Durability Of Fibers Research Articles

Effect of Seawater and Warm Environment on Glass/Epoxy and Glass/Polyurethane Composites

A study of the durability of fiber reinforced polymer (FRP) materials in seawater and warm environment is presented in this paper. The major objective of the study is to evaluate the effects of seawater and temperature on the structural properties of glass/epoxy and glass/polyurethane composite materials. These effects were studied in terms of seawater absorption, permeation of salt and contaminants, chemical and physical bonds at the interface, degradation in mechanical properties, and failure mechanisms. Test parameters included immersion time, ranging from 3 months to 1 year, and temperature including room temperature and 65°C. Seawater absorption increased with immersion time and with temperature. The matrix in both composites was efficient in protecting the fibers from corrosive elements in seawater; however moisture creates a dual mechanism of stress relaxation—swelling—mechanical adhesion, and breakdown of chemical bonds between fiber and matrix at the interface. It is observed that high temperature accelerates the degradation mechanism in the glass/polyurethane composite. No significant changes were observed in tensile strength of glass/epoxy and in the modulus of both glass/epoxy and glass/polyurethane composites. However, the tensile strength of the glass/polyurethane composite decreased by 19% after 1 year of exposure to seawater at room temperature and by 31% after 1 year of exposure at 65°C. Plasticization due to moisture absorption leads to ductile failure in the matrix, but this can be reversed in glass/polyurethane composites after extended exposure to seawater at high temperature where brittle failure of matrix and fiber were observed.

Influence of finish treatment on the durability of aramid fibers aged under an alkaline environment

AbstractAramid fibers are high‐performance materials which have been used in ropes and protective clothing for many years. They are also now being proposed in geotextiles for ground reinforcement. The influence of the surface finish composition and content has been studied in the field of cables and textiles, but there is no published data concerning the effect of a finish treatment on the hydrolytic degradation. Aramid fibers with different finish contents have been aged in an alkaline environment. The degradation has been identified by FTIR, viscosimetry, TGA, SEM, and tensile tests. For Technora fibers, the presence of finish appears to limit the tensile strength loss of aramid fibers at pH 11 by limiting abrasion, as well as bulk and surface degradation. For Twaron fibers, higher finish content only has a slight influence on the fibers durability at pH 11 and pH 9, by limiting abrasion and bulk degradation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Natural Weathering and Sea Water Effects on the Durability of Glass Fiber Reinforced Vinylester: Fractographic Analysis

This paper presents a study of the effects of harsh outdoor weather and warm sea water on the tensile behavior of Glass-Fiber Reinforced Vinylester (GFRV) pipe materials destined for sea water handling and transportation. The effect of Dhahran’s outdoor weather for exposure periods ranging from 3 to 36 months revealed an improvement in tensile strength when compared with the as received GFRV sample. A significant increasing trend of tensile strength from 3 to 12 months was noted. This is attributed mainly to the post curing effects resulting in higher cross linking density. After 12 months of exposure the tensile strength showed a decreasing trend, but remaining still higher than the average tensile strength of as received (baseline) GFRV sample. Similar results of enhanced tensile strength were noted after immersion of GFRV pipes in warm Gulf sea water for 12 months. Fractographic analysis was performed on the tensile tested GFRV samples using optical microscope followed by scanning electron microscope (SEM). The characterization of the controlling failure mechanisms involved from fracture initiation to fracture propagation through the gage section of the specimen were predicted and were justified by correlating the optical and SEM pictures.

Effect of silica fume surface treatment on natural fibres in resisting chloride resistance in concrete

The natural fibre concrete may undergo a reduction in strength as a result of weakening of fibres by the combination of alkali attack and environmental loads. Silica fume slurry treatment is one of the best way to improve the durability of natural fibres in concrete. In this paper, fibre reinforced concrete with natural fibres such as coir and sugarcane baggase of as received condition and silica fume treated were cast at three volume fractions, 0.5%, 1.0% and 1.5% and tested to study the chloride resistance. This experimental program consists of determination of mass loss and strength deterioration against hydrochloric acid attack, rapid chloride penetration and . From the studies, 10 to 20% reduction due to hydrochloric acid attack and 15 to 25% reduction due to freezing and thawing were observed in concrete with as received natural fibres. Concrete with treated natural fibres showed a better resistance against all the durability effects.

