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Environmental sustainability is one of the prime objectives of the manufacturing industries. To accomplish this focus, industries are developing low-energy consumption manufacturing process, which reduces production cost and the environmental impact. The GFRP composites find applications in various structural applications, such as aircraft, wind turbine blades etc. owing to their lightweight, high strength, and stiffness. In this study we explored manufacturing of glass fiber-reinforced polymer (GFRP) composite using vacuum-assisted resin infusion microwave curing (VARIMC) and thermal curing. This study investigated the role of curing parameters (microwave power and cure time) on mechanical performance of the GFRP composites. Analysis of energy consumption during VARIMC and thermal curing were also carried out in this work. The mechanical properties of GFRP composites are observed to be better at 540 W microwave power with cure time of 720 s compared to 8100 s for thermal curing (2000 W). The VARIMCed GFRP samples exhibited better or comparable properties than thermally cured samples. The VARIMC process utilized about 1.186 MJ/kg of energy, which was almost 36 times less than the energy consumed by thermal curing (43.2 MJ/kg). [Display omitted] [ABSTRACT FROM AUTHOR]

Glass Fiber-Reinforced Polymer (GFRP) bars can enhance the flexural bearing capacity and durability of concrete beam members under sustained loading and alkaline environment over an extended period. However, addressing the challenges related to durability and deformation resistance remains crucial for long-term service. In this paper, the flexural performance of GFRP-reinforced concrete beams with different glass fiber contents under the coupling action of the alkaline environment and continuous load is studied, and the mechanism of improving the flexural performance of GFRP-reinforced concrete beams by dispersed fibers is analyzed from a microscopic point of view by scanning electron microscope (SEM) test. In addition, the finite element analysis software was used to simulate and verify the improvement effect of singly dispersed fiber on the bending of GFRP-reinforced concrete beams. The results demonstrate that GFRP-RC beams containing 0.5%, 1.0%, or 1.5% glass fiber exhibit a reduction in deflection ranging from 11% to 23% compared GFRP-RC beams without glass fiber, thereby improving their deformation resistance. The optimal glass fiber content is 1.5%. Simulation analysis demonstrates that the model exhibits enhanced resistance to deformation when the glass fibers are randomly dispersed. Specifically, increasing the random scattering of fibers at the bottom of the beam by two to three times results in a reduction of 7%-12% in mid-span displacement of the model. Additionally, within the cracked area, the fibers bear greater tensile stress compared to those in other uncracked regions, effectively preventing further cracking of GFRP-RC beams. This study offers valuable design guidance for enhancing performance of GFRP-RC members during long-term service. • This paper studied glass fiber GFRP-RC beams. • The working condition is the coupling of sustained loading and alkaline environment. • The influence of fiber on the flexural property of beam was investigated by finite element method. • The corrosion age of alkaline environment is 450 d. [ABSTRACT FROM AUTHOR]

This study addresses the mechanical limitations of concrete fabricated with recycled brick and concrete as partial replacement of coarse aggregates, which exhibit inferior strength and stiffness compared to those with natural aggregates. To rectify this, a cost-effective approach involving low-cost glass fiber-reinforced polymer composites (LOC-GFRP) is proposed. The key parameters considered were the plain concrete compressive strength and the quantity of LOC-GFRP layers. The compressive strength of LOC-GFRP-confined concrete increased with the number of layers, with greater improvements observed in lower-strength plain concrete. Moreover, the improvement in ultimate strain was more significant than the improvement in compressive strength. The compressive strength and ultimate strain were improved by 271% and 478%, respectively. LOC-GFRP confinement resulted in a bilinear compressive stress vs. strain response, showcasing increased ductility and strength with more LOC-GFRP layers. The study evaluated various existing analytical expressions for fiber-reinforced polymers but found them inadequate in predicting parameters accurately. As a result, nonlinear regression analysis was carried out to propose expressions for predicting compressive strength and ultimate strain of LOC-GFRP-confined concrete for different aggregate types. The calculated coefficient of determination values ≥ 0.90 confirmed the good correlation among experimental and predicted values. ● Low-cost glass fiber-reinforced polymer composites (LOC-GFRP) were proposed. ● LOC-GFRP confinement resulted in bilinear compressive stress-strain responses. ● Strength and strains of LOC-GFRP-confined concrete specimens were predicted. [ABSTRACT FROM AUTHOR]

• A novel lightweight GFRP-PU-Graphite powder tube was successfully manufactured. • Hybrid methods were effectively used to manufacture tubes. • Graphite filler percentages influenced material properties. • Tubes filled with 5% graphite exhibited a substantial improvement. • The hybrid tube resists expansion and chemical reactions like corrosion. This research successfully introduced an innovative lightweight tube made from lightweight PU Foam material and reinforced with glass fiber. The key findings from the tests are as follows: Glass fiber-reinforced polymer (GFRP) tubes without polyurethane (PU) foam withstood a pressure of 4.03 kN in compression testing. The specimen with 5 % graphite filler had the highest density at 0.262 g/mm3, while the specimen with 10 % graphite filler had the lowest density. The specimen with 5 % graphite filler also exhibited the highest hardness (19.5 Shore Hardness D), whereas the specimen with 20 % graphite filler had the lowest hardness (13.2 Shore Hardness D). The contraction of PU foam significantly influenced the material strength. GFRP tubes reinforced with PU foam offer advantages in terms of material lightness and improved material strength. These tubes can be applied in structural, automotive, and aerospace applications. [ABSTRACT FROM AUTHOR]

• Superconducting magnet. • Insulation material. • S-glass fiber composite. • Irradiation with fast electron in fission reactor. • Mechanical and electrical performance of insulation material after irradiation at 300 K and 77 K temperatures. In a superconducting (SC) magnet fusion reactor, the insulation material used has to withstand significant fluxes of neutrons and neutron-induced gamma radiation. Epoxy-based glass fiber-reinforced plastic (GFRP) composites are the insulation system for fusion magnets and are highly demanding. This insulation system requires excellent mechanical and electrical performance under mixed neutron and gamma radiation at cryogenic temperatures. The insulation material developed consists of boron-free S-glass fiber impregnated with a two-component modified Diglycidyl ether of Bisphenol-A (DGEBA) epoxy resin. An anhydride-cured DGEBA resin system is not suitable for cryogenic temperatures. Therefore, to overcome this thermal stress issue in cryogenic components of SC magnets, a high-toughness, flexible, aromatic amine-cured epoxy resin system was developed for the insulation system. In order to assess the radiation resistance for mechanical and electrical properties, the composite samples were irradiated in the fast breeder test reactor (FBTR) at IGCAR, Kalpakkam, India. The irradiation experiment was carried out for a neutron fluence of 1.0E+21 n/m2 and a gamma dose of 0.4 MGy at a full reactor power of 32 MWt. The tensile strength, interlaminar shear strength, and breakdown strength measurements were investigated before and after irradiation at room temperature and 77 K. The test results indicate that no significant degradation was observed in the properties of the irradiated samples up to the above-mentioned radiation doses. [ABSTRACT FROM AUTHOR]

