Durability Of Fibers Research Articles

Effect of the addition of modified mica on mechanical and durability properties of FRP composite materials for civil engineering

AbstractThe 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 clay 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 of the addition of modified mica on FRP properties used in civil engineering applications. To conduct this preliminary study, the following steps were taken: (1) prepare and characterize composites made from lab‐made modified mica, (2) determine the maximum water uptake, water absorption rate and coefficient of diffusion, (3) characterize the mechanical properties, and finally, (4) evaluate the UV resistance. The experimental results show that the use of nanoparticles leads to a decrease of the coefficient of diffusion of water and a significant increase of stiffness and UV resistance. POLYM. COMPOS., © 2011 Society of Plastics Engineers.

Recent developments in laser therapy for BPH

AbstractA new generation of lasers for photoselective vaporisation of the prostate operating at 180 watts of power has been introduced for the treatment of benign prostatic hyperplasia. The product was designed to speed up the lasering process and improve fibre durability, while maintaining the safety profile of previous generations. Roger Kirby reviews the history of laser therapy, and discusses whether the treatment can be considered a viable alternative to transurethral resection of the prostate. Copyright © 2011 Wiley Interface Ltd

Study on Hygrothermal Properties of Carbon Fiber Reinforced Composites Aged in Cyclic Environment

In this study, we investigate the cyclic hygrothermal effects of moisture, high temperature and low temperature states on the durability of carbon fiber reinforced epoxy resin composites (CF/Epoxy). CF/Epoxy composites are prepared by curing in autoclave. The moisture diffusion behavior of CF/Epoxy composites is analyzed by moisture content as a function of time. In addition, the effects of cyclic conditions on the inter-laminar shear properties and microstructure of composites are investigated through inter-laminar shear strength (ILSS) tests and scanning electron microscope (SEM) analysis respectively. The test results show that composites have a good retention rate of ILSS. The SEM photographs, associated with the mentioned ILSS test results demonstrate that desorption cycle makes more remarkable degradation of ILSS compared to aging in water, and it is necessary to calculate the effect of low-temperature wet condition when we design accelerated aging cycle.

Steel Fiber Reinforced Concrete Carbonation Simulation Research

Durability of concrete structure due to carbonation problem has attracted worldwide attention. By studying on the performance of steel fiber reinforced concrete carbonation, simulations CO2corrosion environment was simulated. The impacts of the change law of carbonation depth of steel fiber reinforced concrete with water cement ratio (0.35,0.45,0.55), as well as steel fiber content (0%, 0.5%, 1.0%, 1.5% , 2.0%), pouring surface and age, on concrete carbonation depth were studied. Steel fiber reinforced concrete carbonation performance improvement role was analyzed. Thus, providing a experimental basis that can be used in the design and analysis of the durability of steel fiber reinforced concrete structure.

Micro Pore Structure Research of Steel Fiber Reinforced Shotconcrete

Steel fiber reinforced shotconcrete are widely used at home and abroad, compared to the ordinary modelconcrete, this process is not only convenient, fast, and often used in places with poor geological conditions. In this paper, we use mercury intrusion method to test pore structure of steel fiber reinforced shotconcrete, and analyze the change of pore structure under different construction techniques, and then from the microscopic point of view, analyze the effect on the mechanical properties and durability of steel fiber reinforced concrete under thus different construction technology.

The Analysis on the Mechanical Property and Durability of Carbon Fiber Reinforced Concrete

This paper mainly studies the influence pattern of mechanical properties and anti-permeability and carbonation etc durability after adding the carbon fiber into the concrete. Results show that appropriate amount fiber seep into concrete can improve its mechanical properties and durability.

The effect of root canal re-wetting on push-out bond strength and durability of fiber post

To analyze the push-out bond strength of fiber post and the durability of interface between dentin and composite resin during over drying and re-wetting of root canal. Thirty-six extracted human maxillary central incisors were randomly divided into three groups: Group A for the process of over drying, Group B for re-wetting, Group C for control. All teeth were sliced into several thin discs with thickness of 1.0 mm for micro push-out test and scanning electron microscope(SEM) observation. Push-out shear strengths of fiber post immediately after bonding in group A, B and C were (5.97 ± 1.97), (7.67 ± 2.19) and (8.46 ± 2.35) MPa. Push-out strengths of fiber post two months after water storage were (2.08 ± 1.67), (2.99 ± 1.48) and (3.22 ± 1.43) MPa. There was significantly difference in push-out strength between Group A and Group B (P < 0.05). Significantly difference in push-out strength was also found between Group A and Group C. In the condition of immediate testing, there was also significantly difference between push-out strength of cervical slice and middle slice, and between cervical slice and apical slice (P < 0.05). The water storage time has significant effect on the push-out bond strength of fiber posts (P < 0.05). Inappropriate condensation air blowing operation can cause extracted teeth root canal dentin over dry. Dehydration can destroy the formation of general structure of interface between composite resin and dentin. The over dry dentin can be turned back to wetting stage by water pouring, which can help fiber-reinforced composite post regain its normal retention strength and original adhesive durability.

