Glass Filaments Research Articles

Sensor yarns for real-time in situ detection of damage behavior for the purpose of structural health monitoring of textile-reinforced thermoset composites: development of a continuous wet-chemical silvering process for high-performance filament yarn

High-performance textile yarns such as glass filament (GF) yarn will be used as the base material for the development of sensor yarns because glass filament yarns offer both high tensile strengths and moduli of elasticity, as well as high melting temperatures and elongation. A new continuous wet-chemical metallization process has been developed for GF yarns on a laboratory scale to achieve special properties such as electrical conductivity. The aim of the work is to develop a continuous wet-chemical silver plating process for the GF-filament yarn in order to achieve electrical conductivity on the GF-surface. The process was carried out continuously in order to metallize the GF, which is sensitive to the shear force. A homogeneous, completely covered and adhered silver layer on the GF yarn surfaces was obtained by the application of this technology. The surface morphology was been determined by light and scanning electron microscopy to assess the silver layer properties such as structure, homogeneity, and cracking. The chemical structure of the surfaces was analyzed by means of energy dispersive x-ray spectroscopy. For structural analysis, GF yarns were investigated using a Fourier transform infrared spectrometer. The dispersive and polar component of the surface energy of the sized and silvered GF yarn was measured by using a single fiber Tensiometer K100. The silver layer thickness and the silver content were determined after the metallization. Textile physical tests of the tensile strength, elasticity modulus, elongation at break, and yarn fineness of the single GF yarns as well as GF bundle were carried out.

Glass Fibers: Quo Vadis?

Since the early 1930s, the process of melting glass and subsequently forming fibers, in particular discontinuous fiber glass or continuous glass filaments, evolved into commercial-scale manufacturing.[...]

Detailed numerical analysis of evaporation of a micrometer water droplet suspended on a glass filament

For a long time, the single droplet drying (SDD) equipment has been utilized to investigate droplet drying behaviour relevant to spray drying. Typical of the device is a global measurement of droplet’s drying kinetics such as evaporation rate, temperature history, diameter changes, etc., and has been extensively used for such purposes. Utilization of computational fluid dynamics (CFD) enables SDD experiment to be interpreted and examined closely as well as for better exploration of the device with views of improving it in future. Here, for the first time, we have provided detailed numerical simulation of the laboratory condition of SDD using a pure water droplet suspended on a glass filament tip. With CFD, it is therefore possible to determine the local flux of vapour or global evaporation rate across the droplet-air interface using the equations of transport. The Arbitrary Lagrangian-Eulerian (ALE) procedure embedded inside Navier-Stokes ensures interface tracking as well as visualization of the droplet shape evolution. As a concrete demonstration of the SDD situations, effects of different glass knob sizes for different sizes of suspended pure water droplet (0.98–1.56mm initial diameter), upward inflow of humid air and temperature (0.01% and 358.15K), and air velocity 1.11ms−1 were examined on evaporation rate; shape formation; flow velocity and temperature distribution within and around the droplet. Our model is based on the first principles, without adjustable parameters, the predictions made are in good agreement with the available experimental SDD data.

Additive Manufacturing of Transparent Soda-Lime Glass Using a Filament-Fed Process

There are many scientific and engineering applications of transparent glass including optics, communications, electronics, and hermetic seals. However, there has been minimal research toward the additive manufacturing (AM) of transparent glass parts. This paper describes and demonstrates a filament-fed technique for AM of transparent glass. A transparent glass filament is melted by a CO2 laser and solidifies as the workpiece is translated relative to the stationary laser beam. To prevent thermal shock, the workpiece rests on a heated build platform. In order to obtain optically transparent parts, several challenges must be overcome, notably producing index homogeneity and avoiding bubble formation. The effects of key process parameters on the morphology and transparency of the printed glass are explored experimentally. These results are compared to a low-order model relating the process parameters to the temperature of the molten region, which is critical to the quality of the deposited glass. At lower temperatures, the glass is not fully melted, resulting in index variations in the final part, while at higher temperatures, phase separation introduces bubbles and other defects into the part. The correct process avoids these issues and deposits optically transparent glass.