Shape-morphing structures based on pressure actuation promise efficiency gains and performance improvements in aeronautics, but require complex three-dimensional geometries. The compliance of these morphing structures originates from local areas of reduced wall thickness. However, the required high wall thickness ratios are challenging for integral fabrication from high-performance fiber-reinforced plastics, which are demanded to achieve high load-bearing capacity. This study investigates different woven flexure hinges made from a hybrid yarn of glass fibers and the polyamide PA6 for application in pressure-actuated cellular structures. The flexure hinges are mechanically characterized under pure axial and pure bending loading in a tensile and a column bending test method specifically derived for flexure hinges. The specimen quality is further assessed by permeability testing, optical microscopy, and thermogravimetric analysis. This study shows that the stiffness of anisotropic flexure hinges can be determined in simple mechanical tests without the need for complex modeling of reinforcing fibers or consideration of manufacturing-specific effects. The mechanical properties of a double-layer hinge configuration are superior to those of a single-layer configuration, whereas integrating additively manufactured PA6 inlays into the woven preform offers an effective approach for achieving high wall thickness ratios. The most promising hinge configuration is selected for the integral fabrication of the aeronautical morphing structure, which consists of multiple pressurized cells. [ABSTRACT FROM AUTHOR]

Waste Fiber-Reinforced Polymer (FRP) composites have become an environmental issue in China, Europe, and the United States. However, recycling waste FRP composites poses sustainability challenges in the long term because their predominantly cross-linked structure (thermoset matrices coating) typically cannot be re-used or re-processed. Here, for the first time, we studied the merits of introducing recycled glass fibers (rGF) to bitumen to enhance bitumen's durability as measured by resistance to aging and resistance to moisture damage. We compared the reinforcement efficacy of recycled glass fibers (rGF) with recycled glass fibers after the polymer coating was removed (rGFWP) and with virgin glass fibers (vGF). After aging, compared to the bitumen with rGFWP, the bitumen containing rGF showed enhanced resistance to oxidative aging, as evidenced by lower values of two indexes of chemical aging (a 64.5% lower carbonyl index and a 94.5% lower sulfoxide index), a 47.10% lower increase in the ratio of large molecular size, and a 61.41% lower rheological aging index. Moreover, bitumen containing recycled glass fiber demonstrated noticeably improved resistance to moisture damage as compared to base bitumen, particularly for rGFWP, as demonstrated by energy ratio (ER) values that were 478% higher. The resistance to moisture damage of bitumen containing rGF was also significant improved, as evidenced by a 72.78% increase in surface energy, the better MISTI value (the least variation from a value of one), and a 213% higher ER value compared to base bitumen. This indicates that recycled glass fibers have positive effects on the durability of bitumen composites. The outstanding durability of bitumen with recycled glass fibers highlights the feasibility of adding recycled glass fibers to bitumen as a practical application that provides an economic and environmentally friendly solution for waste glass fibers. Use of recycled glass fiber in bitumen enhance its durability and delays aging. [Display omitted] [ABSTRACT FROM AUTHOR]

• The effect of plasma treatment on the mode II interlaminar fracture toughness of glass/epoxy laminates was studied experimentally. • Glass fiber layers at the top and bottom faces of the pre-delamination were treated by a dielectric-barrier discharge (DBD) plasma. • G IIC of glass/epoxy specimens was determined by subjecting end-notched bending (ENF) specimens to a 3-point-bending load. • Plasma treatment increased the G IIC of the specimens by ∼ 50%. • Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods were used to investigate the toughing mechanisms. Despite the key advantages of fiber-reinforced polymer composites, such as high specific strength and stiffness, these materials are characterized by low interlaminar fracture toughness. This study aims to investigate the effect of dielectric-barrier discharge (DBD) plasma treatment of glass fibers on the mode II interlaminar fracture toughness (G IIC) of glass/epoxy composite laminates. To this aim, first, end-notched bending (ENF) specimens were fabricated using the vacuum infusion process. During the laminating process of the specimens, the two adjacent glass layers at the top and bottom faces of the pre-delamination were exposed to an atmospheric DBD plasma for different exposure times (R: reference specimens without plasma treatment, PT2: specimens with two rounds of treatment, and PT5: specimens with five rounds of treatment). Afterward, the ENF specimens were subjected to three-point bending loading according to ASTM D7905 standard. The results showed an increase of ∼ 51% and ∼ 56% in G IIC for PT2 and PT5 specimens compared to the reference specimens (R), respectively. The Fourier-transform infrared spectroscopy (FTIR) analysis indicated that the plasma treatment did not generate new functional groups at the surface of glass fibers; therefore, there was no increase in the chemical bonding strength of the fibers to the resin. However, scanning electron microscopy (SEM) revealed that the plasma treatment increased the adhesion of the glass fibers to epoxy by removing sizing of the glass fibers and increasing the surface roughness of the fibers. The results of the present study showed that the plasma treatment can be considered as a cheap, easy-to-use, cost effective and scalable method for toughening laminated composites instead of the costly and difficult methods such as electrospun nanofibers and z-pinning. [ABSTRACT FROM AUTHOR]

• This paper proposes a damage-resistant Hybrid Fiber Reinforced Polymer Composites (HFRP) design method based on the interface properties. • The microscopic interface properties of composites are introduced into the investigation of interlayer interface properties. • The influence of different hybrid interlayer interfaces on the delamination damage behavior of composites is clarified. • The 3D printing technology was used to prepare specimens of the hybrid fiber-reinforced composites. In this work, the poor impact damage resistance of carbon fiber-reinforced plastic (CFRP) composites was improved by mixing carbon fibers with ductile fibers (glass fibers/Kevlar fibers). The damage behavior of five interfaces of the prepared hybrid fiber-reinforced plastic (HFRP) composites was investigated through mode-I and mode-II interlaminar fracture toughness tests and micro-droplet debonding tests. On this basis, a numerical model for predicting the impact damage of HFRP composites was established. Through a comprehensive evaluation of the impact damage resistance indexes obtained from the numerical simulations, the hybrid fiber type, hybrid ratio between different fibers, and hybrid lay-up sequence could be optimized. The specimens with optimized lay-ups were prepared by 3D printing, and the effectiveness of the numerical model was verified through low-velocity impact and compression after impact (CAI) tests. The results show that the introduction of glass fiber layers in CFRP composites can significantly improve the damage resistance of the composites. Compared with CFRP composites, when the volume fraction of the glass fibers is 25%, HFRP composites have a smaller delamination damage area (reduced by 74.08%), furthermore, the pit depth is reduced by 43.01%, the CAI is increased by 17.29%, and the strength retention rate is increased by 31.94%. [ABSTRACT FROM AUTHOR]

The un-stiffened fiber reinforced polymer (FRP) beams under three-point bending often fail at compression web-flange junction due to low inter-laminar shear and transverse compressive strengths of web. Therefore, the objective of the present work is to study the effect of different stiffening elements on the flexural response of FRP I-beams. Various stiffening elements such as glass fiber reinforced polymer (GFRP) cover plates, cover angles, and bearing stiffeners are connected to the beam separately to examine their effect on the strength, stiffness and failure modes. This study also includes the strengthening of web-flange junction of FRP I-beams using carbon fiber layers with adhesive. It is observed that replacing the chopped strand mats with 45° and 90° unidirectional rovings increases the crushing strength of the beam. Strengthening of web-flange junction using carbon fiber layers or stiffening with short length bearing stiffeners under loading is observed to be most effective in preventing the failure of web-flange junction of FRP I-beams. Beams stiffened with short length bearing stiffeners have higher failure load than other stiffened beams. Strengthening of web-flange junction using wet carbon fiber layers is noted to be more effective than stiffening with GFRP cover angles. Since the stress concentration produced due to the sudden change in the cross-section of beams strengthened with carbon fiber reinforced polymer (CFRP) laminated cover angle is less than that for beams stiffened with GFRP cover angles. • Web-flange junction strength of FRP beams without imperfection is higher than beams with imperfection. • Short length bearing stiffeners avoid the failure at tension web-flange junction of FRP I-beams. • Strengthening using wet (adhesive) carbon fiber layers is more effective than stiffening with cover angles. • Delamination of web-flange junction of I-beams can be avoided by strengthening of web-flange junction with carbon fiber layers. • Flexural strength of beams with short bearing stiffeners under web-flange junction is higher than other stiffening elements. [ABSTRACT FROM AUTHOR]

