Aramid Fiber Reinforced Polymer Research Articles

Multiscale Analysis of the Flexural Performance of FRP Reinforced Concrete Structures

Based on existing experimental data and analysis, seven different FRP bar models including Carbon Fiber Reinforced Polymer (CFRP), Basalt Fiber Reinforced Polymer (BFRP), Aramid Fiber Reinforced Polymer (AFRP), Glass Fiber Reinforced Polymer (GFRP), GFRP and CFRP combined (G-C), GFRP and AFRP combined (G-A), BFRP and CFRP combined (B-C), and BFRP and AFRP combined (B-A) were established. Finite element simulation analysis was conducted on seven different FRP bar combinations under static load bending tests. The flexural behavior of the specimens reinforced with different FRP bar combinations and their influencing factors were analyzed. The results showed that using AFRP as the reinforcement material for FRP composite bars in FRP reinforced concrete beams cannot effectively enhance the overall load-carrying capacity of the composite bars. The combination of CFRP with GFRP and BFRP bars significantly increases the stiffness of the FRP bar structure and improves the structural load-carrying capacity of the concrete beams.

Titanium/FRP hybrid sandwich: in-plane flexural behaviour of short beam specimens

Adopting novel sandwich structures with FRP (Fibre Reinforced Polymer) skins and a metallic lattice core, both of which have high specific strength and stiffness, is one way to achieve better mechanical performance while remaining lightweight. Flexural stress is a load pattern that frequently occurs in the structural frame components of automobiles; nonetheless, while the in-plane load scheme has scarcely been examined, the out-of-plane load one has. As a result, the former configuration received consideration in this work. Moreover, short beam specimens were taken into account. The mechanical response of specimens with three different kinds of composite materials as skin material was analysed. The skins were made of CFRP (Carbon Fiber Reinforced Polymer), with two different weaving styles, and AFRP (Aramid Fiber Reinforced Polymer). All-titanium specimens were studied, too. Similar maximum loads and maximum displacement at break were recorded for both CFRP and AFRP specimens, while the all-titanium one resulted stronger. In terms of the load-displacement curves, the first section featured an initial linear phase, followed by a minor load drop, likely attributed to the breakage of fibres. The CFRP specimens showed a sharp fracture of the skin fibres, while for the AFRP, a fraying was observed.

Experimental and numerical studies on AFRP-reinforced thin-walled tubes under axial impact loading

With the increase in global threats to infrastructure, from unforeseen events particularly in steel structures, there is a growing urgency to strengthen the impact resistance of steel elements. This research aimed to investigate the potential of using AFRP (Aramid Fiber Reinforced Polymer) to improve the energy absorption and crushing resistance of thin-walled circular hollow steel (CHS) tubes subjected to axial impact loads. Key aspects of the investigation include conducting a series of experiments to evaluate the impact of AFRP layer thickness, steel tube thickness, and impact velocity on structural performance. The performance metrics were characterized by analyzing impact force versus displacement, energy absorption capacity, peak crush load, and mean crush load. The results show that AFRP strengthening significantly enhances peak load capacity, energy dissipation, and impact force absorption compared to plain steel tubes. The AFRP-strengthened specimens exhibit higher specific energy absorption (SEA) and crushing force efficiency (CFE) compared to non-strengthened specimens, with peak force increasing by 18 % to 160 % for low external energy and 14 % to 190 % for high external energy. The three-dimensional finite element (FE) model accurately predicts load-carrying capacity and AFRP failure, validated against experimental tests. This study provides quantitative evidence of the effectiveness of AFRP reinforcement in improving the crash performance of thin-walled tubes under axial impact loading, highlighting the potential for optimizing AFRP strengthening techniques in structural applications.

