Hollow Glass Fibers Research Articles

Evaluation of the failure responses of filament wound and pre-preg wrapped glass fiber/epoxy composite tubes under quasi-static torsional loading

This paper introduces an experimental and numerical investigation into hollow cylindrical thin-walled glass fibre reinforced epoxy matrix composite shafts produced by using both pre-preg wrapping and filament winding methods. The filament wound samples were manufactured with four different helix angles ([±30]FW, [±45]FW, [±60]FW, and [±75]FW ), whereas [0, 90]PP pre-pregs was utilised for producing the wrapped kind of samples. In order to assess the quasi-static failure responses, the samples were subjected to increasing amount of torsional load at a fixed angular rotation speed. The experimental findings of [±30]FW, [±45]FW, and [±60]FW samples were found to be very compatible with those obtained via Finite Element Analysis (FEA). Contrarily, the numerical model were not able to describe accurately the load—displacement behaviour of [±75]FW and [0, 90]PP with the exception of the initial loading phase. [±45]FW was found as the most favourable option for designers in terms of torsional stiffness. Whereas, those characterised by [±30]FW, and [±60]FW exhibited very close torsional resistances in a difference range of only 5%. [0, 90]PP exhibited the lowest average torsional failure resistant and stiffness but the highest average rotation angle before rupture.

Development of latticed structures with bolted steel sleeve and plate connection and hollow section GFRP members

An innovative nodal joint system with thin-walled steel sleeve and plate is examined for development of latticed shell structures using hollow section glass fiber reinforced polymer (GFRP) members. In the proposed system, the GFRP members were connected to a steel gusset-plate space node through bolted sleeve joints (BSJs). The mechanical performance of BSJs was first examined through cantilever bending experiments. Then, the performance of the entire nodal joint system incorporating the space node was examined in bending for both in-plane and out-of-plane stiffness. Its performance was then characterized by nonlinear springs and evaluated at a structural level based on a space latticed structure configuration through finite element (FE) analysis and the resulting structural performance satisfied the ultimate limit state (ULS) and serviceability limit state (SLS) requirements as per relevant standards. A parametric study was also conducted to understand the effect of joint rotational stiffness on the overall structural performances.

Blast response of Hollow glass (H-glass) fibre reinforced epoxy matrix composites

The studies on response of materials against explosive blast loads have enormously increased in the recent years due to the increased blast incidents across the globe. Few studies have been reported on the blast performance of glass fibre reinforced composites. However, no studies were reported on the response of the Hollow glass (H- glass) fibre reinforced polymer composites against explosive blast loads. The present paper focuses on the experimental investigation of the response of the H- glass/epoxy composite laminates against air blast loading. The explosive loading on 5mm thick composite laminates at both 300mm and 400mm stand-off distances (SoD) was generated by detonating 142 gms of plastic explosive. The incident and reflected pressures at both the SoDs were recorded using piezo-electric pressure sensors. H-glass composites exhibited mode-I failure (large in-elastic deformation) at both SoDs, whereas E-glass composites showed mode –I failure at 300mm SoD only. The change in failure modes of composites with change in SoD was also discussed. The blast performance of the H-glass composite was compared with the performance of the solid glass fibre (E-glass) composites.

Preparation, characterization and performance evaluation of supported zeolite on porous glass hollow fiber for desalination application

A-type zeolite membranes were synthesized on porous glass hollow fibers that prepared using the in-situ hydrothermal process. The porous glass hollow fibers were prepared using the phase inversion and sintering technique with the addition of yttria stabilized zirconia (YSZ) to improve their porosity. The glass hollow fibers were characterized using the scanning electron microscope (SEM), Fourier transform infrared (FTIR), mechanical properties and water permeability. The porosities of pure glass hollow fiber were improved by the addition of YSZ particles, which lead to an increase in the pure water permeability. The water permeability shows that the glass hollow fiber prepared form spinning suspension E, which has 30 wt% zeolite particles and 20 wt% YSZ particles, has the highest permeability of 155.65 L m−2 hr−1 bar−1 compared to the previous work, which was only 4.0 L m−2 hr−1 bar−1. This glass hollow fiber was later used as the support for the incorporation of zeolite membrane for the desalination application. The performance of membranes is separating sodium chloride (NaCl) salt solution were tested using two different setups, namely pressure driven reverse osmosis (RO) and sweeping liquid assisted reverse osmosis (SLRO). The solute flux for 5,000 and 10,000 ppm NaCl salt solutions were 24.45 and 17.86 L m−2 hr−1, respectively. Both operations enabled the solute rejection up to 98%.

