverse cracks

AbstractModern‐day research in composite material development primarily focuses on tailoring combinations by proportions of constituent materials and monitoring the changes in their targeted properties. In line with this trend, a new class of glass fiber reinforced polymer hybrid composite beam of size 600 mm×50 mm×6 mm is fabricated by adding graphene (average particle size:10 μm), and flyash (average particle size: 60 μm). The dynamic behavior of the hybrid beam by introducing two transverse cracks at different positions with varying crack depths is studied by employing analytical, finite‐element, and experimental approaches. The dimensionless relative natural frequencies of the cracked/faulty hybrid beam obtained by the proposed methods are compared with the intact hybrid beam. Also, a comparison is made for the hybrid beam with a single crack. An increase in relative crack depth resulted in an increase in values of dimensionless compliances. Further, the effect of fiber orientation and lamina stacking sequence on the dynamic parameters of the hybrid beam are also analyzed. The introduction of the second crack induces higher nonlinearity in bending modes of vibration.

Nonlinear analysis of flexural performance of reactive powder concrete beams reinforced with hybrid GFRP and steel bars

In this paper, flexural performance of reactive powder concrete (RPC) beams reinforced with hybrid glass fiber reinforced polymer (GFRP) and steel bars was investigated by finite element (FE) analysis, and predicted formulae of flexural capacity was proposed. First, based on the corresponding tests, the FE models of reinforced RPC beams were built, and the applicability of FE method with RPC material was verified. After that, the FE models of RPC beams reinforced with hybrid GFRP and steel bars was designed, and the flexural performance of such beams was investigated. The influence of GFRP bar ratio, steel bar ratio, and resultant force of hybrid reinforcements on the vertical load – deflection curves were observed. Finally, the formulae of the flexural capacity of the normal section of RPC beams reinforced with hybrid GFRP and steel bars was derived. By comparing the results of proposed formulae and FE analysis, it was found that they were in good agreement. Therefore, the proposed formulae can be used to predict the flexural capacity of such RPC beams with hybrid reinforcements.

Comparison of flexural behaviors between plain and steel-fiber-reinforced concrete beams with hybrid GFRP and steel bars

This study investigates the flexural behavior of steel-fiber-reinforced concrete (SC) beams with hybrid glass fiber reinforced polymer (GFRP) and steel bars. The experimental results of current SC beams are compared with those of the plain concrete (PC) beams conducted in our previous research. Taking account of the differences in nominal reinforcement ratio and reinforcement layout of seven tested SC beams, the test results including cracking load, ultimate load, failure mode, crack spacing and width, and mid-span deflection were firstly discussed. Then, a comprehensive comparison of flexural behaviors between SC beams and PC beams with same reinforcements was conducted in this paper. Especially, the crucial effects of type and strength of concrete on flexural capacity and failure mode of test beams were analyzed in detail. Finally, for concrete beams reinforced with hybrid (GFRP and steel) bars, the optimization of two balanced nominal reinforcement ratios was proposed to ensure the beam’s flexural failure in an appropriate-reinforced mode without rupture of GFRP bars.

Fabrication and Mechanical Performance of Graphene Nanoplatelet/Glass Fiber Reinforced Polymer Hybrid Composites

Glass fiber reinforced polymer (GFRP) composites are promising alternatives for the traditional carbon steel pipes used in the oil and gas industry due to their corrosion and chemical resistance. However, the out-of-plane mechanical properties of GFRPs still need further improvement to achieve this goal. Hence, in this work, two methods combining either vacuum mixing or spray coating with vacuum-assisted resin infusion were studied to fabricate graphene nanoplatelet (GNP)/GFRP hybrid composites. The former method resulted in a severe filtering effect, where the GNPs were not evenly distributed throughout the final composite, whereas the latter process resulted in a uniform GNP distribution on the glass fabrics. The addition of GNPs showed no modest contribution to the tensile performance of the GFRP composites due to the relatively high volume and in-plane alignment of the glass fibers. However, the GNPs did improve the flexural properties of GFRP with an optimal loading of 0.15 wt% GNPs, resulting in flexural strength and modulus increases of 6.8 and 1.6%, respectively. This work indicates how GNPs can be advantageous for out-of-plane mechanical reinforcement in fiber-reinforced composites.

