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This paper presents the results of an experimental study on a full-scale precast concrete frame reinforced with glass fibre reinforced polymer (GFRP) bars that was tested to failure under lateral cyclic loading. Within the frame four different pocket connections are tested that will lead to accelerated construction. Traditionally, a pocket connection is comprised of a column that is extended into a recessed portion of the connecting beam and the pocket is filled with grout to create a moment-resisting connection. In order to accelerate the construction process, quicker setting epoxy resin was used in place of grout. The results show that while the epoxy resin could significantly accelerate and simplify the construction procedure due to its workability in addition to its high early strength and non-shrinkable properties, its thickness and low modulus of elasticity significantly affected the performance of the pocket joint. The test frame showed a flag-shaped hysteretic behaviour with narrow loops and small residual displacement thus illustrating desirable frame self-centring behaviour. This self-centring behaviour was due to rocking of the column in the pocket connection. The frame displaced with a large displacement ductility of approximately 7.0, however, the level of energy dissipation and damping ratio was very low when compared with conventional concrete structures. This experimental study shows that pocket connections can be used for GFRP reinforced precast concrete elements, however, they should be designed carefully to account for the lower stiffness of GFRP reinforcement. Also, to avoid premature failure and achieve a higher capacity of the pocket connections, the material used in the pocket to fill the gap between column and beam is recommended to have higher strength and elastic modulus compared to the surrounding precast concrete. Refereed/Peer-reviewed

Introduction. The article is devoted an analytical overview of the methods of applying the Nature solutions for designing structures made of plastics reinforced with fibers, in particular, using rational curved fiber trajectories. The first section provides an overview of different structural models and some approaches to the micromechanics of composites. Materials and methods. Sections 2-7 discuss: analysis of rational elastic-strength properties of wood and composites for crack arrest by weak interface; methods for constructing curved paths of fibers of “flowing holes”; analyzes the applied and promising technologies for manufacturing attachment points, in which holes are formed using curvilinear fiber paths; “nature-inspired” principles of optimal design of pipe composite structures similar in structure to ladder of bamboo stalk; examples of the effective use of fibrous composites in elastic elements such as leaf springs; developing additive technologies for 3D printing of fiber composite parts with fiber laying along calculated trajectories. Results. Each section of the article presents conclusions related to the peculiarities of composites structures calculation and design: calculations show that in order to increase the crack resistance of fibrous composites, it is necessary to significantly increase the shear characteristics of the binder and strive for rational properties created by Nature in wood; as a result of the calculation, it turns out that the maximum stress per fiber at the optimal reinforcement structure becomes about 3–4 times less than with a uniform rectilinear laying; rational reinforcement leads to a significant reduction in local stresses per fiber, elimination of splits and damages of fibers and an increase in the carrying capacity of the assembly; it has been shown that the bamboo rings are arranged to prevent the barrel from splitting from bending compressive stresses and tangential stresses when the barrel is twisted by wind load; analyzed the relationship of equal-strength profiling with Leonardo’s rule for tree crown branching. The works on creation of bio-similar shape and structure of curvilinear reinforcement of specimens for correct determination of unidirectional composites strength at tension along fibres were discussed; analyzed the role of composite technologies in modern mechanical engineering, in particular, in the creation of composite structures in open space. Conclusions. The article is devoted to the analysis of the tasks of fibrous composites macromechanics, therefore, in the opinion of the authors, the three most promising and related areas in macromechanics of composites that require further research are biomechanics of strength, computer modeling of optimal structures and technological mechanics of composites.

A substantial amount of work was carried out on the use of fiber-reinforced polymer (FRP) in reinforced concrete structural elements, which demonstrated considerable inelasticity or deformity through monotonic and cyclic loads. Even so, the action of FRP bars in reinforced concrete columns and frame structures has not yet been studied during reversed cyclic loading. In this research, reversed cyclic loading was applied on three beam-column joint models using the finite element method with ANSYS software. The first model was for a joint designed with steel rebar for both the longitudinal and transversal reinforcement. Glass fiber reinforced polymer (GFRP) rebar was used in the second joint model for the longitudinal reinforcement with steel transversal reinforcement. The third joint model was designed with hybrid steel/GFRP reinforcement for the longitudinal reinforcement and steel transversal reinforcement. The performance of the three models under reversed cyclic loading, such as load vs. story drift and energy dissipation capacity, were compared. The GFRP-reinforced model displayed a predominantly elastic behavior up to failure. Although its energy dissipation was lower, its performance in terms of total story drift demand was satisfactory

Many of the several authors have reported that reinforced concrete (RC) beams strengthened with externally bonded fibre reinforced polymer (FRP) laminates/sheets considerably reduced its ductility due to increase in stiffness that leads to debonding type of failure without adequate prior notice. This study aims to investigate the strength and ductility of glass fibre reinforced polymer (GFRP) laminated RC beams incorporated with different volume fraction (Vf = 0.5, 1.0, and 1.5) of discrete steel fibres. From the experimental evaluations, the role played by the incorporation of steel fibres is found to be effective in enhancing both the strength and ductility of FRP strengthened beams at all level of volume fractions, used in this study. Finite element analysis based full-scale beam models were developed using ANSYS software to model the response of all beams, as well, and the load-deflection behaviour of the models exhibit good agreement with the experimental results.

In this study, the effect of adding nanosize additive to glass fiber reinforced composite plates on mechanical properties and surface milling was investigated. In the light of the investigations, with the addition of MWCNTs additive in the composite production, the strength of the material has been changed and the more durable composite materials have been obtained. Slots were opened with different cutting speed and feed rate parameters to the composite layers. Surface roughness of the composite layers and slot size were examined and also abrasions of cutting tools used in cutting process were determined. It was observed that the addition of nanoparticles to the laminated glass fiber composite materials played an effective role in the strength of the material and caused cutting tool wear.