Abstract The present work aims to compare two different injection moulding foaming technologies, the already known MuCell® process and the new emerged technology IQ Foam®, as well as the cell structure and mechanical behavior of the obtained components. Glass fiber reinforced-polypropylene (>PP GF<) was employed to produce rectangular plates at solid and foamed conditions by using MuCell® and IQ Foam® processes combined with the complementary Core Back expansion molding technology, and the material structure as well as the tensile, flexural and impact properties were studied. A solid skin-foamed core structure was observed in the samples foamed by both techniques. The mechanical properties decreased gradually with the apparent density of the microcellular plates. By increasing the thickness of the part because of the expansion of the cavity with the Core Back technology, the apparent density decreased but the flexural stiffness was greatly enhanced. Foamed samples obtained by IQ Foam® technology exhibited thicker solid surface layers and lower cell density than that of the MuCell® ones, but consequently higher resistant area, and thus, slightly higher mechanical properties. The new IQ Foam® technology is able to produce foamed parts with properties comparable to that of the MuCell® process, offering additional benefits such as cost-effectiveness, easy to use and machine-independence. [ABSTRACT FROM AUTHOR]

Highlights • The HAZ and maximum bearing strength were predicted in laser drilling of GFRP by GA-ANN. • The HAZ extension was measured by the SEM micrographs. • The relationship between the HAZ and the bearing strength was discussed. • The bearing strength was compared for laser drilled and conventionally drilled samples. • An improvement was obtained by the GA-ANN model in comparison to the trial-and-error method. Abstract Recently, an increasing interest has been emerged on nontraditional drilling methods of FRP materials. This paper aims to study two critical quality criteria pertaining to both surface quality and mechanical properties of laser drilled GFRP laminates. The effect of major laser drilling parameters was investigated on the HAZ and bearing strength through utilizing the combined GA-ANN approach. At first, the experimental design was performed based on a full factorial design with different process parameters, later on the experimental results were used to develop a GA-ANN model. The GA was integrated to the ANN model to determine the optimal ANN architecture through optimizing the number of hidden layer neurons, momentum coefficient and learning rate. The effectiveness of the models was ultimately evaluated on the basis of experimental data and statistical analysis. It was found that the GA-ANN method could predict the HAZ and bearing strength more accurately than trial-and-error ANN. Furthermore, the SEM micrographs from the contact area of the bearing tests were discussed and compared with mechanical drilling method. The results drawn from this study helps to better understanding of the laser drilling process of FRP materials and for predicting the mechanical properties of laser drilled FRP laminates applicable in aircraft part manufacturing. [ABSTRACT FROM AUTHOR]

Highlights • Detailed numerical analysis of S0/A0 mode conversion phenomenon on the delamination based on spectral element method. • Analysis of wavefield (including S0/A0 mode conversion) distribution through the thickness in the delaminated region. • Implementation of the model for impact damage. • Full wavefield measurements and numerical results show good agreement. Abstract In this paper results of numerical analysis of S0/A0 elastic wave mode conversion at discontinuities in glass fibre reinforced polymer (GFRP) plates are presented. Analysis of S0/A0 mode conversion effect at Teflon inserts simulating delamination (circular Teflon inserts located at a different depth, Teflon inserts with different shapes at the same depth) and impact damage with energies 5 J, 10 J and 15 J is conducted. Numerical analysis is based on spectral element method (SEM) in the time domain. Numerical model includes a composite plate, a piezoelectric transducer and bonding layer for transducer and damage. Numerical model takes also into account the influence of material damping. Numerical results are compared with experimental results based on full wavefield measurements using scanning laser Doppler vibrometry (SLDV). It is shown that based on effects of S0/A0 mode conversion it is possible to detect the damage and determine its shape and size. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the usability of hybrid sandwich structures as facade panels. The explored sandwich structure was made of mineral-glass fibre reinforced polymer (GFRP) skins and a GFRP truss core, fabricated by means of a novel manufacturing method. The compressive and shear specific strengths of the panels were assessed and compared with a few common lightweight structures to verify that the manufactured truss core had comparable values. Three-point bending tests indicated that the polyurethane foam used (required for the manufacturing process) had negligible mechanical contribution. Full-scale panels were tested under a distributed load. The tests were simulated using the three-dimensional finite element method to predict the pressure at which mineral cracks appeared in order to avoid their occurrence in the design phase. The simulation results exhibited good agreement with experimental data, and the model was validated in terms of deflection and strain responses. The occurrence of cracks and their propagation were numerically reproduced using the concrete-damage plasticity model. The link between the connector and crack positions in the mineral skin was highlighted in this study. [ABSTRACT FROM AUTHOR]

Abstract The objective of this paper was to investigate the effect of addition of Multiwall Carbon Nanotubes (MWCNTs) with different values of weight percentage (0.5%, 1%, and 1.5%) on the vibration and morphological properties of Short Glass Fiber (SGF) (10, 20, and 30 wt.%) reinforced polypropylene (PP) and the polypropylene foam composites. Nanocomposites were first compounded by using the melt-compounding technique in a twin-screw extruder. Then, azodicarboxamide was added as a foam agent to investigate the foaming behavior of the samples. The free vibration behavior of the samples under clamp-free boundary conditions was studied via Operational Modal Analysis (OMA). In order to confirm the experimental results, the Euler-Bernoulli beam theory was employed to calculate the values of the natural frequencies. The results of analyses indicated that the theoretical natural frequencies had a significant correlation with the experimental results within 18% mean error level. The experimental results showed that addition of SGF particles to the PP and PP foam would significantly increase the natural frequencies, but it would in return decrease the damping factor. The results also indicated that, with addition of MWCNTs to the samples, the damping factor and natural frequencies of the PP and SGF/PP composites would increase. The highest increase in the natural frequencies amounted to 118.8%, which resulted from combination of 20 wt.% SGF and 1 wt.% MWCNT. On the other hand, the highest increase in the damping factor amounted to 68.9%, which resulted from combination of 20 wt.% SGF and 1.5 wt.% MWCNT. Highlights • The free vibration behavior of MWCNTs and SGFs reinforced PP and PP foam was studied through the operational modal analysis (OMA) technique. • The theoretical natural frequencies through the Euler-Bernoulli beam theory had a significant correlation with the experimental results. • OMA is reduces the loading effects of the force transducer by stimulation of a structure through environmental loads. • Addition of the SGF particles to the PP and PP foam would significantly increase the natural frequency, but it would in return decrease the damping factor. • With addition of MWCNTs to the samples, the damping factor and natural frequencies of the PP and SGF/PP composites would increase. [ABSTRACT FROM AUTHOR]