Experimental study on the seismic performance of GFRP reinforced concrete columns actively confined by AFRP strips

This paper proposes a new type of concrete columns, which are reinforced with GFRP bars and actively confined by Aramid Fiber-Reinforced Polymer (AFRP) strips. FRP reinforcement is a non-corrosive material and has the advantages of having lighter weight, higher tensile strength, and long-term durability as compared to steel reinforcement. Active confinement has advantages over non-confined concrete columns and it is expected that the active confinement in the critical area increases the adhesion between the concrete and the rebars, strengthens the concrete cover portion of the rebars, and increases the shear capacity of the column. The literature does not show a comprehensive examination of the actively confined concrete columns that are reinforced by polymer and steel bars. Six reinforced concrete columns were cast, loaded, and tested under simultaneous application of axial and cyclic loads. Four columns were actively confined by AFRP strips at 10% and 30% of the AFRP ultimate strain in the critical area. Two columns were reinforced with steel bars, and the other two were reinforced with GFRP bars. Also, two columns with steel bars and GFRP bars, but without confinement, were utilized as the control specimens. Experimental results showed that the strain in the cover portion of the actively confined columns was reduced due to the effect of active confinement, and the strength of the concrete core increased. The active confinement increased the adhesion between the concrete and the bars and also reduced crack width, which ultimately resulted in increasing concrete strength, ductility, and energy absorption.

Impact of Filler on Mechanical and Dynamic Mechanical Properties of Waste Marble Dust Filled Aramid Fibre Reinforced Polymer Composite

Impact of Filler on Mechanical and Dynamic Mechanical Properties of Waste Marble Dust Filled Aramid Fibre Reinforced Polymer Composite

A Constitutive Model for Circular and Square Cross-Section Concrete Confined with Aramid FRP Laminates

Fiber-reinforced polymer (FRP) has been used for seismic retrofitting and structural reinforcement over recent decades. Numerous researchers have created stress–strain models based on experimental data to predict the mechanical properties of FRP-confined concrete. In this study, circular and square cross-section specimens with different design concrete strength were prepared, and the compressive strength of the specimens confined with different layers of aramid FRP (AFRP) were measured in compressive tests. A constitutive model was proposed to simulate the uniaxial compressive stress–strain relationship of the AFRP-confined concrete, which was derived from the Mohr–Coulomb failure envelope theory, and the corresponding axial strain was determined from the regression analysis. The internal friction angle of the proposed constitutive model was determined for the cylindrical concrete specimens confined with one and two layers of AFRP. The compressive strength of one and two layers of AFRP-confined concrete specimens were used to obtain the parameters of the constitutive model; the absolute average error between experimental and predicted compressive strength was 7.01%. Then, the constitutive model was used to predict the strength of a three-layer AFRP-confined concrete specimen, and the absolute average error was 4.95%. The cross-sectional shape coefficient of the square concrete specimen was obtained analytically. Substituting the cross-sectional shape coefficient into the proposed constitutive model, the average absolute error of the square cross-section concrete specimen was about 3.84%. The results indicated that the proposed constitutive model can predict the compressive strength of circular and square cross-section concrete specimens confined with AFRP.

Compressive behaviour of FRP-confined rubberised alkali-activated concrete

This paper presents experimental and numerical assessments into the compressive stress-strain behaviour of circular FRP-confined rubberised alkali-activated concrete with unidirectional sheets incorporating fibres in the hoop direction. The parameters investigated in the experimental programme include three different rubber contents of 0%, 30% and 60% volumetric replacement of the total natural aggregates and three confinement levels of 1–3 aramid FRP layers. The numerical assessment is performed in ABAQUS/CAE and a new strain hardening-softening function is developed for the compressive behaviour in the Concrete Damaged Plasticity material model, which captures the passive confinement imparted by the FRP jacket on the rubberised concrete. The numerical results are validated against the experimental results and a parametric study involving 240 models covering a wide range of parameters, including varying FRP materials (basalt, glass, aramid, and carbon), reference concrete grades, rubber replacement ratios, and confinement levels, is performed. The experimental results show an increase in the confinement effectiveness, i.e., confined-to-unconfined strength, by 66.7% and 103.4% for specimens with 0% and 60% crumb rubber replacement ratio, respectively, as the number of FRP layers increase from 1 to 3. Test specimens with 0% and 60% crumb rubber replacement ratio indicate an increase in the ultimate axial strain by 228.2% and 76.2%, respectively, as the number of FRP layers increase from 1 to 3. The observed hoop rupture strain reduces by 32.8% and 21.3% for specimens with 0% and 60% crumb rubber replacement ratio as the number of FRP layers increase from 1 to 3, showing a trend of reduction in the hoop rupture strain with higher FRP confinement layers and rubber content. The numerical results show that the enhancement in compressive strength is linearly proportional to the confinement ratio and is only marginally influenced by the FRP jacket stiffness at a given confinement ratio. The ultimate axial strain enhancement is also linearly proportional to the confinement ratio but is dependent on the FRP jacket stiffness. The compressive stress-strain curve for sufficiently confined specimens is also shown to be well represented by a bi-linear curve with hardening. Based on the findings, a design-oriented model is introduced for sufficiently confined specimens and is shown to be in close agreement with the experimental results.

