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Previous research indicates that lightweight aggregate (LWA) concrete exhibits more brittle failure under compression than conventional normal density (ND) concrete. In contrast, angle-ply fiber-reinforced polymer (FRP) filament-wound tubes filled with ND concrete show significant improvements in strength and deformability compared to hollow tubes. This study evaluates the impact of these tubes on LWA concrete to mitigate its brittle behavior. Sixteen concrete-filled FRP filament-wound tubes (CFFTs) made of ±55° filament-wound glass FRP (GFRP) were tested under axial compression. The GFRP tube's mechanical properties and fiber winding angle of ±55° allowed for a compressive strength enhancement factor ranging from two to five for the CFFTs compared to unconfined specimens. Results also revealed substantial nonlinearity and deformability in the LWA-CFFTs due to the angle-ply tube orientation. An iterative analytical model predicted the CFFT's nonlinear response, validated by experimental data. The findings demonstrate that angle-ply FRP tubes effectively enhance the bearing capacity and deformability of inherently brittle unconfined LWA concrete. [ABSTRACT FROM AUTHOR]

To improve the structural performance of precast assembled concrete piers under earthquake, we designed and manufactured two piers confined by carbon fiber reinforced polymer (CFRP) sheets (SPCC1, SPCC2), two piers confined by glass fiber reinforced polymer (GFRP) tubes (SPCG6, SPCG10), and one comparison pier (SPC). The column and bent cap connections were designed with a monolithic construction, whereas the column and pile cap connections had precast joints with grouted sleeves. The effects of the CFRP and GFRP on the seismic performance of the specimens were studied using a quasi-static test and a fiber model based on OpenSees. The failure modes of the specimens included concrete crushing in the plastic hinge zone and buckling fracture of the longitudinal reinforcement. A CFRP tensile fracture occurred in the plastic hinge zone at the top and bottom of the piers; however, damage to the GFRP tubes was minor. Compared with sample SPC, the maximum bearing capacities of SPCG6, SPCG10, SPCC1, and SPCC2 increased by 8.4%, 3.1%, 15.0%, and 4.8%, respectively. At 7% displacement, the residual bearing capacities of SPCG6, SPCG10, SPCC1, and SPCC2 increased by 103.3%, 90.4%, 36.7%, and 82.8%, respectively, compared with SPC. At 6% and 7% displacement, the average stiffness of the CFRP/GFRP-confined specimens increased by 46.2%/58.9% and 59.8%/96.8%, respectively, compared with that of the unconfined specimen. The curvature results also showed that the confined pier exhibited a better flexural performance in most loading processes. The test and simulation results showed that the connection strength of the grouted sleeve in the precast structure should be ensured, and the reinforcement ratio of the pier should be prioritized, followed by an appropriate improvement in the compressive strength of the concrete. The constraint range of the FRP at twice the height of the plastic hinge zone was sufficiently conservative to ensure that the pier maintained good seismic performance under a high axial compression ratio. In practical engineering, the use of a GFRP tube as a template for a prefabricated pier is recommended, and a CFRP sheet is used to strengthen the plastic hinge area of an existing pier with insufficient seismic ability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The adoption of fiber-reinforced polymer (FRP) bars in concrete structures has increased due to their superior mechanical properties and durability. However, the compressive response of FRP bars at high temperatures remains unclear. This article presents an experimental study on the behavior of glass FRP (GFRP) and basalt FRP (BFRP) bars subjected to compressive loads at different elevated temperatures and deformation rates. The study considers four different temperature conditions: ambient temperature (25 °C), 50 °C, 100 °C, and 150 °C, and two different deformation rates: 0.5 mm/min and 1000 mm/min. Digital Image Correlation (DIC) was used to accurately measure strains at high temperatures by generating a suitable speckle pattern over the specimen surface for full-field deformation measurements. The study results revealed that the modulus of elasticity and compressive strength of both GFRP and BFRP bars degraded as the temperature increased from 25 °C to 150 °C. The compressive strength reduction was higher at 150 °C compared to 100 °C, and the reduction was more significant for BFRP bars than GFRP bars. The compressive strength of GFRP bars was comparable under both strain rates for all temperature conditions. However, the elastic modulus of the bars showed a slight variation between the different load rates, especially at an elevated temperature of 150 °C. For the BFRP bars, the study found that different strain rates at ambient temperature resulted in significant deviation in the compressive strength and modulus of elasticity results. At higher temperatures, the reduction in mechanical properties was more pronounced. In summary, the study provides valuable insights into the behavior of GFRP and BFRP bars under compressive loads at elevated temperatures, which is useful for designing and assessing the performance of FRP-reinforced structures under fire conditions. [ABSTRACT FROM AUTHOR]

Studying the mechanical responses of GFRP and aluminum samples under varying loads is crucial for developing methods to enhance their mechanical properties. This research investigates the impact of z-pinning on single-lap adhesive joints through low-velocity shear impact tests. The study involves testing two types of joints: single-lap adhesive joints and single-lap hybrid pin-adhesive joints with six reinforcing pins, subjected to drop weight tests at load levels of 22.5, 27.5, and 32.4 J. The findings demonstrate that z-pinning can increase the joints' load-bearing capacity by up to 18.87% and energy absorption by 20.58%. This enhancement is attributed to the additional composite substrate layers in the hybrid joint, which help absorb impact loads. In contrast, in the single-lap adhesive joint, only the layer adjacent to the adhesive bears the impact load. Observations from the tests indicate that in the single-lap adhesive joint, the first composite layer next to the adhesive undergoes complete delamination, whereas in the hybrid joint, all laminates fracture at the steel pins. In summary, this study underscores the significant potential of z-pinning to improve single-lap adhesive joints, providing an innovative approach to enhance their load-bearing capacity and energy absorption. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer (GFRP) composite tubes have become increasingly popular in crashworthiness applications. On the other hand, square section GFRP tubes are prone to damage in a catastrophic failure mode in the early stages of the crushing process. At this point, triggering mechanisms have great potential to ensure deformation in progressive mode and improve the compression performance of GFRP tubes. Motivated by these facts, this paper aims to optimize the compression performance of square GFRP tubes by implementing notch‐type triggering mechanisms. The effects of notch width, number and length on the axial compression response of tubes were investigated to determine the optimal trigger configurations that would maximize specific energy absorption (SEA) and minimize peak crushing force (PCF). Experiments were conducted based on Taguchi L9 orthogonal array design, and Taguchi coupled Weighted Aggregated Sum Product Assessment (WASPAS) method was employed for optimizing multiple responses. The optimization results revealed that the proposed trigger mechanisms induced progressive crushing by preventing catastrophic failure, thereby significantly improving the compression performance of GFRP tubes. In particular, the results showed that the PCF of intact GFRP tube decreased by up to 38%, while SEA increased by up to 130% with the help of proposed trigger mechanism. Highlights: The compression performance of square GFRP tubes improved by notch‐type triggering.The notch width, length and number were chosen as design parameters.Taguchi experimental design was used to find the best configuration of design parameters.The optimum configurations were examined through the entropy‐WASPAS approach.The results revealed that significant improvements can be achieved using trigger mechanism. [ABSTRACT FROM AUTHOR]

