Fiber-reinforced Polymer Research Articles

Evaluating the Effectiveness of Fiber Reinforced Polymer (FRP) in Structural Strengthening: A Meta-analysis

This study aims to evaluate the effectiveness of Fiber Reinforced Polymer in strengthening structures. This research is a type of meta-analysis research. The data source comes from 9 studies sourced from google scholar, DOAJ, ProQuest and Fronteins published in 2023-2024. Data selection techniques through the PRISMA method in 2020. The data analysis in this study is to calculate the effect size value with the help of the STATA application. The results of this study concluded that the application of Fiber Reinforced Polymer had a positive effect on the strengthening of the structure with an effect size value = 0.813 with a high effect size category. This finding explains that the application of fiber reinforced polymer is effective in strengthening concrete structures in civil engineering.

Characterization of Mechanical and Viscoelastic Properties of Glass Fibre Reinforced Polymer Composites

Characterization of Mechanical and Viscoelastic Properties of Glass Fibre Reinforced Polymer Composites

Seismic Retrofit Case Study of Shear-Critical RC Moment Frame T-Beams Strengthened with Full-Wrap FRP Anchored Strips in a High-Rise Building in Los Angeles

This paper discusses the iteration of a seismic retrofit solution for shear-deficient end regions of 19 reinforced concrete (RC) moment-resisting frame (MRF) T-beams located in a 12-story RC MRF building in downtown Los Angeles, California. Local strengthening with externally bonded (EB) fiber-reinforced polymer (FRP) fabric was chosen as the preferred retrofit strategy due to its cost-effectiveness and proven performance. The FRP-shear-strengthening scheme for the deficient end-hinging regions of the MRF beams was designed and evaluated through large-scale cyclic testing of three replica specimens. The specimens were constructed at 4/5 scale and cantilever T-beam configurations with lengths of 3.40 m or 3.17 m. The cross-sectional geometry was 0.98 × 0.61 m with a top slab of 1.59 m in width and 0.12 m in thickness. Applied to these specimens were three different retrofit configurations, tested sequentially, namely: (a) unanchored continuous U-wrap; (b) anchored continuous U-wrap with conventional FRP-embedded anchors at the ends; and (c) fully closed external FRP hoops made of discrete FRP U-wrap strips and FRP through-anchors that penetrate the top slab and connect both ends of the FRP strips, combined with intermediate crack-control joints. The strengthening concept with FRP hoops precluded the premature debonding and anchor pullout issues of the two more conventional retrofit solutions and, despite a more challenging and labor-intensive installation, was selected for the in-situ implementation. The proposed hooplike EB-FRP shear-strengthening scheme enabled the deficient MRF beams to overcome a 30% shear overstress at the end-yielding region and to develop high-end rotations (e.g., 0.034 rad [3.4% drift] at peak and 0.038 rad [3.8% drift]) at strength loss for a beam that, otherwise, would have prematurely failed in shear. These values are about 30% larger than the ASCE 41 prescriptive value for the Life Safety (LS) performance objective. Energy dissipation achieved with the fully closed scheme was 108% higher than that of the unanchored FRP U-wrap and 45% higher than that of the FRP U-wrap with traditional embedded anchors. The intermediate saw-cut grooves successfully attracted crack formation between the strips and away from the FRP reinforcement, which contributed to not having any discernable debonding of the strips up to 3% drift. This paper presents the experimental evaluation of the three large-scale laboratory specimens that were used as the design basis for the final retrofit solution.

Experimental analysis of the bond-slip characteristics between CFRP and natural stone masonry units

