Fiber Reinforced Polymer Materials Research Articles

Reinforcement effect of shear thickening fluid on impact properties of aramid, basalt, and carbon fiber reinforced polymer using a split Hopkinson pressure bar

This study focuses on investigating the impact properties of fiber-reinforced polymer (FRP) materials impregnated with shear thickening fluid (STF) under high strain rates using a split Hopkinson pressure bar (SHPB) test. The study involves the preparation of three types of FRP materials, namely aramid FRP (AFRP), basalt FRP (BFRP), and carbon FRP (CFRP), which are subsequently impregnated with STF to develop FRP composite materials (referred to as FRP-STF). The STF used in the experiment is synthesized by dispersing 15.0 wt.% and 20.0 wt.% of 12 nm silica in Polyethylene glycol. The results of rheological tests show a significant shear thickening effect on viscosity for both STFs. Furthermore, the SHPB tests demonstrate a noteworthy improvement in the impact performance of AFRP, BFRP, and CFRP under high strain rates when impregnated with STF. However, the extent of this improvement varies among the different types of FRP materials. For instance, BFRP exhibits the highest increase in stress peak, reaching 58.9% under a strain rate of 3800 s⁻1 and an STF mass fraction of 20%. AFRP demonstrates the most significant increase in energy absorption, reaching 226.8%. When subjected to a strain rate of 6100 s⁻1, the AFRP-20% STF composite exhibits a highly favorable stress response, while the CFRP-20% STF composite shows an energy absorption of 710.5 J, approximately 3.3 times higher than that of pure CFRP. These trends are also evident in the energy absorption per unit density curve.

A Flexibility Analysis of Single-shear CFRP-metal Hybrid Joints under Static Tensile Testing

In this paper, three static tests were carried out on Carbon Fiber Reinforced Polymer material (CFRP)-metal joints with single bolted connections. The effects of fastener diameter, fastener material, fastener clamping force, fixture, and fatigue on the flexibility of the joint were investigated. The reasonableness of secant and tangential flexibility was compared and discussed based on the load-displacement curve of the joints. The test results indicated that the fixture reduced the out-of-plane buckling of the structure and increased the flexibility of the joint. The joint became stiffer after the fatigue cycles. At the same time, the flexibility was strongly affected by the fastener diameter and materials. The clamping force had a slight effect on the flexibility.

Induction Heating Characteristics of Electroless Ni-Coated CFRP for Deicing and Anti-Icing

Ice accumulation on the surface of aircraft is a serious threat to flight safety and a fatal factor causing air accidents. However, traditional aircraft deicing methods no longer meet the requirements of safe flight due to changes in aircraft structural materials. In recent years, the application of carbon fiber-reinforced polymer (CFRP) materials in the aviation structure industry has increased. In this study, we demonstrate an economical, easy-to-prepare, and pollution-free approach to deice an aircraft through induction heating. The nickel-coated carbon fiber-reinforced polymer used as the induction heater for aircraft deicing is obtained by electroless nickel plating on the surface of the CFRP. The result shows that it takes just 110 s to achieve a temperature of 205 °C on the nickel-plated CFRP when the input voltage is 30 V, as well as melting the ice layer with a thickness of 30 mm, while the temperature of this material can reach up to 81 °C by electric heating when the input voltage is 1.5 V. Meanwhile, the nickel-plated CFRP exhibits good repeatability during the induction heating. Based on the excellent electrothermal properties, the nickel-plated CFRP polymer shows a prominent deicing ability, which provides a promising strategy for the deicing of aircraft.

An ultrathin polymer-derived UHTCs coating on CFRP substrate: Effective electromagnetic wave absorber

The utilization of carbon fiber-reinforced polymer (CFRP) materials in electronic equipment encounters notable challenges of electronic warfare operations and the risk of detection by various sensors. A novel ceramic coating comprising TiC/SiOC with added Al2O3 adhesive was formulated to address these issues. The TiC/SiOC-50 wt% Al2O3 coating demonstrated exceptional microwave-effective absorption bandwidth (EAB) of 13.5 GHz, effectively covering the entire Ka-band, while maintaining a thin thickness of 0.60 mm. The TiC/SiOC-80 wt% Al2O3 system exhibited remarkable EM characteristics, including a minimum reflection loss (RLmin) of −58.26 dB, an EAB of 10.74 GHz, and an ultra-thin thickness of 0.38 mm, which sets a new record as the thinnest reported coating in the existing literature. The outstanding electromagnetic performance, coupled with their lightweight and thin characteristics, positions these coatings as highly viable solutions for various electromagnetic shielding and absorption applications in extreme environments.

