Durability Of Fiber Reinforced Polymer Research Articles

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A Review on Durability Analysis of FRP Bars based on Different Factors in Alkaline Environment

The primary issue with concrete structures is steel bar corrosion. Therefore, FRP (Fiber Reinforced Polymer) bars are often to substitute steel bars to tackle the issue of concrete swelling and cracking brought about by steel corrosion. FRP bars feature improved corrosion resistance, a stronger strength-to-quality ratio, and better fatigue resistance. However, the alkaline environment will affect the long-term strength and durability of FRP, according to certain research, which will cause the FRP bars mechanical characteristics to deteriorate. In this paper, the properties of FRP bars under alkaline conditions are reviewed, considering the harsh external environment and physical properties of FRP bars. Comprehensive investigation concludes that lowering the PH value of concrete and changing the kind of fiber material may considerably increase the endurance of FRP in alkaline environments. By demonstrating the microscopic breakdown process of FRP bars in an alkaline conditions using scanning electron microscopy. The Arrhenius acceleration theory was used to construct the present model for forecasting the long-term mechanical behavior of FRP bars, which shows how this material degrades under alkaline circumstances. This study may be utilized as a reference for FRP bars used in alkaline environments in terms of durability studies.

Effect of Immersion in Water or Alkali Solution on the Structures and Properties of Epoxy Resin.

The durability of fiber-reinforced polymer (FRP) composites is significantly dependent on the structures and properties of the resin matrix. In the present paper, the effects of physical or chemical interactions between the molecular chain of the epoxy resin matrix and water molecules or alkaline groups on the water absorption, mechanical structures, and microstructures of epoxy resin samples were studied experimentally. The results showed that the water uptake curves of the epoxy resin immersed in water and an alkali solution over time presented a three-stage variation. At different immersion stages, the water uptake behavior of the resin showed unique characteristics owing to the coupling effects of the solution concentration gradient diffusion, molecular hydrolysis reaction, and molecular segment movement. In comparison with the water immersion, the alkali solution environment promoted the hydrolysis reaction of the epoxy resin molecular chain. After the immersion in water or the alkali solution for one month, the water uptake of the resin was close to saturate, and the viscoelasticity was observed to decrease significantly. The micropore and free volume space on the surface and in the interior of the resin gradually increased, while the original large-scale free volume space decreased. The tensile strength decreased to the lowest point after the immersion in water and the alkali solution for one month, and the decrease percentages at 20 °C and 60 °C water or 60 °C alkali solution were 24%, 28%, and 22%, respectively. Afterward, the tensile strength recovered with the further extension of immersion time. In addition, it can be found that the effect of the alkali solution and water on the tensile strength of the epoxy resin was basically the same.

Method to test the durability of fiber-reinforced polymers based on elastic modulus

The performance degradation of fiber-reinforced polymer is often assessed based on the ultimate strength obtained during a destructive test. This method has the advantages of simple operation, clear internal mechanism, and noticeable data variation. However, because fiber-reinforced polymers are composed of high molecular compounds, their properties are influenced by several factors, such as the manufacturing process and composition ratio. Without a unified benchmark, it is difficult to unify destructive test data obtained by different researchers and organizations. In this study, a new test method named SNFT (Same Non-failure FRP Test) is proposed for assessing the durability of fiber-reinforced polymers. SNFT is a testing method in which the same specimen can be repeatedly tested at different aging periods. The rationality of the SNFT method is analyzed using the displacement compatibility between the degraded zone and the undegraded zone. The conversion principle based on the degraded degree between the destructive test and the SNFT method is deduced by calculation. An experimental test was designed to investigate the test conditions and control parameters of the SNFT method. SNFT and synchronous destructive tests on glass fiber–reinforced plastic were carried out under the conditions of wet heat and alkali solution, and the theoretical results were compared and verified with data in the literature. The results show that compared with the traditional durability destructive test method, the SNFT method shows more consistent data and less data fluctuation and incurs a lower test cost. The elastic modulus, adopted as the durability benchmark, can be similar to the test results of traditional destructive test methods and could be transformed based on the transformation relationship proposed in this article. The degradation of fiber-reinforced polymer in different environments is characterized by the variation in elastic modulus measured using the SNFT method. This study provides a theoretical basis for establishing a unified benchmark of durability tests and data and supports the quantitative design of durability.

Durability of FRP - concrete bonded joints in structural rehabilitation: A review

Fibre Reinforced Polymer (FRP) composites have been the source of an increasing interest in the field of rehabilitation, namely for repair and strengthening of reinforced concrete (RC) structures. One of the most effective techniques comprises externally bonded FRP composites, in which the efficacy of rehabilitation depends considerably on the integrity and durability of the bond established between the FRP and the substrate, which is provided by a structural adhesive. This paper presents a concise review of critical durability issues associated with the structural bond between FRP and concrete for rehabilitation purposes. A number of factors determining the durability of FRP-concrete bonded joints have been identified and grouped into the following categories: materials – adhesive and adherends, joint characteristics and in-service conditions. For each of those factors, the main findings obtained in previous studies are summarized and the aspects that need further investigation are outlined.