Purpose Although the reinforcement of concrete and brick masonry with fiber-reinforced polymer (FRP) has been extensively researched, its application and impact on natural stone, especially in historic preservation, have received less attention. This study aims to examine the bond-slip characteristics of carbon fiber-reinforced polymer (CFRP) with two types of natural stone masonry, aiming to enhance their effectiveness in reinforcing historic structures. The stones studied include one from the Chouf-Lekdad region (A) and another from a historic structure in Sétif City (B). Both stones were strengthened using CFRP and carbon fiber fabric (CFF) through near-surface mount (NSM) and external bonding (EBR) techniques. Design/methodology/approach The interaction was assessed during the pull-out test by analyzing the stress transfer mechanisms, adhesion and deformation. This study also examines the effects of the following parameters on the bond between CFRP and stone: type of stone (A and B), type of reinforcement (plat CFRP and CFF), various notch shapes and sizes (bp, tp and Lb), and reinforcement techniques (NSM and EBR). Findings This study demonstrated the practicality and effectiveness of enhancing natural stone masonry of old buildings by integrating NSM and EBR techniques with CFRP. With a bond length of 30 mm, the pull-out force correlates with the strength of the stone. This indicates the importance of stone strength in obtaining better adhesion. The CFF–resin interface is more cohesive than the CFRP plate–resin interface because the resin penetrates the flexible CFF strip, ensuring better adhesion. In contrast, the CFRP plate interface is rigid and smooth. The results suggest that natural stone–CFRP adhesion is more effective than CFRP bonded to concrete and brick masonry due to the stone's strong resistance. Originality/value This experimental investigation provides new study into the bond-slip behavior of CFRP-reinforced natural stone masonry, filling the gap in existing research. The findings offer useful direction for creating FRP strengthening solutions that are specifically adapted to the properties of natural stone used in historic constructions. This study helps to improve preservation procedures by guiding the selection of reinforcing techniques, such as NSM versus EBR, and finding ideal bond lengths. This work's novelty stems from its ability to improve the structural integrity of culturally significant buildings while preserving their historical authenticity.

Nano aluminum nitride fillers for enhanced mechanical and thermal properties of GFRP in cryogenic temperature settings

Glass fiber-reinforced polymer (GFRP) composites, with epoxy resin or a blend of cyanate and epoxy resins as the matrix, have been used as insulating materials of high-field, large-scale superconducting magnets for accelerators and magnetic confinement fusion. However, the GFRP does not fully meet the requirements for the next generation of magnetic confinement fusion with respect to the mechanical and thermal performance at cryogenic temperature and huge electromagnetic stress. This paper introduces a method for enhancing both the mechanical and thermal properties of the GFRP composites using aluminum nitride (AlN) nanoparticles. The fabrication of the AlN-GFRP composite involved a method that combines “dip absorption” with vacuum-assisted resin transfer molding (VARTM). The dip absorption method was utilized to deposit AlN nanopowders onto glass fibers, resulting in the preparation of AlN-glass fiber layers. Subsequently, the AlN-woven glass fibers were incorporated to reinforce the cyanate ester/epoxy based composites using the VARTM technology. The mechanical and thermal properties of the AlN-GFRP composites were assessed across varying temperatures. The results indicate that the short-beam shear strength (SBS strength) of the AlN-GFRP composites improves at cryogenic temperatures compared to that of the GFRP composites without AlN. Additionally, enhanced thermal conductivities are observed across different temperature ranges for the AlN-GFRP composites. The coefficient of thermal expansion between 77 K and 300 K of the composites significantly decreases with the addition of the AlN nanopowders.

The Effects of Mechanical Loading on Resonant Response of a Conformal Load-Bearing Antenna System.

Glass fibre-reinforced polymer (GFRP) is a suitable substrate material for constructing a Conformal Load-Bearing Antenna Structure (CLAS). The relative permittivity of the CLAS substrate, which determines its resonant frequency, is affected by damage sustained by GFRP. This paper investigates the effects of damage (induced by mechanically loading the substrate) on the resonant response of the CLAS. Decoupling the antenna from the substrate was essential to evaluate the CLAS's true response to the induced damage. This paper details a systematic investigation examining how the frequency response of a "pristine" antenna and a surface-mounted antenna respond to a substrate subjected to quasi-statically induced mechanical damage and cyclic fatigue loading. The results demonstrate that the resonant frequency of the CLAS varies as a function of the substrate's mechanical damage. The prepared CLAS is tolerant to a certain degree of mechanical loading and related damage with its resonant frequency remaining within an acceptable bandwidth.

