Rapid reinforcement for fusion mass-spliced fibers using low-power induction heating

A rapid reinforcement method using low-power induction heating is developed. The reinforcement of a mass-spliced fiber ribbon unit comprising five graded-index multimode fibers was completed in 30 sec with good performance by supplying 30 W of electric power.     

Dynamic mechanical behavior of polymer modified bitumen

The dynamic mechanical behaviour of bitumen (BIT) modified with styrene/butadiene/styrene block copolymer (SBS) were investigated. Dynamic mechanical analysis (DMA) were performed in the temperature range –80 to 60 °C. The primary viscoelastic functions were determined at the traffic frequency, 5 Hz. The BIT+SBS blends were investigated in creep fatigue regime at temperature 10, 20, 30, 40 and 50 °C. Dynamic mechanical behaviour of BIT+SBS blends depends on their morphological characteristics, number of phases, phase compositions and phase content in blend, as well as time and temperature. The curves of primary viscoelastic functions, storage modulus (E′), loss modulus (E′′) and loss tangent (tg δ) vs. temperature of polymer modified bitumen differ from unmodified bitumen and indicate the presence of the swollen polybutadiene and polystyrene phases in bitumen phase. The curve E′ vs. temperature of polymer modified bitumen show the rubbery plateau. With the increment of SBS content the rubbery plateau is shifted to high temperatures. At the constant load the creep values of BIT-SBS blends increase and those of creep modulus decrease over a period of time. These effect are more pronounced in samples with higer content of SBS. The time-temperature correspondence principle was applied to create master curves for the reference temperature 10 °C for the creep modulus of BIT + SBS blends. The data were analysed using WLF and Arrhenius equations. Electronic Publication     

Bundle strength of polyester fibers determined using a series-parallel combination model

This paper describes the bundle strengths of PET filaments from a statistical point of view. A bundle is an arrangement of a number of filaments. We applied the weakest-link theory and probabilistic load-sharing rules to estimate the bundle strength from the breaking strength data of PET filaments. We analyzed the breaking behavior of 12 filament bundles according to their length and number of filaments and compared the breaking behavior of a prepared specimen yarn with that of a commercial PET filament yarn. The breaking strength of the PET filaments, which we tested using a MANTIS® tester, was compared with that of the actual yarn. We compared the actual tested values obtained by INSTRON® with the expected values, which we calculated from the MANTIS® data by using Peirce's theory and Knox's hazard function. The key effects that determine the actual random breakage behavior of a bundle include not only the load-sharing rules in the constituent filaments but also the slippage and friction between adjacent filaments, the appearance of which we distinguished especially in the bundle consisting of a large number of filaments and in small-denier filaments. The PET filaments were better approximated when using the Peirce's weakest-link theory than they were by Knox's hazard function. In a series-parallel model, we found that the number of parallel filaments and their load-sharing behavior had larger effects on the bundle strength than did the weakest-link effects of continuous elements.     

Constitution and strength of glass fibers

Five characteristic ranges of glass strength are described with respect to the sizes of its associated surface flaw. Particular attention is directed to the substantial difference in behavior between commercial and flawless glass fibers. It has been discovered in the latter case that a surface layer one order of magnitude thinner than normally detected is present, probably as a consequence of the drawing process. Distinct differences in behavior of the two kinds of layers was noted by using ultra-violet light absorption and hydrofluoric acid etching. Basic strength of the flawless glass fibers in vacuum can reach one million pounds per square inch.

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Zusammenfassung Fünf charakteristische Glasstärkebereiche wurden mit Rücksicht auf die Größen ihrer dazugehörigen Oberflächenfehlerhaftigkeit beschrieben. Besondere Aufmerksamkeit wurde auf den wesentlichen Unterschied im Verhalten zwischen kommerziellen und fehlerfreien Glasfibern gelenkt. Es wurde im letzteren Fall festgestellt, daß eine Oberflächenschicht, ein Größenverhältnis dünner als gewöhnlich beobachtet, gegenwärtig ist. Dieses ist wahrscheinlich eine Folge des Ziehungsvorganges. Deutliche Unterschiede im Verhalten der beiden Schichten wurden bemerkt. Man gebrauchte ultra-violette Lichtaufnahme and Fluorwasserstoffsäuere Ätzung. Die fundamentale Stärke der fehlerfreien Glasfibern im Vakuum kann eine Million Psi erreichen.