Background: Glass fiber-reinforced polymer (GFRP) bars offer a superior alternative to steel bars in concrete reinforcement but are associated with wider cracks and higher deformation rates. This study introduces a novel approach by combining steel fibers (SFs) and carbon nanotubes (CNTs) to address these drawbacks and enhance the performance of GFRP-reinforced concrete beams. The unique contribution of this study lies in the simultaneous use of SFs and CNTs, which has not been extensively investigated, particularly in the context of GFRP-reinforced concrete. The study involved testing three sets of nine specimens with different concrete mixtures and reinforcement forms. Results: The results showed that adding 0.04% CNTs by cement weight and 0.6% SFs by volume fraction significantly improved the mechanical performance of GFRP and steel reinforced beams. GFRP reinforced beams with CNTs and SFs exhibited a reduction in crack width, a 20% increase in load-carrying capacity, and a 25% reduction in deflection compared to reference specimens. Scanning electron microscope analysis further revealed that CNTs effectively enhanced tensile load transfer, improving flexural behavior of the beams. The finite element analysis using ANSYS confirmed the experimental findings, highlighting the improved stress distribution in the modified concrete mixtures. Conclusions: Incorporating SFs and CNTs in concrete significantly improves the mechanical performance of GFRP-reinforced beams, making them more durable and resilient. These findings suggest that the proposed approach can enhance the longevity and sustainability of concrete structures, particularly in dynamic load applications such as bridges and high-rise buildings. Further experimental and analytical studies are recommended to assess the practical implications and cost-effectiveness of these materials in large-scale construction projects. [ABSTRACT FROM AUTHOR]

Purpose: Glass fiber reinforced polymer (GFRP) composite structures are extensively utilized across the globe due to their lightweight, corrosion resistance, high specific strength and stiffness. Generally, fatigue failures are common in composite structures such as aircraft structures, mechanical components, windmill structures, etc. The crack initiates and propagates in relative orientation between the crack and loading direction which adversely affects the performance of composite structures. Therefore, it is essential to detect the crack location and orientation to avoid catastrophic failure. This research article explores the investigation of transverse cracks with different orientations in GFRP composite beams using a modal data-based Artificial Neural Network (ANN). Methods: The composite beam laminate is fabricated using vacuum-assisted resin transfer molding with bi-directional GFRP lamina. Crack with consistent depth and triangular shape made on the specimen using a hacksaw. Experimental modal analysis is carried out on four beam specimens with different damage conditions such as without crack and transverse crack with 30, 60, and 90-degree orientations under cantilever boundary conditions. Further, ANN is applied to the modal parameters to predict the frequency response functions (FRFs). Results: To comprehend the specimen's behavior for notable changes, modal parameters such as natural frequencies, mode shapes, damping ratios and FRFs are acquired and briefly examined for various experimental cases. Then, FRFs for all four cases are predicted using ANN, and the accuracy of the model is computed. Conclusion: It is observed that for the fundamental mode, natural frequencies decrease and damping ratios increase respectively with the formation of crack. The predicted FRFs using ANN have agreed well with the experimental FRFs for all different criterion. [ABSTRACT FROM AUTHOR]

In this study, the analysis of reinforced concrete (RC) beams strengthened with Fiber Reinforced Polymer (FRP) composites against bending and shear loads was carried out with the finite element technique, using ABAQUS software, which is widely used in simulating experimental circumstances in numerical studies. It has been reported that buildings in areas damaged by earthquakes are generally constructed using low-strength concrete and inadequate reinforcement. Additionally, construction errors also contribute to reducing the load-bearing capacity of structural elements. For this purpose, nine rectangular cross-section RC beams were experimentally constructed using low-strength concrete and inadequate bending and shear reinforcement. These beams were strengthened by wrapping them in different configurations with Carbon and Glass FRP (CFRP and GFRP) composites to resist shear and bending forces in both transverse and longitudinal directions, and their load-displacement curves were obtained. Subsequently, a three-dimensional Finite Element Model (FEM) was created to validate the experimental results. The FEM validation demonstrated high accuracy in replicating experimental outcomes, emphasizing the influence of mesh size, dilation angle, and concrete constitutive models on simulation fidelity. Parametric studies revealed that increasing longitudinal reinforcement diameters had minimal effect on load capacity but highlighted the critical role of transverse reinforcement, as reducing stirrup spacing significantly improved load-bearing capacity. GFRP-reinforced beams exhibited superior ductility and a 15% higher strength compared to CFRP, suggesting their suitability for applications demanding enhanced displacement capacity. Furthermore, the findings underline the need for refined FEM models to better capture inclined fiber orientations and optimize structural reinforcement strategies. [ABSTRACT FROM AUTHOR]

Glass Fiber-Reinforced Composite (GFRP) has found widespread use in engineering structures due to its lightweight construction, high strength, and design flexibility. However, pure GFRP beams exhibit weaknesses in terms of stiffness, stability, and local compressive strength, which compromise their bending properties. In addressing these limitations, this study introduces innovative square GFRP beams infused with gypsum-based composites (GBIGCs). Comprehensive experiments and theoretical analyses have been conducted to explore their manufacturing process and bending characteristics. Initially, four types of GBIGC—namely, hollow GFRP beams, pure gypsum, steel-reinforced gypsum, and fiber-mixed gypsum-infused beams—were designed and fabricated for comparative analysis. Material tests were conducted to assess the coagulation characteristics of gypsum and its mechanical performance influenced by polyvinyl acetate fibers (PVAs). Subsequently, eight GFRP square beams (length: 1.5 m, section size: 150 mm × 150 mm) infused with different gypsum-based composites underwent four-point bending tests to determine their ultimate bending capacity and deflection patterns. The findings revealed that a 0.12% dosage of protein retarder effectively extends the coagulation time of gypsum, making it suitable for specimen preparation, with initial and final setting times of 113 min and 135 min, respectively. The ultimate bending load of PVA-mixed gypsum-infused GFRP beams is 203.84% higher than that of hollow beams, followed by pure gypsum and steel-reinforced gypsum, with increased values of 136.97% and 186.91%, respectively. The ultimate load values from the theoretical and experimental results showed good agreement, with an error within 7.68%. These three types of GBIGCs with significantly enhanced flexural performance can be filled with different materials to meet specific load-bearing requirements for various scenarios. Their improved flexural strength and lightweight characteristics make GBIGCs well suited for applications such as repairing roof beams, light prefabricated frames, coastal and offshore buildings. [ABSTRACT FROM AUTHOR]