Experimental investigation on the smart self‐healing composites based on the short hollow glass fibers and shape memory alloy strips

In the present study, self‐healing composites based on randomly oriented short hollow glass fibers and shape memory alloy (SMA) strips are investigated. Charpy impact tests were conducted to determine the healing efficiency of the specimens. The obtained results showed that an efficient healing process occurs after 7 days from the initial damage. According to the results, the presence of embedded SMA strips caused enhancement in the healing efficiency of the composites due to induced recovery force in the SMA, which leads to crack closure in the specimens. The healing efficiency of composites were calculated to be 36%, 49%, 55%, and 34% for the specimens without embedded SMA strips, and with 0%, 2%, and 4% pre‐strain SMA strips, respectively. According to the results, the healing efficiency of the specimens is affected significantly by the interfacial shear strength between the SMA strips and the glass fibers/epoxy composites. In this regards, the results showed that using 2% pre‐strained strip in the composites resulted in the highest healing efficiency. POLYM. COMPOS., 40:1883–1889, 2019. © 2018 Society of Plastics Engineers

Effect of hierarchical structure on electrical properties and percolation behavior of multiscale composites modified by carbon nanotube coating

The hierarchical composites integrated by micro-/nano-fillers have been considered to be the multifunctional materials of the next generation. However, the effects of the hierarchical architecture on the electrical properties of composites remains poorly understood. Here, the fabrication of polymer-based multiscale composites with hollow glass fibers coated by carbon nanotubes (CNTs) and the investigation of their morphology, conductivity and dielectric properties are reported. Owing to CNTs introduced into the interfaces, various electrical parameters of the composites are obviously improved. The composite exhibits a stronger anisotropy than that of carbon fiber or CNTs filled composites and an ultralow percolation threshold. These unique behaviors are shown to be related to the hierarchical morphology giving rise to the existence of two percolation levels with different thresholds: a local threshold in the nanoscale CNT networks at the fiber-polymer interfaces and a global threshold in 3D network formed by the fibers. Furthermore, we find and explain some behaviors uncharacteristic of binary composites and the other hierarchical composites. This work provides a deeper understanding of the relationship between the structure and properties of multiscale composites and other complex percolating systems, potentially opening up new ways for designing novel materials.

Strong Anisotropy and Ultralow Percolation Threshold in Multiscale Composites Modified by Carbon Nanotubes Coated Hollow Glass Fiber

Inspired by biological materials, the use of combined fillers of different types and sizes has led to multiscale, hierarchical composites which are considered to be the multifunctional materials of the next generation. However, the effects of hierarchical architecture on the electrical properties and percolation behavior remain poorly understood. Here, a multiscale polymer‐based micro‐/nano‐composite with hollow glass fibers coated by carbon nanotubes (CNTs) has been produced based on a simple dip‐coating approach. Besides a significant increase in electrical performance, the composites exhibit a very strong anisotropy of electrical properties with the difference of 2–5 orders of magnitude in different directions. In the longitudinal direction of composites, an ultralow percolation threshold is found. These unique properties are shown to be related to the hierarchical morphology, which gives rise to the existence of two percolation levels with different thresholds: a local threshold in the nanoscale 2D CNT networks at the fiber‐polymer interfaces and a global threshold in 3D network formed by the fibers. This study helps to deeper understand the macroscopic electrical performance of the hierarchical composites, potentially opening up new ways for designing novel materials via flexible tailoring the orientation of fiber and the morphology of interfaces.

Preparation and characterization of glass hollow fiber membrane for water purification applications.