Explainable Data-Driven Ensemble Learning Models for the Mechanical Properties Prediction of Concrete Confined by Aramid Fiber-Reinforced Polymer Wraps Using Generative Adversarial Networks

The current study offers a data-driven methodology to predict the ultimate strain and compressive strength of concrete reinforced by aramid FRP wraps. An experimental database was collected from the literature, on which seven different machine learning (ML) models were trained. The diameter and length of the cylindrical specimens, the compressive strength of unconfined concrete, the thickness, elasticity modulus and ultimate tensile strength of the FRP wrap were used as the input features of the machine learning models, to predict the ultimate strength and strain of the specimens. The experimental dataset was further enhanced with synthetic data using the tabular generative adversarial network (TGAN) approach. The machine learning models’ performances were compared to the predictions of the existing strain capacity and compressive strength prediction equations for aramid FRP-confined concrete. The accuracy of the predictive models was measured using state-of-the-art statistical metrics such as the coefficient of determination, mean absolute error and root mean squared error. On average, the machine learning models were found to perform better than the available equations in the literature. In particular, the extra trees regressor, XGBoost and K-nearest neighbors algorithms performed significantly better than the remaining algorithms, with R2 scores greater than 0.98. Furthermore, the SHapley Additive exPlanations (SHAP) method and individual conditional expectation (ICE) plots were used to visualize the effects of various input parameters on the predicted ultimate strain and strength values. The unconfined compressive strength of concrete and the ultimate tensile strength of the FRP wrap were found to have the greatest impact on the machine learning model outputs.

The effects of graphene oxide addition on low velocity impact performance of aramid fiber reinforced epoxy composites

AbstractIn this study, the impact of incorporating graphene oxide (GO) nanoparticles into the matrix of aramid fiber reinforced polymer (AFRP) composites was investigated. The GO nanoparticles were dispersed in the AFRP matrix at three different weight percentages: 0.1%, 0.3%, and 0.5%. The fabrication of the GO dispersed AFRP nanocomposites was achieved using the vacuum assisted resin infusion molding (VARIM) method, and the AFRP plates were cut using a water jet. The sectioned specimens of the fabricated nanocomposites were subjected to low velocity impact tests. The effects of introducing GO nanoparticles at different percentages were evaluated by analyzing the contact force, deflection, maximum absorbed energy versus time and contact force versus deflection curves. Finally, the key parameters of low velocity impact, including contact force, deflection, and maximum absorbed energy, were compared for the different fabricated AFRP nanocomposites. Based on the results, the AFRP composite with 0.3 wt.% of GO nanoparticles exhibited the best performance under low velocity impact loading conditions. However, the agglomeration of nanoparticles became a significant challenge when higher percentages of GO nanoparticles were added to the composite structure. The findings highlight the importance of determining the optimal percentage of nano materials for incorporation into composite structures.

Hysteretic performance of prestressed concrete beams with AFRP tendons under cyclic loading

AbstractThis paper aims to evaluate the hysteretic performance of prestressed concrete beams with aramid fiber‐reinforced polymer (AFRP) tendons. Eight beams were constructed and tested under cyclic loading, with test variables covering the type of prestressing tendons (AFRP and steel), the ratio of internal tendons to external tendons (3:0 and 1:2) and the bond condition of internal tendons (fully bonded, partially bonded, and unbonded). Results showed that the failure of all the beams was dominated by concrete crushing and nonprestressed rebars rupturing at pure bending sections. AFRP prestressed beams exhibited commensurate bearing capacity, displacement ductility, energy dissipation and residual deformation with steel prestressed beams. The combination of internal and external tendons, and using unbonded or partially bonded tendons could improve the ductility of AFRP prestressed beams. Additionally, the finite element (FE) models of AFRP prestressed beams were developed using ABAQUS based on the coupling method under the local coordinate system. The simulated results closely matched the experimental results in terms of the failure mode and load–displacement curve. Parametric predictions, including the unbonded length of AFRP tendon, partial prestressing ratio, jacking stress and concrete strength were presented to extend the experimental works.