This study examines how structural discontinuities created during production affect glass fiber-reinforced composite plates. Due to geometrical constraints, the composite microstructure's discontinuities can be categorized as inter-ply and intra-ply. Material testing was conducted at the coupon level as an initial step to ascertain material characteristics. Two full-scale models of intra-ply composite samples were manufactured by employing layers of glass fiber-reinforced prepregs. Discontinuities were generated in the samples using a computer numeric control cutter and then manually applied. The discontinuities' impact on the composite laminate's mechanical properties was assessed through full-scale pieces using three-point bending quasi-static tests. Servo-hydraulic actuators were used to conduct tests on the items. The experimental test results were compared with CAE analysis predictions by evaluating sectional fiber volume fraction. The characteristics of local discontinuities were analyzed using a microscope to enhance the findings of the CAE model. This comprehensive approach offers insights into the intricate connection between internal structural inconsistencies and the mechanical properties of continuous glass fiber-reinforced materials. It supports optimizing composite manufacturing processes and improves composite parts' structural reliability. Dislocation areas were found to result in the formation of resin-rich zones in this investigation. The exothermic curing process in the component's zones results in elevated temperatures, leading to a color change in the resin from clear to yellow. The yellow areas are easily recognizable and show decreased mechanical durability. [ABSTRACT FROM AUTHOR]

This paper presents a study on manufacturing a range of hybrid laminated structures made of thermoplastic polyurethan (TPU), glass fibre reinforced plastic (GFRP), styrene-butadiene rubber (SBR) and metal mesh materials, and further on investigating the structural response of the TPU based composite sandwich laminated structures. These laminated structures were tested under quasi-static perforation and low velocity impact loading to determine their structural responses and energy absorption characteristics. It has been shown that three-layer and five-layer laminates with lay-ups of GFRP-TPU-GFRP or TPU-GFRP-TPU and GFRP-TPU-GFRP-TPU-GFRP or TPU-GFRP-TPU-GFRP-TPU subjected to quasi-static perforation demonstrate an increased peak load and stiffness with the core thickness from 1 to 4 mm. Also, the TPU core laminates show a superior ductility in comparison to their GFRP core counterparts. The energy absorption values of the three-layer and five-layer TPU and GFRP based laminated structures under low velocity impact are higher than those under quasi-static loading due to strain-rate effect. However, the hybrid laminates with SBR and wire mesh as a core do not give much improvement on the impact perforation resistance of the laminates with the different size of wire mesh, as metal mesh plays a less important role in the laminated structures to resist perforation. In overall, TPU-GFRP-TPU-GFRP-TPU structure with 4mm thick GFRP core demonstrates the highest peak force, and the GFRP-TPU-GFRP-TPU-GFRP structure with 4mm thick TPU core offers the highest energy absorption. [ABSTRACT FROM AUTHOR]

This study investigates the influence of various transverse reinforcement configurations on the torsional performance of glass fiber reinforced plastic (GFRP) reinforced concrete beams. A comprehensive experimental investigation includes five specimens, each characterized by unique transverse reinforcement designs in terms of stirrup spacing and inclination angles. The implementation of transverse torsional reinforcements within the beams exhibited a remarkable post-cracking hardening response, contributing to enhanced strength recovery. The experimental findings are subsequently compared with a reliable three-dimensional finite element model developed using the ABAQUS software. Finally, a parametric study is conducted to examine the influence of concrete and GFRP bar strength, along with longitudinal and transverse reinforcement ratios, on the torsional behavior of GFRP reinforced concrete beams. The results emphasize the significant impact of concrete tensile strength and transverse reinforcement on the cracking torque, while the parameters related to longitudinal reinforcement have only marginal effects. [ABSTRACT FROM AUTHOR]

Concrete columns with hollow-core sections find widespread application owing to their excellent structural efficiency and efficient material utilization. However, corrosion poses a challenge in concrete buildings with steel reinforcement. This paper explores the possibility of using glass fiber-reinforced polymer (GFRP) reinforcement as a non-corrosive and economically viable substitute for steel reinforcement in short square hollow concrete columns. Twelve hollow short columns were meticulously prepared in the laboratory experiments and subjected to pure axial compressive loads until failure. All columns featured a hollow square section with exterior dimensions of (180 × 180) mm and 900 mm height. The columns were categorized into four separate groups with different variables: steel and GFRP longitudinal reinforcement ratio, hollow ratio, spacing between ties, and reinforcement type. The experimental findings point to the compressive participation of longitudinal GFRP bars, estimated to be approximately 35% of the tensile strength of GFRP bars. Notably, increasing GFRP longitudinal reinforcement significantly improved the ultimate load capability of hollow square GFRP column specimens. Specifically, elevating the ratio of GFRP reinforcement from 1.46% to 2.9%, 3.29%, 4.9%, and 5.85% resulted in axial load capacity improvements of 32.3%, 43.9%, 60.5%, and 71.7%, respectively. Specifically, the GFRP specimens showed a decrease in capacity of 13.1%, 9.2%, and 9.4%, respectively. Notably, the load contribution of steel reinforcement to GFRP reinforcement (with similar sectional areas) was from approximately three to four times the axial peak load, highlighting the greater load participation of steel reinforcement due to its higher elastic modulus. In addition, the numerical modeling and analysis conducted using ABAQUS/CAE 2019 software exhibited strong concordance with experimental findings concerning failure modes and capacity to carry axial loads. [ABSTRACT FROM AUTHOR]

To promote the application of molybdenum tailings as the fine aggregate in concrete in construction engineering and verify the feasibility of fiber-reinforced polymer (FRP) material for strengthening molybdenum tailings concrete columns, this study takes a short circular molybdenum tailings concrete column reinforced by glass FRP (GFRP) as the research object. The influences of the molybdenum tailings content (0%, 25%, 50%, 75%, and 100%), the concrete grade (C30, C40, and C50), and the layer number (0, 1, and 2) of the GFRP sheet on the axial compressive capacity of the molybdenum tailings concrete column are investigated. The experimental phenomena and failure modes of the unreinforced and GFRP-reinforced columns are analyzed. The axial compressive strengths of the unreinforced and GFRP-reinforced columns are then compared. The load–strain curve and load–displacement curve of typical molybdenum tailings concrete columns are presented. Subsequently, six classical strength models for FRP-reinforced concrete are used to calculate the axial compressive strength of the confined specimens. The results show that the best classical model has a predictive accuracy with an absolute relative deviation (ARD) of 8.5%. To provide a better prediction of the compressive strength of the GFRP-reinforced molybdenum tailings concrete column, the best classical model is further improved, and the ARD of the modified model is only 5.87%. [ABSTRACT FROM AUTHOR]

