Use Of Fiber Reinforced Polymer Composites Research Articles

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.

A Review of Fibre Reinforced Polymer Bridges

Fibre-reinforced polymer composites (FRPs) offer various benefits for bridge construction. Lightweight, durability, design flexibility and fast erection in inaccessible areas are their unique selling points for bridge engineering. FRPs are used in four bridge applications: (1) FRP rebars/tendons in concrete; (2) repair and strengthening of existing bridges; (3) new hybrid–FRP bridges with conventional materials and (4) all–FRP composite new bridges made entirely of FRP materials. This paper reviews FRP bridges, including all–FRP and hybrid–FRP bridges. FRP bridges’ history, materials, processes and bridge components—deck, girder, truss, moulded parts and cables/rebars are considered. This paper does not discuss the use of FRP as an architectural element and a strengthening system. While lack of design codes, material specifications and recycling are the major challenges, the high cost of FRPs still remains the most critical barrier to the progress of FRPs in bridges.

Water Absorption Study on Kenaf/ABS Composites

Many manufacturers have lately expressed an interest in the use of fiber-reinforced polymer composites (FRPs) in structural applications. Carbon and glass fibers, for example, have been commercialized globally for decades. However, they are harmful to the environment since synthetic fibers are non-biodegradable and difficult to recycle once they have fulfilled their purpose. As a result of their better physical and mechanical qualities, natural fiber composites such as kenaf are a prospective substitute for synthetic fiber. Kenaf is the most promising alternative for replacing synthetic fibers in order to achieve the environmental preservation while simultaneously exhibiting great properties such as equivalent specific strength, low density, and renewable resources. Treated kenaf fiber was added to ABS with varying loading (10, 15, 20 and 25 wt.%) via Two Roll Mill machine. The influence of the fiber on the composites was evaluated for water absorption properties. The water absorption test was conducted for 5 days referring to the ASTM D570. The morphology of produced composite was investigated using JOEL Scanning Electron Microscope (SEM) at 200X magnifications. The incorporation of the treated kenaf fiber has an influence on the properties of kenaf/ABS composites. The fiber was well dispersed in the matrix and showed good adhesion to the ABS. Kenaf/ABS composites showed an increment of water absorbed with an increment of fiber loading.

A Review on the Mechanical Properties of Fiber-Reinforced Polymer Composites and their Application in the Transportation Industry

The application of fiber-reinforced polymer (FRP) composites has achieved significant attention in the industry of transportation, specifically as metal substitutes due to a need for fabricating stable and fuel-efficient airplanes, vehicles, and ships. Excellent strength, resistance to corrosion, lightweight, and suitable fatigue endurance are some of the desirable properties that would encourage the use of FRP composites in the transportation sector. Polymer-based composite materials, combining the favorable properties of both polymer matrix and reinforcing fibers, can contribute to several excellent behaviors of the obtained material. Epoxy, polyethylene, and polypropylene are the primary polymer matrices used in FRP composites. The main reinforcing fibers incorporated in fiber-reinforced composites are made out of glass, carbon, basalt, hemp, or natural resources (e.g., sisal and jute). Due to high cost, low Young's modulus, low durability, and linear stress?strain behavior to failure of the FRP materials, which are used in transportation infrastructure, the objective of this review article is to study the recent aspect of reinforced polymers with a close focus on their mechanical properties in order to evaluate their application in maritime, automotive, and aerospace.

Observing progressive damage in carbon fiber epoxy laminate composites via 3D in-situ X-ray tomography

As the use of fiber-reinforced polymer composites grows in aerospace structures, there is an emerging need to implement damage tolerant approaches. The use of in-situ synchrotron X-ray tomography enables direct observations of progressive damage relative to the microstructural features, which are studied in a T650/5320 laminate composite with two layups via monotonic tension. Specifically, the interactions of micromechanical damage mechanisms at the notch tip were analyzed through 3D image processing as the crack grew. The analysis showed intralaminar cracking was dominant during crack initiation, delamination became prevalent during the later stages of crack progression, and fiber breakage was, in general, largely related to intralaminar cracking.