Filamentation and supercontinuum generation in lanthanum glass

A broadband supercontinuum (SC) covering 400–2800 nm in a 20 dB dynamic range is reported in a piece of highly nonlinear, low-dispersion bulk lanthanum glass without employing any lens to focus the pump pulse. The spectrum width obtained in this study is broader than the maximum spectrum width obtained in silica photonic crystal fibers. The filaments and bright conical visible emission patterns of the SC are analyzed. Under optimum pump conditions, an SC conversion efficiency of 75% is obtained. The SC conversion efficiency is confirmed to be stable. Additionally, the relationship between the input peak intensity and the output beam radius is elucidated by simulating the propagation of a Gaussian beam in the bulk lanthanum glass. A 0.20 mm stable laser beam radius at the end of the propagation domain is demonstrated in a certain input peak intensity range. This small value of the beam radius indicates that most of the output power is localized over a small region because of the Kerr focusing effect despite the existence of conical emission in the SC generation by filamentation. The findings of this study are of significance for the development of ultra-broadband SC sources based on bulk glasses and high peak power lasers.

Unraveling the droplet drying characteristics of crystallization‐prone mannitol – experiments and modeling

Spray‐dried mannitol is a potential lactose replacement in pharmaceutical formulations, yet the drying behavior of individual mannitol droplets within the spray chamber has not been fully understood. This work explored the drying characteristics of mannitol by employing the reaction engineering approach (REA) in data analysis. A glass filament single droplet drying technique was used to monitor the changes in droplet temperature, mass, and diameter. The drying kinetics data obtained clearly demonstrated the droplet “wet‐bulb” period, the crust formation, and the crystallization phenomena. The master activation‐energy curves developed from REA modeling responded sensitively to varying drying temperatures, which could have led to different crystallization events. The deviation of these plots from the expected norms that do not encounter a phase change was used effectively to discern the physics involved. A REA kinetic model was proposed to assist in process optimization of large‐scale spray‐drying operations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 1839–1852, 2017

Solvent Based 3D Printing of Biopolymer/Bioactive Glass Composite and Hydrogel for Tissue Engineering Applications

Three-dimensional (3D) bioprinting is an emerging technology in which scaffolding materials and cell-laden hydrogels may be deposited in a pre-determined fashion to create 3D porous constructs. A major challenge in 3D bioprinting is the slow degradation of melt deposited biopolymer. In this paper, we describe a new method for printing poly-caprolactone (PCL)/bioactive borate glass composite as a scaffolding material and Pluronic F127 hydrogel as a cell suspension medium. Bioactive borate glass was added to a mixture of PCL and organic solvent to make an extrudable paste using one syringe while hydrogel was extruded and deposited in between the PCL/borate glass filaments using a second syringe. The degradation of the PCL/borate glass composite scaffold with and without the presence of hydrogel was investigated by soaking the scaffold in minimum essential medium. The weight loss of the scaffold together with formation of a hydroxyapatite-like layer on the surface shows the excellent bioactivity of the scaffold.

Hierarchical porous carbon with ordered straight micro-channels templated by continuous filament glass fiber arrays for high performance supercapacitors

Hierarchical porous carbon with highly ordered straight micro-channels was prepared though a facile melt vacuum infiltration method using continuous filament glass fiber arrays as the template and glucose as the precursor.

