Plastic coating of glass fibers and its influence on strength

Abstract

Sodium borosilicate glass fibers pulled from the melt were plastic coated “on-line” to preserve the fiber strength. By the use of tapered nozzles within the coating applicator the coating could be made concentric around the fiber, and a 40-μm concentric coating was found to be sufficient for the fiber to withstand a mild abrasion test with no deterioration in strength. Strength measurements made in ambient conditions showed that the fiber had a uniform breaking strain of 4% elongation. The same fiber measured at liquid nitrogen temperatures had a breaking strain of 14%, even after extensive handling, which is close to the theoretical glass cohesive strength.     

Deformation and strength of silica fibers in three-point bending in consideration of nonlinear elasticity of glass

We consider the problem of asymmetric strain and stress distribution in silica fiber under threepoint bending. The parameters of nonlinear elasticity of silica glass under tension and compression are estimated using available data from the literature. It has been found that consideration of the nonlinear elasticity of silica glass leads to a slight increase in the calculated values of strength compared to the data obtained from estimates based on the linear theory of elasticity.     

Influence of amorphous hydrogenated carbon coating on the strength and cracking resistance of a glass in the high-strength state

The strength of sheet glass treated by etching in a hydrofluoric acid with subsequent deposition of an amorphous hydrogenated carbon coating 50 nm thick is investigated. The carbon coating is applied by ion magnetron sputtering of a chemically pure graphite target. It is shown that the strength of the sheet glass after coating is retained at a level of 2.4 GPa. The leaching of the surface glass layer upon treatment in water at a temperature of 96°C prior to the deposition of a coating leads to an increase in the strength by 12%. The cracking resistance of the glass is examined by the microindentation technique. It is revealed that the load P _c which corresponds to the formation of 50% of all the cracks increases by a factor of three upon deposition of the coating and by a factor of 15 after the preliminary leaching of the glass surface. The assumption is made that the preliminary leaching of the glass surface considerably enhances the adhesion of the hydrogenated carbon film to the glass surface and, thus, improves its protective properties.     

The influence of glass coating on the single domain wall potential in amorphous glass-coated Fe-based microwires

The effect of the glass coating on the single domain wall potential in amorphous glass-coated Fe-based microwire has been studied by the switching field distribution technique. The thermoactivated mechanism model is used to describe the thermally activated switching through the complex energy barrier in amorphous FeSiB microwires. Glass removal leads to the increase of the probability of the thermally activated switching pointing to the decrease of the energy barrier.     

Interfacial strength in glass fibre-polypropylene composites: influence of chemical bonding and physical entanglement

For glass fibre–polypropylene (PP) composites, the non-polar nature of polypropylene presents a problem. The present investigation shows that it is necessary to introduce a functionalised PP, for example PP-g-MAH, in order to enhance the bond strength between the PP matrix and aminosilane treated glass fibre. To achieve a better bonding between the substances, three different systems (1–3) in addition to a reference system (0), have been investigated in this study. The two first are based on PP-g-MAH coupling agents, with different concentrations of acid anhydride groups, and the third is a directly reacting system. In the first system, the silane treated glass fibre is exposed to molten mixture of 95 wt% PP homopolymer and 5 wt% PP-g-MAH. In the second system, the silane treated glass fibre is covered by a thin layer of PP-g-MAH and thereafter exposed to the molten PP. The interfacial shear strength is highest for the systems with the pre-compounded graft-copolymer. The resulting influence of the selected coupling systems on the interfacial bond strength of single fibre composite is studied by fragmentation testing. The intermolecular shear strength between fibre and matrix increases with the intermolecular entanglement length of the PP-g-MAH and not by the degree of functionalisation. The PP-g-MAH mixed into the PP gave better results than the route of first covering the glass fibre with a thin layer of PP-g-MAH. This is explained in terms of the probability of generating entanglements and in terms of a weak boundary layer at the glass surface. This conclusion is also supported by the results from using the third principle, i.e. direct reaction between the PP matrix and azidosilane treated glass fibres.     

The strength of glass

Large differences exist between the theoretical and experimental values of the mechanical strength of solids. Features of this phenomenon for glass are outlined together with a review of the current, incomplete explanation.     

Effect of polymer coating on leakage losses in Bragg fibers

It is found that the reflection of leaky radiation from the interface between the outer silica cladding and the coating polymer greatly modifies the loss spectrum of Bragg fibers. A simple model that describes this effect is proposed and confirmed by measurement and computation.     