Compression and flexure members such as columns and beams are critical in a structure as its failure could lead to the collapse of the structure. In the present work, numerical analysis of square and circle short columns, and reinforced concrete (RC) beams reinforced with fiber reinforced polymer composites are carried out. This work is divided into two parts. In the first part, numerical study of axial behavior of square and circular concrete columns reinforced with Glass Fiber Reinforced Polymer (GFRP) and Basalt Fiber Reinforced Polymer (BFRP)bars and spiral, and Carbon Fiber Reinforced Polymer (CFRP) wraps is conducted. The results of the first part showed that the axial capacity of the circular RC columns reinforced with GFRP increases with the increase of the longitudinal reinforcement ratio. In addition, the results of the numerical analysis showed good correlation with the experimental ones. An interaction diagram for BFRP RC columns is also developed with considering various eccentricities. The results of numerical modeling of RC columns strengthened with CFRP wraps revealed that the number and the spacing between the CFRP wraps provide different levels of ductility enhancement to the column. For the cases considered in this study, column with two middle closely spaced CFRP wraps demonstrated the best performance. In the second part of this research, flexural behavior of RC beams reinforced with BFRP, GFRP and CFRP bars is investigated along with validation of the numerical model with the experimental tests. The results resembled the experimental observations that indicate significant effect of the FRP bar diameter and type ont he flexural capacity of the RC beams. It was also shown that Increasing the number of bars while keeping the same reinforcement ratio enhanced the stiffness of the RC beam.

This paper presents the concept, design, fabrication, application and experimental validation of a new type of composite sandwich matting. The composite sandwich matting comprises a paulownia woods as core material and glass fiber reinforced plastic (GFRP) as face-skins and lattice-webs. The matting was fabricated by vacuum infusion moulding process (VIMP). The mechanical properties of the component materials were studied. Four-point bending tests were also performed to investigate the flexural properties of the paulownia wood core sandwich panels. The experimental results showed that the failure mode of the structures was upper facesheet compressive yielding. The structures have good integrity against transverse load, there was a large plateau region after the initial failure and can prevent the structures from catastrophic failure. The finite element (FE) analysis showed a good agreement with the experimental results in predicting the load-displacement curve. The developed composite sandwich matting has been successfully used in military engineering, emergency rescue and large infrastructure construction owing to its excellent mechanical properties.

Nanofibers can be interleaved into polymers and improvements in mechanical properties such as resistance to impact, delamination and debonding as well as enhanced ductility can be obtained. In this work, GFRP laminated composites were interleaved to non-woven nylon 6,6 nanofiber mats which were generated by the electrospinning method. Four kinds of configurations were considered; two pure configurations where GFRP had two and four glass fiber layers and the other two kinds of nanofiber modified configurations that had one and three nylon 6,6 nanofiber mats being interleaved in GFRP. Those specimens were then investigated for their impact resistance, energy absorption and tensile strength capabilities in regard to low-velocity impact and tensile tests. The results showed that adding nylon 6,6 nanofiber mats can increase energy absorption values of the modified specimens, but some decrease in load capacities could be observed.

This study investigated the influence of fuel absorption on the mechanical properties of glass-fiber-reinforced polymer (GFRP) composite. Three types of fuel, namely, aviation fuel, biofuel, and a blended fuel mixture between kerosene and biofuel, were used to perform complete immersion on the GFRP specimens through immersion-bath technique. The degradation of the tension and compression properties of GFRP composite caused by fuel attack were experimentally investigated. Three types of aviation fuel were used to environmentally age the GFRP specimens through immersion-bath technique. The GFRP specimens were manufactured using vacuum-assisted resin-transfer molding to achieve a volume fraction of 0.55 with

This paper presents the results of an experimental study that investigates the compression behavior of concrete and evaluates the effect of hybrid reinforcement by multiple geometries, and total and partial confinement, using CFRP and GFRP composite materials. A total of nine (09) variants of concrete cylindrical specimens, including one (01) variant of unconfined concrete and eight (08) variants of confined concrete with different geometries were subjected to axial load compression. The objectives of this study were to verify the applicability and effectiveness of partial and total confinement to improve the behavior of concrete, evaluate the effect of the hybrid confinement used, and obtain a typical reinforced model. The results obtained clearly show the effectiveness of the hybrid confinement and partially confined concrete in improving the compressive strength and deformation of the concrete, so it is possible to replace CFRP total confinement by partially confined concrete with two CFRP layers or by a hybrid confinement with a CFRP layer in the central zone and GFRP layers on the top and bottom of the specimen.

The mechanical properties as well as sustainability of the fibre reinforced composites in the varied environment has need analyzed by researchers with particle dispersion favouring property enhancement. In this present work, crushed conch shell particles are used in composite making. Conch seashells begin harmless to the environment, used in many artistic works has finds its engineering application recently. In this line, conch shell particles of sieve size 600 μm and below is dispersed in varying weight percentage (25%, 35%, 45% and 55%) in the making of E-glass fibre epoxy composite by hand lay-up technique. The significance of conch particle addition in the glass fibre reinforced polymer (GFRP) composite has been evaluated by mechanical characterization and dynamic mechanical analyzer (DMA). Tests as per ASTM standards are conducted on the prepared GFRP laminate with and without particle dispersion. The impact energy of the laminate with 35% conch particle records a higher value of 29.80 J than the laminate without conch particle (11.52 J). Whereas, the tensile strength of laminate with 35% conch particle is 405.7 MPa with 10% rise than without conch (364.7 MPa). The dynamic mechanical analysis revealed the possibility of marginal raise in glass transition temperature (Tg) and reduction in loss modulus (E″ on conch particle addition. The extent of conch particle contribution to the mechanical properties is substantiated by surface morphology. Thus, this work directs the application of conch particle bio-waste as particulate filler in the composite with an ability to enhance property.

A lot of researches are focused on decreasing the weight of manufactured components and increasing their mechanical properties, or achieve additional unique properties. One of the results of their effort is a composite material. This kind of material consists of two phases – matrix and reinforcing phase. This unique combination of phases causes the superior properties of the composite material. However, since material properties of the matrix differ from the material properties of the reinforcing material, certain difficulties during machining are caused. Between those difficulties are included: delamination of the machined composite and reduced tool life. Those facts motivate other researches to investigate the machinability of the composite materials. There has been described a few possibilities on how to improve the machining process during machining of composite materials. For example, Seco Tools Company starts with developing a new shape of the cutting tools; DMG Mori Company has successfully implemented assistance of the ultrasound into milling process and therefore achieved enhanced machinability od the materials; the scientists from the Stan-ford University have developed a diamond-like carbon (DLC) coating, which is available to satisfactory cut the reinforcing fibres as well as the soft matrix. In this article is compared ultrasonic-assisted face milling of the carbon fibre reinforced plastic (CFRP) and glass fibre reinforced plastic (GFRP) by a unique shaped milling cutter. There were observed delamination of those composite materials during mill-ing process via 3D digitization devices. The results of the research could be applied to determine how fibre material can affect ultrasonic assistance during the milling process. There were achieved lower delamination during machining of GFRP, however, lower surface roughness was achieved during machining of CFRP.