Shear transferring mechanism of the FPR-to-concrete bonded joint with end U-jacketing: A theoretical study

Installation of fiber reinforced polymer (FRP) U-jackets is an effective method for improving the low utilization rate of the expensive FRP material in the application of flexural strengthening of the reinforced concrete (RC) beam. The stress transfer mechanism of the FPR-to-concrete bonded joint with end U-jacket still remains poorly understood. This study proposed a new analytical model to predict the interfacial debonding process and the load carrying capacity of the joint with end U-jacket. The failure process of the FRP-to-concrete joint with an inclined U-jacket features five stages including elastic, elastic-softening, elastic-softening-debonding, softening-debonding and completely debonding stages. Expressions for the interfacial shear stress distribution and load–displacement relation are derived for these five stages. The load–displacement curve predicted by the analytical model, indicating that the bearing capacity of the joint with end U-jacket has increased by 200%, is in good agreement with the experimental and FE analysis results. Finally, the results from analytical solutions are presented to clarify the effects of the bond length, the FRP plate stiffness and the elasticity coefficient of end U-jacket on the load–displacement relations, the ultimate load and the effective bond length.

Damage and Defects in Fiber-Reinforced Polymer Reinforced and Strengthened Concrete Elements

Fiber-reinforced polymer (FRP) composites are becoming increasingly popular as an alternative to conventional civil engineering materials in existing structures as externally applied systems for strengthening purposes, and in new structures as internal reinforcements in the form of bars, meshes, and strands. The next phase of development in the application of FRPs in concrete structures could culminate in elements possessing both internal and external FRP systems simultaneously. With these advancements in the application of FRP in civil engineering, it is conceivable that traditional steel reinforcements could become obsolete in certain aggressive and hostile environments, such as coastal areas. Although higher durability and performance are associated with FRP materials in some respects when compared to steel, concerns remain regarding the damage and defects in this material, many of them related to their unique features. Regardless, similarly to other structural materials, it is necessary to understand the damage and defects associated with the use of FRP composites, as well as to identify their sources. This knowledge will support the positive prospects for FRP technology, promoting its application in civil infrastructure. Accordingly, this study investigated the types, characteristics, and identification of the observed or expected damage and defects associated with using FRP in reinforced and strengthened concrete elements. The damage was classified according to location and time of initiation. In addition, the sources of these defects and damage were determined, and a damage etiology was established for preventing the occurrence of such damage in future use. The results of this study are intended to provide the background for the development of a guide and training material for the inspection of structures that use FRP materials. The ability to inspect and properly maintain structures containing FRP will result in the enhanced durability and service life of concrete structures reinforced or strengthened with FRP materials.

Flexural Strengthening of Concrete Structures Using Externally Bonded and Unbonded Prestressed CFRP Laminates: A Literature Review

Carbon fiber-reinforced polymer (CFRP) materials have been widely used in prestressed and non-prestressed systems for the flexural strengthening of concrete structures in many construction projects worldwide. Strengthening with non-prestressed CFRP materials, which is known as passive repair, could lead to an increase in the ultimate capacity of the concrete member. However, it has little effect on its serviceability performance (e.g., cracking, yielding, and deflection properties). Flexural strengthening with prestressed CFRPs provides an active repair technique that positively effects the strength and serviceability of structures. In addition, strengthening with prestressed fiber-reinforced composites efficiently uses the material’s high tensile strength. Although different fiber-reinforced polymer (FRP) materials and forms have been used in prestressing applications, this paper focused on the use of CFRP laminates (e.g., sheets, strips, or plates). These laminates have been widely used due to their excellent mechanical properties, ease of application in various geometrical shapes, good conforming surface area of contact with structures, and low installation costs. A comprehensive literature review was presented on strengthening using prestressed CFRP laminates in conventionally and internally prestressed concrete structures (PCSs). The externally bonded and unbonded prestressed CFRP laminate applications that used different anchorage systems were presented. The flexural behavior, failure modes, and serviceability performance of the strengthened concrete members were discussed. The effects of the prestressing level on ductility and energy absorption and a summary of the recommended optimum prestressing level discussions were presented in this paper. Furthermore, a review of the theoretical studies that were conducted for prestressed CFRP applications was provided. The knowledge gaps in the research area and future research recommendations were presented.