Probability of fatigue failure in glass fibers

Abstract

Fracture mechanics provides the background for making long-term failure predictions to assure the mechanical reliability of glass fibers. The fatigue parameters necessary for making these predictions can be obtained from static and dynamic fatigue strength experiments. The failure calculations are best understood by expressing the predictions in terms of a design diagram. The probability of failure in service as well as the proof test stress necessary to ensure a minimum lifetime in service can be obtained from a design diagram.     

Probability of fatigue failure in glass fibers

Fracture mechanics provides the background for making long-term failure predictions to assure the mechanical reliability of glass fibers. The fatigue parameters necessary for making these predictions can be obtained from static and dynamic fatigue strength experiments. The failure calculations are best understood by expressing the predictions in terms of a design diagram. The probability of failure in service as well as the proof test stress necessary to ensure a minimum lifetime in service can be obtained from a design diagram.     

Roughness of boundary interfaces in polycrystals and its influence on the yield strength of nanocrystalline materials

The distribution in roughness of grain-boundary interfaces in polycrystals is measured metallographically. The result shows that there are high populations of localized interface areas with roughness much lower than the average in polycrystals. Effects of the roughness on the boundary sliding in nanocrystalline materials are discussed, suggesting that the sliding in the localized interface areas produces stress concentrations to cause a reduction in the yield strength of nanocrystalline materials.     

Linear and nonlinear properties of multicomponent glass photonic crystal fibers

Processes resulting in supercontinuum generation in multicomponent glass photonic crystal fibers are reviewed in this paper. Multicomponent glass photonic crystal fibers are shown to have a broad transmission range, extending up to 4.5 μm in selected cases. Pumping with a 1240-nm femtosecond pulse at very low sub-nJ energies resulted in soliton formation and dispersive wave generation in a multicomponent PCF sample having a double-core square-lattice structure. These processes were described using a phase-matching model derived from the simulated dispersive properties of the fiber. Third-harmonic generation was observed in the radiation modes of a different cobweb sample with the simultaneous formation of a soliton in the NIR.     

光纤基底TiNi形状记忆合金薄膜制备工艺

将TiNi基记忆合金薄膜与光纤相结合可制成智能化、集成化且成本经济的微机电系统和微传感器件.本文采用磁控溅射法在二氧化硅光纤基底上制备TiNi记忆合金薄膜,系统讨论了溅射工艺参数以及后续退火处理对薄膜质量的影响.采用自研制光纤镀膜掩膜装置在直径为125μm的光纤圆周表面上形成均匀薄膜.实验表明:在靶基距、背底真空度、Ar气流量和溅射时间一定的条件下,溅射功率存在最佳值;溅射压强较大时,薄膜沉积速率较低,但薄膜表面粗糙度较小.进行退火处理后,薄膜形成较良好的晶体结构,Ti_49.09Ni_50.91薄膜中马氏体B19′相和奥氏体B2相共存,但以B19′为主.根据本文研究结果,在玻璃光纤基底上制备高质量的TiNi基记忆合金薄膜是可实现的,本工作为下一步研制微机电系统和微型传感器做了基础准备.     

Metallic glass coating on metals plate by adjusted explosive welding technique

Using an adjusted explosive welding technique, an aluminum plate has been coated by a Fe-based metallic glass foil in this work. Scanning electronic micrographs reveal a defect-free metallurgical bonding between the Fe-based metallic glass foil and the aluminum plate. Experimental evidence indicates that the Fe-based metallic glass foil almost retains its amorphous state and mechanical properties after the explosive welding process. Additionally, the detailed explosive welding process has been simulated by a self-developed hydro-code and the bonding mechanism has been investigated by numerical analysis. The successful welding between the Fe-based metallic glass foil and the aluminum plate provides a new way to obtain amorphous coating on general metal substrates.     

光纤基底TiNi形状记忆合金薄膜制备工艺

将TiNi基记忆合金薄膜与光纤相结合可制成智能化、集成化且成本经济的微机电系统和微传感器件.本文采用磁控溅射法在二氧化硅光纤基底上制备TiNi记忆合金薄膜,系统讨论了溅射工艺参数以及后续退火处理对薄膜质量的影响.采用自研制光纤镀膜掩膜装置在直径为125μm的光纤圆周表面上形成均匀薄膜.实验表明:在靶基距、背底真空度、Ar气流量和溅射时间一定的条件下,溅射功率存在最佳值;溅射压强较大时,薄膜沉积速率较低,但薄膜表面粗糙度较小.进行退火处理后,薄膜形成较良好的晶体结构,Ti_49.09Ni_50.91薄膜中马氏体B19′相和奥氏体B2相共存,但以B19′为主.根据本文研究结果,在玻璃光纤基底上制备高质量的TiNi基记忆合金薄膜是可实现的,本工作为下一步研制微机电系统和微型传感器做了基础准备.     