Highlights • Tensile behaviour of different GFRP laminates under elevate temperatures has is investigated. • Laminates with continuous unidirectional fibers showed the best tensile performance. • Laminates with chopped strand fibers showed the weakest tensile performance. • Laminates with continuous woven fibers performed better than chopped strand and weaker than unidirectional laminates. Abstract This study was aimed at gaining an improved understanding of the behavior of glass fiber-reinforced polymer laminates at elevated temperatures by means of testing laminate specimens with unidirectional, woven, and randomly distributed (chopped strand mat) fibers. The testing parameters were temperature, the type of fiber, and the thickness of the laminates. The failure modes of the specimens and their elasticity moduli at ambient temperature were investigated, and analysis of variance was conducted to determine the contribution of each parameter to the behavioral test results. The findings showed that among the parameters, an increase in temperature exerted the strongest effect on the specimens. The unidirectional laminate specimens exhibited the best performance, maintaining nearly 40% of their loading capacity at 550 °C. At this temperature, the woven laminate specimens could not carry any tensile load, and at 400 °C, the laminate specimens containing randomly distributed fibers lost all their strength. [ABSTRACT FROM AUTHOR]

Highlights • Bond of GFRP bars in high strength concrete was investigated using hinged beams. • Bond performance was studied with showing the effect of main parameters on bond. • Design code predictions were compared to the experimental results. Abstract Although several research studies have been conducted on investigating the bond stress – slip behaviour of Glass-Fibre Reinforced Polymer (GFRP) bars embedded in high strength concrete (HSC) using a pull-out method, there is no published work on the bond behaviour of GFRP bars embedded in high strength concrete using a hinged beam. This paper presents the experimental work consisted of testing 28 hinged beams prepared according to RILEM specifications. The investigation of bond performance of GFRP bars in HSC was carried out by analysing the effect of the following parameters: bar diameter (9.5, 12.7 and 15.9 mm), embedment length (5 and 10 times bar diameter), surface configuration (helical wrapping with slight sand coating (HW-SC) and sand coating (SC)) and bar location (top and bottom). Four hinged beams reinforced with 16 mm steel bar were also tested for comparison purposes. The majority of beam specimens failed by pull-out. Visual inspection of the test specimens showed that the bond failure of GFRP (HW-SC) bars usually occurred owing to the bar surface damage, while the bond failure of GFRP (SC) bars was caused due to the detachment of sand coating. The GFRP bars with helical wrapping and sand coated surface configurations showed different bond behaviour and it was found that the bond performance of the sand coated surface was better than that of the helically wrapped surface. Bond strength reduced as the embedment length and bar diameter increased. It was also observed that the bond strength for the bottom bars was higher than that of the top bars. The bond strength was compared against the prediction methods given in ACI-440.1R, CSA-S806 and CSA-S6 codes. All design guidelines underestimated the bond strength of both GFRP re-bars embedded in high strength concrete. [ABSTRACT FROM AUTHOR]

Abstract Fibre reinforced polymer composite materials (FRP) have been extensively used worldwide as substitutes of other traditional materials due to their lightness, high mechanical performance, high chemical resistance and the possibility of having any shape required. The waste management of these materials is critical because most of the wastes produced are sent to landfills. This research intends to evaluate the influence of Glass Fibre Reinforced Polymer (GFRP) waste as a filler in cement-based mortars. The technical performance of the renders with GFRP was analysed in order to find a viable solution to recycle this waste. Two sets of mortars were analysed: mortars with a similar workability and mortars with the same water/binder ratio both with percentages of GFRP waste incorporation of 10%, 15%, 20% and 50%. The water behaviour was analysed through the water absorption by capillarity test and drying test. The mechanical behaviour was analysed through the dynamic modulus of elasticity, velocity of ultrasound waves, flexural strength and compressive strength. The incorporation of GFRP by-products in mortars is a viable solution for the reutilization of this waste. The GFRP waste improved the workability of the mortars and reduced their bulk density. The modified mortar with best technical performance was the mortar with 50% of GFRP by-product as substitute of natural aggregate. The initial water absorption of these mortar was reduced by over 80% (measured by the coefficient of capillarity) and the mechanical strength was significantly improved: at 365 days, there was an increase in flexural strength of 155% and in compressive strength of 166%. Highlights • GFRP waste significantly improves the workability of the mortars. • Water absorption is significantly reduced by the incorporation of GFRP waste. • Drying is slower when Glass Fibre Reinforced Polymer waste is incorporated. • Mechanical strengths are significantly improved by the incorporation of GFRP waste. [ABSTRACT FROM AUTHOR]

Abstract This paper presents an experimental study to assess the effects of food chemicals and temperature on the mechanical performance of glass fiber reinforced bio-based polyamide. The diffusion of food chemicals was mainly driven by thermal energy, following Arrhenius law in all tested environments. Degradation of mechanical properties and decrease in reliability were assessed, due to the plasticization of polymer matrix. Secondary but not negligible effect on flexural strength degradation is given by the different chemical interaction between polymeric chains and molecules of food chemicals. Colour change was measured and resulted to be positively correlated to diffusion. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Patterned GFRP superhydrophobic surface was fabricated by laser texturing. • Achieve over 88% of the underwater acoustic absorption from 50 kHz to 250 kHz. • High acoustic absorption ascribes to the multiple interface scattering effect. Abstract Underwater acoustic absorption metasurfaces (UAAMs), featured with artificial periodic unit cells as acoustic micro-absorbers, are crucial for the enhancement of the underwater stealth, energy transition, sonar detection, etc. How to implement the acoustic metasurfaces for practical engineering applications requires the support of efficient manufacturing techniques. Here we present a simple way of laser texturing for fabrication of the patterned superhydrophobic surface on glass fiber reinforced plastic (GFRP). Unlike the traditional acoustic absorbing material whose thickness should match the corresponding wavelength, the laser textured superhydrophobic micro-grooves have thickness less than the absorption sound wavelength by 2–3 orders of magnitude but promisingly demonstrate over 88% of the underwater incident acoustic power absorption from 50 kHz to 250 kHz. The physical mechanism of the UAAM ascribes to the multiple interface scattering effect induced by the air layer between water and superhydrophobic micro-nano structures. [ABSTRACT FROM AUTHOR]

Abstract The aim of this study is to compare two different standardized testing procedures, tensile testing and Mode-I double cantilever beam (DCB) testing, to evaluate a possible correlation between the dominant failure in glass fibre-reinforced plastics and their according acoustic emissions (AE). AE is processed by using a burst collection of all recorded transient signals and is further analysed with the k-means clustering algorithm. To generate damage related AE, a series of experiments for tensile testing and Mode-I DCB testing is performed on 16-layer glass fibre/epoxy specimens with a cross-ply lay-up for tensile and an unidirectional lay-up for Mode-I DCB testing. Three sensors at tensile testing and one sensor at Mode-I DCB testing gather AE data. The results of clustered burst signals show a good accordance between both testing procedures, with a similar weighted peak frequency (WPF) range in each classified cluster. In total, three different clusters are determined. An assignment of these three clusters to the three dominant damage mechanisms, visually observed by microscopy, is suggested. [ABSTRACT FROM AUTHOR]

In a recent paper, Zhou et al. (2017) studied the time-dependent properties of Glass Fiber Reinforced Polymers composites by employing a new rheological model with a time-dependent viscosity coefficient. This rheological model is essentially based on a generalized Scott-Blair body with a time-dependent viscosity coefficient. Motivated by this study, in this note we suggest a different generalization of the Scott-Blair model based on the application of Caputo-type fractional derivatives of a function with respect to another function. This new mathematical approach can be useful in viscoelasticity and diffusion processes in order to model systems with time-dependent features. In this paper we also provide the general solution of the creep experiment for our improved Scott-Blair model together with some explicit examples and illuminating plots. [ABSTRACT FROM AUTHOR]