Compressive testing of specimens taken from relatively thin composite plates is difficult, especially due to the occurrence of buckling. To prevent buckling, the central portion of the specimens used for the compression test has smaller dimensions, and the specimens can be guided along their entire length. For these reasons, optical methods, such as digital image correlation (DIC), cannot be used for the compression test and strain rosettes cannot be glued onto the samples to determine Poisson's ratio. In this study, compression tests of a glass fiber-reinforced polymer (GFRP) were conducted using both the ASTM D695 (Boeing version) and a newly proposed method. The new method involves using special specimens that allow T-type rosettes to be bonded to determine Poisson's ratio, whose value of 0.14 was thus determined. SEM images of the failure surfaces were presented and interpreted. A finite element analysis (FEA) of the specimens tested in compression is also presented. The first analyzed case considers the homogeneous and orthotropic composite, loaded with a uniformly distributed force. The normal stress in the central section of the specimen, determined with FEA, has an error of 6.52% compared to that determined experimentally. Additionally, the strain in the center of the strain gauge, determined with FEA, has an error of 4.76% compared to the measured one. In the second case studied with FEA, the sample is loaded with a quasi-concentrated force, which can move in the direction of the symmetry axes of the cross-section, to study the effect of the eccentricity of the compression force on the state of stress. It was shown that the eccentricity of the force has a great influence: the stress distribution in the section of the specimen becomes strongly non-uniform. For a force eccentricity of 0.4 mm in the direction of the OX axis, the minimum stress decreases by 53.7%, and the maximum stress increases by 55.4%. In order to analyze the influence of some manufacturing defects, two other cases were analyzed by FEA, in which it was assumed that the thicknesses of the outer resin layers were modified, making them asymmetrical. For this final FEA, the specimen was considered to be composed of laminates. These results demonstrate the special attention that must be paid to the centric application of force in compression testing. [ABSTRACT FROM AUTHOR]

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This paper aims to investigate the effect of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) strengthening materials on the static and dynamic behavior of reinforced concrete (R/C) beams subjected to progressive damage. Four identical beams, each strengthened with either GFRP or CFRP, are tested under a cyclic quasi-static loading pattern. Impact hammer tests are performed for undamaged states and various damage levels of the beams. The dynamic test data are analyzed using the Enhanced Frequency Domain Decomposition (EFDD) method to estimate the dynamic characteristics of the beams. In this context, the first three vibration modes in both vertical and horizontal directions are considered. Strengthening is applied to both pre-damaged and undamaged beams, enabling a comparison of their performance before and after the strengthening procedure. Beams strengthened with CFRP exhibit a higher load-bearing capacity and stiffness but also fail at lower displacement levels compared to those strengthened with GFRP, which demonstrate more ductile behavior. Furthermore, the modal frequency ratios indicate that the first vibration mode is more sensitive to damage than the second and third modes. This study highlights the effectiveness of both strengthening materials in enhancing the structural performance of both undamaged and damaged beams. [ABSTRACT FROM AUTHOR]

This study investigated the mechanical behaviour of glass fibre epoxy composites with and without an embedded polyethylene terephthalate (PET) substrate used for printed electronic applications, with the mechanical behaviour integrity studied under different loading modes: three-point bending, tensile, and short-beam stress (SBS) tests. The main objective of this study was to investigate the influence of the substrate location within the laminate. Fracture profiles were observed by visual inspection during the mechanical tests and scanning electron microscopy (SEM) after failure to identify differences in the damage mechanisms and their propagation. Tensile tests indicated that embedding the PET substrate did not affect the ultimate strength of the laminate, while the bending and SBS tests indicated that the substrate integration reduced the bending strength and ILSS by 10% and 50%, respectively, depending on the substrate location. [ABSTRACT FROM AUTHOR]

Trends in the automotive industry are changing rapidly due to environmental factors, including climate change-induced exhaust gas regulations, urban traffic congestion, and the merging of communication and mobility technologies. As a result, new technologies such as electrification, autonomous driving, and mobility as a service (MaaS) are emerging, leading to the development of various types of mobility solutions, including battery electric and hydrogen vehicles, advanced air mobility (AAM), and purpose built vehicle (PBV). In response to these developments, research on a wide range of lightweight materials is being conducted to meet the requirements of these various modes of transportation. Carbon fiber-reinforced plastic (CFRP) is the most effective lightweight material for weight reduction; however, its high cost limits its application. To overcome this limitation, one solution is to produce composite materials using lower cost alternative materials and mass production processes. Another approach is to develop lightweight composite materials that offer additional advantages. Nevertheless, in mobility modes such as AAM, weight reduction is far more critical than cost sensitivity, indicating a potential increase in composite part application in this field. [ABSTRACT FROM AUTHOR]

A full-scale deck slab (15,240 mm × 3,890 mm × 210 mm) supported by steel girders spaced at 3.05 m, including a 3,810 mm × 3,890 mm section incorporating a new design of glass fiber–reinforced polymer (GFRP) stay-in-place (SIP) structural form, is tested under 3M rolling load cycles. The SIP form comprises transverse GFRP I-beams spanning the steel girders and GFRP ribbed plates (planks) spanning the transverse GFRP I-beams and supported by their lower flanges. The design of the SIP form was governed by readily available pultruded sections such that they meet deflection limits under self-weight of fresh concrete and also provide reinforcement ratios comparable to, or exceeding, the Canadian Highway Bridge Design Code (CHBDC) requirements for GFRP rebar. This deck section is compared with another section designed according to CHBDC with top and bottom GFRP rebar meshes. The deck was tested using the 250 kN Rolling Load Simulator (ROLLS) at Queen's University, Canada, which is equipped with two half-axles spaced at 1.2 m, each comprising nitrogen-inflated dual tires. After 3M cycles, the section with SIP structural form showed very similar performance to that of the GFRP rebar section with the stiffness reducing by 72% in both. Nearly 90% of stiffness reduction occurred in the first 0.4M cycles. The residual deflection of the SIP form section was only 60% of that of the rebar section at 3M cycles. Live load deflection ratio reached 3.4 at 3M cycles, almost identical to the rebar section. The span/800 deflection limit was reached at 0.8M cycles, compared with 1.1M cycles for the rebar section. The maximum tensile strain reached in the GFRP SIP form system after 3M cycles was only 11% of its ultimate value. Practical Applications: The use of glass fiber–reinforced polymer material as reinforcement for bridge decks has been well investigated. Researchers have also investigated the applicability of a reinforcement design concept, stay-in-place (SIP) form, which acts as both formwork for casting concrete and permanent reinforcement. This paper investigates the rolling load fatigue performance of a full-scale GFRP SIP form reinforced bridge deck. The GFRP SIP form system featured in this study is made from an off-the-shelf product. The experiment simulated actual traffic load with air-inflated rubber tires for 3 million cycles and the bridge deck exhibited adequate performance. [ABSTRACT FROM AUTHOR]

The automobile industry is exploring the use of HP-RTM (high-pressure resin transfer molding) for mass-producing glass fiber-reinforced plastic (GFRP) chassis parts to achieve weight reduction. In this process, dry fabric is used as a material. However, the fatigue endurance performance of these parts deteriorates due to the bobbin threads in the dry fabric. This study aims to propose a laminating method to prevent the deterioration of the durability of GFRP chassis parts with bobbin threads. Specimens were fabricated with different fiber volume fractions (Vf) and bobbin thread positions. After manufacturing, static properties were evaluated to compare the physical properties of each specimen, and the stress for fatigue durability evaluation was determined based on these static properties. Finally, fatigue endurance performance evaluations were conducted to determine the optimal lamination conditions for GFRP chassis parts. The results showed that for the three laminating methods applied in this study, an increase in Vf not only enhanced the static properties but also reduced waviness, as confirmed through OM images and changes in the slope of the stress–strain curve. Additionally, fatigue endurance tests revealed that, along with the improvement in waviness, adjusting the position of the bobbin threads—which negatively impact durability—resulted in an increase in fatigue endurance performance from approximately 67,000 cycles to about 870,000 cycles, an improvement of approximately twelve times. [ABSTRACT FROM AUTHOR]

