Papers by Keyword: GFRP

Abstract: This study evaluates the direct machining of internal threads in glass fiber-reinforced (GFRP) and carbon fiber-reinforced (CFRP) composite materials, comparing the performance of cutting taps, conventional thread milling, and orbital thread milling. GFRP and CFRP samples were prepared and drilled under optimized conditions to minimize delamination, followed by thread production using the three different technologies. Visual and microscopic inspections revealed that orbital thread milling consistently produced the highest thread quality with minimal fiber damage, while cutting taps resulted in the most defects. Tensile testing showed that, in GFRP, orbital thread milling achieved the highest maximum load (18.05 kN), only slightly exceeding other methods. In CFRP, thread strength was similar across all technologies for 4 mm thick samples (around 4 kN), but increasing the thickness to 8 mm nearly doubled the strength, regardless of the threading method. The results demonstrate that orbital thread milling is optimal for thread quality, but in CFRP, material thickness is the dominant factor influencing joint strength. Direct threading in composites is feasible when appropriate machining parameters and technologies are applied.

Abstract: Traditionally, reinforced concrete structures are constructed using steel rebars as reinforcement which is more susceptible to reinforcement corrosion in severe exposure conditions. This leads to many disadvantages, like deterioration of concrete, reduction in strength, and increase in maintenance costs, which leads to a decrease in the serviceability of critical infrastructure. Fiber Reinforced Polymer bars are often used as alternative materials for steel bars because they are anti-corrosive, exhibit an excellent strength-to-weight ratio and are easy to handle but the main disadvantage is its brittle nature. Hence, the combination of steel and FRP bars was effectively used to augment both flexural capacity and ductility. As the ductility performance of hybrid Reinforcement is lower than conventional reinforced beams, Polyvinyl Alcohol Fibers in volume fraction were added in this investigation. The present investigation aims to determine the flexural capacity of reinforced concrete beams using Glass Fiber Reinforced Polymer (GFRP) bars and Steel bars. The optimum dosage of PVA fibers while evaluating compressive and split tensile strength is observed at 0.25% in volume fraction. Total six types of concrete beam specimens with and without PVA fibers were experimentally under four-point bending test tested such as beams reinforced with only steel bars, only GFRP bars, GFRP and steel bars. From the experimental results, it is observed that inclusion of PVA fibers in proposed beams with hybrid reinforcement enhanced the crack resistance by 80% and ultimate load capacity by 39% when compared with conventional beam.

Abstract: This study addresses the reinforcement of corroded API 5L X42 pipelines using Glass Fiber Reinforced Polymer (GFRP) composite wraps, focusing on optimizing fiber orientation to enhance burst pressure performance. Pipeline corrosion poses significant risks to structural integrity and safety in the oil and gas industry. Experimental burst pressure testing, and Finite Element Method (FEM) were conducted to evaluate unidirectional (0/0/0), bidirectional (0/90/0) and multi-axial (0/45/-45) GFRP wraps. The FEM model, validated against experimental data, showed minimal error with 1.16%. Major findings show that the bidirectional had a maximum stress (501.29 MPa) and burst pressure (44.72 MPa) higher than the unidirectional and multi-axial. Better stress distribution given by the bidirectional structure helped to lower stress concentrations. These results show that pipeline repair techniques can be much improved by orienting fibers correctly. This study found that it helpful in field application of composite repair techniques for corroded subsea pipes.

Abstract: Fiber Reinforced Polymer (FRP) has been used in construction as it is lightweight, has flexural strength, is more durable and resistant to corrosion, impact, and fire. Finite Element Analysis (FEA) is a modern technique to predict the tensile behavior and cracking pattern of structural members using nonlinear finite element analysis (NLFEA). In this current study, 11 specimens of Glass Fiber Reinforced Polymer (GFRP) reinforced concrete (RC) Beams with different reinforcement bars (#5, #6 and #8 bars) and spacing (30mm, 38mm and 50 mm) along with two different concrete strengths (Normal and high strength) were modelled to predict the flexural behavior, Moment deflection behavior and cracking pattern using ABAQUS 6.12. These specimens were modeled in ABAQUS using CDP Model and calibration was performed on basis of viscosity, dilation angle and meshing size. The outcomes of numerical modeling were compared with those of the experimental results. It has been shown that there is a slight disparity with very small differences between the experimental and numerical results.

Abstract: Traditionally, reinforced concrete structures are constructed using steel rebars as reinforcement which is more susceptible to reinforcement corrosion in severe exposure conditions. This leads to many disadvantages, like deterioration of concrete, reduction in strength, and increase in maintenance costs, which leads to a decrease in the serviceability of critical infrastructure. Fiber Reinforced Polymer bars are often used as alternative materials for steel bars because they are anti-corrosive, exhibit an excellent strength-to-weight ratio and are easy to handle but the main disadvantage is its brittle nature. Hence, the combination of steel and FRP bars was effectively used to augment both flexural capacity and ductility. As the ductility performance of hybrid Reinforcement is lower than conventional reinforced beams, Polyvinyl Alcohol Fibers in volume fraction were added in this investigation.The present investigation aims to determine the flexural capacity of reinforced concrete beams using Glass Fiber Reinforced Polymer (GFRP) bars and Steel bars. The optimum dosage of PVA fibers while evaluating compressive and split tensile strength is observed at 0.25% in volume fraction. Total six types of concrete beam specimens with and without PVA fibers were experimentally under four-point bending test tested such as beams reinforced with only steel bars, only GFRP bars, GFRP and steel bars. From the experimental results, it is observed that inclusion of PVA fibers in proposed beams with hybrid reinforcement enhanced the crack resistance by 80% and ultimate load capacity by 39% when compared with conventional beam.