Stress Corrosion Cracking of Basalt/Epoxy Composites under Bending Loading

The purpose of this research is to study the stress corrosion behavior of basalt/epoxy composites under bending loading and submerged in 5% sulfuric acid corrosive medium. There are limited numbers of research in durability of fiber reinforced polymer composites. Moreover, studies on basalt fibers and its composites are very limited. In this research, mechanical property degradation of basalt/epoxy composites under bending loading and submerged in acidic corrosive medium is investigated. Three states of stress, equal to 30%, 50% and 70% of the ultimate strength of composites, are applied on samples. High stress states are applied to the samples to accelerate the testing procedure. Mechanical properties degradation consists of bending strength, bending modulus of elasticity and fracture energy of samples are examined. Also, a normalized strength degradation model for stress corrosion condition is presented. Finally, microscopic images of broken cross sections of samples are examined.

Preparation of Polyrotaxane Fibers. Part I: Influence of Dope Solvents on the Physical Properties of Wet-spun Polyrotaxane Fibers

The preparation of polyrotaxane fibers by wet spinning of polyrotaxane, consisting of poly(ethylene glycol) (PEG) and α-cyclodextrins (α-CDs), was examined using three different types of dope solvents: dimethylacetamide (DMAc) containing 8 wt% lithium chloride (LiCl), dimethylformamide (DMF) containing 8 wt% LiCl, and dimethylsulfoxide (DMSO). In DMSO, polyrotaxane concentrations of 20 and 30 wt% were favorable for the smooth spinning of fibers with sufficient tenacity, while other polyrotaxane concentrations (10, 15, and 40 wt%) were unsuitable for the wet spinning of durable fibers. All of the fibers had nearly identical scanning electron microscopy (SEM) images and X-ray diffraction patterns. Although the values for tenacity at break and initial modulus also were similar for all fibers, elongation at break of fibers from DMSO was higher than the values for the other two fibers. The poorer physical properties of the latter two fibers may be affected by the slight amount of lithium salt remaining in the fibers.

Study of strength durability models for GRC: Theoretical overview

Durability of glass fibre reinforced concrete (GRC) remains a widely studied topic, despite significant material optimization over recent decades. Evaluation of strength durability normally employs accelerated ageing tests involving immersion of specimens in water at a range of temperatures for various durations. These results are then used to calibrate a number of strength durability models available in the literature. Here we present an overview of some of these models, all based on similar assumptions regarding the fundamental strength loss process, examining their robustness. First, the calibration procedure is examined; secondly the influence of quantity and quality of accelerated ageing test results on the determination of model parameters is discussed. The solution spaces are inspected for multiple minima which might lead to non-unique solutions of model parameters for a given test scheme. Parameter studies are also performed in order to establish whether some models are prone to inherent calibration problems.

Experimental investigations on the durability of fibre–matrix interfaces in textile-reinforced concrete

Abstract Changes in the strength and toughness of textile-reinforced concrete with increasing age are determined essentially by the durability of the armouring fibres, the matrix itself, and the bond between the matrix and the fibres. Based on new experimental results, important mechanisms influencing the durability of the fibre–matrix bond are treated in this article and discussed as to their significance. The investigations were conducted on multi-filament yarns of AR-glass which were imbedded in matrices of varying alkalinity and hydration kinetics. The loading capacity of the fibre–matrix bonds was determined in direct tension tests on under-reinforced specimens after they had undergone accelerated aging. Further, the condition of the microstructure between fibre and matrix was ascertained with both image analysis and analytical procedures. It was concluded that measured reductions in the toughness of the composite material could be attributed to the diminishing protective effect of organic polymer sizing on the surface of the filaments as well as to the disadvantageous new formation of solid hydration phases (mainly Portlandite) in the fibre–matrix interface.