The incorporation of filler materials to enhance the properties of fibre-reinforced plastics is a prevalent practise in materials science. Calcium carbonate is a commonly used inorganic filler in composite fabrication. Eggshell, a rich source of calcium carbonate, offers an organic alternative to conventional inorganic fillers. This study investigates the efficacy of different types of eggshells as filler materials. Three variants, viz., unhatched raw eggshell, unhatched boiled eggshell, and post-hatched eggshell, were used to fabricate composite variants, which were then subjected to mechanical characterization and compared with unfilled composites. The results indicated that composites filled with unhatched eggshells outperformed those with post-hatched eggshells. Tensile testing revealed a significant enhancement in the tensile properties of all eggshell-filled composites in comparison to the unfilled ones. The composite variant filled with unhatched raw eggshell filler showcased the utmost tensile modulus and strength, with a notable 36% improvement in comparison with the unfilled variant. Similarly, flexural tests demonstrated a 53% increase in flexural strength for unhatched raw eggshell-filled composites over unfilled composites. SEM imaging confirmed these findings by showing crack arrests, deviations, particle distribution, and strong interfacial bonding in the eggshell-filled composites. [ABSTRACT FROM AUTHOR]

Strengthening of Reinforced Concrete (RC) beams using GFRP to increase flexural capacity often fails due to premature debonding and delamination of old concrete joints and grouting. The current research introduces a method of repairing and strengthening RC beams using grouting mortar, dyna-bold anchors, and Glass composite FRP (GFRP) sheets. Dyna-bold anchors are used as shear connectors between the old concrete and the grouting. In this research, 10 RC beams measuring 150 mm x 200 mm x 3300 mm, consisting of 2 control specimens (BK), 4 GFRP strengthening beams, and 4 GFRP strengthening beams with dyna-bolt anchors, were tested. The results show that the use of dyna-bold anchors in the joints between old concrete and grouting can increase the bending and shear capacity of the beam by 44.70%, indicating that the addition of dyna-bold anchors is able to prevent premature cracking along the joints and increase the stiffness and flexural capacity of the RC beams. These findings have significant practical implications for the repairing and strengthening of RC beams in real-world applications. [ABSTRACT FROM AUTHOR]

Previous studies have reported that the mechanical properties of GFRP, composed of E-glass and unsaturated polyester resin, decrease when subjected to 70 or more thermal cycles ranging from -5 to 40°C (14 hours per cycle). However, there are reports suggesting that the surface temperature of in-service GFRP bridges can exceed 70°C during summer. This indicates that current data on temperature ranges during thermal cycling tests might be insufficient. This study, therefore, investigates the effects of temperature cycling at elevated temperatures on the mechanical properties of GFRP by conducting cycles from -5 to 75°C. Results from the high-temperature range revealed that the strength of unidirectional materials increased in both tensile and bending tests. Conversely, the mechanical properties of bi-directional materials remained relatively unchanged in both tests. Additionally, a slight mass loss in the specimens was noted due to temperature cycling. This suggests that a reduction in water content within the specimens might be a major factor contributing to the observed strength increase. [ABSTRACT FROM AUTHOR]

The compressive strength of composite materials is critical for designers. This study investigates how seawater immersion influences the mechanical properties and compressive behaviour of solid and open-hole glass/epoxy laminates used in aircraft structures. The specimens were divided into three groups: first not immersed, second immersed in seawater for 30 days, and last sun-dried 12 hours after immersion. Immersion in seawater lowered the compressive strength of solid and open-hole specimens by 40 % and 33 %, respectively. The sun-drying process after seawater immersion increased the compressive strength of solid and open-hole specimens by 5 % and 17 %. After drying, the residual strength of solid and open-hole GFRP was 65 % and 84 %, respectively. In solid GFRP composites, the seawater immersion and drying process is irreversible; besides, in open-hole composites it can be reversible. The compressive examination was numerically duplicated using a finite element method (FEM) model of the composite material. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A novel non-destructive testing scheme was proposed for the detection of impact damage in glass fibre-reinforced polymer (GFRP) composites using a microwave planar resonator sensor. The sensor offers the advantages of small size, low cost and simple structure. It is an open-circuited λ/2 long microstrip line and the detection principle is material perturbation. Electromagnetic simulation verifies the sensor design. A GFRP specimen subjected to 5,10 and 20 J impact was examined. The 20 J impact damage was detected through line and two-dimensional scanning. The line scanning enabled accurate localisation of the damage, whereas the two-dimensional scanning facilitated more precise reconstruction of the surface damage features in addition to localisation. The sensor performance for detecting impact damage with lower energy levels was investigated by line scanning. It was found that the sensor could detect and locate 10 J impact damage. Principal component analysis was introduced to significantly reduce the false detection of the 5 J impact damage. It is well demonstrated that the proposed scheme could serve as an alternative method. [ABSTRACT FROM AUTHOR]

The behaviour of lightweight concrete (LWC) edge column-slab connections reinforced with two types of flexural reinforcement glass fiber-reinforced polymer (GFRP) and steel bars with different ratios of shear reinforcement are investigated experimentally and analytically using ABAQUS software. The experimental protocol covered evaluation of eight slabs and edge columns measuring subjected to static loading. Slabs are evaluated as supported, free-standing at one edge, and the column connection is included. The slabs are divided into two groupings, with four slabs in each group. The first group was reinforced with steel flexural, while the second group was reinforced with GFRP reinforcement. Within each group, one slab lacked shear reinforcement, while the other was reinforced with a varying shear reinforcement ratio. A good agreement was found between the numerical FE model and experimental outcomes in most tested slabs. [ABSTRACT FROM AUTHOR]

The goal of this study was to determine the effect of cutting methods on the edges of selected materials applied in structural elements and floor sheathing of unmanned air vehicles. Three cutting methods for MGS L285 epoxy resin composites used for production of unmanned air vehicles manufactured in one of the European companies were presented. Composites reinforced by glass and aramid fibres are approved for certified production of air vehicle elements (AMC-20). Cutting was applied to each material using different technologies, such as: milling, laser cutting and abrasive water jet cutting. The authors focused on the edge quality of the tested specimens cut using various methods. Quality assessment was based on electronic microscopic scanning images and measurement of the specimen maximum damage. In summary, the choice of an appropriate composite cutting method depends on the type of material and its parameters, and it is crucial for the quality of the machined product. The authors focused on determining the selection of parameters for chosen cutting methods and materials used in the military unmanned aerial vehicle industry. Among the conducted tests, the results indicate that better cutting effects are obtained for milling methods in the case of GFRP + L285 (0.143 ± 0.073 µm) and CFRP + L285 (0.072 ± 0.027 µm), and the worst for AFRP + L285 (0.831 ± 0.269 µm). The water jet method gives the worst results in the cutting zone (results above 0.224 μm). [ABSTRACT FROM AUTHOR]