Evaluation of impact response of thermal-damaged FRP-RC slabs: Effects of FRP bar type and concrete cover thickness

The purpose of present study is to investigate the impact response of FRP-RC slabs under elevated temperatures. Considering the high-temperature degradation effect and strain rate enhancement effect of FRP bars and concrete materials, a numerical model for studying the fire and impact resistance of FRP-RC slabs was established and verified. The impact failure mechanism of in-fire thermal-damaged FRP-RC slabs was analyzed. The influence of the type of FRP bars, concrete cover thickness and fire duration on the in-fire impact resistance of FRP-RC slabs was revealed. Ultimately, the post-fire residual bearing capacity of the slabs after elevated temperature and impact was obtained. The results show that the typical local punching failure mode is not affected by thermal damage while energy dissipated by concrete accounts for most of the impact energy absorbed by the slabs. When exposed to fire for 60 min, the elevated temperature significantly deteriorates the impact resistance of FRP-RC slabs with a cover thickness of 15 mm. At this time, the greater the concrete cover thickness, the better the impact resistance of FRP-RC slabs. Under the combined action of elevated temperature and impact, Carbon FRP-RC slabs have greater stiffness, lower deflection, greater impact plateau value, less impact duration and lower energy consumption than Aramid FRP, Basalt FRP and Glass FRP-RC slabs. Moreover, the damage index of the slab based on residual bearing capacity and peak displacement is approximately linearly positively correlated. The influence of the concrete cover thickness is more prominent on the damage index based on the peak displacement.

Experimental assessment and effective bond length for RC columns strengthened with aramid FRP sheets under cyclic loading

Fiber reinforced polymer (FRP) materials continue to demonstrate outstanding performance for strengthening and repairing reinforced concrete structures. However, one of the most significant problems that still has to be tackled is premature failure brought on by the FRP debonding. This research sought to determine how damaged RC columns could be strengthened with aramid (one type of FRP) composites and how that would affect their seismic responses. To further understand the individual effects of each strengthening material on seismic performance, hysteretic responses, such as strength, ductility, and energy dissipation, were examined and compared. Analytical modeling is validated based on the experimental results. Experimental results are validated with comparative study against other solid experimental results within the broader field. Effective bond length (EBL) is crucial for understanding the bonding between aramid fibers and concrete, however various models have different ways of calculating the value of EBL. Therefore, this research examined earlier experimental investigations of EBL and employing finite element (FE) methods established a novel relationship between the EBL and the aramid-to-concrete bond, based on experimental results.

Experimental and numerical investigations on RC beams flexurally strengthened utilizing hybrid FRP sheets

During structural evaluations and inspections of existing buildings to determine their soundness, a number of structural defects are usually identified, especially in older buildings whose functional lifespan and safety could be increased by timely retrofitting or rehabilitation operations. Due to their superior performance as reinforcing material for restoration projects, fiber reinforced polymer (FRP) composites are widely used in various civil engineering applications. This research study focuses on the execution of, reinforced concrete (RC) beams whose flexural strength is significantly improved with the usage of hybrid-FRP (HFRP) composites, a combination of aramid-FRP (AFRP) and glass-FRP (GFRP) laminates/sheets. Five RC beams are cast and tested using a four-point bending configuration as sample for experimental and numerical studies. The steel reinforcement ratio used for designing RC beams is 0.47%. The thickness of HFRP laminates is the main varied test factor used in this investigation. One of the five beams is designated as the control beam, while the other four were strengthened using HFRP laminates. The findings of the present study demonstrate that using HFRP laminates effectively improves the load-bearing capability of the RC beams. However, using thicker HFRP sheets to increase strength is not advised because flexural strength is controlled by epoxy properties and surface quality of the concrete. According to the experimental findings, the increase in the ultimate load of the HFRP3-strengthened beam (SH3) is noted to be 202.63%, as compared to the control beam. Furthermore, the experimental outcomes are compared with that of the finite element (FE) analysis using a finite element software and it is observed that there is good agreement between these results.