5th International Conference on Durability of Fibre Reinforced Polymer (FRP) Composites for Construction & Rehabilitation of Structures 参加報告

5th International Conference on Durability of Fibre Reinforced Polymer (FRP) Composites for Construction & Rehabilitation of Structures 参加報告

Fiber Reinforced Polymers in Civil Engineering: Durability Issues

In the last decades, the use of fiber reinforced polymers (FRP) composites to repair and/or upgrade existing buildings or infrastructure systems proved to be an effective solution, being able to overcome some of the drawbacks experienced with traditional interventions. The knowledge of durability behavior of polymer composite materials in terms of their degradation/aging causes and mechanisms is a critical issue for a safe and advantageous implementation of FRP. The durability of FRP employed in civil infrastructure applications mainly depends on the durability of any single component and on the environment (service conditions) in which the system operates. The components of FRP are: polymeric resins (more frequently thermosetting resins cured in service, i.e. at ambient temperature), fibers and the interface between them. Referring to the resins, heavy concerns arise from the behavior of “Cold-cured” thermosetting resins, often epoxy, used as matrices to manufacture (through wet layup technique) and adhesives to apply, also precured, FRP. The experimental studies present in current literature on the effect of environmental agents on the properties of FRP highlight the crucial role of the adhesive/matrix on the behavior of the whole system. Many other parameters (i.e. direction and disposition of fibers, direction of load application) are involved in the assessment of the durability of FRP. However, in the durability studies of FRP and their components, a lack of specific standards for such materials is recognized. In addition, the results of durability studies do not always agree, possibly due to different curing/conditioning conditions employed. The aim of this work is to critically illustrate the durability studies carried out on FRP for civil engineering applications and appeared in current literature, highlighting the issues that are not yet assessed and addressed.

Numerical modelling of moisture diffusion in FRP with clustered microstructures

This paper presents a numerical study of moisture propagation in fibre reinforced polymer (FRP) materials with spatial tortuosity. An algorithm for creation of microstructures with clustered fibre architecture is presented. Several controls for different characteristics of the clusters are described. Different statistical descriptors of geometry are used to quantify the clustering. A Fickian diffusion process has been modelled. The effect of clustering on moisture diffusion through the FRP is reported. It is observed that microstructures greatly affect the diffusion behaviour of the FRP. Correlation between moisture diffusion and the statistical descriptors has been examined. The statistical measures that depict the global characteristics of the microstructure are found to have a better correlation with time to saturate the representative volume element. The results should help in prediction of macroscopic response and durability of FRPs.

Durability study of vinylester/silicate nanocomposites for civil engineering applications

The durability of fiber-reinforced polymer (FRP) composite materials in humid and harsh environments is an important consideration for acceptance of these materials in civil engineering applications. Reducing the moisture ingress may improve the durability of FRPs. The addition of modified inorganic powder, such as silicate nanoparticles, may improve several important properties of polymers, such as barrier properties, fire retardancy, dimensional stability and mechanical strength. The present work aims to evaluate the effect(s) of the addition of silicate nanoparticles on the durability-related properties of vinylester polymer used as matrix for FRPs in civil engineering applications. To conduct this preliminary study, nanocomposites containing 5% organo-modified or untreated silicate were characterized by using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The diffusivity of moisture was measured by immersing samples in a 50 °C water bath. Barrier properties were determined by measuring the maximum water uptake, water absorption rate and coefficient of diffusion. Aging was performed by complete immersion of nanocomposites samples in a NaOH solution at 50 °C. Scanning Electron Microscopy (SEM), tensile tests and Fourier Transform Infrared spectroscopy (FTIR) analyses were performed before and after conditioning to evaluate the matrix degradation. Experimental results show that the use of organo-silicate leads to an improvement of barrier properties characterized by a decrease of the coefficient of diffusion. It also increases mechanical properties and leads to a significant decrease of chemical degradation.