Fiber and metal materials used in Fiber Metal Laminate (FML) have different machinability properties due to their different structures. This case has made it a research topic to obtain good hole quality in these materials. A good match between the parameters used is required for the machinability of FML. Traditional and non-traditional machining methods in the machining of FML in this article were investigated and a comprehensive review regarding the machining parameters and hole quality were conducted. Considering the methods and parameters used, the defects occurring in the holes (delamination, hole size and circularity, surface roughness, etc.) were determined and the most suitable processing methods and parameters were picked in order to minimize these defects. As a result, the most suitable machining method and optimum cutting parameters for a better hole quality in FML machinability are determined, and it is aimed that this study will be beneficial to scientific and industrial societies.

In recent years, the application of fiber-reinforced plastics (FRPs) as structural members has been promoted. Metallic bolts and rivets are often used for the connection of FRP structures, but there are some problems caused by corrosion and stress concentration at the bearing position. Fiber-reinforced thermoplastics (FRTPs) have attracted attention in composite material fields because they can be remolded by heating and manufactured with excellent speed compared with thermosetting plastics. In this paper, we propose and evaluate the connection method using rivets produced of FRTPs for FRP members. It was confirmed through material tests that an FRTP rivet provides stable tensile, shear, and bending strength. Then, it was clarified that non-clearance connection could be achieved by the proposed connection method, so initial sliding was not observed, and connection strength linearly increased as the number of FRTP rivets increased through the double-lapped tensile shear tests. Furthermore, the joint strength of the beam using FRTP rivets could be calculated with high accuracy using the method for bolt joints in steel structures through a four-point beam bending test.

Epoxy nanocomposites reinforced with glass fiber, have been prepared with various weight percentages (1, 3, and 5 wt.%) of MgO nanofillers to improve their electrical and thermal performance. An increase in MgO nanofiller content up to 3 wt.% tends to enhance surface discharge and corona inception voltages measured using fluorescence and UHF methods, under both AC and DC voltage profiles. Reduced initial surface potential along with increased decay rate is observed after inclusion of MgO nanoparticles. Before and after the polarity reversal phenomena, heterocharge formation is observed in the bulk of test specimens. In comparison with other test samples, the 3 wt.% sample had reflected lower electric field enhancement factor. After MgO filler was added to glass fiber reinforced polymer (GFRP) composites, the coefficient of thermal expansion (CTE) has reduced, with the 3 wt.% specimen having the lowest CTE value. TGA measurements revealed an improvement in thermal stability of the GFRP nanocomposites up on the inclusion of MgO nanofillers. Overall, the GFRP nanocomposite sample filled with 3 wt.% nano-MgO outperformed the other test samples in terms of electrical and thermal performance.

This article provides experimental data on the punching shear behavior of synthetic fiber-reinforced slabs reinforced with glass fiber reinforced polymer (GFRP) bars and cast from self-consolidating concrete (SCC). The data was collected from tests performed on six full-scale specimens centrically loaded until failure as indicated by penetration of the column stub into the slab and achieving a sharp drop in the load carrying capacity. Three different reinforcement bar spacings were used to consider the effect of reinforcement ratio on punching shear resistance. Three of the specimens tested were reinforced by 1.25% of volume of synthetic fiber, and three were control specimens cast from regular SCC. Applied load, central deflections, and bar strain were monitored during the experiment and are provided in the supplementary data. Any future models for analyzing the punching shear behavior and capacity of flat slabs reinforced with GFRP rebars will find this data valuable for model validation, and for establishing suitable safety factors for design. Numerical studies on the simulation of fiber-reinforced concrete would also find value in this data to validate the numerical model and enable it to be used for further studies.

This paper attempts to investigate the effect of various parameters on the axial compressive behavior of nano-silica concrete-filled angle steel reinforced GFRP tubular columns. The proposed new composite column consists of three parts: the outer GFRP tube, the inner angle section steel and the nano-silica concrete filled between GFRP tube and angle section steel. Twenty-seven specimens with different nano-silica concrete compressive strength (20MPa, 30MPa and 40MPa), diameter-to-thickness ratio of GFRP tube (20, 25 and 40) and steel ratio (0.008, 0.022 and 0.034) were tested under axial load. The main purpose of this study is to examine the effect of the three parameters on the following: failure modes, deformation capacity, load bearing capacity, ductility and initial stiffness of the new composite column under axial load. It was found that the load bearing capacity and initial stiffness increased as the nano-silica concrete compressive strength of the specimens increased. But the specimens with higher nano-silica concrete compressive strength showed lower deformation capacity than that of the specimens with lower nano-silica concrete compressive strength. The varieties of the steel ratio have no significant effect on the specimens’ axial deformation behavior. Experimental results also showed that both load bearing capacity and deformation capacity increased with the decrease of diameter-to-thickness ratio of GFRP tube. However, diameter-to-thickness ratio of GFRP tube has no significant effect on the initial stiffness of specimens. The confinement coefficient was proposed to better evaluate the confinement effect of GFRP tube on the inner angle section steel reinforced core nano-silica concrete. The confinement effect of GFRP tube on lower strength concrete was better, and the confinement effect reduced as the diameter-to-thickness ratio of GFRP tube increased. The design formulas for the load bearing capacity of the nano-silica concrete-filled angle steel reinforced GFRP tubular columns under axial load were proposed.

