Use Of Fiber Reinforced Polymer Materials Research Articles

Universal Bond Models of FRP Reinforcements Externally Bonded and Near-Surface Mounted to RC Elements in Bending.

The use of fibre-reinforced polymer materials (FRPs) for the retrofitting of reinforced concrete (RC) structures has become very popular. However, the main concern for the exploitation of FRPs is their premature debonding failure modes. This paper presents two different universal models for calculating flexed RC elements strengthened with externally bonded and near-surface mounted FRP reinforcements, which were derived by coupling principles of the fracture mechanics of solids and generally accepted assumptions. The first model allows a complete analysis of the behaviour, development, and propagation of rupture of the joint. The main advantages of the proposed model, compared to existing ones, are that it does not require additional bond shear tests to identify missing factors, and it is versatile and suitable for both externally bonded reinforcements (EBR) and near surface mounted (NSM) strengthening techniques. In addition, the concrete-FRP connection is divided into zones and the current phase and length of each zone are determined, allowing for more detailed analysis of the connection at different load stages. The proposed computational model and its derivation focus on the performance of the joint between the two cracks and the distribution of the shear stresses in that joint. The second one requires fewer computations and can be fully exploited when the joint is treated as a unit, without division. The results of the calculations have been validated using the experimental database of 77 RC beams and strengthened with externally bonded and near-surface mounted carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) sheets, plates, strips, and bars taken from 13 different studies. Both the prestress force and the initial stress state before strengthening were evaluated.

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.

FRP-Reinforced/Strengthened Concrete: State-of-the-Art Review on Durability and Mechanical Effects

Fiber-reinforced polymer (FRP) composites have gained increasing recognition and application in the field of civil engineering in recent decades due to their notable mechanical properties and chemical resistance. However, FRP composites may also be affected by harsh environmental conditions (e.g., water, alkaline solutions, saline solutions, elevated temperature) and exhibit mechanical phenomena (e.g., creep rupture, fatigue, shrinkage) that could affect the performance of the FRP reinforced/strengthened concrete (FRP-RSC) elements. This paper presents the current state-of-the-art on the key environmental and mechanical conditions affecting the durability and mechanical properties of the main FRP composites used in reinforced concrete (RC) structures (i.e., Glass/vinyl-ester FRP bars and Carbon/epoxy FRP fabrics for internal and external application, respectively). The most likely sources and their effects on the physical/mechanical properties of FRP composites are highlighted herein. In general, no more than 20% tensile strength was reported in the literature for the different exposures without combined effects. Additionally, some provisions for the serviceability design of FRP-RSC elements (e.g., environmental factors, creep reduction factor) are examined and commented upon to understand the implications of the durability and mechanical properties. Furthermore, the differences in serviceability criteria for FRP and steel RC elements are highlighted. Through familiarity with their behavior and effects on enhancing the long-term performance of RSC elements, it is expected that the results of this study will help in the proper use of FRP materials for concrete structures.

Materials for lightweight electric motors – a review

Electric motors are widely used in automobiles and large electric vehicles would be introduced in market in the near future to reduce global warming. Reduction in electric motor weight also reduces the overall weight of automobiles. The use of fiber-reinforced polymer materials reduces the weight of electric motors. Lightweight electric motors promote energy savings owing to the reduction of self-weight. Researchers all over the World are trying to make all parts of electric motors using lightweight materials. This review paper presents the outcome of research carried out by researchers from Germany and UK. Fiber reinforced plastics (FRP) reduce weight and increase mechanical and electrical properties. Phenolic composite materials gave promising results due to its electrical insulation properties and corrosion resistance. Thermosets do not swell when they are exposed to chemicals unlike thermoplastics. Aluminium matrix composites (AMC) are used to improve the motor efficiency resulting in a considerable weight reduction. Electric motors have 90 percent or above, which means that a high mechanical energy is derived from electrical energy. The remaining electrical energy is converted into heat. To prevent overheating, the heat is conducted through housing to a cooling jacket having cold water. Researchers have replaced the circular wire by rectangular flat wire that can be coiled tightly on the stator. Newer cooling concepts are developed for making housings using polymer materials. Carbon fiber reinforced materials with metal pins are used for reducing weight and to increase thermal conductivity. Use of high modulus fibers increase damping properties and reduce noise produced by electric motors. Comparisons between electric motors made of lightweight materials and traditional metals in terms of weight, efficiency, cooling rate are presented.