Fatigue performance improvement of U-rib butt-welded connections of steel bridge decks using externally bonded CFRP strips

U-rib butt-welded connections in steel bridge decks are known to be highly susceptible to fatigue cracking, which can pose a direct threat to the safety and durability of bridge structures. Carbon fiber-reinforced polymer (CFRP) materials have shown promising potential for fatigue strengthening. This study investigated the effectiveness of CFRP application on the fatigue performance of U-rib butt-welded connections by employing full-scale fatigue tests and finite element analysis. Two single U-rib specimens with welded splice joints were initially tested to initiate real fatigue cracks under cyclic loading. Different techniques of CFRP installation were then proposed to promote the fatigue performance of cracked butt-welded connections. The failure modes and fatigue strength of the tested specimens were evaluated before and after strengthening. Research results showed that fatigue cracks were observed at the arc transition of butt welds, where remarkable incomplete penetration was also discovered. The fatigue strength grade of the tested U-rib butt-welded details was less than 71 MPa stipulated by Eurocode 3. However, after being repaired by CFRP sheet bonding, the equivalent fatigue life of U-rib butt welds with different damage degrees can be extended by 0.5–16.6 times that of the original ones. These findings suggest that CFRP strengthening should be applied instantly on U-rib butt-welded connections once fatigue cracks are found.

Structural behavior of retrofitted RC beam-column joint using FRP wrapping technique

To improve the seismic performance of reinforced concrete (RC) beam-column junction in structures, fibre reinforced polymer (FRP) are used by wrapping it externally. The failure of these connections is a significant issue in seismic design and retrofitting techniques are necessary to improve their behavior. Utilising basalt geogrid and basalt fibre fabric, RC exterior beam-column junctions are repaired, and the specimens are tested under cyclic seismic loading until failure to evaluate their structural performance. The use of FRP materials, which are available in various forms and types, has been found to improve the strength, ductility, and other important parameters of structural elements. This research highlights the potential of these materials in retrofitting and enhancing RC buildings' seismic performance.

Experimental investigation of FRP strengthened reinforced concrete T-beams in torsion

In general, reinforced concrete (RC) members are most commonly influenced by flexural moments, axial and shear forces. However, they may also be subject to torsional moments. Torsion in reinforced concrete (RC) beams is an important phenomenon that affects the structural behaviour of buildings. Both the concrete and steel reinforcement contribute to the torsional resistance of a RC member. However, the contribution of concrete is usually neglected by the modern design codes, due to cracking. Moreover, the subject of maintenance and repair or strengthening of existing RC structures is a significant problem. The last years, fibre reinforced polymer (FRP) is widely used as external reinforcement in flexural and shear strengthening. Nevertheless, its use in torsional strengthening is not so widely investigated. Ιn this paper, the torsional behaviour of RC T-beams reinforced in shear with FRPs is experimentally investigated. Five groups of T-beams subject to pure torsion, two of which are control beams and other three beams are strengthened in shear with U-jacketed FRP fabrics. Experimental results reveal that FRPs can increase the ultimate torsional capacity of the member.