Approximately 90,000 ships are registered in South Korea, and about 80,000 of these ships are used in domestic shipping. Among these, 84% are small ships, such as a fishing vessels that weigh less than 20 tons and are made mostly of an FRP (Fiber Reinforced Plastics). When this fact is taken into account, the greenhouse gas emissions that are released per ton of a composite vessel are sizeable. In this study, the laminated structures of an FRP fishing vessel, many of which currently are being built in Korea, were analyzed by ISO (International Organization for Standardization) and international design rules, and the structures of the hulls are lightweight with optimum glass fiber mass content as determined by the laminate weight minimization algorithm. As a result, it was confirmed that the laminations of the vessels in accordance with the Korean rule could have 6.4% to approximately 11% more design margin compared to the requirements of ISO and other international rules. And the case study of the application of the laminate weight minimization algorithm showed the possibility of reducing the weight of the hull bottom plating by as much as about 19.32% and by as much as about 18.06% in the overall structure.

Corrosion is a major factor in the deterioration of reinforced concrete (RC) structures. To mitigate this problem, steel bars can be replaced with glass-fiber-reinforced-polymer (GFRP) bars. However, the lack of ductility of GFRP-RC elements has prevented their use in many structural applications, especially in seismic areas. Superelastic shape memory alloy (SMA) bars have been proposed to be used in seismic areas because of their self-centering characteristics. Also, they have the added advantage of being corrosion resistant. This paper examines the combined use of SMA and GFRP bars to achieve ductile self-centering and corrosion-free elements. The first challenge for such a proposal relates to designing concrete frames, reinforced with SMA and GFRP bars, that have adequate lateral performance in terms of initial stiffness, ductility, and strength. A comprehensive parametric study is conducted to better understand the structural behavior of concrete elements reinforced with SMA and/or GFRP bars. Results from the study are utilized to develop design equations that allow designing an SMA/GFRP RC section to replace a steel RC section, while maintaining lateral strength, stiffness, and ductility. To examine the adequacy of the developed equations, a six-storey concrete frame is designed, and its lateral performance is examined using pushover analysis.

The low-velocity impact behavior of polyester glass fiber composite laminates has been investigated under different clamping conditions, by wetting the specimens surface with fluids having different densities. Unidirectional composite laminates, based on polymer resin and fibers of naval interest, with different thicknesses have been manufactured by resin transfer molding process in order to have a high control of the final properties and a high fiber volume fraction. Impact tests in air have been, first, performed up to penetration on all manufactured composites having four different thicknesses to get information on the material impact behavior. The effect of the clamping conditions and the interaction of the laminates with two fluids different in density, i.e., water and paraffin oil, have been investigated, then, only on the thickest laminates that showed a lower tendency to impact damage. In particular, the impact tests have been performed by impacting the front surface of the sample and by wetting the back surface of the composite samples under unclamped and clamped conditions, replicating the boundary constraints suggested by ASTM D7136 Standard for the conventional impact tests. Experimental results showed a lower initial rigidity, higher absorbed energy and deflection for specimens exposed to liquids with respect to those exposed to air, confirming the need of taking into account the fluid interaction in the case of marine composite applications.

The use of glass fibre reinforced polymer (GFRP) composites in civil engineering structures has seen considerable growth in recent years due to their high strength, low self-weight, and corrosion resistance, namely when compared to traditional materials, such as steel and reinforced concrete. To enable the structural use of GFRP composite materials in civil engineering applications, especially in footbridges, it is necessary to gather knowledge on their structural behaviour, particularly under dynamic loads, and to evaluate the ability of current design tools to predict their response. In fact, excessive vibration has a major influence on the in-service performance (comfort) of slender structures as well on their service life. The use of composite materials that combine high damping capacity with relatively high stiffness and low mass can provide functional and economic benefits, especially for footbridges. This paper aims to investigate the dynamic behaviour of GFRP free-supported beams to evaluate their modal characteristics (frequency, damping, and modal shape). To assess the benefits of using a structure made of pultruded GFRP rather than a conventional material—steel, a comparative analysis between the dynamic characteristics of GFRP and steel beams is performed. To specifically address material damping and to minimize the interference of the boundary conditions, the beams are tested in a free condition, resting on a low-density foam base. The results show that the damping capacity of GFRP is much higher than that of steel, as the measured damping factor of GFRP is five times higher than that of steel for the same boundary conditions and similar geometry. Furthermore, the fact that the frequencies of the tested specimens resemble for the two different materials highlights the perceived damping qualities of the polymer-based composite material. Finally, an energy method for evaluating the influence of the scale factor on material damping is applied, which made it possible to infer that the damping varies as a function of frequency but is not explicitly affected by the length of the specimens.

This study describes a methodology that allows evaluating the behavior of a glass fibre reinforced polymer (GFRP) laminate impacted by a vertical weight drop, analyzing the damage that occurred inside. The purpose of the designers was, by means of characterization tests of the curing processes, evaluation of the cohesion of a particular laminate, application of vertical tests by weight drops and with the use of the readings of an accelerometer in a single direction, know the trend of how intralaminar breaks in the matrix and interlaminar breaks between layers occur. It is proposed to establish the behavior of the laminate before the tests by analyzing curing times, for after the tests by observations with penetrating fluorescent inks. This allows researchers to know the response of the laminate to the loads imposed on the applied structure. For the tests, prepreg material cured outside the autoclave in an oven was used and qualitative quantification of the damage by observing sections of the tested material infiltrated with penetrating fluorescent ink exposed to ultraviolet light.

Concrete and glass fiber reinforced polymer (GFRP) bar samples from an 18-year old repair project executed on an existing dry-dock were obtained by coring the dry dock in two regions. Several destructive and non-destructive tests were performed on both materials. Testing performed on the concrete showed substantial variability and clear evidence of damage occurring over the years. Further, there were significant differences in the concrete obtained from two different regions of the dock. The concrete was carbonated and chloride from seawater had penetrated significantly into its depth. The GFRP bars showed relatively lower variability in terms of test results. Electron microscopy and horizontal shear strength results suggest that the GFRP surface of the bars had suffered some damage, whereas the core had remained unaltered. These findings regarding limited damage to the GFRP, taken together with recent advances in GFRP production technology, support the notion that concrete reinforced with GFRP bars is an attractive alternative to conventional steel reinforced concrete for marine infrastructure applications.

