Glass Fiber Reinforced Polymer Research Articles

Experimental and numerical investigation of the flexural behavior of one–way RC slabs strengthened with near–surface mounted and externally bonded systems

This study investigated the flexural performance of one-way reinforced concrete (RC) slabs strengthened with two distinct strengthening systems: near–surface mounted (NSM) bars and externally bonded (EB) carbon fiber-reinforced polymer (FRP) strips. The NSM bars comprised four types: carbon FRP (CFRP), basalt FRP (BFRP), glass FRP (GFRP), and stainless–steel (SS) bars. The NSM–strengthened slabs showcased substantial enhancements in yield and ultimate load capacity, ranging from 20 % to 55 % and 59–123 %, respectively. In comparison, those strengthened with EB–CFRP strips displayed increases from 46 % to 107 % and 45–177 %, respectively, depending on the axial stiffness ratio of the strengthening system provided. Furthermore, the slabs reinforced with NSM–BFRP bars showed an 11–25 % improvement in their ductility indices. In contrast, the slabs reinforced with EB experienced a decrease in ductility ranging from 38 % to 50 %. This reduction was attributed to the differences in the modes of failure observed in both strengthening systems. The rupture of the NSM–FRP bars and the strain readings associated at the end of testing confirmed that the tensile strength of the NSM–FRP bars was fully exploited whereas the EB–CFRP strips utilized only 29–36 % of their ultimate tensile strain due to debonding. A finite element (FE) model was formulated to anticipate the behavior of the strengthened slabs. A strong correlation between the numerical predictions and the experimental outcomes was observed. The experimental–to–numerical ratios of the ultimate load ranged between 1.0 and 1.08 for the NSM–strengthened slabs and between 0.98 and 1.38 for the EB–strengthened slabs. This validated the FE models’ ability to capture the nonlinear performance of the strengthened slabs.

Transforming GFRP into silicon carbide

Rice University researchers develop an energy-efficient method to upcycle glass fiber-reinforced plastic (GFRP).

Strengthening of slender webs of steel plate girders using FRP composites

Web buckling of steel plate girders creates an undesirable failure mode as it can limit the ultimate load capacity of plate girders. This paper presents details of an experimental investigation aimed at strengthening slender end panels of steel plate girders using three different types of fibre-reinforced polymer (FRP) composite materials (glass-fibre-reinforced polymer (GFRP) pultruded section stiffeners and woven carbon-fibre-reinforced polymer (CFRP) and GFRP fabrics). The plate girders were fabricated using non-rigid end posts and were tested in three-point bending. The test results showed an increase of up to 54% in the ultimate strength of the FRP-strengthened end panels compared with the non-strengthened control panel, which was the result of increased out-of-plane stiffness of the web. A breakdown of the bond between the steel and the FRP fabric occurred in the end panels strengthened with CFRP and GFRP fabrics, while no bond breakdown of the pultruded sections was observed at the ultimate load. Analytical methods proposed by some of the design codes underestimated the critical buckling load and overestimated the ultimate load of the non-strengthened end panel.

Five year operation of a cooler Dewar assembly for infrared scanner on board GCOM-C

Global Change Observation Mission – Climate (GCOM-C) “Shikisai”, a satellite designed to observe global climate change, was launched from Tanegashima Space Center on December 23, 2017 by an H2A launch vehicle. The Second-generation GLobal Imager (SGLI) on GCOM-C is a multi-channel optical sensor for observing aerosols, vegetation, and temperatures. Through long-term monitoring, our understanding of climate change mechanisms will be improved. The infrared scanner (IRS) on SGLI has a Thermal InfraRed (TIR) detector requested to operate at 55 K. A Cooler Dewar Assembly (CDA) developed to keep the detector at 55 K is designed to minimize the heat load for the small cooler. The detector is supported on a thermal isolator made of Glass FRP and is thermally connected to the cooler by flexible thermal link. The Cooler Control Electronics (CCE) uses a heater to compensate heat load fluctuations, thereby maintaining temperature and stability. The heater power decreases gradually during five years, consequently decreasing the cooling power. Despite that cooler degradation, the detector temperature has been maintained at 55 ± 0.1 K for 5 years in orbit and has continued operating with 36 W power consumption. This paper describes the cooler Dewar Assembly and its five years of operation in orbit.