The work analyzes the fracture topography of composite specimens subjected to three-point bending - static and impact. Scanning electron microscopy was used for this purpose. The tests were performed for two different materials, namely polypropylene and polyamide PA6, each reinforced with unidirectional glass fibers. In one case, the fibers were distributed evenly, and in the other, there were areas more and less reinforced with fibers. It was observed that in all cases the tension and compression parts could be clearly distinguished. However, for different materials and with different methods of destruction, varying failure mechanisms were observed, noted based on the analysis of the fracture topography. It was observed that regardless of the loading method and material, in the tensile part there were visibly protruding fibers, and in the compressed part it was the matrix, rather than the fibers, that was destroyed. In the case of statically loaded samples, damage occurred at the macrostructural level, and in the case of dynamically loaded samples, at the microstructural level. Additionally, the samples with uneven fiber distribution were more susceptible to delamination. [ABSTRACT FROM AUTHOR]

The present study deals with fabricating and characterizing glass fiber reinforced epoxy composites with heavy mineral filler (magnetite particles) for potential low-energy radiation shielding applications. The composite materials were fabricated by the hand layup method. Glass/epoxy composite was used as control sample, and radiation shielding composites were manufactured by mixing 20 and 30% (by weight) magnetite particles with epoxy resin. It was revealed that the tensile properties of the magnetite-modified composites were increased, and the composites containing 30% filler exhibited maximum improvement than the control ones. Further assessment of the composite samples was performed by DMA (Dynamic Mechanical Analysis), TGA (Thermogravimetric Analysis), FTIR (Fourier-Transform Infrared) spectroscopy, water uptake (%), and SEM (Scanning Electron Microscopy) testing. The radiation shielding ability of the control and filler-modified composites was assessed by using a gamma (γ) radiation source (60Co). Then, the shielding efficiency was characterized by radiation-reduced intensity (%), LAC (Linear Attenuation Coefficient), MAC (Mass Attenuation Coefficient), HVL (Half Value Layer), TVL (Tenth Value Layer), and SVL (Sixteenth Value Layer). It was revealed that the 30% magnetite filler content composite experienced relatively good attenuation performance against γ-ray than other studied composites. [ABSTRACT FROM AUTHOR]

This research paper offers an in‐depth comparative analysis focused on the long‐term durability of shear connectors fabricated from composite materials within a composite and concrete beam structure, extending over a length of six meters. To carry out this evaluation, the experiment employs a four‐point bending test designed to rigorously assess the performance and efficacy of two distinct types of tie straps utilized within the structure. The central element of this investigation, a composite beam integrated within a concrete deck, serves as the primary test specimen, providing a realistic and applicable context for the assessment. The overarching goal of this study is to meticulously examine and compare the resilience and resistance of these shear connectors when subjected to realistic, practical loading conditions. By doing so, the research aims to shed light on the critical performance characteristics of composite shear connectors, especially their role and effectiveness in enhancing the structural integrity and durability of composite and concrete beams in various structural applications. The outcomes of this study are expected to offer significant insights and contribute valuable knowledge to the field of structural engineering, particularly in understanding and improving the performance of composite shear connectors in structural frameworks. [ABSTRACT FROM AUTHOR]

For hard-to-cut materials and composites abrasive water jet machine (AWJM) has been identified as a lucrative and competent material removal technique, in which a high-speed jet of abrasive and water strikes the workpiece surface to erode the desired material. In this paper, the influence of key input parameters (water pressure, standoff distance, traverse rate and abrasive mass flow rate) on responses such as surface roughness (Ra), kerf taper (Kt), and maximum delamination length (Max. DLL) of machined specimen during AWJM of glass fibre reinforced polymer (GFRP) composite is examined through experimental investigations. Response surface methodology (RSM) based central composite design (CCD) approach and Taguchi design based L16 orthogonal array is used for experimentation. Moreover, a hybrid approach of RSM-Desirability and Taguchi Methodology-Grey Relational Analysis (TM-GRA) are used for Multi-response optimization (MRO) and their results are compared for evaluation of process parameters of AWJM on GFRP. Confirmation tests are carried out to validate the experimental results, and they showed that using the RSM-Desirability approach, at the optimum level of parameters, the percentage errors for Ra, Kt, and Max. DLL have been less than 6.312%, 7.229%, and 6.78%, respectively. As per the results Ra, Kt and Max. DLL improves by 12.6%, 14.4% and 73.6% respectively by using RSM-Desirability approach as compared to TM-GRA. The microscopic features of optimally machined surfaces are investigated using the scanning electron microscope (SEM). [ABSTRACT FROM AUTHOR]

In recent years, fiber-reinforced plastics (FRPs) materials like glass fiber-reinforced plastic (GFRP) and carbon fiber-reinforced plastic (CFRP) are next-generation polymer-based composite materials tailored for lightweight engineering applications in aerospace, marine, chemical, and automotive industries. Applying inclined holes in GFRP material is essentially used in producing robotic parts, microelectronics components, wind turbine blades, etc. The bending actuators and microhinges of microrobots constructed from CFRP materials also require inclined holes. Laser percussion drilling techniques produce a high aspect ratio of high-resolution inclined holes. The geometrical deviation of the laser-drilled hole is usually evaluated in terms of hole circularity and hole taper. No literature is available for inclined hole drilling of the above two types of FRPs using infrared (IR) laser. In this paper, the thickness of each FRP is taken as 1, 3 and 5 mm, respectively. The one-parameter-at-a-time (OPAT) method was used to analyze the individual effects of laser input parameters, such as pulse current, pulse width, assist gas pressure, workpiece thickness, and incidence angle, on output performance characteristics of hole circularity at top (THC), bottom (BHC), and taper (TH) during laser percussion-inclined drilling with millisecond (ms) pulsed Nd: YAG. Pulse current of 200–225A or 275–300A does not affect THC at a zero-degree angle of incidence. A greater pulse current (300 A) is produced during inclined drilling at 100∘ and 200∘. SEM/EDX investigation reveals hole surface and material composition. [ABSTRACT FROM AUTHOR]

The detection of impact and depth defects in Glass Fiber Reinforced Polymer (GFRP) composites has been extensively studied to develop effective, reliable, and cost-efficient assessment methods through various Non-Destructive Testing (NDT) techniques. Challenges in detecting these defects arise from varying responses based on the geometrical shape, thickness, and defect types. Long Pulse Thermography (LPT), utilizing an uncooled microbolometer and a low-resolution infrared (IR) camera, presents a promising solution for detecting both depth and impact defects in GFRP materials with a single setup and minimal tools at an economical cost. Despite its potential, the application of LPT has been limited due to susceptibility to noise from environmental radiation and reflections, leading to blurry images. This study focuses on optimizing LPT parameters to achieve accurate defect detection. Specifically, we investigated 11 flat-bottom hole (FBH) depth defects and impact defects ranging from 8 J to 15 J in GFRP materials. The key parameters examined include the environmental temperature, background reflection, background color reflection, and surface emissivity. Additionally, we employed image processing techniques to classify composite defects and automatically highlight defective areas. The Tanimoto Criterion (TC) was used to evaluate the accuracy of LPT both for raw images and post-processed images. The results demonstrate that through parameter optimization, the depth defects in GFRP materials were successfully detected. The TC success rate reached 0.91 for detecting FBH depth defects in raw images, which improved significantly after post-processing using Canny edge detection and Hough circle detection algorithms. This study underscores the potential of optimized LPT as a cost-effective and reliable method for detecting defects in GFRP composites. [ABSTRACT FROM AUTHOR]