Silane treatment of bagasse fiber for reinforcement of cementitious composites

Silane coating of fibers is a promising process for improving durability and adhesion of vegetable fibers used as reinforcement material in a cementitious matrix. The work presented in this paper gives an insight into the effect of combining pyrolysis treatment with silane treatment. Indeed, this study focuses on silane treatment of unpyrolyzed and pyrolyzed sugar cane bagasse fibers with an alkyltrialkoxysilane (RSi(OR′)3), S1 or a dialkyldialkoxysilane (R2Si(OR″)2), S2. The silane solutions used vary from 0.5% to 8% by volume. This paper describes the effect of two silane compounds on parameters such as the porosity, dimension, morphology and hygroscopic character of silane-coated sugar cane bagasse fibers. Preliminary studies on natural fiber reinforced composite setting time show the importance of the silane chemistry/structure, for fiber treatments with silane solution containing up to 6% (volume percent) silane. In the case of composites reinforced with unpyrolyzed bagasse fibers, setting time increases with silane coating. Combining pyrolysis and silane treatment improve the water resistance of the fibers, which become more hydrophobic.

Chemical Durability and Mechanical Properties of Alkali-proof Basalt Fiber and its Reinforced Epoxy Composites

The chemical durability and mechanical properties of a kind of alkali-proof basalt fiber BF-CMD-01 and its reinforced F46 epoxy resin matrix composites are presented. The basalt fiber was boiled in distilled water, sodium hydroxide and hydrochloric acid, respectively. Then the mass loss and strength change of the fibers were studied showing that the alkali resistance of the basalt fiber is better than acid resistance. The flexural properties and surface morphologies of the composites were investigated after being immersed in 8 kinds of chemical mediums for 15, 30 and 90 days. Due to the difference of basalt fiber resistance in two kinds of mediums, the composites corrosion behaviors differ greatly in acid and alkaline reactions. In acid mediums, the flexural strength and flexural modulus change in the same way. In alkaline mediums, the flexural modulus keeps close to the original value while the flexural strength declines gradually. Additionally, the mechanical properties of basalt fiber reinforced polymer (BFRP) and S-2 glass fiber reinforced polymer (GFRP) have been tested, and analyzed contrastively. The results show that the interface formed between basalt fiber and epoxy resin is better than that of glass fiber and epoxy resin.

Macrophage Culture as a Suitable Paradigm for Evaluation of Synthetic Vitreous Fibers

The ultimate goal of toxicologic investigation of synthetic vitreous fibers (SVFs) is to provide essential input for the assessment of human risk to their exposure. Toxicity of mineral fibers is usually evaluated by testing biopersistence in rodent model. However, a cellular model would be much appreciated in order to reduce, refine, and replace animal models. Pulmonary disorders triggered by inhalation of occupational or environmental mineral particulates can be the endpoints of a chronic inflammatory process in which alveolar macrophages (AMs) play a crucial role. Depending on the type of SVF involved, phagocytosis of fiber leads to activation of macrophages, resulting in release of fiber components and potent mediators, such as reactive oxygen or nitrogen species and cytokines. As a matter of fact, macrophages should be the cells of choice since SVF toxicity is the consequence of fibers and alveolar macrophages interaction. Today, monocytes and macrophages culture are firmly established as a paradigm in toxicology when several endpoints are assayed in macrophages: (1) fiber durability, (2) fiber surface changes, (3) oxidative stress and genotoxicity in macrophage, and (4) macrophage cell viability and apoptosis. This article is a review of up-to-date knowledge of in vitro studies involving macrophages, and assesses endpoints of macrophage toxicity with an emphasis on (1) dissolution, (2) scanning electron microscopy analysis, (3) cytotoxicity, and (4) gene expression.

A101 耐久性に優れた高温用光ファイバAEセンサの開発とAE検出能力の評価(検査・モニタリング-1(疲労,SCC,熱流動),OS6 保全・設備診断技術(1),一般講演,地球温暖化防止と動力エネルギー技術)

A101 耐久性に優れた高温用光ファイバAEセンサの開発とAE検出能力の評価(検査・モニタリング-1(疲労,SCC,熱流動),OS6 保全・設備診断技術(1),一般講演,地球温暖化防止と動力エネルギー技術)

Evaluation of the strand in cement (SIC) test for GRCs with improved durability

Even today the durability of glass fibre reinforced concrete composites (GRC) remains a widely studied topic. The accelerated ageing technique and the strand-in-cement (SIC) test method were developed to study the durability of GRCs in the early days. Within this paper it is shown that the standard SIC specimen preparation is not always suitable to evaluate the durability of new GRCs. A modified SIC set-up is proposed and the influence of the number of tested specimens per series on the trustworthiness of the results is discussed. Moreover, the modified SIC set-up will be used within two sequences of accelerated ageing: the first sequence of series of specimens contains an ordinary Portland cement (OPC) mixture and the second series a modified matrix. The usefulness of “accelerated ageing” is discussed and commented for both series.