Evaluation of the Flexural Behavior of One-Way Slabs by the Amount of Carbon Grid Manufactured by Adhesive Bonding

Fiber-reinforced polymers (FRPs), which are resistant to corrosion, are used as reinforcement material for concrete. However, the flexural behavior of concrete members reinforced with FRPs can vary depending on the properties of FRPs. In this study, the flexural behavior of one-way concrete slab specimens reinforced with a new grid-type carbon-fiber-reinforced polymer (CFRP) (carbon grid) manufactured by bonding pultruded CFRP strands to an adhesive was investigated. The experimental results indicated differences in the load–deflection relationships of the specimens depending on the carbon grid reinforcement amount. Specimens in which the carbon grids were over-reinforced or reinforced close to the balanced reinforcement ratio reached the maximum load due to concrete crushing and exhibited ductile failure. The specimen under-reinforced with the carbon grid exhibited brittle failure. Specimens with carbon grid reinforcement close to a balanced reinforcement ratio exhibited maximum loads ranging from 0.43 to 0.61 times the calculated flexural strength, which resulted in becoming 0.86–1.00 lower in the specimens with a wider width of the CFRP strands. This study proposes coefficients to estimate the stiffness of carbon-grid-reinforced concrete flexural members after cracking. Applying these coefficients resulted in stiffness calculations that reasonably simulated the behavior of the specimens reinforced with carbon grids after crack formation.

Numerical investigation on a precast bridge using GPC and BFRP reinforcements subjected to cross-fault rupture and fling step excitation

This study investigates the seismic performances of a precast bridge made of geopolymer concrete (GPC) with fibre-reinforced polymer (FRP) reinforcements subjected to cross-fault ground motions. A numerical model was developed and verified against experimental results from a previous study and then used to evaluate the bridge's performances under earthquake excitations. The study found that a simplified model was able to reliably capture the failure pattern and displacement response of the bridge, reducing simulation time significantly. Additionally, the numerical results indicated the combination of torsional and flexural cracks was the primarily damage mode of the columns, which was not observed in the experimental test. This study also revealed that while the performances of the bridge using ordinary Portland cement (OPC) and GPC were similar under low ground excitations, GPC columns were more susceptible to brittle failure under higher ground excitations due to their brittleness. The use of FRP reinforcements led to similar displacement response as steel reinforcements under low ground displacement excitation, although severe flexural and shear damages on the column of Bent 2 were observed due to the lower elastic modulus and shear resistance of Basalt FRP material than steel. To address the disadvantages of brittle GPC and low-modulus of basalt FRP reinforcements, it is suggested to reinforce GPC with fibres and/or increase stirrup ratios if green GPC and corrosion-resistant basalt FRP reinforcements are used to construct bridges for seismic resistance.

Seismic Performance Evaluation of Pipelines Buried in Sandy Soils Reinforced with FRP Micropiles: A Numerical Study

Unstable sandy soil poses significant challenges for buried pipelines, particularly due to the increased risk of displacement and stress-induced fractures resulting from soil settlement and earthquake-induced ground deformation. These concerns are especially critical in seismically active regions where underground infrastructure is at higher risk. Fiber-reinforced polymer (FRP) composites present a promising and sustainable alternative for deep foundations, offering durability and reduced maintenance costs compared to conventional materials. This study introduces a novel approach to enhancing the seismic performance of pipelines buried in sandy soils by numerically investigating a three-dimensional (3D) multipipe grouting micro anti-slide pile system, utilizing a polyurethane polymer slurry as the grouting material. Key parameters such as pile spacing, diameter, and length, along with the effects of soil wetting and various earthquake intensities, were examined under the influence of surface loads exerted by a fully loaded truck. The results demonstrate that using polymer micropiles significantly reduces soil and pipeline settlement by 15% to 50%, with larger pile diameters and lengths further decreasing settlement and strain on pipelines. While seismic excitation increases settlement, polymer grouting effectively mitigates this impact, leading to substantial reductions in settlement.

Factors affecting flexural and impact strength of natural fiber reinforced polymer composites: a review

The surging demand for energy-efficient products and their environmental implications are important propelling factors contributing to the growing popularity of natural fiber-reinforced polymer composites (NFRPCs) in several domains. NFRP composites diversification significantly influenced the study and their development in recent years. The intrinsic characteristics of natural fibers have posed difficulties in the growth and use of NFRPCs. A significant amount of study has recently been performed to solve these sorts of problems in order to enhance the performance of NFRPCs and their uses. This review article aims to provide a comprehensive overview of the chemical composition of natural fibers, their physical and mechanical characteristics, and factors affecting the flexural and impact strength of NFRPCs, such as type of fiber, weight percentage of fiber, fiber geometry, surface treatments, stacking, hybridization, orientation, fillers, and information accomplished with them. The product life-cycle evaluation and sustainability development of plant-based NFRCs and the growing uses of NFRPCs, focusing on the automobile sector, are also explored. Finally, multiple perceptions were concluded with the expectation that this study may contribute to future improvements in the flexural and impact strength of NFRPCs.