Heat durability of carbon fiber reinforced nickel composites

Carbon fiber is a highly heat resistive material in an oxygen free atmosphere. Nickel is also a heat resistive metal and an important element for a superalloy. We can expect an excellent heat durable composite when they are combined. Nickel was electroplated on a carbon yarn to form a monofilament composite. When the high strength fiber was tested, the composite started to lose its strength at 600°C. The deterioration was caused by graphitization of the carbon in the fiber. This is caused by the difference of the graphitization degree between crystallites in a fiber. A high modulus carbon fiber has little difference of the graphitization degree in a fiber. The high modulus fiber did not react when tested and the fiber strength was maintained after heat treatment at 1100°C for 9 h. From the results, the high modulus carbon fiber composite is promising to be durable at a high temperature.

Durability of carbon fibre reinforced polymer laminates used to reinforced concrete structures

Due to their excellent mechanical properties and easy application Carbon Fibre Reinforced Polymers (CFRP) are being successfully used to repair and renew old and damaged civil engineering infrastructures. In particular, the method of strengthening concrete members with externally bonding of CFRP laminates has become increasingly popular. In fact, extensive research has shown that this technique can lead to a substantial improvement in the fl exural and shear strength capacities of the member repaired. In such applications, materials involved will be exposed to outdoor environmental conditions, including humidity, water from rain, saline-water, ground water and high alkalinity solutions due to chemical composition of the concrete itself, as well as solar ultraviolet (UV) radiation. Thus, it is of great relevancy to study the durability of the materials involved, namely epoxy adhesives and CFRP laminates, as well as, the integrity of the entire system, when subjected to those environmental factors. This work is part of a much larger research study to predict the long-term behaviour of several commercial CFRP laminate/adhesive systems used in the rehabilitation of concrete structures. In the whole project it is recognised that the durability of these solutions depends not only on the durability of the composite materials but also on the performance of the systems used to bond them to the concrete. This present document provides details about the durability of CFRP laminates and the study carried out to investigate the environmental and accelerated ageing effects on three types of commercially available CFRP laminates. The changes in CFRP laminates properties after exposure up to 18 months under different environmental conditions – immersion in demineralised water, saline and alkaline solutions at room temperature, 40 ° C and 60 ° C, as well as under constant humidity condensation atmosphere at 40 ° C – are reported and discussed. The results of tests performed in accelerated weathering chambers – with UV radiation – are also included. Results obtained offer valuable information about the progression of material degradation under different ageing conditions (some of them accelerated), which can be used, not only to characterise the behaviour of CFRP laminates, but also for a better understanding of the degradation mechanisms involved, which is a base for the design of service life-prediction models.

Obituary: Dr John MG Davis PhD, DSc, FRCPath

Obituary: Dr John MG Davis PhD, DSc, FRCPath

Nanotoxicology--a pathologist's perspective.

Advances in chemistry and engineering have created a new technology, nanotechnology, involving the tiniest known manufactured products. These products have a rapidly increasing market share and appear poised to revolutionize engineering, cosmetics, and medicine. Unfortunately, nanotoxicology, the study of nanoparticulate health effects, lags behind advances in nanotechnology. Over the past decade, existing literature on ultrafine particles and respirable durable fibers has been supplemented by studies of first-generation nanotechnology products. These studies suggest that nanosizing increases the toxicity of many particulates. First, as size decreases, surface area increases, thereby speeding up dissolution of soluble particulates and exposing more of the reactive surface of durable but reactive particulates. Second, nanosizing facilitates movement of particulates across cellular and intracellular barriers. Third, nanosizing allows particulates to interact with, and sometimes even hybridize with, subcellular structures, including in some cases microtubules and DNA. Finally, nanosizing of some particulates, increases pathologic and physiologic responses, including inflammation, fibrosis, allergic responses, genotoxicity, and carcinogenicity, and may alter cardiovascular and lymphatic function. Knowing how the size and physiochemical properties of nanoparticulates affect bioactivity is important in assuring that the exciting new products of nanotechnology are used safely. This review provides an introduction to the pathology and toxicology of nanoparticulates.