Implementing surface treatment and adhesive variations for bonded joints between composite gfrp and aluminum at 200 °C

Bonding dissimilar materials, specifically Glass Fiber Reinforced Polymer (GFRP) and Aluminum 6061 T651, at elevated temperatures, such as in fire accidents is challenging, where structural integrity and reliability are critical. We studied how surface roughness treatment affects the joint strength of three common adhesives in aircraft (Click Bond CB394-43, Loctite A9396, A9394) at 200 °C. The GFRP, composed of Gurit Prime 37 epoxy resin and E-Glass 7781 fibers produced through vacuum infusion with dimensions following ASTM D5868 standards, was lap shear tested with 2 mm/s stroke. Findings showed a substantial enhancement in joint strength due to surface treatment, sanding with 100-grid sandpaper for 20 seconds in parallel with the fiber direction, for all adhesives. A9396, A9394, and CB394-43 exhibited remarkable improvements of 1091.67 %, 45.92 %, and 30.09 %, respectively. The strain at break showed significant increases of 51.61 %, 121.95 %, and 100 %, respectively. Both surface-treated and untreated A9394 samples showed the highest strength among the adhesives. A9396 exhibited lower strength than CB394-43 without surface treatment, but it outperformed when surface-treated, highlighting its response to surface modification. Adhesive viscosity influences penetration on material surfaces, with A9396 being stiffer than the other adhesives. The analysis of ISO 4287 Ra values revealed that surface treatment led to increased roughness on the Aluminum surface while reducing roughness on the GFRP surface. These results offer valuable insights for optimizing GFRP-Aluminum bonding under elevated temperature conditions. Adjusting surface roughness significantly improves the interaction between Aluminum and GFRP with adhesives, resulting in enhanced joint strength. This knowledge can be applied in various engineering applications, particularly in industries where the performance and reliability of bonded joints are critical under high-temperature environments

Strengthening of Laminated Veneer Lumber Slabs with Fiber-Reinforced Polymer Sheets—Preliminary Study

Analyzing the feasibility of reinforcing new and existing wooden structures is a valid problem, being the subject of numerous scientific papers. The paper presents the preliminary results of a study on reinforcing Laminated Veneer Lumber (LVL) panels with composite materials bonded to exterior surfaces using epoxy resin. Glass-Fiber-Reinforced Polymer (GFRP) sheets, Carbon-Fiber-Reinforced Polymer (CFRP) sheets, and Ultra-High-Modulus (UHM) CFRP sheets were used as reinforcement. The variables in the analysis were the type of reinforcement and the number of reinforcement layers. The tests were carried out on small samples (45 × 45 × 900 mm) subjected to the so-called four-point bending test. Reinforcement positively affected the mechanical properties of composite section. The highest increases in load bearing were 37 and 48% for two layers of GFRP and CFRP, respectively. The bending stiffness increased up to 53 and 62% for two layers of CFRP and UHM CFRP, respectively. There was a change in failure mode from cracking in the tension zone for unreinforced beams to veneer shear in the support zone (for CFRP and GFRP sheets) and sheet rupture (UHM CFRP). Good agreement was obtained for estimating bending stiffness with the presented numerical and mathematical model; the relative error was up to 6% for CFRP and GFRP and up to 20% for UHM CFRP. This preliminary study proved the effectiveness of combining LVL with FRP sheets and indicated their weak spots, which should be further analyzed to improve their competitiveness against the traditional structures. The key limitation was the shear strength of LVL.

Flexural behaviour of reinforced concrete beams reinforced with Glass Fibre Reinforced Polymer (GFRP) bars: experimental and analytical study

Flexural behaviour of reinforced concrete beams reinforced with Glass Fibre Reinforced Polymer (GFRP) bars: experimental and analytical study