This article investigates the behavior of hybrid FRP Concrete-Steel columns with an elliptical cross section. The investigation was carried out by gathering information through literature and conducting a parametric study, which resulted in 116 data points. Moreover, multiple machine learning predictive models were developed to accurately estimate the confined ultimate strain and the ultimate load of confined concrete at the rupture of FRP tube. Decision Tree (DT), Random Forest (RF), Adaptive Boosting (ADAB), Categorical Boosting (CATB), and eXtreme Gradient Boosting (XGB) machine learning techniques were utilized for the proposed models. Finally, these models were visually and quantitatively verified and evaluated. It was concluded that the CATB and XGB are standout models, offering high accuracy and strong generalization capabilities. The CATB model is slightly superior due to its consistently lower error rates during testing, indicating it is the best model for this dataset when considering both accuracy and robustness against overfitting. [ABSTRACT FROM AUTHOR]

In coastal regions, the deterioration of structures and bridges due to environmental conditions and corrosion is a significant concern. To combat these issues, the use of corrosion-resistant materials like fiber-reinforced polymers (FRPs) materials, engineered cementitious composites (ECCs), and rubberized ECCs (RECC) shows promise as normal concrete (NC) alternatives by providing increased ductility and energy absorption properties. The effectiveness of confining concrete columns using GFRP tubes with ECC/RECC was assessed in this research by evaluating their performance through compression and push-out tests. The study explored key parameters such as GFRP tube thickness and the presence of shear connectors along the tube height, as well as examining various types of concrete. Additionally, a comprehensive parametric investigation utilizing finite element analysis (FEA) was conducted to analyze how different factors influence the behavior of confined concrete columns. These factors included the effect of GFRP tube thickness and diameter on the overall behavior of different types of confined concretes. The results demonstrate that GFRP tubes significantly enhance column capacity, while the presence of ECC/RECC exhibits even greater improvements in capacity, stiffness, and toughness compared to NC. This approach shows promise in reinforcing coastal infrastructure and addressing corrosion-related concerns effectively. [ABSTRACT FROM AUTHOR]

Over the course of many years of use, impingement wear from dust, sand, and other materials can damage wind turbine blades, necessitating repairs and other maintenance work. Recently, wind turbine operators are turning to protective films, which allow such work to be completed more efficiently, as an alternative to the conventional approach of using paint to repair wind turbine blades. However, the erosion resistance characteristics of repaired blades remain unclear. In this study, we create paint- and protective film-coated samples to reproduce repairs, measure their erosion resistance, and study underlying factors in an effort to verify the erosion resistance of repaired materials and associated mechanisms. The low erosion resistance of GFRP can be significantly improved by applying a protective film made of a ductile material. Such material effectively protects the surface of the GFRP. Moreover, the erosion resistance of protective films made from polyurethane material is superior to that of paint. We recommend use of protective film with wind turbine blades when manufacturing blades and regular maintenance. [ABSTRACT FROM AUTHOR]

This paper proposes a technique for detecting impact-induced surface and subsurface fractures in Glass Fibre Reinforced Composites (GFRPs) and hybrid composite materials. Various categories of composite samples, namely Unidirectional GFRP, Bidirectional GFRP, Woven mat GFRP and Carbon-flax hybrid composites are fabricated by the hand-layup process, and cracks are induced in the samples by three-point flexural bending test using a Universal Testing Machine. Near-field microwave Non-Destructive Testing (NDT) is employed in detecting the above cracks by recording the S11 parameter from the microwave transceiver probe throughout the sample. For image rendering the resulting outputs are passed as a 2-dimensional array to the image-rendering algorithms, namely Iterative Curve-Based Interpolation (ICBI), Improved New Edge-Directed Interpolation (INEDI) and the Lanczos algorithm. The most suitable algorithm to identify the clear picture and size of crack is identified, and the effectiveness of Microwave NDT for these composites is analysed. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the nonlinear structural behavior of concrete deep beams internally reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bars and containing a web opening of various sizes and locations within the shear span. Three-dimensional (3D) numerical simulation models were developed for large-scale GFRP-reinforced concrete deep beams (300 mm × 1200 mm × 5000 mm) with a shear span-to-depth ratio (a/h) of 1.04. Predictions of the numerical models were validated against published experimental data. A parametric study was conducted to examine the effect of varying the opening size and location on the shear response. Results of the numerical analysis indicated that the strength of the deep beam models with an opening in the middle of the shear span decreased with an increase in either the opening width or height. The rate of the strength reduction caused by increasing the opening height was, however, more significant than that produced by increasing the opening width. Placing a web opening in the compression zone close to the load plate was very detrimental to the beam strength. Conversely, a negligible strength reduction was recorded when the web opening was placed in the tension side above the flexural reinforcement and away from the natural load path. Data of the parametric study were utilized to introduce simplified analytical formulas capable of predicting the shear capacity of GFRP-reinforced concrete deep beams with a web opening in the shear span. [ABSTRACT FROM AUTHOR]

The current code provisions in ACI 440.11 are based on the flexural theory that applies to slender members and may not represent the actual structural behavior when the shear span-to-reinforcement depth ratio is less than 2.5 (i.e., deep members). The Strut-and-tie method (STM) can be a better approach to design deep members; however, this chapter is not included in the code. Research has shown that STM models used for steel-reinforced concrete (RC) give satisfactory results when applied to glass fiber-reinforced polymer-reinforced (GFRP)-RC members with a/d less than 2.5. Therefore, this study is carried out to provide insights into the use of STM for GFRP-RC deep members based on the available literature and to highlight the necessity for the inclusion of a new chapter addressing the use of STM in the ACI 440.11 Code. It includes a design example to show the implications of ACI 440.11 code provisions when applied to GFRP-RC deep members (i.e., isolated footings) and compares it when designed as per STM provided in ACI 318-19. It was observed that current code provisions in ACI 440.11 required more concrete thickness (i.e., h = 1.12 m) leading to implementation challenges. However, the required dimensions decreased (i.e., h = 0.91 m) when the design was carried out as per STM. Due to the novelty of GFRP reinforcement, current code provisions may limit its extensive use in RC buildings, particularly in footings given the water table issues and excavation costs. Therefore, it is necessary to adopt innovative methods such as STM to design GFRP-RC deep members if allowed by the code. [ABSTRACT FROM AUTHOR]