Experimental Study on the Durability of Glass Fiber Reinforced Polymer Pole and Tower for Power Transmission

This paper studied the durability of Glass Fiber Reinforced Polymer (GFRP) Pole and Tower for power transmission under the UV and adverse temperature environment. The results show that both UV and adverse temperature environment influence the performance of GFRP material, with its strength significantly reduced, and its elastic modulus increased, while the Poisson's ratio changed slightly. Xenon lamp aging affects the material properties of the specimens with protective coatings more slightly than those without any protective coatings. High temperature environment affects the material properties of specimens more obviously than low temperature environment does. Therefore, when designing the GFRP Pole and Tower for power transmission exposed in UV and adverse temperature environment long-term, designers should consider the negative impacts of the external environment, and take appropriate protective treatments.

Durability of E-Glass Fiber Reinforced Polymer Subjected to Freeze-Thaw Cycle and Sustained Load

Strengthening concrete structure with E-glass fiber reinforced polymer (GFRP) is gaining more popularity, mainly due to their superior mechanical properties. However, there is insufficient information on environmental durability of glass fiber reinforced polymer, especially in harsh environmental conditions combined with sustained load. In this paper, the durability of an E-glass/ composite material under freeze-thaw cycle either in an unstressed state or loaded in about 30% of the initial ultimate load are investigated. The residual tensile properties of the GFRP are studied after coupled action of freeze-thaw cycle and sustained load. The results indicate that the single action of freeze-thaw cycle reduces the ultimate tensile strength and strain of the GFRP, and the coupled action of sustained load and freeze-thaw cycle further reduces the ultimate strength and strain of the GFRP.

Study on durability of natural fibre concrete composites using mechanical strength and microstructural properties

Investigations to overcome the brittle response and limiting post-yield energy absorption of concrete led to the development of fibre reinforced concrete using discrete fibres within the concrete mass. Out of the commonly used fibres, easily available low cost natural fibres are renewable source materials. Though these fibres are ecologically advantageous, they have some limitations such as lower durability and lesser strength. But recent research provides several treatment processes to enhance the durability of natural fibres. In this paper, the durability of natural fibres such as coconut coir and sugarcane bagasse has been reported by conducting an experimental investigation. This investigation includes two parts. The first part focuses on the determination of mechanical strength properties such as compressive, tensile, modulus of rupture and flexural properties of natural fibre reinforced concrete specimens once every 3 months for a period for 2 years under alternate wetting and drying conditions. Gain or loss in strength of composite concrete at 9 intervals were computed and are reported here. The second part covers the microstructural properties of fresh natural fibres in as received condition and natural fibres reacted with concrete under accelerated curing conditions for two years. SEM and EDAC test results are discussed.

Durability of CFRP–concrete joints under freeze–thaw cycling

Abstract The long-term durability of fiber reinforced polymer (FRP) strengthening systems under freeze–thaw cycling is crucial to the safety of structures in cold climates. The durability of the FRP–concrete bond interface under freeze–thaw cycling was investigated in the study reported here, with exposure condition, concrete grade, and number of freeze–thaw cycles as the parameters considered. The behavior of the carbon FRP (CFRP)–concrete bond interface was investigated with single-face shear tests. The results indicate that the bond strength, bond stiffness, interfacial fracture energy, and maximum slip of the joints decrease with increases in the number of freeze–thaw cycles, and they are also affected by the exposure environment. The depth of cracking and effective bond length increase with increases in cycle number, thus affecting bond stiffness and strength. The deterioration of bond strength can be attributed to the damage caused to the concrete by the freeze–thaw cycling.

Laser ablation of the prostate: a safe effective treatment of obstructive benign prostatic disease

Laser ablation of the prostate: a safe effective treatment of obstructive benign prostatic disease

Experiment Study on the Frost Resistance of Steel Fiber Reinforced Concrete

In order to study various factor affecting durability of steel fiber reinforced concrete (SFRC), basic experimental research that combine the action of freezing-thawing cycles and deicing salt to SFRC was conducted. In the experiment, the volume fraction of steel fiber and number of freeze-thaw circulation are taken as variable parameter. Based on the different numbers of freeze-thaw circulation, weight losing of SFRC, splitting strength and the dynamic modulus of elasticity were measured. Furthermore, the reinforced mechanism of the SFRC under the action of freeze-thaw was analysed. The test results show that after adding a certain amount of steel fiber to the concrete, cracks in concrete at early stage are effectively prevented and the permeability of concrete is obviously reduced, thus the durability of concrete is improved. The reinforced actions of steel fiber on splitting strength of concrete are notable and the influence of steel fiber volume fraction on the frost-resisting property is obvious. On the contrary, the negative effects of steel fiber with high volume fraction on the splitting strength of concrete exist. The best performance of SFRC can be got when the steel fiber quantity is 1.5%.