Lap splice assessment of GFRP rebars in reinforced concrete beams under flexure

To increase the knowledge and experience gained from the existing literature regarding the bond behavior of glass fiber-reinforced polymer (GFRP) rebars, a total of sixteen full-scale GFRP-reinforced concrete beams were subjected to a four-point bending test. The GFRP reinforcement comprised a single M16 (No.5) GFRP sand-coated bar without confinement reinforcement in the constant moment region. The research parameters encompassed three different lap-spliced lengths (i.e., 40-, 60- and 80-db) and two distinct concrete clear covers (i.e., 19 mm and 38 mm) to assess their impact on bond strength and failure modes. Strain gauges along the GFRP rebar and small potentiometers positioned at the end of the splice within the constant moment zone allowed detailed measurements. Rebar slippage in lap-spliced specimens was observed to have a limited impact on bond stress transfer capacity and member flexural stiffness until reaching maximum slippage. Concrete cover significantly influenced the behavior of lap-spliced GFRP-RC beams, with 38 mm-cc specimens exhibiting an average 21% higher capacity compared to 19 mm-cc specimens. The ACI expression exhibited an average overestimation of 24% for 19 mm-cc specimens, whereas for 38 mm-cc specimens, it offered a more accurate estimation, with only a 10% over-prediction. However, the computed lap splice length to achieve the required tensile stress was reduced from the one required by ACI due to extra factors implemented in the development length equation. This aligns with prior research findings that identified unconservative values of bond stress when employing the ACI provisions for specific combinations of parameters, highlighting the necessity for refinements in predictive models.

Fire resistance of square concrete columns reinforced with GFRP bars, experimental and numerical investigation

Glass Fiber Reinforced Polymer (GFRP) materials have proven its efficiency in reinforcing concrete elements. The performance of Glass reinforced concrete columns (GRC columns) under axial loads have been studied well experimentally and numerically, While there are a very limited studies about the behavior of reinforced concrete GRC columns when exposed to fire. The weak performance of GFRP bars under fire compared to steel gave a warning about ignoring the fire behavior of GRC columns in fields. The fire performance of square GRC columns has been investigated experimentally and numerically in this study. The experimental program was done by testing nine GRC columns under design fire curve. All columns were tested under constant load during fire. Fire temperature was controlled to follow the design fire curve. Different parameters were investigated in this research; applied load ratio, concrete cover, and column configurations on the fire performance of GRC columns. Fire resistance (FR) of all tested columns were recorded and some recommendations about the FR of GRC columns were developed. The numerical study was conducted using the nonlinear finite element software. 3D-model using ABAQUS program was calibrated to reach the best simulation of GRC columns exposed to design or standard fire curve. The numerical study was done to extend the investigation of the experimental program. The influence of the various parameters have been examined to govern the fire performance of GRC columns. The experimental and numerical studies revealed that the fire resistance of GRC columns is highly affected by the applied load during fire. The difference between FR of GRC columns compared to steel-RC columns (SRC columns) was significant at eccentricity to width ratio greater than or equal to 0.2 and at higher applied load ratios. Spalling has a significant influence on the fire resistance and modes of failure of GRC columns.

Wall-frame interactive behavior in GFRP-reinforced steel plate shear walls with circular cutout openings

The present study investigates the effect of glass fiber reinforced polymers (GFRPs) on the nonlinear and energy dissipation behavior characteristics of steel plate shear walls (SPSWs) with a single circular cutout opening using the finite element method. In the study, the effect of the opening features (diameter and location), geometrical properties of the SPSW systems (aspect ratio and height) and properties of fiber laminates (number of layers and orientation angle) on the FRP-wall-frame interactive behavior is investigated. The results show that the introduction of opening does affect the distribution of stresses across the wall. The use of an adequate amount of FRPs can successfully compensate the impact of the opening on the system strength and energy dissipation capacity. The use of fibers does not change the system initial stiffness significantly, while it reduces the ductility to some extent. There is an interaction effect between FRPs, infill wall and frame, and the use of FRPs results in a better distribution of stresses across the perforated wall area at the ultimate state, although it causes a delay in the onset of wall yielding. The presence of opening in the infill wall of different SPSWs, especially in taller multi-story cases, improves the system ductility. Finally, a procedure is presented for design of FRP-reinforced perforated SPSWs and the accuracy of the proposed equations is compared with the finite element results.