Mechanical characterizations of waste face masks reinforced polyester composites: Recycling wastes into resources

Face masks are made of non-decomposable thin polypropylene sheets. People are discarding them in parks, beaches, drains, landfills, and roadsides because of a deficiency in recycling efforts. It poses health and environmental risks through soil, water, and air pollution, as well as implanting microplastics into aquatic and different active organisms via food chains. Therefore, the environment and ecosystem become unsustainable. This study explored the potential of recycling waste face masks (WFM) into composite materials. In this sense, WFM-reinforced three distinct polyester composites are developed with a 20 % fiber loading in the compression molding machine and employing shredded, parallel, and crisscross patterns of WFM. The tensile, flexural, and impact strengths of composites are assessed as per ASTM guidelines and contrasted with NFRP (natural fiber-reinforced polymer) composites. Besides, void contents and morphological features are investigated using the Field Emission Scanning Electronic Microscope (FE-SEM) to confirm the interaction between WFM and polyester. The maximum tensile and flexural strengths of 32.06 and 41.13 MPa, respectively, are found in the crisscross pattern WFM composite. The maximum impact strength of 0.053 J/mm is found in parallel, and the least void content of 0.63 % is found in crisscross WFM composites. Compared to NFRP composites, the mechanical strengths, void contents, and morphological properties of WFM composites are found promising. It proclaimed that WFM is an appropriate candidate for recycling into composites. It will deter environmental pollution and microplastic insinuation into living things, elevate sustainable development goals, and develop a circular economy by generating resources from WFM.

In situ growth of graphene on carbon fibers to enhance the mechanical and thermal conductivity of epoxy composites

High-strength and high-thermal-conductivity composite materials have become crucial requirements for thermal control systems in various field. Carbon fiber-reinforced polymer (CFRP) has demonstrated potential superior performance. However, the application of CFRP is limited by the chemical inertness of the carbon fiber surface and the shortness of low surface energy. Therefore, surface modification of carbon fibers is necessary. This research employs a pulse plasma discharge method, to in-situ grow graphene on the surface of carbon fibers by disrupting some polymer structures on the carbon fiber surface in a “bottom-up” approach. This method offers advantages such as rapid, simple, convenient, economical, and environmentally friendly preparation process., the modified carbon fibers used in CFRP exhibit superior mechanical and thermal conductivity properties. The flexural strength increased by 218 % to reach 109.5 MPa, and the thermal conductivity increased by 251 % to achieve 1.153 W/(m*K).

Smart Carbon Fiber-Reinforced Polymer Composites for Damage Sensing and On-Line Structural Health Monitoring Applications.

High electrical conductivity, along with high piezoresistive sensitivity and stretchability, are crucial for designing and developing nanocomposite strain sensors for damage sensing and on-line structural health monitoring of smart carbon fiber-reinforced polymer (CFRP) composites. In this study, the influence of the geometric features and loadings of carbon-based nanomaterials, including reduced graphene oxide (rGO) or carbon nanofibers (CNFs), on the tunable strain-sensing capabilities of epoxy-based nanocomposites was investigated. This work revealed distinct strain-sensing behavior and sensitivities (gauge factor, GF) depending on both factors. The highest GF values were attained with 0.13 wt.% of rGO at various strains. The stability and reproducibility of the most promising self-sensing nanocomposites were also evaluated through ten stretching/relaxing cycles, and a distinct behavior was observed. While the deformation of the conductive network formed by rGO proved to be predominantly elastic and reversible, nanocomposite sensors containing 0.714 wt.% of CNFs showed that new conductive pathways were established between neighboring CNFs. Based on the best results, formulations were selected for the manufacturing of pre-impregnated materials and related smart CFRP composites. Digital image correlation was synchronized with electrical resistance variation to study the strain-sensing capabilities of modified CFRP composites (at 90° orientation). Promising results were achieved through the incorporation of CNFs since they are able to form new conductive pathways and penetrate between micrometer-sized fibers.