Influence of graphene fillers on vibration characteristics of tapered hybrid GFRP composite beams under elevated temperature condition: Numerical and experimental study

In this study, numerically and experimentally the dynamic characteristics of graphene-reinforced glass fiber–reinforced polymer hybrid uniform and thickness tapered laminated composite beams were investigated. First, the graphene-epoxy nanocomposite solution without and with 0.25, 0.50, and 0.75 wt.% of graphene reinforcement is prepared by the heat shearing technique and then used for the fabrication of glass fiber–reinforced polymer hybrid uniform and thickness tapered composite beams using the hand lay-up method. The elastic properties of the hybrid beams were evaluated using the impulse excitation of vibration technique (ASTM E1876-15) under elevated temperature. Further, the numerical and experimental modal analysis of the hybrid beams with uniform and tapered configurations were conducted with variation in wt.% of graphene particles under fixed-fixed and fixed–free end supports. The results reveal that the natural frequencies of the glass fiber–reinforced polymer hybrid uniform and tapered configurations with 0.25 wt.% of graphene are greater than those of the glass fiber–reinforced polymer beams without graphene reinforcement and observed lesser for 0.5 and 0.75 wt.% of graphene under fixed-fixed and fixed-free end supports, respectively, due to unavoidable agglomeration effects. Furthermore, the parametric study was performed with the influence of weight fraction of graphene and temperature on the transverse response of the tapered composite beam. Hence, it can be concluded that the use of graphene filler in the glass fiber–reinforced polymer composites in the tapered composite beams improves the bending natural frequencies significantly when the weight fraction of the graphene is used lesser as agglomeration is unavoidable in practical condition. Therefore, the comprehensive numerical and experimental work presented in this study will be useful to the designers while using graphene fillers to improve the bending characteristics of the tapered composite beams.

Experimental evaluation of flexural behavior of HPFRCC beams reinforced with hybrid steel and GFRP bars

In this paper, seven beams were reinforced with the steel and Glass Fiber Reinforced Polymer (GFRP) bars in a hybrid system and the experimental behavior of beams was investigated. Three groups of beams were reinforced, including only-GFRP, only-steel, and hybrid steel-GFRP rebar subjected to four-point bending tests, respectively. To enhance the ductility of beams, conventional concrete was substituted with the High Performance Fiber Reinforced Cementitious Composites (HPFRCC). The beams of the first and second group were separately constructed by conventional concrete and HPFRCC; however, the third group was only consisted of HPFRCC. Moreover, the beams were reinforced in proportion to the percentages of the balanced ratio of longitudinal rebar. The results indicated that HPFRCC concrete positively influenced on the strength, ductility, and energy absorption of reinforced beams using composite and hybrid bars. The flexural capacity of hybrid reinforced concrete beams was between 86 and 115% of only-GFRPs and between 47 and 63% of only-steel beams and their ductility was between 88 and 235% compared to only-steel fiber reinforced concrete beams. Energy absorption in only-GFRP and only-steel samples were 50 and 34% compared to the hybrid beams. In hybrid beams, the higher ratios of effective (ρsf,f) was, the greater energy absorption was observed.

Experimental and Theoretical Analysis of Cracking Moment of Concrete Beams Reinforced with Hybrid Fiber Reinforced Polymer and Steel Rebars

This study aims at experimentally and theoretically investigating the cracking moment (Mcrc) of hybrid Fiber Reinforced Polymer (FRP)/steel Reinforced Concrete (RC) beams. Six hybrid Glass FRP (GFRP)/steel and three GFRP RC beams with various GFRP and steel reinforcement ratios are tested in four-point bending scheme. Experimental results indicate that both GFRP and steel rebars affect Mcrc, but the effect of steel reinforcement is more significant. When the steel reinforcement ratio increases to 1.17%, Mcrc goes up to 15.9%, while the same value for GFRP is only 9.7%. An analytical method is proposed based on the plain section assumption and nonlinear behavior of materials for estimating Mcrc. The proposed model shows a good agreement with the experimental data conducted in this study and collected from the literature. The results of the parametric study give evidence of the positive effects of hybrid reinforcement ratios and elastic modulus of FRP on Mcrc of hybrid RC beams.