Highlights • The behavior of spliced GFRP and steel bars in normal concrete (NC) and self-consolidated concrete (SCC) are presented. • Failure modes of spliced GFRP and steel bars in NC and SCC are presented and discussed. • The effect of splice length and section height along with the type of concrete on the bond capacity were discussed. • The accuracy of the current design provisions is assessed based on the test results. Abstract The bond behavior of reinforcing bars is one of the critical issues in the design of reinforced-concrete (RC) structures. This paper sheds light on the effect of various parameters on the bond behavior of spliced glass-fiber-reinforced-polymer (GFRP) bars in self-consolidating concrete (SCC) and normal concrete (NC). A total of 11 full-scale RC beams measuring 4300 mm in length, 250 mm in width, and 400 or 600 mm in height were constructed and tested under four-point bending up to failure. The test parameters included (1) concrete type; (2) splice length (20 db and 40 db, where db is the bar diameter); (3) beam height (400 or 600 mm); and (4) longitudinal-reinforcement type (GFRP or steel). The test results are reported and discussed. In addition, the splice-length predictions using JSCE-97, CSA S806-12, CSA S6-14, and ACI 440.1R-15 were assessed. Furthermore, a recommendation was made to improve the design equation suggested in CSA S6-14. The test results show that the SCC beams exhibited load capacity, crack pattern, failure mode, and load-deflection response similar to their NC counterparts. The bond strength of the reinforcing bars in the SCC beams was similar or slightly lower than that of the NC beams. Moreover, the JSCE-97 provisions gave the highest safety margin. [ABSTRACT FROM AUTHOR]

Highlights • Tensile test results on conditioned GFRP bars were collected from the literature. • Bars were subjected to contemporary sustained stress and aggressive environment. • The sustained stress had a limited influence on the bar residual tensile strength. • Characteristic and design reduction factors for long-term behavior were calibrated. Abstract Glass fiber reinforced polymer (GFRP) bars can be employed as an alternative to steel bars for internal reinforcement of concrete elements. Although GFRP bars have been used to reinforce concrete for the last two decades, their long-term behavior is still an open issue. The tensile strength of bars subjected to aggressive exposure conditions has been investigated by different authors. However, clear and reliable indications on the bar residual strength are still lacking. Furthermore, the effect of sustained stress on the bar tensile strength is not completely clear and severe limitations on the stress level attained by the bar are imposed by available design guidelines. In this paper, the effect of sustained stress on GFRP bars exposed to different environmental conditions, namely air, alkaline environments, deionized water, and salt solutions, is studied by analyzing a database comprising 127 GFRP bar tensile tests collected from the literature. The results are analyzed and discussed to investigate the effect of sustained stress on the tensile strength of GFRP bars and to calibrate characteristic and design values for tensile strength long-term reduction factors. [ABSTRACT FROM AUTHOR]

Highlights • Recycled glass fiber reinforced polymer (GFRP) was used as reinforcement in the mortar. • Fiber-like GFRP shapes replaced fine aggregate in mortar. • Aspect ratios were compared in terms of toughness and strength. • Volumetric percentages of 1 and 3 showed the most successful results. Abstract Glass fiber reinforced polymer (GFRP) panels from retired wind turbines were recycled into discrete structural elements in mortar. Based on 7-day testing, out of Powder, Small, Medium, and Large fiber size groups, the Large group was identified as the optimum size due to the highest modulus of rupture (MR) and toughness index (TI) while maintaining comparable compressive strength (f’ c) relative to control. Implementing the Large group at 1, 3, and 5% replacement of sand resulted in 5, 25 and 35% increases in 90-day MR with significant increases in TI and minimal reductions in f’ c and no expansion due to alkali-silica reaction. [ABSTRACT FROM AUTHOR]

Abstract To develop a composite that also functions as an impact sensor, a piezoelectric glass fiber-reinforced polymer (GFRP) was fabricated using a mixture of Pb(Ni 1/3 Nb 2/3)O 3 -Pb(Zr, Ti)O 3 (PNN-PZT) piezoelectric powder and epoxy as a smart resin. Prepreg sheets were prepared by impregnating glass fiber with the smart resin and the specimen was fabricated by autoclave molding. To utilize the composite as a sensor for detecting impacts, electrodes were added to the two sides of the composite, and the specimen was poled briefly at room temperature to activate its piezoelectric properties. A calibrated and instrumented impact test was conducted to demonstrate impact response and measure the sensitivity; a signal processing device was developed that matched the high impedance of the piezoelectric GFRP. The sensitivity of the piezoelectric GFRP sensor was measured by comparing the impact force signals from an impact hammer with the corresponding output voltage from the sensor. The threshold for detection of impacts was below 15 N. The tests confirmed that the piezoelectric GFRP itself could be utilized as an impact sensor. [ABSTRACT FROM AUTHOR]

Abstract Fiber reinforced polymer (FRP) composites are commonly used in the chemical industry for storage tanks and pipelines, since most metallic alloys suffer from corrosion and result in costly maintenance and safety hazards. E-glass fiber is commonly used because of its low cost, but it is extremely susceptible to rapid degradation in low-pH environments. C-glass is an acid-resistant substitute, and while not as durable as carbon, it is much cheaper. Nevertheless, durable fibers are not the only key aspect of designing corrosion-resistant composites, as various degradation mechanisms must be considered. In this study, plain-weave laminates of C-glass and amine-cured epoxy are exposed to water and sulfuric acid solutions, and the relationship between diffusion kinetics and strength-loss is discussed. Results show that both solutions attack the fiber surface to some degree, but more importantly sulfuric acid increases the saturation uptake of water in the material, causing high swelling stresses that significantly reduce mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract This paper presents experimental and numerical investigations about the effects of thermal cycles on adhesively bonded joints between pultruded glass fibre reinforced polymer – unsaturated polyester (GFRP) adherends used in civil engineering structural applications. Single lap bonded joints were produced with two commercial polymeric adhesives – epoxy (EP) and polyurethane (PUR) – and exposed to a mild (Mediterranean) range of thermal variations (−5 °C–40 °C) for up to 350 cycles in a dry condition. The mechanical performance of the adhesively bonded joints was assessed by means of single lap shear tests. Regardless of the inherent differences between both adhesives, results obtained show that the global effect of thermal cycles on the load vs. displacement response of EP-GFRP and PUR-GFRP joints was similar. For both adhesives, thermal cycles caused considerable reduction of joint stiffness and strength, with maximum reductions of 18% and 22% for EP-GFRP joints, respectively, and 19% and 11% for PUR-GFRP joints. The degradation of performance was influenced by post-curing effects, more relevant in the PUR adhesive. Before exposure to thermal cycles, both types of specimens exhibited similar failure mechanisms, which generally (80–90% of cases) involved light fibre tear and fibre tear modes, attesting the effectiveness of the adhesion process and material compatibility. Exposure to thermal cycles did not influence the failure modes of the PUR-GFRP joints; however, EP-GFRP joints became more prone to adhesive failure after being subjected to thermal cycles. Three-dimensional finite element models were used to estimate the magnitude of the internal stresses developed during the thermal cycles. For both types of bonded joints, the numerical results showed a relatively low magnitude of both shear and normal stresses developed due to the mismatch of the coefficients of thermal expansion (CTE) of the adherends and the adhesives. Overall, the results obtained indicate that thermal cycles degrade bonded joints between pultruded GFRP adherends and this degradation seems to be due mostly to detrimental effects on the constituent materials, namely the adhesives; however, for the conditions used in this study, this degradation seems to be compatible with the structural use of this type of joints in civil infrastructure. [ABSTRACT FROM AUTHOR]