Engineering software development for strengthening concrete structures using fiber-reinforced polymers

In this study, engineering software for the calculations of the strengthening applications of reinforced concrete (RC) load-bearing elements with Fiber Reinforced Polymer (FRP) composite materials is developed. This software is developed to increase the axial compression strength and ductility capacity of columns and improve the shear capacity of beams using FRP material according to provisions of the Turkısh Building Earthquake Code 2018 (TBEC-2018). In addition, this software offers designers the opportunity to perform calculations to increase the bending moment capacity of beams using FRP composite material, according to the American Concrete Institute 440-2R.17 (ACI 440-2R.17). Algorithms to be used to increase the capacities of RC load-bearing elements with FRP composite materials are formed according to the provisions of the mentioned codes. Then, computer and web-based engineering software with different coding languages are developed depending on these algorithms.

Effect of the NSM material and area on the flexural response of normal strength concrete beams internally reinforced with GFRP and steel bars

Strengthening the steel-reinforced concrete (RC) beams by fiber-reinforced polymer (FRP) elements have become common several years ago. Recently, the RC beams internally reinforced with FRP reinforcement, especially Glass FRP (GFRP) bars, became popular worldwide. The carbon FRP (CFRP) elements (strips and bars) were recently used to strengthen the internally GFRP RC beams. In contrast, using the GFRP elements to upgrade the RC beams, especially those with GFRP bars as the main tensile reinforcement, was rarely studied. In this paper, the GFRP bars were implemented as near-surface mounted (NSM) elements to upgrade the beams reinforced in their tension side with GFRP or steel bars. All beams were experimentally loaded in flexure using a four-point loading scheme. The experimentally studied parameters were the main tensile reinforcement area, NSM area, and main reinforcement properties. Moreover, a numerical model was established and validated using the available experimental data to investigate the impact of main and NSM materials properties and areas on RC beam response. The experimental results highlighted that increasing the internal and NSM GFRP area by 96% and 100 % increased the beam capacity by 61.6% and 59.7%, respectively, which underlined a slightly higher efficiency of the main reinforcement than NSM bars on the beam load capacity. In addition, substituting the main steel with GFRP bars for the beams upgraded with NSM GFRP reinforcement enhanced their capacities by 11.33–15.1%. This emphasized the great effect of the linear response of the FRP materials and their higher tensile strengths than steel on the interaction between the main and NSM reinforcement, especially after the steel yielding. The FE results showed the highest load capacity using CFRP and GFRP bars as main and NSM reinforcement for the simulated beams. Conversely, using CFRP bars as NSM strengthening was more efficient than GFRP bars for the RC beams with steel or GFRP bars.

Strengthening of RC beams in shear with novel near-surface mounted (NSM) U-shaped fiber-reinforced polymer (FRP) composites

Over the last three decades, various researchers have proven the high efficiency of the near-surface-mounted (NSM) fiber-reinforced polymer (FRP) method for strengthening reinforced concrete (RC) beams. The shear strengthening of RC beams by embedding FRP bars or strips onto the side concrete cover is a primary application of NSM FRP investigated in numerous studies. These studies revealed that despite the high bond efficiency between the NSM FRP and concrete, NSM FRP shear-strengthened beams frequently failed in debonding modes, such as FRP–concrete interfacial debonding or side concrete cover separation. Such debonding failures limit the strength utilization and strengthening efficiency of the FRP material. Anchoring measures have been proposed for NSM FRPs to mitigate such debonding failures. However, the manufacturing and installation processes of these anchoring devices are complicated. Moreover, interfacial debonding between the NSM FRPs and anchoring devices can still occur. Therefore, this study proposes a novel NSM U-shaped FRP (NUF) device for the shear strengthening of RC beams. The proposed NUF device was fabricated using a fiber sheet through a wet lay-up process. The device can effectively increase the bond efficiency between the FRP and strengthened beam. The concept, manufacturing, and installation processes of this device are discussed. Subsequently, an experiment was performed on seven full-scale RC beams. The test results showed that the proposed NUF device is able to postpone/prevent the debonding failure between NSM FRP and concrete thus largely increase the strengthening efficiency of NSM FRP method.