Effect of Rebar Harsh Storage Conditions on the Flexural Behavior of Glass FRP Concrete

Nowadays, fiber-reinforced polymer (FRP) has become a widely accepted alternative reinforcement to steel bars in concrete members due to its many sustainability traits, as represented by its high strength-to-weight ratio, corrosion resistance, non-conductive properties, and electromagnet neutrality. However, FRP bar exposure for an extended period of time to harsh environmental conditions and chemicals can have an adverse effect on their mechanical properties. In this investigation, glass FRP bars were exposed to indoor controlled temperature, outdoor direct sunlight, outdoor shade, seawater, and alkaline solution for six months prior to using them as reinforcement in concrete flexural members. This research involves the fabrication and testing of five pairs of 3 m-long concrete beams with 200 mm by 300 mm cross-sections embedded in the tension zone with the exposed GFRP bars. The 10 beams were instrumented with strain gauges and tested following a four-point loading scheme using a hydraulic jack attached to a rigid steel frame. Crack width records from the tests showed the inferior serviceability of the beams that contained rebars stored in an outdoor environment relative to the control beams. GFRP bar exposure to an alkaline solution or outdoor direct sunlight slightly affected the cracking and ultimate moment capacities, reducing them by 5% and 3% in terms of the same parameters as the controlled indoor exposure, respectively. The influence of GFRP bar exposure to open-air shade or sunlight decreased the pre-cracking stiffness by 25% and flexural ductility by 10–20% when compared with the control specimens. The predicted ultimate flexural strength using the ACI 440 provisions gave comparable results to the experimentally obtained values. A simple mathematical equation that envelops the moment–deflection relationship for GFRP over-reinforced concrete beams and only requires information about initial cracking and ultimate flexural conditions is proposed.

Vibration analysis of bio-inspired sandwich composite beam under rotating environment based on the Internet of Things technology

Sandwich composite materials with corrugated cores are mostly used in industries like aircraft, marine construction, automobiles, and construction. Sandwich composite constructions are made for their lightweight, high strength, and high stiffness, and also the sandwich core composite structures are useful for dynamic studies. A novel design inspired by a woodpecker beak microstructure creates fillet edge and champer edge designs. This novel design motivates us to achieve the energy absorbing results starting with free vibration studies followed by rotating environment vibration studies. ASTM E1876 standards, a non-destructive approach, are used to determine the material properties of carbon fiber-polylactic acid (CF-PLA) and glass fiber reinforced polymer (GFRP), along with alternative dynamic method (ADM) for core property evaluation. The hand lay-up technique is used for fabrication and evaluated for free vibration testing with appropriate boundary conditions. Internet of Things technology has been used for analyzing vibrations of sandwich structures in rotating environment setup with 250, 500, 750, and 1000 rpm. It was observed that the fillet edge pattern has a more efficient natural frequency than the champer edge pattern. Furthermore, the parametric evaluations were performed in various ply configurations in numerical simulations for free vibration and the rotating Environment. Also, the effective results are seen in fillet core bioinspired sandwich structure that achieves efficient stiffness in both free vibration and rotational environments, despite various boundary conditions and parametric circumstances. Therefore, the fillet edge 3D printed core design with particular GFRP factsheet orientation brings out the novelty of this research.

Bond durability between steel-FRP composite bars and concrete under seawater corrosion environments

Steel fiber-reinforced polymer (FRP) composite bars (SFCBs) can enhance the damage-controllable features of reinforced concrete (RC) structures, offering a potential solution to corrosion issues in conventional RC structures. However, the durability of SFCBs bonded to concrete remains insufficiently studied. Seawater exposure experiments were conducted on SFCBs-concrete specimens with two diameters (12 and 16 mm) at different exposure times (30, 180, and 360 days) and temperatures (23, 40, and 60 °C) in this study. Subsequent pull-out tests were performed to assess long-term bonding behaviors. The results indicate that the hydrolysis of the glass FRP (GFRP) matrix is the primary cause for the reduction in shear capacity of SFCB ribs and the degradation of bond properties between SFCB and concrete. With increasing aging time and temperature, the bond strength of SFCB-concrete gradually decreases. Thicker GFRP layer SFCB-concrete specimens exhibit better bond strength retention rates. Moreover, a predictive model for the bond strength of SFCB-concrete was proposed. As per the model predictions, the bond strength retention after 10 years of seawater immersion is 50% for 12 mm diameter SFCB, while the 16 mm diameter SFCB achieves a retention of 70%. These findings will provide valuable references for the implementation of SFCB-reinforced concrete structures.