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Résumé On décrit cinq catégories de fibres de verre et leur resistance en fonction des dimensions des défauts de surface qu'elles comportent. L'attention est particulièrement attirée sur les différences substantielles de comportement que présentent les fibres de verre courantes et les fibres de verre sans défauts.On a pu determiner que ces dernières comportaent une couche superficielle dont l'épaisseur est d'un ordre de grandeur plus faible que celle que I'on détecte habituellement, cette couche étant probablement due au procédé de fabrication par filage.Des différences nettes de comportement de ces deux sortes de couches ont été observées, en mesurant l'absorption des rayons ultraviolets et en recourant à une attaque à l'acide hydrofluorique.La résistance de base de fibres de verre sans defauts pent atteindre dans le vide un million de psi.

     

Development of a lightweight space debris shield using high strength fibers

In order to protect space structure against space debris impacts, it is indispensable to develop a shield with high strength materials. A high strength fiber is one of potential materials from a viewpoint of strength, lightweight, and flexibility. The purpose of this study was to develop a new lightweight shield composed of high strength fibers against medium size debris impacts. We developed four kinds of shields using Vectran fibers, and hypervelocity impact tests were carried out by a railgun accelerator. The experimental results showed that the developed shield could stop the polycarbonate projectile with 13 mm in diameter, 1 gram in weight, and 6.9 km/sec in velocity. Adoption of the high strength fiber in the bumper materials may reinforce the protection capability and reduce the weight drastically.     

Enhancing tensile and compressive strength of magnesium using ball milled Al+CNT reinforcement

In this work, Mg/Al–CNT nano-composites were fabricated using powder metallurgy route involving microwave assisted rapid sintering and hot extrusion. Ball milled Al–CNT particles comprising different contents of CNTs coated with fixed amount of Al were used for strengthening. Microstructural characterization of these Mg/Al–CNT nano-composites reveal reasonably uniform distribution of Al–CNT particles up to CNT content of 0.30% by weight, significant grain refinement and the presence of minimal porosity compared to monolithic Mg. Importantly, for the nominally identical processing conditions, the textures of as-extruded nano-composite specimens is significantly influenced by the presence of Al–CNT particles. Nano-composite configurations exhibit different tensile and compressive response as a function of CNT content. Among the different Mg/Al–CNT formulations synthesized, the Mg/Al–CNT configuration with Al–CNT particles composition of 1.00% Al and 0.30% CNT by weight (Mg/1.00Al–0.30CNT) exhibit higher tensile yield strength (0.2% YS), ultimate tensile strength (UTS) and failure strain (FS) (up to +72%, +48%, +9%, respectively) compared to monolithic Mg.     

Development of high strength magnesium based composites using elemental nickel particulates as reinforcement

Magnesium based materials due to their inherently low density and ensuing potential to exhibit high specific mechanical properties are actively sought for weight-critical structural application. In the present study, elemental and nickel reinforced magnesium materials were synthesized using an innovative disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization of the composite samples showed uniform distribution of nickel particulates in the matrix material, good interfacial integrity of magnesium matrix with nickel particulates and Mg-Ni based intermetallics, and the presence of minimal porosity. Physical properties characterization revealed that addition of nickel as reinforcement improves the dimensional stability of pure magnesium. Mechanical properties characterization revealed that the presence of nickel reinforcement lead to significant improvement in hardness, elastic modulus, 0.2% yield strength and UTS while the ductility was adversely affected. The results further revealed that the combination of 0.2% yield strength, UTS, and ductility exhibited by nickel reinforced magnesium remained much superior even when compared to high strength magnesium alloy AZ91 reinforced with much higher volume percentage of SiC. An attempt is made in the present study to correlate the effect of nickel as reinforcement and its increasing amount with the microstructural, physical and mechanical properties of magnesium.     