The application of laser fabrication of fiber-reinforced polymer (FRP) has an irreplaceable advantage. However, the effect of the plasma generated in laser fabrication on the damage process is rarely mentioned. In order to further study the law and mechanism of laser processing, the laser process was measured. CFRP and GFRP materials were damaged by a 1064 nm millisecond pulsed laser. Moreover, the propagation velocity and breakdown time of plasma plume were compared. The results show that GFRP is more vulnerable to breakdown than CFRP under the same conditions. In addition, the variation of plasma plume and material surface temperature with the number of pulses was also studied. The results show that the variation trend is correlated, that is, the singularities occur at the second pulse. Based on the analysis of experimental phenomena, this paper provides guidance for plasma phenomena in laser processing of composite materials.

This paper examines the immature rupture of glass fiber reinforced plastic composite (GFRP) mitered elbow pipes. The GFRP composite mitered elbow pipe’s lifespan was twenty-five years; however, the pipes in question experienced immature failures, resulting in the reduction of their lifetimes to seven, nine, and ten years, respectively. The GFRP cooling water mitered elbow pipe’s service conditions operate at a pressure of up to 7 bar and temperatures between 15–36 °C. The root cause of failure was determined using visual inspection, analytical, microstructural, mechanical characterizations, and chemical analysis. The initial visualization inspection revealed an improper joint between the composite overwrapped and the straight pipe sections. Mechanical properties along the axial, hoop and 45° from the axial direction were obtained. The results from the analytical analysis indicated that the elbow might withstand the operating pressure depending on the quality factor, which was confirmed to be low due to the elbow joint’s improper fabrication process. As evidence of this, the numerical analyses’ results indicated that the safety factor in withstanding the operating pressure of 5 bar is dropped down in the radial region where the thickness is reduced to simulate the failure zone. This study’s findings recommend that thickness of less than 15 mm be reinforced using overwrapped composites. It is recommended for future installations that the fabrication process be appropriately monitored and controlled and avoids using 45°/−45° fiber orientation and multiple layers of chopped strand mat glass fiber.

Background: In timber structures, connections are the most important and critical section which supply the strength of each structural element. The aim of this study was evaluation the behavior of epoxy resin reinforced by nanoclay (at three levels) on the pull-out strength of glued-in GFRP rods in glulam. For this purpose, two rods with three lengths (50, 150 and 250 mm) and diameters (6.4, 12.7 and 19.1 mm) were inserted at two opposite sides of glulam blocks (with dimension of 8.89 x 8.89 x 29.94 cm) which were glued by epoxy resin. Samples underwent tensile testing and their tensile strength and shear strength were measured. The obtained data were analyzed statistically and the effects of studied factors on bond strength were evaluated. Results: The results showed that the strength of bonding increased with the addition of a low amount of nanoclay, and the length of the rod had a greater effect than its diameter. Furthermore, the amount of nanoclay, rod length and diameter could not significantly affect simultaneously, the performance and strength of glued-in GFRP rods. Conclusion: Nanoclay particle can be considered as a reinforcement for epoxy resin in glued-in GFRP rods and its effect may cause a considerable increase in the mechanical strengths of joints.

The high-strength-to-weight ratio and corrosion resistance properties of glass-fiber-reinforced polymer (GFRP) composites makes them potentially well-suited for application in ship structures, bridges and off-shore oil platforms. These structures are often formed by stiffened plates and are subjected to axial load and out-of-plane load. Cutouts and openings are provided in the plates for access and maintenance. The main objective of this study was to examine the buckling behavior of GFRP-stiffened composite plates with square cutouts under a combination of axial and out-of-plane load up to failure. Four blade-stiffened composite plates without a cutout and four with square cutout were fabricated with stiffeners as a continuous layup of the flange plate using glass fiber and epoxy resin. The initial geometric imperfections were measured, and plate imperfections (Δx), stiffener imperfections (Δsy) and overall imperfections (Δsx) were calculated from the measurements. All fabricated-stiffened composite plates were tested up to failure. The finite element model was developed in ANSYS software and validated with the experimental results. It was observed that GFRP-stiffened composite plates failed by stiffener compression/stiffener tension mode of failure. The presence of out-of-plane loads and cutouts reduced the axial load carrying capacity of the stiffened composite plates.

A novel concept of polymer railway sleeper is proposed in this study that has the potential to meet static performance requirements within the cost of hardwood timber. The existing challenges of composite sleepers, such as low performance or high cost, can be overcome using this innovative concept. Such a proclamation is proven through limit state design criteria and a series of experimentations. Results show that polyurethane foam as an infill material can provide sufficient strength and stiffness properties to the sleeper, but the inadequate screw holding capacity could be a problem. This limitation, however, can be overcome using a particulate filled resin system. The findings of this study will help the railway industry to develop a timber replacement sleeper.

This paper presents the experimental results of composite rebars based on GFRP manufactured by a pultrusion system. The bending and radial compression strength of rods was determined. The elastic modulus of GFRP rebars is significantly lower than for steel rebars, while the static flexural properties are higher. The microstructure of the selected rebars was studied and discussed in light of the obtained results—failure processes such as the delamination and fibers fracture can be observed. The bending fatigue test was performed under a constant load amplitude sinusoidal waveform. All rebars were subjected to fatigue tests under the R = 0.1 condition. As a result, the S-N curve was obtained, and basic fatigue characteristics were determined. The fatigue mechanism of bar failure under bending was further analyzed using SEM microscopy. It is worth noting that the failure and fracture mechanism plays a crucial role as a material quality indicator in the manufacturing process. The main mechanism of failure under static and cyclic loading during the bending test is widely discussed in this paper. The results obtained from fatigue tests encourage further analysis. The diametral compression test reflects the weakest nature of the composite materials based on the interlaminar compressive strength. The proposed methodology allows us to invariantly describe the experimental transversal strength of the composite materials. Considering the expected durability of the structure, the failure mechanism is likely to significantly improve their fatigue behavior under the influence of cyclic bending. The reasonable direction of searching for reinforcements of composite structures should be the improvement of the bearing capacity of the outer layers. In comparison with steel rebars (fatigue tensile test), the obtained results for GFRP are comparable in the HCF regime. It is worth noting that in the near fatigue endurance regime (2–5 × 106 cycles) both rebars exhibit similar behavior.