Experimental study and simulation analysis of the fracture mechanism in AFRP milling

The finite element model of aramid fiber reinforced polymer (AFRP) was established using the finite element analysis software, and milling simulation analysis was carried out. The influence of cutting speed and tool diameter on cutting force was obtained. Based on the motion law of the milling cutter, a fiber cutting mechanical model was established, and the influence of shear force and transverse pressure on the quality of the fiber section was analyzed. The milling experiment on AFRP specimens was carried out, and the milling appearance and cutting force variation of cutting speeds at 18.850–31.415 m/min and tool diameters of 1 –5 mm were studied. The results show that the diameter of a 5 mm milling cutter has a neater cutting fiber section and fewer burrs than the diameter of a 1 mm milling cutter, but inadequate sharpness can easily cause serious entrance burrs. Due to the influence of the feed motion, the milling tool feeding direction (X direction) is 42.456% higher than the Y direction cutting force, which can easily cause tool fracture. Increasing cutting speed can reduce cutting force to a certain extent and improve cutting quality. Therefore, choosing a large-diameter milling cutter with a large rake angle or relief angle for high-speed cutting can effectively improve the quality of the AFRP milling entrance and section.

Analytical truss model for concrete beams reinforced with FRP bars

A truss model supplementing the concrete contribution is introduced in this paper to predict the shear strength of concrete beams reinforced with various types of FRP bars. The contributions from truss and direct strut mechanisms are considered in the analytical model. The truss model which has struts at various angles considering concrete contribution is derived in this paper. The concept of equivalent transverse FRP reinforcement is applied to integrate the concrete contribution into the proposed truss model. The shear strengths of concrete and FRP transverse reinforcements in the proposed model are calculated based on El-sayed et al. and CSA S806, respectively. The validity and applicability of the proposed model are evaluated by comparison with available experimental database, which consists of concrete beams reinforced with glass, carbon, aramid and basalt FRP bars. The comparison has shown a good correlation between the experimental data and analytical results. The proposed model is also compared with ACI 440.1R and CSA S806’s shear strength models and the better correlation is found. The results from this research shows that the properly-treated truss analogy can be used to assess the shear strength of concrete beams reinforced with various types of FRP bars.

Tin Slag Polymer Concrete Strengthening by Basalt and Aramid Fiber Reinforced Polymer Confinement

This study investigates the potential of Tin Slag Polymer Concrete (TSPC) strengthening through confinement using basalt fiber reinforced polymer (BFRP) and aramid fiber reinforced polymer(AFRP) confinement. TSPC short cylindrical column samples have been wrapped with BFRP and AFRP in a single layer (30 mm overlap) using Sikadur-330 epoxy and final samples were coded as TSPC-UC, TSPC-BF and TSPC-AF for unconfined, BFRP and AFRP for confined respectively. After curing for 30 days at room temperature, compressive test has been performed to know the strength, modulus, strain, fracture energy and failure modes of unconfined and confined TSPC.

Numerical investigation on the flexural behavior of geopolymer concrete beam reinforced with different types of fiber-reinforced polymer bars

Concrete is a highly versatile and durable building material. The risk of greenhouse gas emissions and the subsequent environmental deterioration associated with the use of concrete has prompted research on concrete substitutes. Geopolymer concrete (GPC) reinforced with fiber-reinforced polymer (FRP) rebars has gained acceptance as FRP rebars typically possess more tensile strength and are corrosion-resistant compared to steel. The commonly used FRP rebars are Carbon FRP (CFRP), Glass FRP (GFRP), Aramid FRP (AFRP), and Basalt FRP (BFRP). Though research has been done on GPC reinforced with CFRP, GFRP, and BFRP rebars; work has yet to be explicitly reported on GPC reinforced with AFRP. Furthermore, comparative studies on the flexural strength of GPC beams reinforced with different FRP rebars are not available, which calls for additional research on GPC reinforced with various FRPs. This paper compares the flexural behavior of GPC beams reinforced with various FRP bars by performing a nonlinear finite element analysis using Abaqus. The different material constitutive models and parameters of concrete and FRP rebars are analyzed to model their complex nature in Abaqus. The load-deflection behavior and the failure modes of these beams are studied by simulating a four-point bending test in Abaqus. Different parametric studies are conducted on GPC with FRP rebars by varying the parameters of concrete and reinforcements. The results indicate that among the four FRPs considered in this study, CFRP bars performed better for tensile reinforcement, while steel stirrups showed better results for shear reinforcement. As there are no specific design standards for FRP-reinforced GPC beams, these results may be successfully applied to modifying the existing standards.