This work discusses the preparation and characterizations of glass hollow fiber membranes prepared using zeolite-5A as a starting material. Zeolite was formed into a hollow fiber configuration using the phase inversion technique. It was later sintered at high temperatures to burn off organic materials and change the zeolite into glass membrane. A preliminary study, that used thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier transform infrared (FTIR), confirmed that zeolite used in this study changed to glass at temperatures above 1000°C. The glass hollow fiber membranes prepared using the phase inversion technique has three different microstructures, namely (i) sandwich-like structure that originates from inner layer, (ii) sandwich-like that originates from outer layer, and (iii) symmetric sponge like. These variations were influenced by zeolite weight loading and the flow rate of water used to form the lumen. The separation performances of the glass hollow fiber membrane were studied using the pure water permeability and the rejection test of bovine serum albumin (BSA). The glass hollow fiber membrane prepared from using 48wt% zeolite loading and bore fluid with 9mLmin-1 flow rate has the highest BSA rejection of 85% with the water permeability of 0.7Lm-2h-1bar-1. The results showed that the separation performance of glass hollow fiber membranes was in the ultrafiltration range, enabled the retention of solutes with molecular sizes larger than 67kDa such as milk proteins, endotoxin pyrogen, virus, and colloidal silica.

Preparation of Hollow Fiber Membrane Precursor from Glass and PVDF by Non-Solvent Induced Phase Separation

Glass hollow fiber membrane precursor was well prepared using glass and polyvinylidene fluoride (PVDF) as starting materials by non-solvent-induced phase separation. The spinning dope including glass powders and PVDF was obtained firstly. Then the hollow fiber membrane precursors were spinning via dry-wet spinning method. The parameters about preparation process were listed. The viscosity of spinning dope were also measured. The results showed that the viscosity increased with a function of the content of PVDF. The suitable viscosity for spinning technology was selected. The scanning electron microscopy showed that the glass powders with the diameter of several micrometer were connected by PVDF binder. The water flux was also tested, and it decreased with the time. The preparation technology of glass hollow fiber membrane precursor could provide support for the glass hollow fiber membrane via sintering process.

Drug release kinetics from biodegradable UV-transparent hollow calcium-phosphate glass fibers

Upcoming medical procedures, such as photodynamic therapy or photochemical tissue bonding, require the local delivery of light and photosensitive dyes in selected deep tissues of the body. To achieve this purpose, it is essential to understand the dye/surface interaction of the materials involved. This work explores the employment of resorbable hollow glass fibers as controlled drug delivery systems and characterizes the release kinetics of four drugs with different chemical behaviors. The designed glass results to be optically transparent, biodegradable and biocompatible. The drugs were chosen in order to understand the interaction mechanism of different chemical species with the glass surface and to assess possible reactions. The results show that all drugs can be delivered, but ionized species tend to be withheld more than neutral molecules, suggesting the occurrence of hydrogen bonding and electrostatic interaction with the hydrophilic glass surface.

Hollow glass fibers in reinforcing glass ionomer cements

ObjectiveThis study investigated the reinforcing effect of hollow and solid discontinuous glass fiber fillers with two different loading fractions on select mechanical properties of conventional and resin modified glass ionomer cements (GICs). MethodsExperimental fiber reinforced GIC was prepared by adding discontinuous glass fiber (hollow/solid) of 0.5mm in length to the powder of commercial GICs (GC Fuji IX and II LC) with two different weight ratios (5 and 10wt%) using a high speed mixing machine. Fracture toughness, work of fracture, flexural strength, flexural modulus, compressive strength and diametral tensile strength were determined for each experimental and control material. The specimens (n=7) were wet stored (37°C for one day) before testing. Scanning electron microscopy was used to evaluate the microstructure of the experimental fiber reinforced GICs. Fiber length analysis was carried out to investigate the fiber length distribution of experimental GICs. The results were analyzed statistically using ANOVA followed by Tukey's post hoc test. Level of significance was set at 0.05. ResultsAn increase in fracture toughness (280 and 200%) and flexural strength (170 and 140%) of hollow discontinuous glass fiber reinforced (10wt%) conventional and resin modified GICs respectively, were achieved compared to unreinforced materials (p<0.05). Compressive strength did not show any significant differences (p>0.05) between the fiber reinforced and unreinforced GICs. SignificanceThe use of hollow discontinuous glass fiber fillers with conventional and resin modified GIC matrix is a novel reinforcement. It yielded superior toughening and flexural performance compared to the particulate GICs used.

Multi-element hollow-core anti-resonant fiber for infrared thermal imaging.

A bundle composed of 245 anti-resonant glass hollow optical fibers with a total diameter of 1 mm and fiber core diameter of 60 μm is fabricated for endoscopic infrared-thermal imaging. The bundle fiber shows low losses in the wavelength range of 3 to 4 μm owing to the anti-resonant effect of the thin glass wall. An image resolution of around 420 μm with a field-of-view of 3-mm diameter is obtained although crosstalk between adjacent fibers is observed. The experimental results of an imaging system using the fiber bundle with a half-ball lens at the distal end, which can be inserted into a working channel of endoscopes, are also shown.