Appraisal on Varied Natural and Artificial Fiber Reinforced Polymeric Composites

Abstract Professionals, experts and scientists of modern era treasure the use of Fiber-reinforced Polymer Composites and find these very significant due to the necessity in countless arenas like automobiles, infrastructure, marine vessels and equipment, chemical industry, sporting goods, domestic articles etc. These mixtures of amalgams of strengthened fibers also develop extensively as possible fixings for the construction of composites of diverse applications. These inventions are not only used as an alternative reinforcement due to their high level of specific strength but also hail with the rewards of low price, less heaviness and adequate good mechanical possessions or properties. Here, experts must take note of the lavish obtainability of natural and synthetic elements in India like kenaf, jute, oil palm, cotton flax, hemp, sisal, nylon, polyester, etc. These elements are the boundless gift of the nature and acquiring thorough attention in every nook and corner of today’s technology. These crossbred complex materials are undoubtedly a combination of more than one dissimilar kinds of filament which are armored in a single chemical compound or contrariwise and display inimitable possessions that are challenging to attain from a single sort of hybrid complex materials of strengthened fiber polyamide. Complex chemical compounds or polyamides do demonstrate an important and remarkable function of congeniality over filaments besides the heftiness of cross complex materials. Therefore the assortment of polymer with fibers should be always considered cautiously

Study of the flexural behaviour of FRP-strengthened steel-concrete composite beams

Flexural strengthening of steel-concrete composite beams with fiber-reinforced polymer (FRP) materials has recently become a topic of considerable interest, due to the many advantages it may offer in both enhancing the design prospects of new structures and restoring the functioning condition of deficient existing structures. During the past two decades, a substantial number of experimental, numerical and analytical studies has been concerned with this topic. Although these studies have provided significant insights into the problem, a lack of simplified methods for assessing the FRP-strengthening effects in a quantitative manner still exists. Motivated by this need, a study that seeks to establish a sound understanding of the mechanics of the problem – which is a fundamental component for the development of simple and reliable analysis approaches – is presented in this paper. The basis of the study is the development of a new analytical method for the prediction of the moment-curvature relationship and the overall flexural response of FRP-strengthened steel-concrete beams, by assuming perfect bond between the constitutive components. The method only requires accessible spreadsheet calculations, which makes it both suitable for routine use in design practice and particularly useful for the scientific study of the problem. The new method is first validated against available experimental results and it is then employed in conducting a systematic parametric study, from which several conclusions of essential practical significance for the optimum use of FRP composites in strengthening the flexural behaviour of steel-concrete composite beams are derived.

Thermo-mechanical behaviour of composite moulding compounds at elevated temperatures

The use of fibre-reinforced polymer composites as a lightweight metal replacement for automotive componentry is constantly expanding into new and more challenging application areas (e.g. whole range of under-bonnet, exhaust applications and other automotive components), where service temperatures are not expected to go beyond 150 °C. This study seeks to provide some useful baseline data on the bending stiffness performance of a large range of commercially available composite moulding compounds, in order to provide guidance in selecting appropriate materials for various applications requiring higher operating temperatures, where retention of bending stiffness is a key parameter. Whilst glass transition data can give some indication, this study seeks to go further. Three point bending flexural tests and Dynamic Mechanical Analysis were used to investigate and compare properties both at ambient and 150 °C comparing various composite systems, particularly phenolics, one of the fastest-growing systems in the thermoset moulding compounds market.

Estimations of the debonding process of aged joints through a new analytical method

The estimation of the long-term durability of adhesively bonded interfaces between Fiber Reinforced Polymers (FRP) and concrete substrates is crucial because degradation potentiates FRP premature debonding. One of the main reasons for mistrusting the use of FRP composites is the premature debonding phenomenon, which, associated to degradation, has been preventing their widespread use. In this research work, an analytical model is proposed that introduces ageing to estimate the effects of degradation of Glass (G) FRP externally bonded to concrete. Cycles were used to experimentally accelerate ageing of beam specimens, namely, (i) salt fog cycles; (ii) wet-dry cycles with salted water; (iii) temperature cycles between −10 °C and +30 °C; and (iv) temperature cycles between +7.5 °C and +47.5 °C. Based on the experimental results obtained and a corresponding bond-slip curve, the analytical model predicts the complete debonding process between FRP composites and a substrate. Consequently, the temporal evolution of the degradation of the bonded interfaces can be calculated and compared with the initial situation prior to exposure. The effects of the environmental conditions are reported and compared.