Axial Compressive Performance of CFRP Confined Self-stressing High-strength Concrete Cylinders

Due to the advantages of FRP (fiber reinforced polymer), such as light weight, high strength and corrosion resistance, FRP-confined concrete columns are gradually applied in civil engineering structures and have drawn wide attention from the engineering community. In order to avoid the stress hysteresis of CFRP (carbon fiber reinforced polymer) and make full use of FRP materials, expansive agent was added to concrete to make self-stressing high-strength concrete. In this study, the axial compression performance of 18 CFRP-confined self-stressing high-strength concrete cylinders was examined. The parameters include the CFRP layers and the level of prestress (with or without prestress). Experimental results show that 3.53–5.34 MPa prestress in concrete and 799.3–1584.2 MPa prestress in CFRP are produced in the composite cylinder. The stress-strain curves obtained from the experiment shows that the intercept stress, inflection stress and peak stress of the self-stressing specimens are all higher than those of the non-prestressed specimens. With the application of prestress, the utilization ratio of CFRP increases as well. In the theoretical calculation of intercept and peak stress, by modifying the existing models, the experimental results are in good agreement with the calculated results.

FRP-FLEXURAL STRENGTHENING OF STEEL BEAMS: A FINITE ELEMENT ANALYSIS STUDY

Fiber reinforced polymer (FRP) strengthening has been widely used for concrete structures. However, limited studies have been conducted on its application to steel structures. The use of FRP materials to retrofit steel members is an effective replacement for welded or bolted steel plates and offer high strength-to-weight ratio, resilience to environmental degradation, and a robust fatigue performance. Past studies have shown that the application of FRP to steel is a promising technical solution to help against corrosion and also to increase the load carrying capacity of steel members. In the present study, finite element analysis (FEA) model of a steel beam strengthened with carbon fiber reinforced polymer (CFRP) laminates was developed using ANSYS Mechanical finite element software program. The model was validated by comparing the FEA and experimental results of an existing study in the literature and they were in good agreement. A parametric study was conducted on the validated steel beam model with the aim to investigate the effects of basalt fiber reinforced polymer (BFRP) and two types of adhesives on its performance under static loading. The FRP laminates provided an increase in flexural capacity and pseudo ductility of the beams. The optimum bond length was found to be 2/5 of the span length for the beam in this study.

Modelling of Thin Structural Polymer Composites for Use of Automobiles -Review-

This review article introduces first a number of previous works and commercial examples on the use of fiber-reinforced polymer materials in the application to automobile structural components, and secondly considers the modeling for thin components of fiber-reinforced polymer composites with emphasis on the roofs and fenders of the automobiles. The need of this study seems obvious, since particularly in the sportive and high-grade automobiles, the composite materials have already replaced conventional metal materials resulting in the significant reduction of structural weight. In such application, laminated composite panels (shallow shells) are used for models of automotive panels. The structural components in the automobile are extensively exposed to vibration excitation and other external disturbances in practical use, and resonance phenomenon may cause disturbing effects such as noise and fatigue. One countermeasure for such negative effects is to make use of tailoring advantages for fiber reinforced laminated composites and the feasibility for optimization process is suggested.

Performance of FRP confined and unconfined geopolymer concrete exposed to sulfate attacks

In this study, the effects of magnesium sulfate on the mechanical performance and the durability of confined and unconfined geopolymer concrete (GPC) specimens were investigated. The carbon and basalt fiber reinforced polymer (FRP) fabrics with 1-layer and 3-layers were used to evaluate the performances of the specimens under static and cyclic loading in the ambient and magnesium sulfate environments. In addition, the use of FRP materials as a rehabilitation technique was also studied. For the geopolymerization process of GPC specimens, the alkaline activator has selected a mixture of sodium silicate solution (Na2SiO3) and sodium hydroxide solution (NaOH) with a ratio (Na2SiO3/NaOH) of 2.5. In addition to GPC specimens, an ordinary concrete (NC) specimens were also produced as a reference specimens and some of the GPC and NC specimens were immersed in 5% magnesium sulfate solutions. The mechanical performance and the durability of the specimens were evaluated by visual appearance, weight change, static and cyclic loading, and failure modes of the specimens under magnesium sulfate and ambient environments. In addition, the microscopic changes of the specimens due to sulfate attack were also assessed by scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that geopolymer specimens produced with nano-silica and fly ash showed superior performance than the NC specimens in the sulfate environment. In addition, confined specimens with FRP fabrics significantly improved the compressive strength, ductility and durability resistance of the specimens and the improvement was found higher with the increased number of FRP layers. Specimens wrapped with carbon FRP fabrics showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabrics. Both FRP materials can be used as a rehabilitation material in the sulfate environment.

Limit state design criteria for FRP strengthening of RC bridge components

Fiber-reinforced polymer (FRP) composite materials provide novel, effective and potentially economical solutions for rehabilitating and strengthening existing reinforced and pre-stressed concrete bridges, buildings and other structures where deterioration has occurred or performance requirements have changed. FRP composites may be designed to act as external flexural, shear or confinement reinforcement to increase the load capacity of the strengthened structural components. This paper summarizes research to develop technical support for practical limit state (strength) design criteria for repair and strengthening of reinforced and pre-stressed concrete bridge elements for compression and/or flexure using externally bonded FRP composite systems. The limit state design criteria take uncertainties in structural strength and stiffness into account using structural reliability methods, and will support and enhance the use of FRP materials in civil construction by providing engineers with rational guidelines for repair and strengthening.