Abstract: In this study, an experiment was performed on flexural behavior of RC beam that experienced spalling due to corrosion. The spalled concrete was repaired using grouted mortar, while the lost reinforcement area was replaced with Glass Fiber Reinforced Polymer (GFRP) sheets. The effectiveness of these repairs relied heavily on the bond between the existing and new concrete, ensuring no delamination occurred under maximum load. To enhance this bond, connectors or dyna-bolt anchors were incorporated into the joint area. Eight RC beam were prepared, each with a cross-section of 150 mm x 200 mm and length of 3300 mm, consisting of 1) two existing beams (BE), 2) two beams repaired with grouting and GFRP sheet (BGS), 3) two beams with grouting, GFRP sheet, and the addition of 4 anchors (BGS-DN4), and 4) two beams with grouting, GFRP sheet, and the addition of 8 anchors (BGS-DN8). The repaired area was 2700 mm long and 50 mm thick, and then flexural testing using four-point loads was conducted on all specimens. The results showed that RC beam repaired with mortar grouting and GFRP sheets, along with the inclusion of 4 dyna-bolt anchors in the connection area (BGS-DN4), could increase the maximum load by 61% compared to BE. This repair method improved the bond between the existing concrete and the repair material, effectively preventing delamination.

Abstract: Fiber-reinforced plastic (FRP) composites are subjected to micro-level defects such as fiber-matrix debond and/or matrix cracks after a period of their service due to the increasing brittleness of matrix material. Prediction of the degraded elastic properties of a lamina through micromechanical studies by incorporating micro-level defects gives an idea of the health condition of such structures. Due to the limitations of classical mathematical approaches in solving complex structures, numerical mathematical methods like the finite element method (FEM) can be employed. The present investigation deals with the micromechanical analysis of Glass fiber-reinforced plastic (GFRP) composite with micro-level defects to predict some of the elastic properties. The composite is idealized as an array of square unit cells, and the micromechanical behavior of one such unit cell is simulated in ANSYS software using the three-dimensional finite element method to predict Young’s moduli and Poisson’s ratios in principal material directions. The converged finite element solution for longitudinal modulus is validated by the rule of mixtures and the other properties using the Maxwell–Betti reciprocal theorem. Variations of Young’s moduli and Poisson’s ratios due to an incremental internal failure of composite such as low-level, medium-level, and high-level defects at an expected range of fiber volume fractions (50% - 60%) are evaluated and estimated the percentage degradation with respect to a corresponding defect-free composite.

Abstract: The use of viscoelastic sheets in the hull of vessels built from GFRP has been raised in previous works as an option to protect the vessel from the destructive damage of slamming. The present work proposes its use in boats previously built by adhering to the outside of the hulls of the ships. Its installation process is shown, and this new type of installation is compared. Through impact tests with GFRP panels, it is shown that the viscoelastic material maintains its property of absorbing slamming energy and protecting the interior of the laminate. Fatigue tests on the order of 5x10⁴ cycles are carried out to evaluate the impact force, the accelerations that deform the laminate and the virtual energy work imposed on the panel. This option shows that designers have a new option to protect the hull of already built boats.

Abstract: This paper explores the thermal characterization of eggshell composition at different sizes and concentrations in glass-fiber-reinforced polymer (GFRP) composites as a potential flame retardants material. The eggshell powder (ESP) with different sizes (53 μm and 100 μm) and concentrations (10 wt% and 30 wt% ) was mixed with epoxy and laminated with four layers of 800 gsm E-glass. Thermo-gravimetric analysis (TGA) has been performed to analyze the thermal properties of the GFRP laminates. The finding reveals that incorporating the ESP in the GFRP composites material does not affect the epoxy matrix’s thermal properties as all the trails deteriorate between 450 °C to 480 °C. The combination of 100 μm filler size and 30 wt% ESP improved the fire resistance by 4.68% when compared to 53 μm size and 30 wt% ESP. In addition, the increment of filler loading from 10 wt% to 30 wt% of the 100 μm filler size showed an improvement of 10.9%. This concludes the potential of ESP as a fire retardant material.

Abstract: The ecological thinking and the development of new materials foreground the composite structures made of FRP (fiber reinforced polymers) and concrete. Before the use in real concrete structures, the material characteristics and composite action with concrete need numerical, analytical, and experimental evaluation. The key to developing the composite action of an FRP reinforcement in concrete is a sufficient bond between the reinforcement and concrete. The GFRP (Glass Fiber Reinforced Polymer) bars as the most common and affordable alternative to steel bars are used in this study to investigate the bond with concrete on the analytical model. The finite element model simulates the beam-bond test of GFRP and steel bars to concrete. The effect of bar diameter and type of reinforcement on the bond behavior are analyzed. Finally, the results obtained from the analytical model are compared with the experimental results from the literature.