Experimental studies to evaluate tensile and bond strength of Stainless-Steel Wire Mesh (SSWM)

Structural strengthening is vital to improve the load-carrying capacity partially or severely damaged Reinforced Concrete (RC) elements. Fiber Reinforced Polymers (FRPs) are widely used for strengthening purposes. In this study, use of Stainless-Steel Wire Mesh (SSWM) is explored, as FRPs are having limitations like high cost, less fire resistance, and brittle behavior. The experimental studies are conducted to evaluate the mechanical properties of the SSWM, to explore its feasibility as a strengthening material. Three different variants of SSWM i.e., 30×32, 40×32 and 50×34 is considered for the study. SSWM used in present study is a woven mesh made from stainless-steel wires manufactured in India. Important mechanical properties such as tensile strength and bond strength with concrete surface is experimentally evaluated in this study. Response of test specimens are evaluated with respect to ultimate load carrying capacity, corresponding deformations, rupture strain, crack formation and failure propagation. SSWM exhibits a tensile strength of 600-1000 MPa which is comparable to tensile strength of various types of fibers used for strengthening. Based on experimental studies, it is found that SSWM 40×32 performs the better in different aspect, so it can be a good alternative for strengthening of RC elements compared to other FRP materials.

Mechanical performance of fiber-reinforced polymer tank under road pavements for stormwater storage

Due to increasing precipitation intensity, rising sea level, and land development, urban flooding has become a major issue in many places around the world. This research aims to develop underground storage tanks (USTs) using fiber-reinforced polymer (FRP) materials for stormwater detention, storage, and reuse. The USTs are intended to be placed underneath highway or street pavements. FRP as one of the emerging structural materials possesses several advantages including high strength-to-weight ratio and corrosion resistance. The mechanical performance of USTs has rarely been visited in the literature, the majority of which focuses on leakage issues and associated environmental problems. This paper presents detailed analyses of the mechanical performance of FRP USTs, including a laboratory test on a small-scale FRP UST and a verified finite element (FE) analysis on full-scale FRP USTs. The influences of various factors on the mechanical performance of the USTs were examined, including wall thickness, water storage, interfacial roughness between FRP and soil, and tank sizes. Both results from experiments and FE studies agree satisfactorily and reveal that (i) underground FRP UST developed tensile axial strains at the top surface at the mid-span of the tank and the side surface at the mid-height; (ii) compressive axial strains developed in most of the cap region; and (iii) large compressive circumference strains developed in the FRP UST in most locations. Insights gained from the laboratory test and the FE analysis are expected to provide a general guidance on the design of FRP USTs under road pavements for urban flooding mitigation and stormwater harvesting.

Serviceability behavior of High Strength Concrete I-beams reinforced with Carbon Fiber Reinforced Polymer bars

Fiber Reinforced Polymer (FRP) bars are anisotropic in nature and have high tensile strength in the fiber direction. The use of High-Strength Concrete (HSC) allows for better use of the high-strength properties of FRP bars. The mechanical properties of FRP bars can yield to large crack widths and deflections. As a result, the design of concrete elements reinforced with FRP materials is often governed by the Serviceability Limit States (SLS). This study investigates the short-term serviceability behavior of FRP RC I-beams. Eight RC I-beams reinforced with carbon-FRP (CFRP) and four steel RC I-beams, for comparison purposes, were tested under two-point loading. Deformations on the concrete and crack widths and spacing are measured and analyzed. A discussion on the main aspects of the SLS of FRP RC is introduced. The service load that fulfills the serviceability requirements, at a cross-section level, ranges between 0.27 and 0.38 times the ultimate load for sections dimensioned to fail in concrete crushing. The determinant criterion is the deflection limitation

Effect of fibre orientation and thermal exposure on the post‐fire mechanical behaviour of carbon fibre reinforced polymer material

AbstractThis study investigates the influence of fibre orientation and heat flux on the post‐fire (residual) load‐bearing properties of carbon fibre‐reinforced polymer (CFRP) laminates. As a result, a deep insight into the post‐fire load‐bearing response is gained, which is necessary to fully understand and assess the advantages of CFRP laminates containing different fibre orientations for use in load‐bearing structures. Specimens were produced from three CFRP laminates containing different fibre orientations, exposed to varying heat fluxes up to 40 and then loaded in either tension or three‐point bending at ambient room temperature. The study's results have shown that the post‐fire behaviour of CFRP specimens is sensitive to changes in fibre orientation and heat flux. For example, specimens with an anisotropic fibre orientation in tension had the highest tensile load‐bearing capacity, whereas those with bidirectional and multi‐directional fibre orientations demonstrated lower tensile load‐bearing capacities. In bending, however, specimens containing bidirectional and multidirectional fibre orientations had higher load‐bearing capacities than specimens with an anisotropic fibre orientation. Furthermore, the data also shows that exposure to a heat flux reduces the load‐bearing capacity in both the bending and tensile specimens.