Decreasing polycyclic aromatic hydrocarbons emission from bitumen using alternative bitumen production process

In 1988, the National Institute for Occupational Safety and Health (NIOSH) recommended that bitumen fumes should also be considered a potential occupational carcinogen and management practices such as engineering controls should be implemented. Changing the production process of bitumen, as a source control method, was investigated in our study. For the first time, a novel alternative process was used to produce paving grade bitumen with decreased PAH emissions as well as improved bitumen performance grade (PG). Post-consumer latex and natural bitumen (NB) were used as additives to obtain 60/70 modified bitumen directly from the vacuum bottom (VB) without any need for air-blowing. The emissions were produced by a laboratory fume generation rig and were sampled and analyzed by GC-Mass and GC-FID as described in NIOSH method 5515. The PG of the resulting modified 60/70 bitumen in this study covers a wider range of climatic conditions and has higher total resistance against deformation than conventional 60/70 bitumen. The total PAH emissions from modified 60/70 bitumen (100.2619 ng/g) were decreased approximately to 50% of PAHs emitted from conventional 60/70 bitumen (197.696 ng/g). Therefore, it is possible to obtain modified bitumen with lower PAH emissions and better quality than conventional bitumen via additives and without air-blowing.     

Effective viscoelastic behavior of short fibers composites using virtual DMA experiments

Mechanics of Time-Dependent Materials - May it be for environmental or economic reasons, mass reduction has become one of the main goals in mechanics. The short fiber thermoplastics composite is an...     

External reinforcement of high strength concrete columns

With the technology development on the compressive strength of concrete over the years, the use of high strength concrete has proved most popular in terms of economy, superior strength, stiffness and durability due to many advantages it could offer. However, strength and ductility are inversely proportional [J. Mater. Civil Eng. 11 (1999) 21]. High strength concrete is a brittle material causing failure to be quite sudden and ‘explosive' under loads. It is also known that structural concrete columns axially compressed rarely occur in practice. The stress concentrations caused by the eccentric loading further reduce the strength and ductility of high strength concrete. Therefore, studies for high strength concrete columns under eccentric loading are essential for the practical use.

This paper experimentally investigates a number of high strength concrete columns that are externally reinforced with galvanised steel straps and fibre-reinforced polymers subjected to concentric and eccentric loading. The experimental results show that external reinforcement can enhance the properties of high strength concrete columns.     

Ageing in modified bitumen using FTIR spectroscopy

Modified binders exhibit complex rheological behaviour due to the interaction of the modifiers with the base binder and the manner in which they age during field applications. Quantification of the interaction and the ageing of such modified binders is currently a necessity. In this investigation, three modified binders (elastomer, plastomer, and crumb rubber) and the base bitumen were subjected to different ageing conditions and the evolution of the chemical functionalities during ageing were tracked using FTIR spectroscopy. Analysis of the spectra of modified binders immediately after the production process showed that while the elastomer modified binders exhibited physical interaction, the plastomer and crumb rubber modified binders exhibited physical and chemical interactions. During ageing, there was no subsequent evolution of the interactions and one could only see chemical functionalities related to oxidation. Analysis of the spectra showed that the carbonyl and sulphoxide exhibit identical trends whereas aliphaticity and aromaticity deviate drastically.     

高强度卡拉胶纤维的制备及性能测试

通过卡拉胶与环氧氯丙烷交联反应制得改性卡拉胶;并将改性卡拉胶溶于热水制得纺丝液,采用湿法纺丝制备高强度卡拉胶纤维。红外光谱测试及粘度提高证明交联反应的发生;用单因素实验法找到影响因素的最佳范围,通过正交实验法得到最佳合成条件为温度90℃、交联剂加入量为6.25%、反应时间2.0h、pH值为10.0;利用万能材料试验机测得纯卡拉胶纤维的断裂强度为2.17cN/tex,改性卡拉胶纤维的最大断裂强度为3.99cN/tex,交联后断裂强度提高85%。     

Determination of mechanical strength properties of hemp fibers using near-infrared fourier transform Raman microspectroscopy