Moisture Effects on Acoustic Emission Characteristics and Damage Mechanisms of Balsa Wood Core Composite Sandwich under 4-Point Bending.

To contribute to the development of sustainable composites, this work investigates the effects of moisture on the key AE characteristics related to the damage mechanisms of a bio-based balsa wood core sandwich in 4-point bending tests, including cumulative counts, amplitude, peak frequency, and duration. Novel triple dog-bone balsa wood core sandwich specimens with different MC (moisture content) were studied by comparing microscopic observations and a proposed two-step clustering approach in AE analysis. Three MC states, i.e., dry, 50% MC, and 120% MC, are discussed. GFRP (glass-fiber-reinforced polymer) laminate skin damages were found to be predominant in most GFRP-balsa sandwich specimens, but balsa wood core damages play a more important role as MC increases. The degradation of the bending stiffness of the sandwich was proven to be faster in the first linear stage of the moisture absorption curve, while the decrease in bending strength was more pronounced at the MC saturation level. Finally, for all of the dry and wet sandwich specimens, peak frequency and duration were proven to be more helpful in identifying damages associated with the lighter bio-based balsa wood core, such as balsa core damages and skin/core debonding.

Durability assessment of GFRP bars embedded in UHP-ECCs subjected to an accelerated aging environment with sustained loading

Ultra high-performance engineered cementitious composites (UHP-ECCs) have garnered significant attention in the field of civil engineering primarily due to their exceptional tensile strain-hardening performance and excellent compressive strength. To further enhance their tensile strength, particularly in meeting the rigorous environmental and mechanical demands frequently encountered in marine environments, fiber-reinforced polymer (FRP) bars can be employed as the internal tensile reinforcement for UHP-ECCs (referred to as “FRP-UHP-ECC members”). While numerous studies have focused on the durability of FRP bars in concrete environments, the durability of FRP bars embedded within UHP-ECCs, especially with sustained loads, remains unexplored. Glass FRP bars are commonly utilized in civil engineering due to their cost-effectiveness and favorable mechanical properties. Therefore, this paper investigated the durability performance of GFRP bars made from three different matrix resins (i.e. epoxy, vinyl ester and polyester). These bars were centrally embedded in UHP-ECCs and subsequently immersed in alkaline solutions at elevated temperatures while under sustained loads. Their tensile properties over a specified period were evaluated after exposure. The test results revealed a larger degradation in polyester-based GFRP bars compared to vinyl ester-based and epoxy-based bars. In addition, GFRP bars with UHP-ECC covers exhibited less degradation than the bare bars, but this protective effect diminished under sustained loads. Scanning electron microscope (SEM) and X-ray computed tomography (CT) analysis demonstrated that the degradation of GFRP bars was primarily attributed to matrix hydrolysis, which led to a reduction in stress transfer efficiency between fibers, contributing to the tensile strength reduction in GFRP bars.

Thermo-Mechanical Characterization of Metal-Polymer Friction Stir Composite Joints-A Full Factorial Design of Experiments.

With the increasing demand for lighter, more environmentally friendly, and affordable solutions in the mobility sector, designers and engineers are actively promoting the use of innovative integral dissimilar structures. In this field, friction stir-based technologies offer unique advantages compared with conventional joining technologies, such as mechanical fastening and adhesive bonding, which recently demonstrated promising results. In this study, an aluminum alloy and a glass fiber-reinforced polymer were friction stir joined in an overlap configuration. To assess the main effects, interactions, and influence of processing parameters on the mechanical strength and processing temperature of the fabricated joints, a full factorial design study with three factors and two levels was carried out. The design of experiments resulted in statistical models with excellent fit to the experimental data, enabling a thorough understanding of the influence of rotational speed, travel speed, and tool tilt angle on dissimilar metal-to-polymer friction stir composite joints. The mechanical strength of the composite joints ranged from 1708.1 ± 45.5 N to 3414.2 ± 317.1, while the processing temperature was between 203.6 ± 10.7 °C and 251.5 ± 9.7.