First Report of Crotalaria spectabilis Fasciation Associated with 'Candidatus Phytoplasma asteris' in India.

Crotalaria spectabilis Roth. (Fabaceae), commonly known as showy rattlebox, is an herbaceous legume mainly used as a green manure crop to improve soil properties and as a source of durable fiber. However, the plant is toxic to mammals and birds because of the presence of pyrrolidizine alkaloids. A native of India and the Malay Peninsula, the species has been introduced into other areas such as the United States and Pacific Islands where the plant is an invader of cultivated lands. Fasciated rattlebox plants were sighted in fields in New Delhi in February 2010, with approximately 99% of the examined plants symptomatic. Symptoms included flattening of stems in a descending gradient of severity from the apex to the base of each affected branch. Shoots showed longitudinal undulations bearing highly reduced leaves and uneven distribution of flowers and fruits. To identify the causal agent, 10 symptomatic plants and 8 asymptomatic plants (latter sampled from a field approximately 1.5 km away) were collected for nucleic acid analysis. Total genomic DNA was extracted from flattened stems as well as the roots of symptomatic plants, and from the same tissues of asymptomatic plants, and subjected to nested-PCR using phytoplasma 16S ribosomal DNA universal primer pair P1/P7, followed by R16F2/R2 (4). A known aster yellows-infected Catharanthus roseus plant was used as a control sample. Results depicted a characteristic phytoplasma amplicon of 1.25 kb in all samples from symptomatic plants and the control plant. No amplification was observed from asymptomatic plants. To obtain a full-length sequence, a representative amplicon was purified with the QIAquick gel extraction kit (QIAGEN, Valencia, CA), cloned into pGEM-T Easy vector (Promega, Madison, WI), and sequenced. Comparison of the 1,243-bp sequence (Genbank Accession No. HM137557) using BLAST analysis of the NCBI database showed 99% homology with sequences of members of 16SrI group phytoplasmas, i.e., 'Candidatus Phytoplasma asteris' such as Japanese spurge yellows (AB551736.1), Mulberry yellow dwarf (GQ249410.1), and Bamboo witches'-broom (FJ853161.1) phytoplasmas. The profiles of in vitro restriction fragment length polymorphism (RFLP) analysis obtained by digestion of the nested-PCR products with HhaI, KpnI, and AluI were similar to those of in silico RFLP analyses and coincided with the pattern of the 16SrI-B subgroup. Phylogenetic analysis of phytoplasma 16S rDNA sequences based on the maximum likelihood method using MEGA Version 4.1 also placed the Crotalaria fasciation (CF) phytoplasma within the 16SrI-B cluster. In India, C. tetragona plants infected with 16SrI phytoplasma (FJ185141) causing witches'-broom symptoms (1) showed 98% similarity with the CF phytoplasma. However, the results support previous molecular investigations associating 16SrI phytoplasma with fasciation of herbaceous plants, including Lilium spp. (2) and Asparagus officinalis (3). To our knowledge, C. spectabilis represents a new host that can be fasciated as a result of phytoplasma infection. Because of the weedy nature of C. spectabilis, this host could facilitate spread of the phytoplasma.

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

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

Effects of harsh weather and seawater on glass fiber reinforced epoxy composite

The lack of reliable engineering data on the durability of glass fiber reinforced Epoxy (GFRE) pipes when exposed to harsh Arabian Gulf outdoor environment has limited their wide use for saltwater and crude oil handling and transportation. This article explores the combined effect of natural and accelerated weathering and seawater on tensile properties of GFRE pipe materials. Saltwater filled pipes were exposed to outdoor environment in Dhahran, Saudi Arabia for periods ranging from 6 to 12 months. Ring-shaped tensile test specimens were also immersed in oxygenated saltwater at room temperature for time periods ranging from 300 to 10,000 h. The natural exposures resulted in gradual reduction of tensile strength and fracture strain with exposure time in saltwater filled pipes. The exposure to oxygenated saltwater immersion also showed detrimental effects after 300 h of exposure. Longer immersion periods did not result in further strength degradation. The stiffness of the GFRE pipe specimens remained more or less unaffected by exposure to seawater. Fractographic analysis of unexposed specimens showed a combination of Mode I and Mode II failure characterized by inclined hackles as well as fiber breakage. High outdoor temperature and moisture absorption decreased fiber—matrix interface strength and caused degradation at the fiber level resulting in lower ultimate strength, fracture strain, and stiffness of the GFRE.