Mathematical Modelling of Fibre Winding Process for Composite Frames

This article describes the authors´ own mathematical modelling designed for the production process of a new type of low-weight composite frame. The used real technology is based on the winding of carbon or glass filament rovings around a polyurethane core which is a frame with a circular cross section (this type of composites is used, for example, to reinforce the doors and windows of airplanes). The core is attached to the end-effector of the robot (robot-end-effector) and successively passes through the fibre-processing head during the winding process. Quality production depends primarily on the correct winding of fibres around the polyurethane core. It is especially needed to ensure the correct angles of the fibre winding around the polyurethane core and the homogeneity of individual winding layers. The numerical model described in Euclidean space E3 of the manufacturing process is used when the fibre-processing frame is passing through the fibre-processing head. We use the described mathematical model and matrix calculus to enumerate the trajectory of the robot-end-effector to determine the desired passage of the core through the fibre-processing head. The calculated sequence of "tool-centre-point" values of the robot allows us to define the desired trajectory of the robot-end-effector and, thereby, the passage of the frame through the fibre-processing head. The calculation of the trajectory was programmed in the Delphi development environment. A practical example is analysed in the article.

Influence of selected process parameters on changes of the fiber orientation in unidirectional reinforced thermoplastics during a hot pressing process

The research described in this paper is part of SFB 639 “Textile‐reinforced composite components for function integrating multi‐material design in complex lightweight applications.” In this study, changes in fiber orientation of unidirectional (UD) aligned glass polypropylene hybrid yarn were investigated. A new model for simulating changes in fiber orientation of unidirectional reinforced thermoplastics during a hot pressing process was developed. The material observed during this study is a hybrid yarn made out of homogenous aligned glass and polypropylene filaments. The mechanistic model, which was used to simulate the fiber behavior, allows the user to define different input data, such as velocity, vorticity, and viscosity of the molten polymer as well as fiber radius, initial fiber positions and fiber stiffness to characterize material properties. To determine fiber orientations, a program was written in MATLAB. Hence, it is possible to calculate the angle of any desired segment at any point of time during the hot pressing process. Thereby, it was feasible to compare the numerical obtained changes in fiber orientation with those measured during the experiments conducted at the end of the research. The post‐processing algorithm was used to determine the effects of selected processing parameters and model parameters on the fiber behavior respectively. POLYM. COMPOS., 39:2241–2249, 2018. © 2016 Society of Plastics Engineers

Transverse pump-probe microscopy of moving breakdown, filamentation and self-organized absorption in alkali aluminosilicate glass using ultrashort pulse laser.

We present time and space resolved transverse pump-probe measurements of the free electron and defect generation induced by nonlinear absorption of ultra short pulsed laser radiation in unhardened Corning Gorilla glass. The applied setup exhibits a 100 fs probe pulse duration and an independent pump pulse duration up to 5 ps. Hence, our work comprises the absorption of ultra short pulsed laser radiation at a wavelength of 800 nm and pulse energies from 10 μJ to 50 μJ up to a delay of 6 ns. Our investigations reveal different absorption regimes like filamentation and moving breakdown as well as the formation of permanent modifications. Finally, the deposition of multiple pulses in the incubation regime is examined, observing a self-organizing absorption effect.

A Comparative Study on the Textile Processing of Carbon and Multifunctional Glass Fiber Sensor Yarns for Structural Health Monitoring

In this comparative study two sensor yarns, such as carbon filament yarns and carbon nanotube coated glass filament yarns are analyzed regarding their electrical property changes during textile manufacturing into multi‐layer weft knitted structures as well as during compression molding into a composite plate due to the different electro‐mechanical behavior, various sensitivities, and changing ways of acting as an in‐situ sensor: yarns act either as a conductive fiber itself (carbon) or as an electrical conductive sizing (CNT‐coated glass). Both sensor yarns under investigation have to be considered differently with regard to changes in the electrical conductivity due to mechanical loading during textile processing and possible healing of cracks during compression molding.

Multifunctional Interphases: Percolation Behavior, Interphase Modification, and Electro‐Mechanical Response of Carbon Nanotubes in Glass Fiber Polypropylene Composites

Carbon nanotube dispersions have been immersedin a maleated polypropylene film former system andapplied to insulating glass filament yarns compatible to polypropylene matrix. The percolation threshold can be reached below 0.5 wt% carbon nanotubecontent. In order to achieve a homogeneous multifunctional interphase, the average sizing thickness must be above 450 nm tailored during a coating process by varying the solid content of the sizing. The temperature and the velocity of the coating process have a great impact on the volume resistivity of the multifunctional interphase. Electro‐mechanical behavior as sensors in unidirectional composites containing 50 vol% glass fiber reinforcement is monitored during tensile and compression loading. The largest electrical sensitivity is achieved for tensile loading in the axis of fibers.