State of the practice of FRP composites in highway bridges

This case study presents the use of fiber reinforced polymer (FRP) composites in highway infrastructure. The state of current practice of FRP materials is established through a survey questionnaire and follow-up interviews with 46 responding transportation jurisdictions in North America (44 United States Departments of Transportation and 2 Canadian agencies) to identify current challenges requiring technical and administrative efforts to facilitate the employment of this promising construction material. FRP composites for infrastructure projects are generally satisfactory and promising. Most agencies have used FRP since 1996, although some agencies reveal pioneering endeavors in the early 1990s. The nature of construction projects determines whether FRP applications are experimental or a standard practice. The survey shows that CFRP-strengthening for upgrading bridge piers (primarily columns) is the most accepted standard practice, followed by GFRP-reinforced bridge decks. Challenges experienced by the responding agencies are detailed and analyzed. Various tests at material and structure levels are conducted to examine the performance of structural members constructed with FRP composites. Despite these endeavors, the long-term durability of in-situ FRP still requires additional research to generate technical data and to convince end-users. Lessons learned from sites are elaborated to assist practitioners who are interested in FRP-based projects. The majority of respondents state that more training is necessary to help understand the use of FRP composites in construction projects.

Review on the use of FRP Composites for Facades and Building Skins

Fiber Reinforced Polymer (FRP) composites represent a class of materials typically able to offer excellent mechanical, thermal and insulation properties, taking advantage of a combination of their constitutive fibers and polymers. Due to their intrinsic lightweight properties, FRP composites are in use for aerospace, automotive, marine industries and ballistic armor since several decades. Only in a subsequent phase, i.e. since the late 1990s, FRP composites found application in civil engineering constructions, including both building systems and infrastructures, for retrofitting purposes in existing structural systems, as well as for pure architectural or structural purposes in novel assemblies. This review paper aims to highlight the most recent applications of FRPs in facades and building skins, with careful attention for case studies and novel design concepts.

Probabilistic capacity models and fragility estimates for RC columns retrofitted with FRP composites

This paper proposes a probabilistic formulation to assess the effectiveness of the fiber reinforced polymer (FRP) retrofit schemes in enhancing the structural performance of reinforced concrete (RC) bridge columns. Two probabilistic models are proposed to predict the deformation capacities of retrofitted columns. One deformation model corresponds to the flexural failure and the other considers the bond failure in the lap-splice region. A Markov Chain Monte Carlo (MCMC) simulation method is used to estimate unknown model parameters in the context of a Bayesian updating approach. The probabilistic capacity models are used to estimate the fragility curves of three example columns. In this paper, fragility is defined as the conditional probability of failure for given deformation demand. The results compare the column fragilities before and after the application of the retrofit measure. The results from the example columns indicate that the use of FRP composites considerably reduced the fragility for the bond failure mode and is also beneficial but with a moderate impact when considering the flexural failure.

Field Issues Associated with the Use of Fiber-Reinforced Polymer Composite Bridge Decks and Superstructures in Harsh Environments

There has been ample time for the United States to evaluate the use of fiber-reinforced polymer (FRP) composites to serve as bridge decks and superstructures under real-world environmental and operating conditions. This provides a great opportunity to weigh in on the decision to move forward with these materials. By studying the successes and failures, materials and techniques used for the design and construction of these bridges can be improved so that we can move closer to the goals of maintenance-free bridges and service lives exceeding 100 years. Though only a few of these structures are instrumented for structural health monitoring, there are a sufficient number of lessons that can be gleaned from the experiences of various owners during the fabrication, installation, operation, and inspection of these structures. By addressing these issues head-on, advocates will be better equipped to have direct dialogue with those in the profession who remain skeptical about the hidden potential for a construction material that is strong, light, and corrosion resistant.

Evaluation of a Life Prediction Model and Environmental Effects of Fatigue for Glass Fiber Composite Materials

Fiber-reinforced polymer (FRP) composites are being utilized in an increasing number of applications in structural industries. Establishing values for longterm fatigue response is essential for widespread use of FRP composites. The variety of available fibers, matrix materials, and manufacturing processes makes the fatigue response difficult to predict without extensive empirical testing. A proposed fatigue life prediction model uses the internal strain energy release rate as the metric for predicting fatigue life from a minimum of data points. The objective of this research was to apply the above model to fatigue data for various composite coupons and components in order to evaluate its applicability in predicting fatigue life. The model was found to be able to regularly fit and predict fatigue data within 5% log error at both coupon and component levels. The effects of environmental conditions, including 12 MPa pressurized absorption and fatiguing in salt water and elevated temperatures, were also explored for a glass/vinyl ester FRP. The results of this research can be used to aid in the design of numerous structural FRP applications, such as windmill blades, bridge decks, or deep sea piping.