Abstract The aim of this work to investigate the effect of glass fiber (GF) on the thermal properties of sugar palm (SP)/thermoplastic polyurethane (TPU) hybrid composites. Sugar palm/glass fiber hybrid composites at the different weight fraction of 0/40, 10/30, 20/20 and 30/10 were prepared by using melt-mixing compounding followed by hot pressing machine. Thermal properties of hybrid composites carried out by using Dynamic mechanical analyzer (DMA) and thermo-gravimetric analyzer (TGA). The storage modulus (E′), loss modulus (E″) and damping factor (tan δ) were evaluated as a function of different relative sugar palm/glass fiber weight fraction. Also, the peak height was investigated for tan δ curves. At higher glass fiber loading exhibited the highest storage and loss modulus while the lowest damping factor was observed for higher sugar palm fiber loading. Thermogravimetric analysis (TGA) demonstrated that the amount of residue decreased as the glass fiber loading decreased. Overall, the hybridization of glass fiber with sugar palm/TPU composites enhances the thermal properties of the hybrid composites for automotive applications. [ABSTRACT FROM AUTHOR]

Abstract Glued-in-rods (GiR) represent a class of joints being used in timber engineering that are mostly used to transfer axial loads in structural members with Glass Fibre Reinforced Polymers (G-FRP) increasingly being considered as rod material in substitution for the usually considered metallic rods. The primary objective of the research presented herein was to apply a probabilistic capacity prediction method to timber joints with G-FRP GiR. Necessary secondary objectives were to mechanically characterise the involved components (adhesive, rods, and timber) and to numerically investigate the stress state inside the tested joints. The methodology shall be applied to a recently reported in literature Zhu et al. (2017) that was specific in two ways: firstly, G-FRP rods were bonded into both ends of the timber block with both ends being tested to failure—a deviation from common practice; and secondly, as opposed to most previous studies exhibiting stiff adhesives, a ductile Polyurethane with markedly non-linear behaviour was used. All material characterisation was performed with methods that can be reproduced by any standard laboratory equipment, to provide parameters for the subsequent numerical analyses. Based thereupon, a probabilistic method was used and provided reasonably accurate predictions of the joint capacities of 25 different geometrical GiR configurations. The probabilistic method was extended for realistic estimations of the experimental capacity scattering in form of upper and lower percentiles. [ABSTRACT FROM AUTHOR]

Abstract This paper reports on an epoxy matrix for glass fibre reinforced polymers equipped with low cost optical fibre sensors for the early detection of water diffusion, with devised applications in the oil and gas industry. Novel evanescent wave optical fibre sensors were designed, fabricated and embedded in epoxy resin samples. The tips of the optical fibre sensors were coated with a silver layer to work in reflection, so that they could be used as probes. Accelerated diffusion tests were performed: the samples were exposed to simulated sea water at 80 °C for up to 148 h. The water diffusion resulted in a remarkable change of the reflected signal from the sensors, a result that was then confirmed through gravimetric measurements and a theoretical prediction, according to Fick's diffusion law. The results corroborate the feasibility of "sensitive" fibre reinforced polymers in harsh environments and that chemicals diffusion in these materials can be remotely and continuously monitored by means of the presented sensing system. Highlights • Epoxy matrix for glass fibre reinforced polymers. • Low cost optical fibre sensors for the early detection of water diffusion. • Accelerated diffusion tests. • Water diffusion resulted in a remarkable change of the reflected signal from the sensors. [ABSTRACT FROM AUTHOR]

Concrete-filled fiber-reinforced polymer tube (CFFT) columns have demonstrated superior advantages on mechanical behavior and ease of construction during the past few decades. The fiber-reinforced polymer (FRP) tube not only improves the mechanical properties of the concrete core by confinement, but also provides a protection layer for the concrete against the outer corrosive environment. However, one obstacle hindering the greater acceptance of the FRP composite as a conventional construction material in civil engineering applications is the susceptibility of FRP to complex, severe environmental exposure. The purpose of this study is to investigate the durability of CFFT cylinders with glass fiber reinforced polymer (GFRP) tubes under exposure to combined freeze/thaw, heating/cooling, and wet/dry cycles. The effects of combined sustained load and environmental conditions were also investigated during this study. Compression and hoop tensile tests were carried out on both conditioned and controlled specimens. In addition, scanning electron microscopy (SEM) and differential-scanning calorimetry (DSC) tests were used to characterize the aging effect on physical and thermal properties of FRP material. Test results showed that more pronounced degradation occurred on the ultimate strain than on the ultimate strength. The sustained load had a negative effect on CFFT cylinders by creating more microcracks in the GFRP tube. [ABSTRACT FROM AUTHOR]

Effective shear transfer at the interface of glass fibre reinforced polymer (GFRP) and concrete sections is crucial to achieve structural integrity of the composite panel. This study proposed a shear connector consisting of circular hollow sections (CHS) to enhance shear transfer between concrete and GFRP. Push-out and three-point bending tests were conducted to evaluate the static response of the proposed connectors compared to the adhesive bonding. The results showed that GFRP-concrete composite section using proposed shear connectors achieved partial composite action and non-linear behavior could be observed before the GFRP section failed in shear along the fibre direction at the contact zone. The mechanical properties of the connectors can affect the bearing capacity and stiffness of the composite structure. Numerical simulation using finite element (FE) method was able to capture the overall mechanical response with respect to loading force and deformation. Using a validated FE modelling technique, a comprehensive parametric study was carried out. Results showed that flange thickness, fibre orientation and shear connector arrangement can significantly affect the flexural capacity of GFRP-concrete composite. [ABSTRACT FROM AUTHOR]

Fiber reinforced polymer (FRP) rebars have recently been gaining popularity in the construction industry all around the world while steel rebars have been widely used so far. FRP bars, which have higher tensile strength compared to steel rebars with the same nominal diameter under normal conditions, are composed of resin matrix and fibers. In this study, mechanical and bonding properties of glass fiber reinforced polymer (GFRP) and steel rebars subjected to elevated temperature effects were investigated throughout a correlative comparison. Axial tensile tests and pull-out tests of these materials were performed subsequent to exposing them into elevated temperature effects in the range of 23–800 °C. Severe effects on the tensile properties of bare steel bars were observed after 600 °C, while this critical limit is 300 °C for bare GFRP bars. Test results show that bond strength degradation is almost linear for both type of rebars, however, 600 °C is also the critical temperature regarding the serious deterioration on concrete. Additionally, an empirical modeling approach on the bond strength degradation of rebars at elevated temperatures was proposed and it was found that comparison results have quite promising consistency based on the modeling process. [ABSTRACT FROM AUTHOR]

Coupon test data from five pultruded GFRP profiles is used to generate longitudinal/transverse, tensile/compressive ultimate stresses, elastic moduli, minor/major Poisson's ratios and ultimate strains (some of which are not in the pultruders' design manuals). Characteristic ultimate stresses/elastic moduli are compared to design manual minimum values. The former depend on profile size/shape, whereas the latter are shape-/size-independent. Limit state design stresses are shown to be larger than permissible stress design stresses. However, most of the limit state longitudinal design elastic moduli are smaller and all of the transverse design elastic moduli are larger than the permissible stress values. [ABSTRACT FROM AUTHOR]