절연용 유리장섬유의 정전기 대전완화 특성에 관한 연구

In this study, the characteristics of electrostatic attenuation in plain shape glass filament sample (0.29 mm thickness, cross section of 12.25 cm 2 , 16 cm 2 , 20.25 cm 2 ) for insulator has been measured at temperature of 5℃∼ 38℃, humidity of 50%∼90%. The results of this study are as follows. In case of samples that the cross section is 12.25 cm 2 , 16 cm 2 , 20.25 cm 2 at humidity of 50%∼90%, it found that the electrification voltage of electrostatic increased with increasing temperature, with a return to decrease at 20℃. In case of samples that the cross section is 12.25 cm 2 , 16 cm 2 , 20.25 cm 2 at temperature of 5℃~38℃, it found that the electrification voltage of electrostatic decreased with increasing humidity. In case of the sample at temperature of 20℃ and humidity of 65%, 75%, it found that the electrification voltage of electrostatic increased with increasing cross section. In case of the sample at humidity of 65% and cross section of 12.25 cm 2 , the time that it takes to reduce electrification voltage of electrostatic in half decreased to 0.912s, 0.736s, 0.673s with increasing temperature to 10℃ 20℃, 30℃.

Broadening of white-light continuum by filamentation in BK7 glass at its zero-dispersion point

Broadening of white-light continuum is observed by filamentation of near-infrared femtosecond laser pulses with peak power exceeding the megawatt level in BK7 glass with the presence of the zero-dispersion point. The simulated results show that, due to the low dispersion at the zero-dispersion point, the broadening of white-light continuum can be wider and the filament can persist in propagating stably longer distance.

Cytotoxicity, oxidative stress and genotoxicity induced by glass fibers on human alveolar epithelial cell line A549

Man-made vitreous fibers have been widely used as insulation material as asbestos substitutes; however their morphology and composition raises concerns. In 1988 the International Agency for Research on Cancer classified fiberglass, rock wool, slag wool, and ceramic fibers as Group 2B, i.e. possibly carcinogenic to humans. In 2002 it reassigned fiberglass, rock and slag wool, and continuous glass filaments to Group 3, not classifiable as carcinogenic to humans. The aim of this study was to verify the cytotoxic and genotoxic effects and oxidative stress production induced by in vitro exposure of human alveolar epithelial cells A549 to glass fibers with a predominant diameter <3μm (97%) and length >5μm (93%). A549 cells were incubated with 5, 50, or 100μg/ml (2.1, 21, and 42μg/cm2, respectively) of glass fibers for 72h. Cytotoxicity and DNA damage were tested by the MTT and the Comet assay, respectively. Oxidative stress was determined by measuring inducible nitric oxide synthase (iNOS) expression by Western blotting, production of nitric oxide (NO) with Griess reagent, and concentration of reactive oxygen species by fluorescent quantitative analysis with 2′,7′-dichlorofluorescein-diacetate (DCFH-DA). The results showed that glass fiber exposure significantly reduced cell viability and increased DNA damage and oxidative stress production in a concentration-dependent manner, demonstrating that glass fibers exert cytotoxic and genotoxic effects related to increased oxidative stress on the human alveolar cell line A549.