Exploration And Research on The Durability of FRP Composite Materials

Concrete cracking caused by steel corrosion is the main form of concrete structure deterioration at present. In order to solve the problem of steel corrosion, people begin to seek to replace steel with corrosion-resistant materials. Fiber reinforced polymer (FRP) has the advantages of high strength to mass ratio, good fatigue resistance, simple construction, corrosion resistance, etc., and has been widely used in engineering in recent years. In this paper, it analyzes the research status of FRP composites and introduces the properties of different kinds of FRP composites in detail. Then, by comparing with ordinary steel bar, the advantages of steel bar containing FRP material are highlighted. Subsequently, the durability of FRP composite materials in corrosion environment is studied. Finally, this paper introduces the practical application of FRP composites in engineering. The results are helpful to popularize the application of FRP composites in practical engineering.

Ultimate behavior of RC beams strengthened in flexure using FRP material

The present paper investigates the ultimate flexural behavior of strengthened reinforced concrete (RC) beams with Externally Bonded (EB) or Near-Surface Mounted (NSM) Fiber-Reinforced Polymers (FRP) reinforcement. For the purpose of predicting the ultimate loads and deflections of strengthened RC beams, numerical and analytical models were developed. Both models were developed for strengthened RC beams that fail in flexure by FRP rupture. First, an analytical model was developed based on the moment-area theorem and the equilibrium of internal forces. Second, based on the finite element (FE) method, an 3D numerical model was developed using Cast3M software, version 21. The reliability of the numerical model was tested against the analytical and experimental results collected from previous research. The selected RC beams were made with Normal-Strength (NS) and High-Strength Concrete (HSC). The comparison showed that the numerical model has an excellent performance in predicting the load–deflection response until failure. Moreover, the beam damage obtained from the numerical modeling agreed with the experimental results. Finally, a numerical comparative study between EB and NSM systems was conducted. The comparison showed the effectiveness of the NSM system in terms of strength and ductility. Further, the analysis of stress and strain showed that NSM system reduces the stresses and strains in concrete and steel reinforcement and prevents cracks propagation.

Static and Fatigue Mechanical Performance of Abutments Materials for Dental Restorations.

The choice of the proper restorative material is essential for the long-term success of implant-supported rehabilitations. This study aimed to analyze and compare the mechanical properties of four different types of commercial abutment materials for implant-supported restorations. These materials included: lithium disilicate (A), translucent zirconia (B), fiber-reinforced polymethyl methacrylate (PMMA) (C), and ceramic-reinforced polyether ether ketone (PEEK) (D). Tests were carried out under combined bending-compression conditions, which involved applying a compressive force tilted with respect to the abutment axis. Static and fatigue tests were performed on two different geometries for each material, and the results were analyzed according to ISO standard 14801:2016. Monotonic loads were applied to measure static strength, whereas alternating loads with a frequency of 10 Hz and a runout of 5 × 106 cycles were applied for fatigue life estimation, corresponding to five years of clinical service. Fatigue tests were carried out with a load ratio of 0.1 and at least four load levels for each material, and the peak value of the load levels was reduced accordingly in subsequent levels. The results showed that the static and fatigue strengths of Type A and Type B materials were better than those of Type C and Type D. Moreover, the fiber-reinforced polymer material, Type C, showed marked material-geometry coupling. The study revealed that the final properties of the restoration depended on manufacturing techniques and the operator's experience. The findings of this study can be used to inform clinicians' choice of restorative materials for implant-supported rehabilitation, considering factors such as esthetics, mechanical properties, and cost.