The temperature-dependent off-axis tensile behavior of quasi-unidirectional E-glass fabric reinforced polypropylene composites has been investigated both experimentally and constitutively in this paper. The nonlinearity in composites under off-axis loading is shown to be a combination of damage and plasticity regardless of temperature. A nonlinear constitutive model is established to predict the temperature-dependent nonlinear stress-strain curves of composites, in which the accumulation of plastic strain and evolution of damage in composites are described by the plasticity and damage theories, respectively. A full suite of temperature-dependent plastic and damage parameters in the model are determined through cyclic loading-unloading tests. [ABSTRACT FROM AUTHOR]

In order to alleviate the problem of growing construction waste and utilize the favorable material properties of fibre-reinforced polymer (FRP), a novel form of composites, FRP-recycled aggregate concrete-steel columns (FRSCs), was proposed based on hybrid FRP-concrete-steel double-skin tubular columns (DSTCs). The composite of FRSC consists an outer FRP tube and an inner steel tube with an annular area of recycled aggregate concrete (RAC) filled between both tubes. To further investigate the compressive behavior of these composites, an experiment of Glass FRP-RAC-steel tubular long columns (FRSLCs) was performed subjected to monotonic axial compression. Three parameters were designed in the test, which are the recycled coarse aggregate (RCA) replacement ratio, the slenderness ratio and the cross-section loading method. The influence of these parameters was analyzed on the bearing capacity, lateral deflection performance and the load-strain relationship of FRSLCs. The test results show that FRSLCs have good bearing capacity and excellent ductility. Two models for DSTCs were transformed to apply in FRSLCs, which has found that Lu’s model (2013) is appropriate to predict the ultimate bearing capacity of FRSLCs under the whole area loading. [ABSTRACT FROM AUTHOR]

Repair of structural elements with bonded fiber reinforced polymers (FRPs) is widely used in many engineering applications. Within the strengthening of civil structures, failure usually occurs due to FRP debonding by in-plane shear mode fracture. In this work, mode II fracture behavior of concrete specimens, reinforced with pultruded FRP, was investigated by the authors. Shear tests were performed by using both conventional equipment and a non-contact optical technique, Digital Image Correlation (DIC). Starting from the experimental data, the evaluation of the J-integral and of specimens' fracture toughness was carried out. Subsequently, a cohesive law was associated to the J-integral and thus identified by comparison with experimental data, by means of the theoretical approach proposed by Rice. The proposed cohesive zone (CZ) model can be adopted in a Finite Element (FE) code for simulating the debonding failure in composite structures. [ABSTRACT FROM AUTHOR]

Recently, in responding to the resource shortage and steel corrosion, the combination of seawater and sea sand concrete (SWSSC) and fibre reinforced polymer (FRP) bars was proposed to replace the traditional reinforced concrete structures in civil engineering. For FRP bars in the real service condition of concrete structure, the synergistic effect of sustained load and corrosion environment needs to be considered. This paper presents an investigation on the durability of basalt- and glass-fibre reinforced polymer bars exposed to a SWSSC environment under different sustained stress levels. Scanning electron microscopy was employed to study the degradation mechanism of FRP bars. [ABSTRACT FROM AUTHOR]

This paper aims to present a methodology to predict the anisotropic and non-linear behaviour of glass fibre reinforced plastics using finite element methods. A material model is implemented in order to remedy the need of multiple material definitions, and to control the local plastic behaviour as a function of the fibre orientation. Injection moulding simulations traditionally provide second order orientation tensors, which are considered together with a homogenization scheme to compute local material properties. However, in the present study, fourth order tensors are used in combination with traditional methods to provide more accurate material properties. The elastic and plastic response of the material model is optimized to fit experimental test data, until simulations and experiments overlap. The proposed material model can support design engineers in making more informed decisions, allowing them to create smarter products without the need of excessive safety factors, leading to reduced component weight and environmental impact. [ABSTRACT FROM AUTHOR]

Using seawater and recycled concrete aggregate (RCA) in a concrete mix is potentially advantageous from a sustainability perspective. However, the high chloride levels expected in such a case demands the use of non-corrosive reinforcement in lieu of normal black steel to avoid corrosion problems. Glass fiber reinforced polymer (GFRP) is considered promising as an alternative reinforcement owing to its corrosion resistance and acceptable mechanical properties that minimize maintenance and repairs and extend service life. However, the relatively high initial cost of GFRP bars may mitigate its potential use. To account for these factors, a life cycle cost analysis (LCCA) has been conducted to establish the relative cost savings of structural concrete combining seawater, RCA, and GFRP reinforcement in high-rise buildings compared with a traditional concrete mix and other reinforcement materials, such as black steel and stainless steel. The proposed combination of seawater, RCA, and GFRP in structural concrete was found to achieve cost savings over a 20-year period following initial construction. The life cycle cost (LCC) obtained for the proposed combination was approximately 50% less than that of the conventional counterpart (i.e. concrete with freshwater, natural aggregates, and black steel) based on a 100-year study period. The use of stainless-steel reinforcement to enhance durability was also found to be potentially advantageous but less cost-effective than using GFRP. The LCC of stainless-steel reinforced concrete was estimated to be 15% lower than that of the traditional steel-reinforced counterpart, with a payback period of 50 years. Results were found to be highly sensitive to the assumed discount rate and construction costs. The proposed combination achieved cost savings only with a real discount rate ( r ) of 5.9% or higher. Likewise, using stainless-steel reinforcement was found cost-effective at r ⩽ 1.35 % and nominal construction costs exceeding 85% of the material cost. The differences in concrete mixture cost, however, appeared to have insignificant influence on the ultimate LCCA results compared to those obtained from altering the reinforcement material. [ABSTRACT FROM AUTHOR]

The combined effect of sustained loading and moist seawater-contaminated concrete environment on the durability performance of two types of glass fiber-reinforced polymer (GFRP) bars was investigated. A sustained load of 25% of the ultimate tensile strength was applied to concrete-encased GFRP bars immersed in tap water for up to 15 months at temperatures of 20, 40, and 60 °C. None of the loaded specimens conditioned at 20 °C were creep-ruptured during conditioning. In contrast, many bars were creep-ruptured during conditioning at the higher temperatures of 40 and 60 °C. At a conditioning temperature of 20 °C, Type I and II GFRP bars retained 84 and 70% of their original tensile strength after 15 months of conditioning under a sustained load. At the higher temperature of 60 °C, trivial tensile strength retentions of 15 and 12% were recorded for Type I and Type II GFRP bars, respectively, after 15 months of conditioning under a sustained load. A comparative analysis between results of loaded and unloaded specimens demonstrated the detrimental effect of the presence of a sustained load during conditioning on the tensile strength retention of GFRP bars. The detrimental effect of the sustained load was intensified at the higher temperatures. The accelerated aging test data along with Arrhenius concept were employed to develop a durability design model that can predict the tensile strength retention of both types of GFRP bars in moist seawater-contaminated concrete. [ABSTRACT FROM AUTHOR]