Surface formation phenomena of DHA-containing emulsion during convective droplet drying

Encapsulation of docosahexaenoic acid (DHA) protects this environment-sensitive substance from oxidation and also masks its odor. In this study, DHA was encapsulated with octenyl succinic anhydride modified (OSA) starch and whey protein concentrate. Single droplets of emulsions with different compositions were suspended on a glass filament to observe the dissolution behavior of dried and semi-dried particles. At each drying stage, the drying process were stopped to monitor changes in the semi-dried particle’s morphology, either by attaching an additional water droplet or by keeping the semi-dried particle suspended in the drying chamber without air flow. Based on observations in the above-mentioned test, the crust formation phenomena of emulsion droplets with different compositions were compared at various drying stages. The microstructures of dried particles containing DHA were examined by scanning electron microscopy (SEM). The surface oil coverage and distribution were studied by observing the surface structure before and after oil extraction. The results obtained in this study indicate the underlying particle formation mechanisms during drying of DHA-containing emulsions formed with different wall materials.

A theoretical model with experimental verification for heat and mass transfer of saline water droplets

Heat transfer to and mass transfer from NaCl–water droplets are investigated both numerically and experimentally. A new model is presented and used to simulate saline water droplet evaporation. The model is robust enough to be applied for various initial concentrations and conditions of the droplet, ambient conditions, and dissolved media properties. The model is validated using experimental data obtained in this study on top of those already available in the literature. The experimental apparatus as well as the processing routines to optically measure droplet evaporation at a range of ambient conditions are presented. The droplet was suspended using a glass filament. Data were collected for droplets with an initial radius of 500 μm at three temperatures 25 °C, 35 °C, and 45 °C and three air velocities 0.5 m/s, 1.5 m/s, and 2.5 m/s to provide a comprehensive validation dataset. Based on experimental and simulation data, a correlation is presented that captures the start time of solid formation. This time plays an important role in cooling tower design as it shows the time that the outer surface of the droplet dries. Using the validated model, it is shown that for 500 μm radius droplets with 3% initial mass concentration the start time of reaching the final size is 17% less than evaporation time of a pure water droplet. Also, the net energy required to evaporate the droplet falls by 7.3% compared to a pure water droplet. For 5% initial concentration these values are 24.9% and 12.2%, respectively. Using saline water in spray-cooling has two major effects: the energy extracted from the air per unit droplet volume is reduced (which can be compensated for by increasing the liquid flow rate). Moreover, compared to the time taken for the evaporation of a pure water droplet, the period with wet surface is shorter as a result of crust formation around the saline water droplet. This allows a shorter distance between spray nozzles and heat exchangers.

Characterization of the dynamic friction of woven fabrics: Experimental methods and benchmark results

A benchmark exercise was conducted to compare various friction test set-ups with respect to the measured coefficients of friction. The friction was determined between Twintex®PP, a fabric of commingled yarns of glass and polypropylene filaments, and a metal surface. The same material was supplied to all benchmark participants and the test conditions were prescribed, making the used set-up the most important variable among the laboratories. Tests at ambient temperature as well as tests above the melting point of polypropylene are part of the benchmark, in order to determine both the dry and hydrodynamic friction characteristics. The dependency on sliding velocity, average pressure and temperature was investigated. Systematic differences are observed between the measurements obtained by the different set-ups, which are discussed and related to design characteristics of the devices. The values obtained in this benchmark are comparable and may serve as a reference to evaluate other friction set-ups. The paper concludes with guidelines for the design of a friction tester.

The Design and Weaving of Glass Filament Spacer Fabric

Glass filament reinforced composite materials have become an indispensable material in national economic construction. The main purpose of this project is to produce the spacer fabric adopting glass filament through changing weaving process. First glass filaments were treated with epoxy resin to prevent from its low bending rigidity. Second ground warps and binding warps were separately warped and double warp beams were used in the weaving. At the shed crossing point the height of heald frames was different between the top layer and down layer warps, then the drafting sequence of the top layer of warps, the down layer of warps and binding warps were adjusted. The cotton yarns were chosen as the selvage warps which have good wear resistance and uniform tension. The long and short beat–up method was used. Eventually 3cm thickness of glass filament spacer fabric is achieved. It is hoped that this work will provide meaningful help to the development of glass filament spacer fabric.