Investigation of cladding and coating stripping methods for specialty optical fibers

Fiber optic sensing technology is used extensively in several engineering fields, including smart structures, health and usage monitoring, non-destructive testing, minimum invasive sensing, safety monitoring, and other advanced measurement fields. A general optical fiber consists of a core, cladding, and coating layers. Many sensing principles require that the cladding or coating layer should be removed or modified. In addition, since different sensing systems are needed for different types of optical fibers, it is very important to find and sort out the suitable cladding or coating removal method for a particular fiber. This study focuses on finding the cladding and coating stripping methods for four recent specialty optical fibers, namely: hard polymer-clad fiber, graded-index plastic optical fiber, copper/carbon-coated optical fiber, and aluminum-coated optical fiber. Several methods, including novel laser stripping and conventional chemical and mechanical stripping, were tried to determine the most suitable and efficient technique. Microscopic investigation of the fiber surfaces was used to visually evaluate the mechanical reliability. Optical time domain reflectometric signals of the successful removal cases were investigated to further examine the optical reliability. Based on our results, we describe and summarize the successful and unsuccessful methods.     

Interface and its effect on the interlaminate shear strength of novel glass fiber/hyperbranched polysiloxane modified maleimide-triazine resin composites

Interface is the key topic of developing advanced fiber reinforced polymeric composites. Novel advanced glass woven fabric (GF) reinforced composites, coded as GF/mBT, were prepared, of which the matrix resin was hyperbranched polysiloxane (HBPSi) modified maleimide-triazine (mBT) resin. The influence of the composition of the matrix on the interfacial nature of the GF/mBT composites were studied and compared with that of the composite based on GF and BT resin using contact angle, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and dielectric properties over wide frequency and temperature ranges. Results show that the interfacial nature of the composites is dependent on the chemistries of the matrices, mBT matrices have better interfacial adhesion with GF than BT resin owing to the formation of chemical and hydrogen bonds between mBT resin and GF; while in the case of mBT resins, the content of HBPSi also plays an important role on the interfacial feature and thus the macro-performance. Specifically, with increasing the content of HBPSi in the matrix, the interlaminate shear strength of corresponding composites significantly improves, demonstrating that better interfacial adhesion guarantees outstanding integrated properties of the resultant composites.     

Role of curing conditions and silanization of glass fibers on carbon nanotubes (CNTs) reinforced glass fiber epoxy composites

Curing behavior of amino-functionalized carbon nanotubes (ACNT) used as reinforcing agent in epoxy resin has been examined by thermal analysis. Experiments performed as per supplier’s curing conditions showed that modification of the curing schedule influences the thermo-mechanical properties of the nanocomposites. Specifically, the glass transition temperature (T_g) of ACNT-reinforced composites increased likely due to the immobility of polymer molecules, held strongly by amino carbon nanotubes. Further, a set of composites were prepared by implementing the experimentally determined optimal curing schedule to examine its effect on the mechanical properties of different GFRP compositions, while focusing primarily on reinforced ACNT and pristine nanotube (PCNT) matrix with silane-treated glass fibers. From the silane treatment of glass fibers in ACNT matrix composition it has been observed that amino silane is much better amongst all the mechanical (tensile and flexural) properties studied. This is because of strong interface between amino silane-treated glass fibers and modified epoxy resin containing uniformly dispersed amino-CNTs. On the other hand, PCNT GFRP composites with epoxy silanes demonstrated enhanced results for the mechanical properties under investigation which may be attributed to the presence of strong covalent bonding between epoxy silane of glass fiber and epoxy–amine matrix.     

Intensity measurement bend sensors based on periodically tapered soft glass fibers

We demonstrate a technique for tapering periodically an all-solid soft glass fiber, consisting of two types of lead silicate glasses, by the use of a focused CO(2) laser beam and investigate the bend sensing applications of the periodically tapered soft glass fiber. Such a soft glass fiber with periodic microtapers could be used to develop promising bend sensors with a sensitivity of -27.75 μW/m(-1) by means of measuring the bend-induced change of light intensity. The proposed bend sensor exhibits a very low measurement error of down to ±1%.     

Ultrasound influence on the activation step before electroless coating

This paper is devoted to the electroless plating of non-conductive substrates under ultrasound at 530 kHz. The ultrasonic irradiation is applied to the activation and to the plating steps. Effects are measured by following the final copper thickness obtained in 1 h of plating time, easily correlated to the average plating rate. It appears that ultrasound has a strong influence on the plating rates enhancement, and assumptions can be made that this increase could be linked to the catalyst cleaning. This is confirmed by XPS measurements.