Predictive models play an important role for increasing the reliability of composite structures over time, but a great deal of experimental data is requested. In this paper, results from creep experiments on uniaxial E-glass fiber reinforced polymer (FRP) single ply laminates, performed at different stress levels, are presented. The tests duration was of 42 months. Analytical modeling of the viscous behavior of the tested GFRP composite, under linear and nonlinear viscoelastic hypotheses, is reported. A discussion on the comparison of creep strain response by Burgers model, with parameters obtained from fitting of data for different test duration, is also proposed. Finally, predictive finite element method (FEM) simulations were carried out for discussing the deferred behavior induced by creep, for composite layers used for repair purposes in hydrogen transportation pipes. Numerical results highlighted a non-negligible difference in creep strain values, pointing out that a model based on experimental tests with shorter duration leads to a conservative composite design.

This paper aims to estimate the enhancement in the energy absorption characteristics of the glass fiber reinforced composites (GFRP) by embedding prestrained pseudo-elastic shape memory alloy (SMA) that was used as a secondary reinforcement. The pseudo-elastic SMA (PE-SMA) embedded were in the form of wires and have an equiatomic composition (i.e., 50%&ndash, 50%) of nickel (Ni) and titanium (Ti). These specimens are fabricated using a vacuum-assisted resin infusion process. The estimation is done for the GFRP and SMA/GFRP specimens at four different impact velocities (65, 75, 85, and 103 m/s) using a gas-gun impact set-up. At all different impact velocities, the failure modes change as we switch from GFRP to SMA/GFRP specimen. In the SMA/GFRP specimen, the failure mode changed from delamination in the primary region to SMA-pull out and SMA deformation. This leads to an increase in the ballistic limit. It is observed that energy absorbed by SMA/GFRP specimens is higher than the GFRP specimens subjected to the same levels of impact energy. To understand the damping capabilities of SMA embedment, vibration signals are captured, and the damping ratio is calculated. SMA dampens the vibrations imparted by the projectile to the specimen. The damping ratio of the SMA/GFRP specimens is higher than the GFRP specimens. The damping effect is more prominent below the ballistic limit when the projectile got rebounded (65 m/s).

The behavior of concrete deep beams internally-reinforced with glass fiber-reinforced polymer (GFRP) bars around regions of discontinuity is investigated. Twelve deep beam specimens were tested. One specimen was solid whereas the remaining eleven specimens included an opening in the shear span. Test variables included the opening height, concrete grade, and GFRP reinforcing configuration around the discontinuity regions. Three different GFRP reinforcing schemes around the discontinuity regions were employed. The scheme with diagonal GFRP reinforcement crossing the bottom chord was more effective in improving the shear resistance than that having diagonal GFRP reinforcement crossing the top chord. The strength gain caused by the GFRP reinforcement was more significant for the deep beams with the greater opening height. In contrast, increasing the opening height reduced the strength enhancement caused by increasing the concrete grade. Test results were compared to the strut-and-tie modeling (STM) predictions. The STM tended to provide reasonable predictions for the nominal shear strength of the beams reinforced with GFRP bars around the discontinuity regions. Provisions of the Canadian Standards Association provided more conservative predictions for the nominal strength compared with those provided by provisions of the American Concrete Institute.

An experimental study on the performance of adhesive connection between Glass Fibre Reinforced Polymer (GFRP) plates and Steel Fibre reinforced self-compacting Concrete (FRC) was conducted. Fresh FRC was poured out onto the surface of GFPR plates, to create 40 square specimens (300 by 300 by 45 [mm]). Pull-off tests were performed to evaluate the tensile strength of the adhesive connection when different types of adhesives (four) and surface treatments (three) are used. Furthermore, the effect of five different environmental conditions on the tensile strength of the adhesive connection was also evaluated. After analysing the results and performing a variance analysis (ANOVA), it has been shown that the pull-off behaviour is highly influenced by the type of adhesive and by the environmental action. In spite of that, the dominant failure mode was cohesive failure in the FRC substrate, therefore good bond conditions between both materials were achieved., POCI-01-0247-FEDER-003480; SFRH/BSAB/150266/2019; SIKA, KERAKOLL and MAPEI. project “EasyFloor – Development of composite sandwich panels for rehabilitation of floor buildings”, involving the company ALTO – Perfis Pultrudidos, Lda., ISISE/University of Minho and CERis/Instituto Superior Técnico, supported by FEDER funds through the Operational Program for Operational Program for Competitiveness and Internationalization (POCI) and the Portuguese National Innovation Agency (ANI) – project no. 3480 (POCI-01-0247-FEDER-003480). The first author acknowledges the grant SFRH/BSAB/150266/2019 provided by FCT, financed by European Social Fund and by national funds through the FCT/MCTES. Acknowledgments are extended to LEST – Laboratório de Estruturas for their material support. The authors would like to thank SIKA, KERAKOLL and MAPEI companies for suppling the adhesives

Glass fiber reinforced polymer (GFRP) pultruded rectangular tubes were used externally to confine Reinforced Concrete (RC) beams in this experimental study, aiming to improve the corrosion resistance of the RC beams in the harsh environment (e.g. Hydraulic structures and Marine structures). The flexural behaviour of the composite beams reinforced with GFRP tubes was investigated by using four-point bending test. The experimental program involved the testing of six beam specimens reinforced with or without the GFRP tubes, and the main parameters investigated included the reinforcement ratio of the tensile steel bars and the stirrup spacing. The experimental results show that the flexural strength and stiffness of the RC beam members were significantly improved by using the GFRP tubes. The brittle failure of the beam specimens was caused by the local failure at one loading pints on the top flange of the GFRP tubes. The higher reinforcement ratio of the tensile steel bars contributed to the improvement of the flexural strength and bending stiffness. The stirrup spacing had little effect on the flexural behaviour of the beam specimens in the proposed composite beams.