Design and Field Testing of a First Continuous Slab-on-Girder Bridge with a Hybrid GFRP–Steel-Reinforced Bridge Deck in Canada

Abstract This paper introduces field tests of the first continuous multispan slab-on-girder bridge with hybrid glass fiber-reinforced-polymer (GFRP)–steel reinforcement in Canada. The bridge was co...

Fatigue flexural analysis of concrete beams reinforced with hybrid GFRP and steel bars

This paper presents fatigue behaviors of concrete beams reinforced with hybrid GFRP (glass fiber-reinforced polymer) bars and steel bars. Four beams were tested under fatigue loading, and the influence of effective reinforcement ratio and area ratio of FRP to steel bars (Af/As) were studied. Residual strains in concrete and in reinforcement were investigated in the tests, and it was found that the residual strains in reinforcement cannot be neglected. An analytical model with residual strains considered is proposed to calculate the strain development in reinforcement bars and concrete under fatigue loading. The model without residual strains considered underestimates actual strains, especially under the lower limit of fatigue loading, and the model with residual strains considered fits well with the test results. Parametric analysis shows that fatigue life increases with the increase of effective reinforcement ratio, while the increase of area ratio of FRP to steel bars (Af/As) reduces the fatigue life. And steel bars in members with higher Af/As are subjected to higher stress under fatigue loading.

Flexural behavior of hybrid GFRP - concrete railway sleepers

Abstract This paper aims to present the flexural behavior of hybrid GFRP (glass fiber reinforced polymer) concrete beams as sleepers to railway application. It was tried to obtain sleepers with adequate mechanical resistance, not susceptible to corrosion, durable and lighter than the sleepers in prestressed concrete. Pultruded fiberglass and polyester resin profiles were filled with high strength concrete and polyolefin fiber in the following proportions by volume: 1% and 2.5%. The beams were 1.06 meters long and had a 76 mm x 76 mm x 6 mm cross section, corresponding to a reduced model in a 1: 2.64 scale of a 2.80 meters long sleeper. In the bending tests, the load was applied at the center of the sleeper, as provided in the Brazilian standard NBR 11709 (2015) and American standard AREMA (2016). During the tests the applied load, the vertical deflection and the longitudinal tensile and compression deformations were measured in the center of the span. The influence of fiber addition on the strength, rupture mode and flexural modulus of elasticity of the hybrid beams was analyzed. Finally, the hybrid sleeper performance was compared to that of the prestressed concrete monoblock sleeper. The results obtained were satisfactory, indicating that the proposed hybrid sleeper is a constructively and technically feasible alternative.

Evaluation of mechanical properties and morphology of seawater aged carbon and glass fiber reinforced polymer hybrid composites

The replacement of metallic components by carbon fiber reinforced polymer (CFRP) composites is inhibited due to expensive carbon fiber. This problem may be addressed through hybridization of carbon and glass fiber to reduce the cost and achieve desirable mechanical properties of the hybrid composites. In this article, the influence of stacking sequence of carbon and glass fiber on seawater diffusivity, tensile, flexural and impact strength of hybrid composites were evaluated. The composites were fabricated by hand layup technique and seawater aged for 90 days at room temperature. The results revealed that the flexural strength of [CG2CG]S type of hybrid composite was the highest, i.e. 490 MPa in dry condition. The seawater diffusivity of [CG2CG]S type hybrid composite was reduced by 44% as compared to that of plain glass fiber reinforced polymer composite. The retention of tensile, flexural and impact strength of seawater aged hybrid composite of [CG2CG]S type were about 95%, 82%, and 94% respectively. The failure modes of the hybrid composites in dry and seawater aged condition were observed by field emission scanning electron microscope (FE-SEM) to establish a possible structure properties co-relationship.