Theoretical analysis on flexural strengthening of RC beams using GFRP composites in terms of strength to the weight ratio: A way forward

Aramid, Glass or Carbon Fibre Reinforced Polymer (GFRP/CFRP) are three types of composites that are commonly used in the civil, mechanical and automobile sectors worldwide. GFRP composites are often used for structural member strengthening, repairs, and rehabilitation. In comparison to CFRP and Aramid FRP composites, GFRP is easily available, inexpensive, good strength to the weight ratio, and has several additional benefits. The strength-to-weight ratio of GFRP composites and steel plates for flexural strengthening of RC beams is investigated in this work. Theoretical analysis for the RC beam strengthened with GFRP composites and steel plates were performed using the established equation based on Indian standards and the ACI code. The self-weight of the beam and the superimposed dead load owing to the block/brick work were taken into account in the design calculations. The beam's load carrying capability is inadequate due to the excessive load, thus it must be strengthened with different materials: GFRP Chopped Strand Mat (CSM) composites or steel plates. The evaluations were conducted under the assumptions that the loss of moment carrying capacity due to concrete deformation caused by bolt holes and failure due to GFRP composite delamination would be disregarded. Strength to weight ratio of GFRP composites and steel plate requirements have been computed and compared for the known dimensions, unit weight and tensile strength of the strengthening materials, and load carrying capability of the strengthened RC beam. Comparative study proves that the flexural strengthening of RC beams using GFRP composites, the strength to weight ratio is much higher than when the identical beams are strengthened with steel plate.

Transfer Length vs. Slip of Prestressed Fiber-Reinforced Polymer Reinforcement.

A comprehensive analysis of the relationship between transfer length and slip of different types of prestressed fiber reinforced polymer (FRP) reinforcement is provided. The results of the transfer length and slip together with the main influencing parameters of approximately 170 specimens prestressed with different FRP reinforcement were collected. After the analysis of a larger database of transfer length versus slip, new bond shape factors were proposed for carbon fiber composite cable (CFCC) strands (α = 3.5) and carbon fiber reinforced polymer (CFRP) bars (α = 2.5). It was also determined that the type of prestressed reinforcement has an influence on the transfer length of the aramid fiber reinforced polymer (AFRP) bars. Therefore, α = 4.0 and α = 2.1 were proposed for AFRP Arapree bars and AFRP FiBRA and Technora bars, respectively. Moreover, the main theoretical models are discussed together with the comparison of theoretical and experimental transfer length results based on the slip of reinforcement. Additionally, the analysis of the relationship between transfer length and slip and the proposed new values of the bond shape factor α have the potential to be introduced in the production and quality control processes of precast prestressed concrete members and to stimulate additional research that increases the understanding of the transfer length of FRP reinforcement.

Process Design for Manufacturing Fiber-Reinforced Plastic Helical Gears Using a Rapid Heating and Cooling System

In this study, a lightweight fiber-reinforced plastic (FRP) helical gear was fabricated to investigate the potential application of FRP in automobile parts that require high loads and reduced noise. High-performance aramid FRP processed using the wet-laid method was used in the tooth region, and SCR420 steel was used in the inner hub region. A hot-forming system that combines rapid induction heating and water channel cooling methods was developed to reduce the cycle time. The cooling water flow conditions were analyzed to precisely control the mold temperature. Additionally, a rotating extraction system was developed to mitigate the extraction difficulty owing to the helix angle to the extraction direction. Using the innovative hot-forming system developed in this study, a helical gear without any process-induced defects was fabricated with a significantly reduced cycle time. The performance of the gear was successfully estimated using gear durability, torsional strength, and motion noise tests. The use of FRP materials offers significant potential to realize lightweight components; however, certain challenges related to their properties that may limit their application must be addressed on a case-by-case basis.