Glass Fibre Reinforced Polymer (GRFP) composites are increasingly being used as new materials for civil and petrochemical engineering infrastructures, owing to the combination of relatively high specific strength and stiffness and cost-competitiveness over traditional materials. However, practical concerns remain on the environmental stability of these materials in harsh environments. For instance, diffusion of salty water through the composites can trigger degradation and ageing. For this reason, a continuous monitoring of the integrity of GFRP composites is required. GRFPs health monitoring solutions, being non-destructive, in-situ, real-time, highly reliable and remotely controllable, are as desirable as challenging. Herein we develop and compare two methods for real-time monitoring of GRFP: one based on the electrical sensing signals of percolated carbon nanotubes (CNTs) networks and the other on optical fibre sensors (OFSs). As a proof-of-concept of dual sensory system, both sensors were used in combination to detect the diffusion of water through the composite. Measurements demonstrated that both CNTs and OFSs were able to detect water diffusion through the epoxy matrix successfully, with an on-off sensing behaviour. OFSs exhibit some advantages since they do not require electrical supply as required in hazardous environments and are more suitable for remote operation, which make them attractive for new developments in harsh-environment sensing. On the other hand, CNTs can be easily embedded in the composite without compromising its performance (e.g., mechanical properties) and are easily interrogated by measurement of electrical conductance, therefore could be used as spot sensors in the most failure-prone sections of GFRP components. This study opens up the possibility for an early detection of composites degradation, which could prevent failures in GFRP structures such as pipelines and storage tanks used in the oil and gas industry.

This study reports on the effects of water absorption on the anisotropic mechanical response of an epoxy resin reinforced with E-glass fibres. Composite specimens were conditioned by immersion in pure water at 50 °C for different time durations, up to full saturation. Water-saturation resulted in reduction of stiffness and strength, in the range of strain rate 0.001–700s−1. Experiments on re-dried specimens after water saturation showed a limited recoverability of the original mechanical properties. Water absorption increased the sensitivity of the mechanical response of the GFRPs to the applied strain rate. Finite element simulations of the response of a unit cell of the unidirectional composite were performed to understand the role of the hygroscopic stresses induced by water absorption, and it was found that this is negligible due to the active mechanisms of viscoelastic relaxation.

Microalgae are an ideal source for next-generation biofuels due to their high photosynthetic rate. However, a key process limitation in microalgal biofuel production is harvesting of biomass and extraction of lipids in a cost-effective manner. The harvesting of the algal biomass amounts to approximately 20 to 30% of the total cost of the cultivation, hence, developing an efficient and universal harvesting method will make the commercialization of microalgal bio-cultures sustainable. In this study, we developed, demonstrated, and evaluated a novel harvesting method based on Glass Reinforced Fiber Polymer (GFRP) panels, suitable for industrial-scale installations. The proposed method was based on previous observations of preferential micro-algae development on glass surfaces, as well as in the assumption that the microalgae cells would prefer to attach to and grow on substrates with a similar size as them. At first, we developed a laser micromachining protocol for removing the resin and revealing the glass fibers of the GFRP, available for algal adhesion, thus acting as a microalgae biomass harvesting center. Surface micromachining was realized using a ns pulsed ultraviolet laser emitting at 355 nm. This laser ensured high machining quality of the GFRP, because of its selective material ablation, precise energy deposition, and narrow heat affected zone. A specially built open pond system was used for the cultivation of the microalgae species Scenedesmus rubescens, which was suitable for biofuel production. The cultivation was used for the experimental evaluation of the proposed harvesting method. The cultivation duration was set to 16 days in order for the culture to operate at the exponential growth phase. The biomass maximum recovery due to microalgae attachment on the GFRP surface was 13.54 g/m2, a yield comparable to other studies in the literature. Furthermore, the GFRP surfaces could be upscaled to industrial dimensions and positioned in any geometry dictated by the photobioreactor design. In this study, the glass fiber reinforced polymer used was suitable for the adhesion of Scenedesmus rubescens due to its fiber thickness. Other microalgae species could be cultivated, adhere, and harvested using GFRP of different fiber sizes and/or with a modified laser treatment. These very encouraging results validated GFRPs&rsquo, harvesting capabilities as an attachment substrate for microalgae. Additional studies with more algae species will further strengthen the method.

The article presents the possibilities of using girders made of plastics in hall covering structures in comparison with girders made of traditional materials, such as steel and wood, commonly used in civil engineering. Profiles made of polymers reinforced with glass fibre with the pultrusion method show enormous potential in the construction business. Until today polymers have been used as construction materials only occasionally despite the numerous benefits they offer, such as improved durability in aggressive environments and smaller weight in comparison with traditional materials, to mention but a few of their flag advantages. Polymer composites have a relatively low resistance to high temperatures, especially fire has a very negative influence on them.

The article presents experimental tests of a new type of composite bar that has been used as shear reinforcement for concrete beams. In the case of shearing concrete beams reinforced with steel stirrups, according to the theory of plasticity, the plastic deformation of stirrups and stress redistribution in stirrups cut by a diagonal crack are permitted. Tensile composite reinforcement is characterized by linear-elastic behavior throughout the entire strength range. The most popular type of shear reinforcement is closed frame stirrups, and this type of Fiber Reinforced Polymer (FRP) shear reinforcement was the subject of research by other authors. In the case of FRP stirrups, rupture occurs rapidly without the shear reinforcement being able to redistribute stress. An attempt was made to introduce a quasi-plastic character into the mechanisms transferring shear by appropriately shaping the shear reinforcement. Experimental material tests covered the determination of the strength and deformability of straight Glass Fiber Reinforced Polymer (GFRP) bars and GFRP headed bars. Experimental studies of shear reinforced beams with GFRP stirrups and GFRP headed bars were carried out. This allowed a direct comparison of the shear behavior of beams reinforced with standard GFRP stirrups and a new type of shear reinforcement: GFRP headed bars. Experimental studies demonstrated that GFRP headed bars could be used as shear reinforcement in concrete beams. Unlike GFRP stirrups, these bars allow stress redistribution in bars cut by a diagonal crack.