Parameters Influencing Performance of Fiber-Reinforced Polymer Systems in Concrete

Fiber-reinforced polymers (FRPs) have been increasingly used in concrete repair and retrofitting works. The systems involve the use of FRP composites and adequate adhesives to secure load transfer. While many studies have been conducted on the mechanical properties, durability, and economic aspects of FRP, little information is available on the effect of parameters, such as the thickness of epoxy adhesive, concrete compressive strength, concrete surface roughness, and concrete temperature on the overall performance of the system. An attempt was made to address the influence of these parameters on the FRP systems through studying the flexural failure loads, deflection, and modes of failure for carbon fiber–reinforced polymers (CFRP) applied to concrete beams. Specimens were tested with three surface roughness conditions and three epoxy adhesive thicknesses. Concrete compressive strength and the effect of exposure to 100°C for 2 h were also studied. Results of this work reveal that the surface roughness condition and adhesive thickness have a significant impact on the performance of CFRP systems. Less impact was encountered for the variation in concrete strength and increasing ambient temperature to 100°C. CFRP reinforcement enhanced the toughness of moderate-strength concrete more than for high-strength concrete. Recommendations are provided for applicators as well as for future research.

Case Study of Application of FRP Composites in Strengthening the Reinforced Concrete Headstock of a Bridge Structure

Worldwide interest is being generated in the use of fiber-reinforced polymer composites (FRP) in the rehabilitation of aged or damaged reinforced concrete structures. As a replacement for the traditional steel plates or external posttensioning in strengthening applications, various types of FRP plates, with their high strength-to-weight ratio and good resistance to corrosion, represent a class of ideal material in externally retrofitting. This paper describes a solution proposed to strengthen the damaged reinforced concrete headstock of the Tenthill Creeks Bridge, Queensland, Australia, using FRP composites. A decision was made to consider strengthening the headstock using bonded carbon FRP laminates to increase the load carrying capacity of the headstock in shear and bending. The relevant guidelines and design recommendations were compared and adopted in accordance with AS 3600 and Austroads bridge design code to estimate the shear and flexural capacity of a rectangular cracked FRP reinforced concrete section.

Compression Tests of Circular Timber Column Confined with Carbon Fibers Using Inorganic Matrix

Many engineering wooden components in our nation's infrastructure are deteriorating and are in need of repair and strengthening. Timber piles, timber poles, timber posts, and naval fender systems are examples of timber infrastructure elements that are experiencing significant deterioration due to moisture, extreme temperatures, and weathering and are in need of repair and upgrade. The use of fiber-reinforced polymer composites (FRPC) has proven to be effective in rehabilitating and upgrading infrastructure elements. FRPC are also now being considered for new structures to improve strength, ductility, predictability, and durability. This note describes an experimental investigation of circular columns made of poplar wood confined with carbon fibers in an inorganic matrix and subjected to axial compression. Results from this study showed that carbon fiber confinement increased strength, stiffness, ductility, and reduced the variability in timber column behavior under axial loads. The study showed that the full fiber wrap and full fabric wrap confinement were more effective than spirals and hoops and will make the timber column behavior much more reliable and provide protective coating.

Use of FRP composites in civil structural applications

Fiber reinforced polymer (FRP) composites or advanced composite materials are very attractive for use in civil engineering applications due to their high strength-to-weight and stiffness-to-weight ratios, corrosion resistance, light weight and potentially high durability. Their application is of most importance in the renewal of constructed facilities infrastructure such as buildings, bridges, pipelines, etc. Recently, their use has increased in the rehabilitation of concrete structures, mainly due to their tailorable performance characteristics, ease of application and low life cycle costs. These characteristics and the success of structural rehabilitation measures have led to the development of new lightweight structural concepts utilizing all FRP systems or new FRP/concrete composite systems. This paper presents an overview of the research and development of applications of advanced composites to civil infrastructure renewal at the University of California, San Diego (UCSD).

Retrofitting of shear failed reinforced concrete beams

This paper considers the strength and load carrying capacity enhancement of reinforced concrete beams that have been tested and failed in shear. A total of sixteen sheared beam specimens with a length of 1.2 m and cross-sectional area of 100 by 150 mm were retrofitted by using various types of fibre reinforced polymer (FRP) and then retested. The retrofitted beam specimens wrapped with different amounts and types of FRP were subjected to four-point static loading. Load, deflection and strain data were collected during testing the beam specimens to failure. Results of the experimental program indicate that there are several parameters that affect the strength of the beams. The results also show that the use of FRP composites for shear strengthening provides significant static capacity increase.

Determination of Materials Design Values for the Use of Fibre-reinforced Polymer Composites in Civil Infrastructure

Determination of Materials Design Values for the Use of Fibre-reinforced Polymer Composites in Civil Infrastructure