Mode-I fracture and durability of FRP-concrete bonded interfaces

In this study, a work-of-fracture method using a three-point bend beam (3PBB) specimen, which is commonly used to determine the fracture energy of concrete, was adapted to evaluate the mode-I fracture and durability of fiber-reinforced polymer (FRP) composite-concrete bonded interfaces. Interface fracture properties were evaluated with established data reduction procedures. The proposed test method is primarily for use in evaluating the effects of freeze-thaw (F-T) and wet-dry (W-D) cycles that are the accelerated aging protocols on the mode-I fracture of carbon FRP-concrete bonded interfaces. The results of the mode-I fracture tests of F-T and W-D cycle-conditioned specimens show that both the critical load and fracture energy decrease as the number of cycles increases, and their degradation pattern has a nearly linear relationship with the number of cycles. However, compared with the effect of the F-T cycles, the critical load and fracture energy degrade at a slower rate with W-D cycles, which suggests that F-T cyclic conditioning causes more deterioration of carbon fiber-reinforced polymer (CFRP)-concrete bonded interface. After 50 and 100 conditioning cycles, scaling of concrete was observed in all the specimens subjected to F-T cycles, but not in those subjected to W-D cycles. The examination of interface fracture surfaces along the bonded interfaces with varying numbers of F-T and W-D conditioning cycles shows that (1) cohesive failure of CFRP composites is not observed in all fractured surfaces; (2) for the control specimens that have not been exposed to any conditioning cycles, the majority of interface failure is a result of cohesive fracture of concrete (peeling of concrete from the concrete substrate), which means that the cracks mostly propagate within the concrete; and (3) as the number of F-T or W-D conditioning cycles increases, adhesive failure along the interface begins to emerge and gradually increases. It is thus concluded that the fracture properties (i.e., the critical load and fracture energy) of the bonded interface are controlled primarily by the concrete cohesive fracture before conditioning and by the adhesive interface fracture after many cycles of F-T or W-D conditioning. As demonstrated in this study, a test method using 3PBB specimens combined with a fictitious crack model and experimental conditioning protocols for durability can be used as an effective qualification method to test new hybrid material interface bonds and to evaluate durability-related effects on the interfaces.

Environmental Degradation of Fiber-Reinforced Polymer Fasteners in Wood

This paper examines the durability of fiber-reinforced polymer (FRP) nails in treated wood. The FRP nails were exposed to four conditions: (1) accelerated weathering, consisting of exposure to ultraviolet light and condensation; (2) 100% relative humidity (RH); (3) being driven into untreated wood and exposed to 100% RH; and (4) being driven into wood treated with alkaline copper quaternary (ACQ) and exposed to 100% RH. Changes in the physical, mechanical, and chemical properties were examined with weight loss, dynamical mechanical analysis (DMA), and near-infrared spectroscopy (NIR), respectively. Although fasteners exhibited changes after exposure to treated wood, the changes were not statistically different than the changes that occurred in untreated wood or in the humid environment. Under these three conditions, the fasteners gained 2-3% of their starting mass, and the storage modulus also increased by 20% after exposure. The results suggest that moisture is more important than the wood chemistry or preservative chemistry in determining the durability of FRP fasteners in wood. DOI: 10.1061/(ASCE)MT.1943-5533.0000619. © 2013 American Society of Civil Engineers. CE Database subject headings: Nails; Fastening; Fiber reinforced polymer; Coating; Wood; Degradation. Author keywords: Nail; Preservative-treated wood; Dynamical mechanical analysis (DMA); Near-infrared spectroscopy (NIR).

Instability of the Performances of FRP Composites Implemented in Civil Engineering Environment: Experimental Study and Durability Implications

Various aspects related to the durability of Fibre Reinforced Polymer (FRP) composites used in the rehabilitation, repair and strengthening of existing concrete structures were studied as a function of cure behaviour. The performance of these FRP-composites containing thermoset matrix and implemented under civil engineering conditions, is unstable and their properties will change over time due to their partial cure. The present work attempts to raise awareness about the characteristic changes of FRP-composites materials immediately after their ambient cure, while emphasizing the implication of such phenomena on the durability. Both glass transition temperature Tg and mechanical characterization tests were performed to identify the effects of curing on thermorheological and mechanical stability of the composites immediately after the implementation. The experimental results indicate that overall composite performance was sensitive to the cure conditions. The implication of this sensitivity on the durability of FRP-composites was addressed and clearly identified through accelerated and natural exposure tests which reflected the civil engineering environment.

FIBRE-REINFORCED POLYMER REPAIR MATERIALS - SOME FACTS.

Despite costing up to 10 times more than steel the ultra-lightweight and durability of fibre-reinforced polymer (FRP) makes it an attractive alternative for breathing new life into the world's ageing infrastructure. However, with only a decade of research and experience and very little in the way of design codes, many engineers are still wary of using FRP despite its obvious advantages.This paper reviews the basic mechanical properties of carbon, aramid and glass FRP composites and highlights what designers should look out for—including the risk of brittle failure, sunlight and alkaline damage and toxic fumes when burning.

Fibre-reinforced polymer repair materials—some facts

Despite costing up to 10 times more than steel the ultra-lightweight and durability of fibre-reinforced polymer (FRP) makes it an attractive alternative for breathing new life into the world's ageing infrastructure. However, with only a decade of research and experience and very little in the way of design codes, many engineers are still wary of using FRP despite its obvious advantages.This paper reviews the basic mechanical properties of carbon, aramid and glass FRP composites and highlights what designers should look out for—including the risk of brittle failure, sunlight and alkaline damage and toxic fumes when burning.