This paper deals with analyzing the structural responses of glass-fiber-reinforced polymer (GFRP) tubes filled with recycled and concrete material for developing composite piles, as an alternative to traditional steel reinforced piles in bridge foundations. The full-scale GFRP composite piles included three structural layers, using a fiber-oriented material that was inclined longitudinally. Almost 60% of the fibers were orientated at 35&deg, from the longitudinal direction of the pile and the rest 40 percent were oriented at 86&deg, from the horizontal axis. The segment between the inner and outer layers was inclined 3&deg, from the hoop direction in the tube. The behavior of the filled GFRP tubes was semi-linear and resulted in increasing the total ductility and strength of the piles. Adjusting the material&rsquo, s properties, such as the EAxial, EHoop, and Poisson ratios, optimized the results. The lateral strength of the GFRP composite pile and pre-stressed piles are investigated under both axial compression and bending moment loads. Based on the conducted parametric study, the required axial and bending capacities of piles in different ranges of eccentricities can be reached using the combination of tube wall thickness and GFRP fiber percentages.

The reinforcement of existing masonry vaults against seismic actions is an extremely timing issue and it has already involved many researchers in experimental testing and numerical modelling. However, up to now, the results of the research have been expressed and compared in terms of load-displacement capacity curves. But the designers, in the practice, need to assess the resisting peak ground acceleration of the vault (PGA), so to compare it with the seismic demand. In the paper, a strategy to evaluate this parameter, based on the modified Capacity Spectrum Method and accounting for the level of the vault in the building is proposed. The procedure is applied to a case study of a masonry building with barrel vaults, comparing the performances of plain vaults and vaults strengthened with a GFRP (Glass Fiber Reinforced Polymer) reinforced mortar coating. The results evidenced significant improvements in terms of PGA after the reinforcement, attaining to values from 3.1 to 3.3 times that of the unreinforced vault.

The paper presents research program of bond between glass fiber reinforced polymer bars and concrete in reference to the steel bars. Bond between the reinforcement and concrete is a crucial parameter governing a behaviour of reinforced concrete members and transferring of the internal forces from concrete to the reinforcement. The use of FRP bars as an equivalent reinforcement to steel in concrete structures has increased in recent years. The FRP bars are very different from steel, mainly due to much lower elasticity modulus and their anisotropic structure. Good performance of FRP reinforced concrete requires sufficient interfacial bond between bars and concrete. However, there are no specific standards referring to the surface preparation of these bars, that leads to variable bond behaviour of the composite reinforcement to the concrete. The objective of the study was to investigate the influence of variable parameters on the bond behaviour to concrete. The experimental program consisted of eighteen beam bond specimens varying in: bar diameter (12mm, 16mm, 18mm) and type of reinforcement (GFRP sand – coated and steel bars). Although the GFRP bars indicated good bond behaviour to concrete, the average bond strength was slightly lower than that of steel reinforcement of 16mm and 18 mm, while it was higher for the GFRP bars of 12mm diameter.

In the past, research on the use of FRP in civil engineering has been focused on strengthening existing structures where FRP reinforcements were applied to the surface of concrete elements. Recently, the application of FRP reinforcements has been studied to replace steel reinforcements for use in areas of increased environmental loads, with a need to exclude the corrosion of the reinforcement or to ensure the electromagnetic neutrality of the individual elements of the load-bearing structure. The GFRP reinforcement ratio was verified considering failure modes in flexure and the bond of the GFRP reinforcement with concrete. Besides classical reinforcements, GFRP has also been used in prestressed variants, and the possibility of its use as permanent formwork has been verified. In terms of extending the use of non-metallic reinforcements, it is important to note the long-term exposure and possible degradation of the mechanical properties.

Geopolymer concrete (GPC) reinforced with glass fiber reinforced polymer (GFRP) bars can give a good structure system with high durability and strength. So, this research was described the flexural behavior of the geopolymer Ultra-high-performance concrete (UHPC) beams. Also, the impact of UHPC reinforced with glass fiber reinforced polymer (GFRP) bars was studied. For this purpose, (eight) UHP geopolymer RC beams was studied. Four High Strength Concrete (HSC) beams and another four in UHPC were reinforced using GFRP with different ratios. The Results exhibited increasing the first crack load and ultimate load carrying capacity. GPC beams showed a smaller deflection increase at the same ultimate load. GPC beams reinforced with GFRP bars documented a higher crack width compared with control. Using GFRP bars in reinforcement improved the concrete defection, the patterns of cracks, cracks number of and the failure mode. A non-linear analysis using Ansys 2019-R1 was conducted to validate the experimental results for each beam. Results showed well agreement between experimental results and analytical ones.

Design and execution of fatigue load dominated circular hollow section (CHS) multi-membered structures, such as offshore jacket and floating structures for wind turbines, truss bridges, etc., is hinged on fatigue performance of critical welded joints. An innovative jointing technology of wrapped composite joint connects steel hollow sections by direct bonding through a fibre reinforced polymer composite wrap, which completely avoids welding and therefore has superior fatigue performance than welded joints. In this study first results on fatigue performance of the wrapped composite joints is presented. Tensile cyclic loading tests on wrapped composite X-joint specimens were carried out to characterise their fatigue performance under different constant amplitude load ranges and compare it to equivalent welded joints. In addition, the influence of surface roughness of steel tubes and re-testing (load history) on fatigue performance of wrapped composite joints, as well as the influence of fatigue loading on residual static resistance was investigated in experiments. Preliminary S-N curves of wrapped composite joints are established. The tests results showed that X45 wrapped composite joints exhibited steadier stiffness degradation and 10–100 times longer fatigue life than their welded equivalents. Through 3D DIC surface strain measurements and post-failure microscopic insights to cut specimens, different failure modes including de-bonding at glass fibre composite-to-steel interface, delamination/fracture of the composite layers and fracture of steel brace are distinguished. The relationship between joint stiffness degradation rates, crack propagation rates and nominal stress ranges in the brace are established, based on which a preliminary fatigue life prediction of wrapped composite joints can be made. The re-tested specimens exhibited superior fatigue performance than virgin ones, while specimens with poor steel surface roughness showed worse fatigue performance. After fatigue loading with 40% of stiffness degradation, the specimens were found to still have the potential to sustain its original static resistance.

The effects of high temperature environmental exposition and of soft curing treatment on the interlaminar shear strength for vinylester glass fibre multilayer composites have been studied. The degradation effects on the matrix and fibre–matrix interface are due to scissions of polymer chains, the oxidation process, the weakening of fibre–matrix bonding. Possibility of stabilization of Glassfiber – Vinylester-Bisphenol-A composite for prolonged high temperature service by low temperature curing is established.