Higher-order sensitivity analyses to understand the role of FE input parameters on the simulation of composites in progressive fracture tests

With the rise of data-driven engineering methods, such as machine learning, a comprehensive understanding of the underlying data fed into these algorithms is required for effectively applying these methods. This study presents two highly efficient Finite Element (FE) models that operate at different length scales, based on Continuum Damage Mechanics (CDM). The combination with Random Sampling-High Dimensional Model Representation (RS-HDMR) enables the determination of influential FE input parameters and their correlations to simulate Fibre Reinforced Polymer (FRP) composites subjected to a variety of progressive fracture tests in tension and compression. The results indicate that laminate-based models utilise the FE input parameters efficiently where all parameters are found to be influential. On the other hand, only fibre-related properties are relevant in ply-based FE models, with all input parameters related to transverse properties deemed to be non-influential. The findings of this study aid in identifying suitable fracture tests for a meaningful calibration and validation of CDM-based FE models. Moreover, the study lays the foundation for understanding the role of input parameters within data-driven methods, and for developing efficient reduced-order models or surrogates for uncertainty quantification on the damage tolerance of FRP composites.

Design of an Overhead Crane in Steel, Aluminium and Composite Material Using the Prestress Method

The present research describes a design of an overhead crane using different materials with a prestress method, which corresponds to an external compression force with the aim of reducing the displacement of the beam due to the external load. This study concerns a bridge crane with a span length of 10 m, with a payload equal to 20,000 N and an estimated fatigue life of 50,000 cycles. Three different materials are studied: steel S355JR, aluminium alloy 6061-T6 and carbon fibre-reinforced polymer (CFRP). These materials are analysed with and without the contribution of the prestress method. In reference to the prestressed steel solution (which has a weight equal to 79% of the non-prestressed configuration), this study designed an aluminium solution that is 50.7% of the weight of the steel one and a composite solution that is always 20.3% of the steel configuration. In combining the methods, i.e., the materials and prestress, compared to the non-prestressed steel solution with a weight evaluated to be 758 kg, the weight of the aluminium configuration is equal to 40% of the traditional one, and the composite value is reduced to 16%, with a weight of 121 kg.

Numerical and machine learning models for concentrically and eccentrically loaded CFST columns confined with FRP wraps

AbstractPrevious research largely concentrated on predicting load‐carrying capacities of concrete‐filled steel tubes (CFST) confined with fiber‐reinforced polymer (FRP) wraps under pure concentric loads, neglecting the more complex failure mechanisms that occur under real‐life eccentric loading conditions. This study, therefore, employs both finite element modeling (FEM) and machine learning methods to accurately predict the load‐bearing capacities under both concentric and eccentric loading conditions. This research analyzed a comprehensive dataset comprising 128 experimental tests and an equivalent number of FEM simulations designed to evaluate their eccentric performance. These models have been thoroughly generated and validated against existing literature. Additionally, the developed ML models, particularly a hybrid deep learning model, demonstrated significant predictive accuracy, with an average R2 value of 0.969 across all model folds. Partial dependence analysis further highlighted the significant influence of concrete strength and the interactive effects of steel tube area and FRP wrap thickness on the load‐carrying capacity of the columns. Furthermore, to enhance cost‐efficiency and resource management compared with traditional laboratory testing, a user‐friendly graphical user interface (GUI) has been developed and hosted on an open‐source platform such as GitHub. This interface supports real‐time, precise predictive capabilities and promotes a collaborative environment for ongoing model refinement and improvement.

Normalization and Processing of Rotational Eddy Current Scans for Layup Characterization of CFRP Laminates

ABSTRACT The verification of fiber orientation and layup in carbon fiber-reinforced polymer (CFRP) composite laminates is essential to guarantee the performance of the material. This work reports the background, methodology, and results of a rotational eddy current testing (ECT) system for determining fiber orientation and ply layup of unidirectional CFRP components. The system presented mechanically rotates a 15 MHz directional transmit-receive ECT probe, which poses several speed and consistency advantages. The paper presents a theoretical discussion of how these scans are produced, a unique preprocessing normalization method, and an optimization process for determining the layup from the captured datasets. Results show a high level of accuracy for identifying the unique directions present in a laminate, and the theory-supported model enables the extraction of layup order information of multilayer parts, even where repeated lamina are present within the laminate.