High performance composites in spun-cast elements

Abstract Spin-casting is an effective fabrication method to produce concrete poles, masts or pipes. Through the centrifugal process the concrete is compacted and the desired shape, mostly round or ellipsoidal, is obtained. The concrete generally has to be reinforced with steel bars which are susceptible to corrosion. Furthermore, the placement of the reinforcement is time consuming and hence expensive and leads to rather thick and heavy structural elements. The application of short-fiber reinforced cement pastes or mortar is a suitable alternative. Special requirements regarding workability and strength have to be considered. An optimization of the cement matrix was achieved with a blend of microfine cement and ordinary Portland cement, improving the rheological properties of the fresh mixture and resulting in a dense cement matrix with excellent mechanical properties. Reinforcement with different kinds of short-fibers of carbon and polyvinylalcohol (PVA) was studied. Flow properties of the fiber reinforced cement composite were optimized with regard to the centrifugal process by applying a newly developed cone-consistency test. The mechanical properties of conventionally cast specimens and of centrifuged prototypes were determined and their durability was verified. Workable, high strength, ductile and durable fiber reinforced composites were obtained in spin-cast elements.

2754 水環境下におけるFRPの繊維強度低下(S17-2 複合材料(2),S17 複合材料の動向とその加工技術)

Long-term durability of fiber reinforced plastics (FRP) under hostile environment is strongly influenced by the degradation in the fiber strength. The degradation of the fiber strength has been quantified on the basis of stress corrosion cracking (SCC) of the initial defects on the fiber surface. In this paper, the strength degradation of the embedded fibers under constant loading in water environment has been investigated using the single fiber composite (SFC). Creep test was conducted under water environment using the SFC specimen, to represent the stress corrosion cracking of GFRP. By taking account of the strain concurrent with the water absorption, creep strain, and the thermal expansion, the strain history of the fiber was formulated. From the strain history, the remaining strength distribution was measured by the fragmentation test. The model containing the Paris Law and the Arrhenius model has been developed to predict the remaining strength of fiber embedded in FRP.

Effects of Changing Environment and Loading Speed on Mechanical Behavior of FRP Composites

Durability of fiber reinforced polymer composites (FRP) are controlled by the durability of their constituents: reinforcement fibers, resin matrices, and the status of interfaces. A great deal of research has been focused on attempting to assess the relationship between interfacial structure and properties of fiber-matrix composites. It is at the interfacial area where stress concentration develops because of differences in the thermal expansion coefficients between the reinforcement and the matrix phase. A significant mismatch in the environmentally induced degradation of matrix and fiber leads to the evolution of localized stress and strain fields in the FRP composite. The present investigation aims to study the effects of changing hygrothermal conditioning cycles (either by changing relative humidity (RH) and keeping the temperature constant, or by changing the temperature while RH the same is maintained) on moisture gain/loss kinetics and on interlaminar shear strength (ILSS) of varied weight fraction glass fiber reinforced epoxy and polyester matrices composites. The mechanical assessment is extended to evaluate the loading rate sensitivity of hygrothermally shocked glass/epoxy and glass/polyester laminates at 2 and 50 mm/min crosshead speeds, respectively. Observations on absorption/desorption kinetics are noticed to be dependent on the nature of hygrothermal shock cycle and on the weight fraction of fiber reinforcement. The results of mechanical performance are statistically significant at different stages of conditioning. Shear values are found to be greater at higher crosshead speed for all undertaken situations. Mechanical responses are observed to be dependent on the matrix resin and the type of hygrothermal shock cycle. Very little and limited literature is open to address the important interactions of polymer composites with this kind of realistic environmental situation.