In picture frame testing, influences of the clamping and fiber misalignment have been already studied for dry fabrics. Due to the presence of solid regions near the clamps in picture frame tests of thermoplastic continuous fiber reinforced composites at processing conditions, the influences of the clamping are amplified. This study examines the effects of the presence of unmelted material regions near the clamps on picture frame tests both analytically and experimentally for a polypropylene glass fiber composite, using a custom built picture frame which allows for an inward and outward repositioning of the clamps. The results show the presence of major strains in the composite samples when unmelted material is present near the clamps which can lead to forces up to 6.5 times higher than for supposedly ideal kinematic conditions. An overadjustment of the clamps by an up to 0.5% of the joint distance of the picture frame to allow for a minor amount of compression in the composite has shown favorable results which are comparable to correctly corrected measurements. This setting is hence recommended to generate more reliable and comparable results for intra play shear properties of thermoplastic composites. Further research is necessary to additionally account for fiber misalignment. [ABSTRACT FROM AUTHOR]

A comprehensive fatigue characterization of Glass Fiber Reinforced Plastic (GFRP) and composite sandwich panels under random ocean current loadings is presented in this paper. Two sources of randomness in ocean currents were considered in the calculation of fatigue load: one is turbulence in the ocean currents and the other is the wake flow behind the support structure of the turbine. Calculated random loading was applied to conduct fatigue tests on GFRP and composite sandwich coupons using a materials testing machine. Fatigue life of GFRP coupons followed a power function pattern with respect to number of spectrum passes, while that of sandwich panels was linear in semi-log scale. The failure modes, S-N curve, and the constant life diagram under constant amplitude test are also discussed. [ABSTRACT FROM AUTHOR]

this paper analyses the numerical and experimental results to evaluate the dynamic properties of pultruded GFRP (Glass-Fiber Reinforced Polymers) buckled columns. The profiles are made of glass fiber reinforcement and thermosetting vinylester matrix with thin-walled open or closed cross section. The buckling phenomena of the column with fixed ends were evaluated with a non-destructive method based on experimental modal data through dynamic identification procedure. Numerical analysis has been carried out through Finite Element models calibrated considering two consecutive stages that involve the local and global scale: i) parametric natural frequencies analysis to model the different cross sections taking into account the sti f fness of the rotational constraint between the wall segments of the thin walled pultruded profiles; ii) buckling analysis to identify the inaccuracies in the specimen or in the experimental apparatus through global flexural displacements which increase continuously with the axial load. Experimental, theoretical and numerical results were compared in order to know the wall segment effects of GFRP columns in free vibration field when affected by buckling phenomena. The results allow to investigate the significant role that the manufacturing imperfections of pultruded material play in the structural performance of GFRP buckled columns. [ABSTRACT FROM AUTHOR]

This paper describes an experimental technique based on dynamic mechanical analysis (DMA) that is shown to be useful in separating nonlinear viscoelastic effects from the characterization of irreversible stress-induced damage responsible for stiffness reduction in fiber-reinforced polymer composites. In this work, we characterize the damage evolution of polypropylene (PP) reinforced with long, discontinuous glass fibers (GF) produced by the Direct Long-Fiber Thermoplastic/Compression Molding (D-LFT/CM) process. The experimental technique is comprised of three phases: 1) dynamic stabilization at low load to measure the time-dependent storage and loss moduli, followed by 2) a frequency sweep to provide rate-dependent viscoelastic properties and 3) a quasi-static application of a peak load. These three phases are repeated with the peak load of Phase 3 increased in each iteration. Experimental results for D-LFT/CM PP/GF30 presented here show a direct correlation between peak load and the irreversible stiffness reduction. Furthermore, the stabilization phase following peak load application is shown to lead to a stiffness recovery of up to 40% due to nonlinear viscoelastic recovery. [ABSTRACT FROM AUTHOR]

The present paper aims at investigating the influence of the mortar joints on the FRP-masonry debonding process and providing some insights on the reliability of experimental tests carried out on single bricks and theoretical formulas available to predict the debonding force. Masonry panels were constructed using two types of bricks and two types of mortars with significantly different properties. The masonry specimens were strengthened using glass fiber reinforced polymers and the debonding force was evaluated by a single-lap push-pull set-up. The obtained debonding forces were compared to those obtained by applying the same reinforcements to single bricks and calculated by applying theoretical formulas. The results of the study point out that neglecting the presence of the mortar joints and taking into account only brick mechanical properties, thus neglecting their surface and microstructural properties, may lead to significant inaccuracies in the estimation of the debonding force. [ABSTRACT FROM AUTHOR]

The effect of electrical stress on glass fiber reinforced polymer under wet condition has been investigated in the present study. A specially designed and fabricated test setup was used through which the current passing through the GFRP rod during the test was recorded. Based on the changes in morphology of GFRP rod surface and development trend of current, the degradation process of GFRP rod caused by electrical stress under wet condition was divided into four consecutive stages, namely degradation inception stage, hydrolysis stage, carbonization stage and breakdown stage. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and X-ray Photoelectron Spectroscopy (XPS) analyses were employed to provide the physical and chemical properties of GFRP at different stages. The results showed that the degradation process of GFRP caused by electrical stress under wet condition progressively developed in the form of degraded channel, in which the epoxy resin matrix deteriorated significantly. The occurrences of hydrolysis, oxidation, pyrolysis and carbonization of epoxy resin matrix could be observed sequentially in the degradation process of GFRP during the test. With the development of the degradation process of GFRP, the content of epoxy resin matrix continued to decrease and the relative content of highly oxidized carbons (C-O, C=O and O-C=O) in epoxy resin matrix on GFRP surface increased before the carbonization process and then decreased in the carbonization process. The present study is helpful for better understanding of the electrical performance of GFRP used in high voltage composite insulator as well as in other electrical applications. [ABSTRACT FROM AUTHOR]

The corrugated fiberboard structure is widely used in manufacturing industries as a light-weight high-stiffness structure board and other applications. However, the strength characteristic of a single face fiberboard based on glass fiber reinforced plastic is not well understood. The objective of this study is to propose and estimate the strength of single face glass fiber board using a proposed tensile test method. As a result, a practical fixture method was proposed and the stress-strain relationship was investigated. [ABSTRACT FROM AUTHOR]

The lack of scaling mechanism on glass fiber reinforced plastics (GFRP) pipeline in oilfield environment causes the common misunderstanding of scaling mechanism in oil and gas industry, which in turn results in inappropriate selection of pipeline and unreasonable operation parameters. In this paper, the scale experiments for different surface roughness of GFRP and 13Cr stainless steel were carried out to obtain the corresponding mass gain in real oilfield conditions. The laws of temperature, surface roughness, time, contact angle and surface free energy of pipeline on scaling mechanism were analyzed from the macroscopic and microscopic view. Water quality and scale analysis indicated that the oil field was prone to form calcium carbonate and a small amount of magnesium carbonate mixed scale. GFRP scale deposition experiments revealed that the fouling would increase as time going and temperature rising and there existed a critical temperature at which the scale reached the highest scaling rate. GFRP hydrolysis experiments showed that the slight hydrolysis of GFRP caused by ions erosion would increase as temperature rising and scale deposition process would be adequately affected under high temperature. The surface free energy of 13Cr and GFRP with different roughness would be calculated to study the effects of contact angle and surface free energy on scale deposition. The results indicated that the mass gain had no liner relation with the surface roughness but would increase with the decreasing of contact angle and surface free energy on same material surface. It was also identified that there was a minimum fouling surface roughness, that is, the scale deposition is minimal at this roughness. The microscopic tests indicated that time could have a significant influence on scale grain size, consequently causing larger yield stress or hardness of scale grain formed early in the scale inner layer. GFRP shows better performance when reducing scale formation at the initial period. These results laid the theoretical foundation for the determination of fluid temperature, surface roughness, surface modification and the program of scale removal and inhibition. [ABSTRACT FROM AUTHOR]