Fourier transform near-infrared (FT-NIR) Raman microspectroscopy was adopted for analyzing the micro mechanical tensile deformation behavior of cellulosic plant fibers. Mechanical strength parameters such as tensile strength, failure strain, and Young's modulus of diversified hemp fibers were determined within the range of single fiber cells and fiber filaments. The analysis of fiber deformation at the molecular level was followed by the response of a characteristic Raman signal of fiber cellulose that is sensitive to the tensile load applied. The frequency shift of the Raman signal at 1095 cm(-1) to lower wavenumbers was observed when the fibers were subjected to tensile strain. Microstructural investigations using electron microscopy under environmental conditions supported the discussion of mechanical properties of hemp fibers in relation to several fiber variabilities. Generally, mechanical strength properties of diversified hemp fibers were discussed at the molecular, microstructural, and macroscale level. It was observed that mechanical strength properties of the fibers can be controlled in a broad range by appropriate mercerization parameters such as alkali concentration, fiber shrinkage, and tensile stress applied to the fibers during the alkaline treatments.     

Laboratory studies of diffusion in bitumen using markers

Performance of recycled asphalt pavements depends, among other things, on the degree of mixing of old and new binders. One of the factors contributing to the mixing is diffusion, which increases the homogeneity of recycled binders. In this study, FTIR-ATR (Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance) has been applied to investigate influence of temperature, viscosity of the diffusion medium, and diffusant size and polarity on diffusion characteristics. Several substances, referred to as markers, have been monitored when diffusing through different binders. By careful selection of markers, the importance of diffusant size and polarity on rate of diffusion has been demonstrated. Diffusion has been modelled using Stoke-Einstein's equation and compared with experimental data obtained by FTIR-ATR. The equation has shown useful in explaining the effects of temperature, viscosity and molecular size on diffusion.     

Impact of maltene and asphaltene fraction on mechanical behavior and microstructure of bitumen

As a widely accepted concept, bitumen consists of four fractions that can be distinguished by their polarity. Highly polar asphaltene micelles are dispersed in a viscous phase of saturates, aromatics and resins (maltene phase). Different concentrations of asphaltenes in the bitumen result in a range of mechanical response properties. In an interdisciplinary study the impact of the maltene phase and asphaltenes on the linear viscoelastic behavior and the microstructure of bitumen were analyzed by creep recovery testing in a DSR and by atomic force microscopy (AFM). Therefore, bitumen was separated into the maltene and asphaltene fractions and artificial bitumen samples with different, pre-defined asphaltene concentrations were produced and investigated. It was found that the artificially produced, precipitated bitumen samples can be regarded as a representative, bitumen-like material in terms of mechanical behavior and microstructure. Asphaltenes play an important role in the typical viscoelastic behavior of bitumen being mainly responsible for stiffness and elasticity. Also, their concentration appears to be correlated to the occurrence and shape of the bee-like inclusions which can be typically observed by AFM.     

Mechanical behavior of entangled fibers and entangled cross-linked fibers during compression

Entangled fibrous materials have been manufactured from different fibers: metallic fibers, glass fibers, and carbon fibers. Specimens have been produced with and without cross-links between fibers. Cross-links have been achieved using epoxy spraying. The scope of this article is to analyze the mechanical behavior of these materials and to compare it with available models. The first part of this article deals with entangled fibrous materials without cross-link between fibers. Compression tests are detailed and test reproducibility is checked. In the second part, compression tests were performed on materials manufactured with cross-linked fibers. The specific mechanical behavior obtained is discussed.     

Longitudinal and transverse strength of glass ribbon for plastic reinforcement

The strength measurements for Corning Code 8871 glass ribbon with a rectangular crosssection measuring 0.22 in.×0.002 in. are presented. Owing to the narrow width of the ribbon, tensile strength measurements were carried out only in the longitudinal direction. To establish the isotropy of ribbon strength, flexure tests were conducted in both the longitudinal and transverse directions. It was found that in the as-manufactured condition, the transverse strength is lower than the longitudinal strength, indicating preferred orientation of flaws introduced during manufacturing. After etching in 10% HF/15% HNO₃ solution for different lengths of time, the longitudinal and transverse flexural strengths increased with etch time, reaching an asymptotic value after 20 sec. The transverse strength value, after etching, was generally higher than the longitudinal strength, partly due to the considerably smaller surface area exposed to tension and partly due to the uncertainties in measurement of chord length. The anisotropy of ribbon strength in the as-manufactured condition could partly account for the anisotropic strength of ribbonreinforced composites as reported in the literature [4, 5].