Durability and mechanistic characteristics of fiber reinforced soil–cement mixtures

Over the years, field experiments and research information have been collected and studied on the behavior of soil–cement mixtures, and quite a few studies have been conducted for fiber reinforcement in soil–cement mixtures. This research study focuses on the laboratory durability and mechanistic evaluation of soil–cement mixtures reinforced with Processed Cellulose fibers (PCFs) and polypropylene fibers (PFs). Four soil types from various project sites in the state of Louisiana were acquired. Laboratory tests including the durability, unconfined compressive strength (UCS), indirect tensile strength (ITS), and indirect tensile cyclic load tests (ITCTs) were conducted. The results indicated that the mechanistic characteristics of the soil–cement–fiber mixtures were functions of fiber dosage, soil type and curing time. In general, the durability, UCS, ITS and fracture toughness, and resilient modulus values of soil–cement–fiber mixtures either remained the same or were greater than soil–cement mixtures. Moreover, the horizontal plastic deformation (HPD) rate was significantly lower for soil–cement–fiber mixtures. The implication of the results is that the fiber reinforcement at optimum fiber percentage may resist the tensile or shrinkage crack formation in the soil–cement mixtures for road bases thereby, improving the structural capacity and performance of pavements.

Performance and Safety of Holmium: YAG Laser Optical Fibers

Lower-pole ureteronephroscopy requires transmission of holmium:YAG energy along a deflected fiber. Current ureteroscopes are capable of high degrees of deflection, which may stress laser fibers beyond safe limits during lower-pole use. We hypothesized that optical fiber and safety measures differ among manufacturers. Small (200-273-microm) and medium-diameter (300-400-microm) Ho:YAG fibers were tested in a straight and 180 degrees bent configuration. Energy transmission was measured by an energy detector. Fiber durability was assessed by firing the laser in sequentially tighter bending diameters. The fibers were bent to 180 degrees with a diameter of 6 cm and run at 200- to 4000-mJ pulse energy to determine the minimum energy required to fracture the fiber. The bending diameter was decreased by 1-cm increments and testing repeated until a bending diameter of 1 cm was reached. The maximum deflection of the ACMI DUR-8E ureteroscope with each fiber in the working channel was recorded. The flow rate through the working channel of the DUR-8E was measured for each fiber. The mean energy transmission differed among fibers (P < 0.001). The Lumenis SL 200 and the InnovaQuartz 400 were the best small and medium-diameter fibers, respectively, in resisting thermal breakdown (P < 0.01). The Dornier Lightguide Super 200 fractured repeatedly at a bend diameter of 2 cm and with the lowest energy (200 mJ). The other small fibers fractured only at a bend diameter of 1 cm. The Sharplan 200 and InnovaQuartz Sureflex 273T were the most flexible fibers, the Lumenis SL 365 the least. The flow rate was inversely proportional to four times the power of the diameter of the fiber. Optical performance and safety differ among fibers. Fibers transmit various amounts of energy to their cladding when bent. During lower-pole nephroscopy with the fiber deflected, there is a risk of fiber fracture from thermal breakdown and laser-energy transmission to the endoscope. Some available laser fibers carry a risk of ureteroscope damage.

Durability of glass fibre reinforced composites experimental methods and results

Abstract Even today a main topic of consideration for glass–fibre reinforced cementitious composites is the durability. Several damage mechanisms occur if glass fibres are inserted in a cementitious mixture. To diminish chemical attack of the fibres by hydroxyl ions, inorganic phosphate cement (IPC) was developed at the ‘Vrije Universiteit Brussel’, providing a non-alkaline environment. Since chemical attack is diminished by application of this non-alkaline matrix, IPC is an ideal reference material to study other damage mechanisms. In this paper typical damage mechanisms, occurring in cementitious composites are studied: both the effects of constant environmental loading (typical accelerated ageing tests) and variable environmental loading are studied. A new method to determine the matrix–fibre bundle efficiency is also introduced.

The durability of alkali-resistant glass fibres in cement matrix

The purpose of the paper is to investigate the durability of glass fibres in cement matrix containing silica fume (15, 25, 40 wt. %) with emphasis on the mechanism of their interaction with cement, to elucidate the effect of these interactions on the durability performance of alkali resistant glass fibers and, finally, to present observations obtained by scanning electron microscopy of the environment attack. The accelerated procedure method, Strand in Cement (SIC), in which the specimens are cured at hydrothermal conditions has been applied and the results were used to predict long term behaviour of these glass fibers. AR-glass based on ZrO 2 is alkaline resistant, but it deteriorates during prolonged wet cure. Silica fume, due to its pozzolanic properties has decreased the alkalinity of cement matrix by reacting with Ca(OH) 2 . The treatment of alkali resistant glass fibers with silica fume was effective in improving durability performances of glass fibres in cement matrix and fibres reinforced cement composites.