Digital image correlation and cracked hinge model applied to notched beams reinforced with GFRP bars

In this study, three-point bending fracture tests of notched beams reinforced with a glass fiber-reinforced polymer bar are conducted. Plain concrete beams are also tested for comparison. Two different widths are considered for the beams. Digital image correlation (DIC) is used on the lateral surface of the beam to study the fracture process zone (FPZ) and neutral axis depths at different load stages. A non-linear analytical model named cracked hinge model and cross-sectional analysis are used to obtain the force in the bar and the interfacial slip between bar and concrete, which are compared to the results from pull-out tests.

The ballistic performance of STF impregnated Kevlar fabric coating GFRP composite structure

The shear thickening fluid (STF) impregnated Kevlar fabric coating glass fiber reinforced plastic (GFRP) composite structure has both wearing comfort and high protective ability, which will provide guidance for the development of new protective products. In this study, STF with SiO2 mass fraction of 34% was prepared, the quasi-static/dynamic mechanical behavior of STF, Kevlar and STF impregnated Kevlar fabric coating GFRP were carried out by the high-speed impact experiments, respectively. At the same time, the damage characteristics and energy absorption properties of the composite structure are analyzed by integrating experimental data with numerical simulation. The results showed that the composite structure makes the energy absorption capacity of GFRP improved. STF impregnated 4 layers of Kevlar fabric coating GFRP composite structure was impacted by the projectile at a speed of 244 m/s, and the composite structure consumes 1.54 times the energy of single GFRP laminates. The resistance of composite structures can be improved by placing more layers of Kevlar fabric behind GFRP laminates. The evaluation of the target’s bullet resistance cannot solely rely on the energy consumed by the projectile. A portion of the energy is transferred to the obstacle that impedes the target’s motion.

Numerical prediction of thermal conductivity and thermal expansion coefficient of glass fiber-reinforced polymer hybrid composites filled with hollow spheres

The optimal performance of composites enriched with hollow spheres has been reported in contemporary literature, whereas their thermal properties have received less attention. In this regard, a finite element method (FEM)-based micromechanical model has been developed systematically to investigate the role of intra-matrix embedding of hollow spheres on the thermal conductivity and coefficient of thermal expansion (CTE) of unidirectional fiber-reinforced hybrid composites. In so doing, the concept of representative volume element (RVE) considers microstructures comprising an epoxy matrix, E-glass fiber, and E-glass hollow spheres, assuming perfect bonding (ideal interface) between the components and modified approximate periodic boundary conditions. By computing the longitudinal and transverse temperature gradients generated due to the application of uniform heat flux as well as the geometrical variation in RVE owing to temperature enhancement, thermal conductivity and CTE have been respectively determined. Comprehensive evaluations have been conducted to examine the effects of microstructural-level features, including fiber volume content and orientation, plus volume content and thickness of hollow spheres, on the effective thermal conductivity and CTE of pseudo-porous ternary E-glass/epoxy composites.

Reusing Egyptian in-situ construction &demolition waste(CDW)to produce sustainable concrete.Investigation of compressive &bond strengths using steel & glass fiber reinforced polymer(GFRP)rebars

ABSTRACT This research paper presents the effect of using recycled concrete aggregate (RCA), from the Egyptian construction waste, in different proportions on the bond performance between concrete and its internal reinforcement, where two types of reinforcement were used: a- steel reinforcing bars, and b- glass fiber reinforced polymer (GFRP) bars. 72 samples of concrete were prepared and tested with replacement ratios for natural aggregate (NA) with RCA: 0, 20, 40, 60, 80, and 100 %. The samples were divided into 150 mm cubes to conduct axial compression tests, and pull-out samples to investigate the effect of replacement ratios on the bond between concrete with steel and GFRP rebars. Results showed that concrete loses 26% of its compressive strength after replacing NA with 100% RCA. The results of the pull-out test for steel samples showed 30% higher bonding than GFRP samples. A slight decrease in bond was observed between the control and the tested samples, where the steel and GFRP samples showed a decrease of 5% and 9%, respectively, over the control samples for each, at a replacement percentage of 100%. It was also clear that the steel reinforcement bars had a stronger bond with the concrete, and this can be attributed to the stronger mechanical interlocking of the steel ribs than their counterparts in the GFRP. Failure patterns showed the crushing of concrete with steel bars, in contrast to the GFRP bars, which showed slipping from within the concrete with failure of the ribs in many samples.