Some Issues on the Strengthening of Steel Structures With Fibre-Reinforced Polymer Materials

Fibre-reinforced polymer (FRP) materials are widely accepted in the strengthening of civil engineering structures due to their unique characteristics such as high mechanical properties, low dead weight and very good corrosion resistance. In particular the use of FRP materials for strengthening concrete structures was deeply investigated in the past. More recently the use of FRP materials was also proposed in the strengthening of timber, masonry and steel structures. Several studies have been conducted in the literature on the reinforcement of steel structures by FRP materials. They include bond strength, flexural and fatigue reinforcement, strengthening against local buckling and durability aspects. Future research should be conducted in order to propose more reliable design guidelines and to finally increase the acceptance in practice of this reinforcement technique. This paper illustrates some issues on the strengthening of steel structures with FRP materials starting from previous works from the authors. The paper starts with a discussion on the benefits and drawbacks in the use of FRP materials in the reinforcement of steel structures. Then some issues concerning the reinforcement of steel structures are illustrated. They include bond behaviour between steel and FRP, flexural strengthening of steel beams including the post-yielding behaviour and bond durability under mechanical (fatigue) and environmental actions.

Some issues on the strengthening of steel structures with fibre-reinforced polymer materials

Fibre-reinforced polymer (FRP) materials are widely accepted in the strengthening of civil engineering structures due to their unique characteristics such as high mechanical properties, low dead weight and very good corrosion resistance. In particular the use of FRP materials for strengthening concrete structures was deeply investigated in the past. More recently the use of FRP materials was also proposed in the strengthening of timber, masonry and steel structures. Several studies have been conducted in the literature on the reinforcement of steel structures by FRP materials. They include bond strength, flexural and fatigue reinforcement, strengthening against local buckling and durability aspects. Future research should be conducted in order to propose more reliable design guidelines and to finally increase the acceptance in practice of this reinforcement technique. This paper illustrates some issues on the strengthening of steel structures with FRP materials starting from previous works from the authors. The paper starts with a discussion on the benefits and drawbacks in the use of FRP materials in the reinforcement of steel structures. Then some issues concerning the reinforcement of steel structures are illustrated. They include bond behaviour between steel and FRP, flexural strengthening of steel beams including the post-yielding behaviour and bond durability under mechanical (fatigue) and environmental actions.

Development of Fiber-Reinforced Cement-Based Composite Sheets for Structural Retrofit

In recent years, advanced fiber-reinforced polymer (FRP) composites have been steadily developed and used in a wide spectrum of infrastructure applications. It is, however, recognized that many polymer resins soften rapidly when heated above 82°C (180°F). Hence fire vulnerability may become a future obstacle with the widespread use of FRP materials. In this paper, initial findings from an on-going project, aimed at developing temperature-resistant cement-based composite sheets for structural retrofit, were reported. Following a similar installation procedure to that of FRP sheets, it is essential to examine the effect of mix compositions on the rheological properties of the cement slurry and to develop suitable cement slurries for making thin fiber-reinforced cement sheets on the job sites. Retrofit efficiency of using both epoxy-based and cement-based thin sheets is investigated. Preliminary results are presented and discussed in this paper. It is confirmed that cement sheets could be very likely made in situ and provide a similar retrofit capacity to their FRP counterparts.

Knowledge-based system for use of FRP materials in cold regions

Fibre-Reinforced Polymer (FRP) composites provide significant advantages for construction of infrastructure in cold regions due (i) to lower weight resulting in greater ease in moving prefabricating components and more rapid construction and (ii) to tailorable performance characteristics giving potentially greater durability than conventional materials. However data related to performance characteristics, structural response and design is sparse and not easily available to the user community. The use of an integrated knowledge based system is seen as a means of alleviating this and providing a basis for further development of this class of materials.

Call for Fiber Reinforced Polymer Papers

The Journal of Bridge Engineering is pleased to announce a call for papers for an upcoming special edition focusing on fiber reinforced polymer (FRP) bridge structures and components. The objective of the special edition is to bring together a collection of papers reflecting the state of the art in the use of FRP materials for bridge structures and components. A nonexhaustive list of topics solicited in this call for papers includes • FRP bridge decks; • FRP superstructure elements (girders, stringers, diaphragms, etc.); • Hybrid and composite systems with FRP (composite FRP decks with steel or concrete girders, composite FRP/steel box girder systems, etc.); • FRP elements for long span bridges (cables, hangers, etc.); • Nonstructural FRP elements (crash barriers, lamp and sign standards, etc.); • Innovative FRP systems (e.g., use of FRP to eliminate fatiguecritical details, etc.); and • FRP for bridge erection.