Seismic performance of FRP-repaired RC piers after blast loading

Aiming to evaluate the effectiveness of fiber-reinforced polymer (FRP) repair on the seismic performance of blast-damaged reinforced concrete (RC) piers, the field test and numerical simulation were conducted. Firstly, a successive field explosion test, carbon FRP (CFRP) repair, and lateral cyclic loading test were performed on two 1/2-scale RC pier specimens. The test data including the incident overpressure-time histories of blast wave, damage profiles and lateral force-displacement relationships of pier specimens, etc. were comprehensively recorded and discussed. By comparing with the previous blast-damaged pier specimen, the negative maximum force and ductility of CFRP-repaired pier were increased by 97 % and 44.9 % after 1.0 kg TNT explosion, respectively. Then, an integrated numerical simulation approach based on explicit-implicit switching and full restart algorithms was proposed and validated in predicting the dynamic and quasi-static behaviors of RC piers under successive blast loading, CFRP repair, and lateral cyclic loading. Finally, a prototype RC pier was designed and the suicide vest bomb (TNT equivalence of 9 kg) specified by the Federal Emergency Management Agency was selected as the threat of contact explosion. The influences of FRP type, repair height, and number of FRP layer on restoring the seismic performance of the blast-damaged pier were further discussed. It indicates that, (i) CFRP is more effective than glass FRP and aramid FRP; (ii) increasing the repair height could not significantly improve the seismic performance of pier; (iii) the number of FRP layer has significant effect, e.g., the positive and negative maximum forces after 4-layer CFRP repair are improved by 9.4 % and 45.3 % compared to the unrepaired pier, respectively. The present study could provide a helpful reference for assessing the FRP repair effectiveness on the seismic performance of blast-damaged RC bridge piers.

Prediction of temperature and structural properties of fibre-reinforced polymer laminates under simulated fire exposure using artificial neural networks

Load-bearing fibre reinforced polymer laminates soften and decompose when exposed to high temperature fire which may cause significant deformation and weakening, ultimately leading to failure. A combined experimental and modelling study is presented to predict the fire structural survivability of laminates using artificial neural networks based on machine learning. Multiple experimental fire-under-tension load tests are performed under identical conditions to determine the average values and scatter to the surface temperatures, deformation rates and rupture times for an E-glass/vinyl ester laminate. A data-driven modelling strategy based on artificial neural networks is presented that can predict the temperatures and fire structural properties for the laminate when subject to combined fire exposure and tension loading. It is shown that the model gives excellent agreement to the measured surface temperatures, deformations, and time-to-failure of the laminate when exposed to one-sided heating at a constant heat flux. It is envisioned that the ANN based model could be used to assess the fire structural survivability of load-bearing composite structures exposed to fire.

Effect of concrete strength on the seismic performance of circular reinforced concrete columns confined by basalt and carbon fiber-reinforced polymer

This paper investigated the effect of concrete strength on the seismic performance of circular reinforced concrete (RC) columns confined by basalt and carbon fiber-reinforced polymer (BFRP and CFRP). Eight confined columns and four control columns were tested under a low cyclic lateral load. The variables in the test included concrete compressive strength (i.e., 22.4 MPa, 31.4 MPa, 42.5 MPa and 57.8 MPa) and FRP type (i.e., basalt and carbon fiber). The test results demonstrated that all the columns exhibited flexural failure after confinement. The strength, ductility and energy dissipation capacity of the confined columns were effectively enhanced. With the same confining stress, the peak loads of the BFRP- and CFRP-confined columns were nearly the same. However, the BFRP-confined columns with low and moderate concrete strength showed larger ductility and energy dissipation capacity compared with the CFRP-confined counterparts, and these capacities of the CFRP-confined column with a concrete strength of 57.8 MPa were slightly better than those of the BFRP-confined equivalent. This showed that the FRP jackets with larger modulus had better confinement effect on the columns with higher concrete strength. Finally, formulas for calculating the load carrying and ductility capacities of different FRP-confined circular RC columns were proposed based on the experimental results.