The rotor blades of wind turbines are becoming increasingly longer, which increases the diameter at the blade connection. Transport problems are the result, as the rotor blades no longer fit under highway bridges, for example. The increase in diameter can be prevented by increasing the bearing strength of the laminate using fiber metal laminates (FMLs). Individual layers of fiber material are replaced by metal foils in FMLs. This work is focused on the infusion of thick-walled FMLs, with infiltration experiments being carried out in-plane and out-of-plane. For the out-of-plane infusion tests, the metal foils are perforated and it is investigated whether the holes should be arranged alternately or aligned in the metal foils. It has been shown that greater laminate thicknesses can be realized with aligned holes. For the determination of voids and dry-spots, the metal foils are treated with a release agent before infusion and after curing the laminate can be demolded ply by ply. The samples made of glass fiber-reinforced plastic (GFRP) and steel/aluminum measure 500 mm by 800 mm by 20 mm. [ABSTRACT FROM AUTHOR]

Concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) offer an alternative to traditional reinforced concrete columns for new construction applications due to their high strength, ductility, and corrosion resistance properties. Despite their popularity, there is a lack of accurate analytical models for the cyclic/seismic performance of CFFT columns. This is due to the absence of precise stress–strain models for FRP tubes and confined concrete under cyclic loading. Previous experiments on CFFT columns suggest that even minimal reinforcement (≤1%) provides essential energy dissipation for extreme events. However, existing stress–strain models for FRP-confined concrete often neglect the contribution of longitudinal and transverse steel reinforcement. While some researchers have proposed material models to address this issue, the analytical modeling of confinement effects from both steel reinforcement and FRP tubes, especially under lateral cyclic loading, continues to pose a significant challenge. This study aims to use previously collected experimental data to evaluate current analytical modeling approaches in OpenSeesPy3.5.1.12 to simulate the lateral cyclic behavior of CFFT columns with ±55° glass fiber-reinforced polymer (GFRP) fiber orientation. Both the lumped inelasticity and the distributed inelasticity modeling approaches are applied. The performance of various FRP confinement models is compared. The effect of plastic hinge length is also considered in the lumped plasticity approach. The findings suggest that integrating a fiber element section into the plastic hinge zone enhances the efficiency of the distributed inelasticity approach. This method accurately captures the non-linear behavior in the critical region and precisely predicts the shape of the hysteretic curve, all while reducing computational costs. Conversely, the lumped inelasticity modeling approach effectively forecasts energy dissipation and peak load values across the entire cyclic hysteresis curve, offering significant computational savings. Finally, a generalized modeling methodology for predicting the response of CFFTs under cyclic lateral load is proposed and subsequently validated using experimental results found in the existing literature. [ABSTRACT FROM AUTHOR]

The main, well-known scientific results were obtained by outstanding scientist Yu. N. Rabotnov in the field of creep theory, hereditary elasticity, damage mechanics, technical theory of shells. However, in the last years of his life, the academician Yu. N. Rabotnov was keen on some problems in the field of mechanics of fiber-reinforced composite materials. He proposed new, original strength criteria, simplified methods for ply-by-ply calculation of composite laminates. One of Yu. N. Rabotnov's scientific passions were connected with description of specific fracture modes of layered fibrous composites having the types of delamination and splitting. On the base of energy fracture criterion, it's possible to estimate the scale effect of strength – the dependence of critical stresses on the absolute sizes of composite members. Such models of specific fracture modes make it possible to estimate the danger of such technological defects as thin polymeric film between composite layers. [ABSTRACT FROM AUTHOR]

In this research, the effects of imbedding steel wires into the polyurethane foam of GFRP/Foam sandwich panel under three-point bending has been investigated. For this reason, three samples of non-reinforced, reinforced with two wires above and below and reinforced with three wires above and below the foam inside the GFRP sandwich panel were manufactured by vacuum bagging and tested under three-point bending in order to measure the specific strength of each sample. Moreover, a finite element model (FEM) was utilized using the Abaqus/Explicit package to further observe and analyze the stresses inside the samples. The results showed that imbedding steel wire inside the foam of the GFRP sandwich panel increased the bending strength by 25.2% in the two wire and 56.75% in the three-wire sample and bending modulus by 51.8% in two and 86% in three wire sample respectively. Since the weight of the wires with respect to the whole structure in negligible, the specific bending modulus of the sandwich panel was also improved by 21% in two and 44.8% in the three-wire sample. Finally, the results obtained from the experiments showed to have a decent agreement with the simulated model. [ABSTRACT FROM AUTHOR]

E‐glass fibers are widely preferred due to ease of processing and its low cost, which has substantial scope in the fields of electronics and electrical insulation applications. Because of its low strength and corrosion resistance, use of E‐glass fibers is limited in aerospace and automotive applications. There is a need for enhancing the properties of the composite to overcome such limitations. Therefore, an attempt is made to introduce multi‐walled carbon nanotubes (MWCNT) as fillers into E‐glass fibers to meet the industry needs. In the current study, woven glass fiber of 5 layers and multi‐walled nano carbon fillers of 2, 4 and 6 by wt%, LY556 epoxy resin, and HY951 hardener were used to prepare 4 different type of composites along with the neat epoxy glass fiber reinforced polymer composites (GFRP). The hand‐layup route was used in the composite preparation due to its low cost, technological feasibility, and simple process setup. The developed samples were characterized for mechanical properties via tensile, flexural and impact tests. Tribological characteristics were performed by air jet erosion test. Chauvenet's criterion is applied for identifying the outliers (if any) from the data of repeated test properties. Taguchi's L9OA (orthogonal array) is selected for obtaining optimal hybrid composite, which yield better mechanical properties. Empirical relations are developed for the material properties in terms of process variables. The sample (4 wt% MWCNT) exhibited enhancement of 17.27% in tensile strength, 6% of impact strength and 7.3% of flexural strength when compared with neat epoxy GFRP. This hybrid composite is considered for thermal aging and observed at 60°C, 8% increase in tensile, 7% increase of impact and 15% in flexural strength due to the precipitation on carbon nano tubes along the gain boundaries. The present study recommends 4% MWCNT fillers in developing hybrid glass epoxy polymer composites for use in aerospace, automotive and civil construction industries due to economic and technological feasibility. Highlights: Utilize low‐cost E‐glass fibers in electronics and electrical insulation applications.Improve composite properties for aerospace and automotive industries.Develop hybrid glass epoxy composites with 2 to 6 wt% MWCNT fillers.Examine wear characteristics under air jet erosion and study the impact of thermal aging on mechanical properties.Apply Chauvenet's criterion for outlier identification in measured properties datasets. [ABSTRACT FROM AUTHOR]

The drilling of composite structure leads to its damage, near the peripheral areas of the drilled hole, due to the laminar structure of the composites. The goodness of a drilling process can be evaluated by measuring the extent of the damage caused by it. In the present study, lock-in thermography non-destructive inspection method is proposed to characterise the drilling damages in glass fiber–reinforced polymer panel. A semi-automated image processing methodology is proposed to calculate damage parameters, namely delamination area and size, and delamination factor. The effect of excitation frequency on the damage characterisation is studied to decide the optimum frequency range to measure the damage parameters through signal-to-noise ratio and damage visibility. The damage parameters are measured at optimum frequency. The study showed that the lock-in thermography technique has the potential to characterise drilling damage. [ABSTRACT FROM AUTHOR]

Copyright of Chemie Ingenieur Technik (CIT) is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)