Tailoring the moduli of composites using hollow reinforcement

Effects of hollow reinforcement on homogenized moduli and stress fields in unidirectional composites are investigated using an elasticity-based homogenization theory for periodic materials with hexagonal symmetries. The theory employs Fourier series representations for hollow fiber and matrix displacement fields in the cylindrical coordinate system which satisfy exactly the equilibrium equations and continuity conditions in the interior of the unit cell. The inseparable exterior problem requires satisfaction of periodicity conditions efficiently accomplished using previously introduced balanced variational principle. This principle ensures rapid solution convergence in the presence of thick or very thin-walled hollow fibers with relatively few harmonic terms. The solution’s analytical framework and stability facilitate parametric and optimization studies aimed at rapid identification of fiber wall-thickness impact on homogenized moduli and local fields in wide range of fiber volume fractions. This is illustrated for two material systems containing hollow glass fibers and alumina nanotubes as reinforcement, revealing new results of interest in the design of multifunctional porous materials. The results of parametric studies are made more precise upon incorporation of the locally-exact homogenization theory into the Particle Swarm Optimization algorithm, with the new computational capability employed to identify tube thickness as a function of the porosity volume fraction which minimizes the differences between target homogenized moduli and the corresponding matrix moduli. Analysis of a generalized Kirsch problem with an underlying microstructure based on targeted homogenized moduli around the cylindrical cavity demonstrates the homogenization theory’s utility in tailoring the local stress field with the aim of enhancing material toughness.

Elastic and plastic properties of epoxy resin syntactic foams filled with hollow glass microspheres and glass fibers

ABSTRACTRepresentative volume elements of syntactic foams with a random filling of short glass fibers and hollow glass microspheres in epoxy resin were established by a random sequential adsorption method. The fiber volume fraction was set at 4%, and the microsphere volume fraction range was from 5 to 30%. This numerical simulation was studied with ANSYS software. The influence on the elastic and plastic mechanical properties of syntactic foams of the microsphere volume fraction and relative wall thickness were investigated, and the plastic strain evolution process in the composites was analyzed. The results show that the compressive yield limit and Young's modulus values of the syntactic foams decreased with increasing microsphere volume fraction when the microsphere relative wall thickness was 0.02, but these properties were enhanced with increasing microsphere volume fraction when the relative wall thickness exceeded 0.04. The specific strength and tangent modulus values of the composites increased with increasing microsphere volume fraction. In addition, we observed that the yield stress, Young's modulus, and tangent modulus values of the syntactic foams were obviously enhanced by the addition of glass fibers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44188.

New method for determining the bending modulus of solid and hollow fibers from deflection tests

The bending moduli of solid and hollow glass fibers were determined by means of fiber deflection tests. The test method was modified by measuring both the vertical and horizontal displacements of the end of the deflected fiber, without increasing the number of tested fibers, in order to reduce the high scatter of conventional test results obtained by measuring only the vertical displacement. Upper and lower boundary curves of the fiber end displacements were determined to filter out inaccurate measurements, for example, when the neutral line of the fiber is not a plane but a spatial curve. The mean and coefficient of variation of the fiber bending modulus were estimated from the recorded coordinates of the fiber ends, applying two newly-developed statistical evaluation methods based on the individual coordinates or on their average. After comparing several evaluation methods, it was demonstrated that the individual coordinate-based method provided the least relative error of the average.

Characterisation of Hollow Glass Fibre Reinforced Vinyl-Ester Composites

Objectives: The core objective of this characterization study is to clarify the effect of reniforement and the geometry of the reinforcement on the mechanical behavior of the vinyl-ester polymer composites. Methods: In this study, Polymer Matrix Composites (PMC) reinforced with both solid glass fiber (E glass) and hollow glass fiber (H glass) is prepared using traditional hand layup technique. Mechanical characterizations are carried out to find the effect of reinforcement on the tensile, compressive, flexural strength and impact resistance of the composites using Universal Testing Machine (UTM) and Charpy Impact. Findings: The characterization study on the mechanical behavior revealed that the hollowness of the fibre reinforcement significantly increased the strength and impact energy absorption capacity of the Hollow glass (H glass) fiber reinforced vinyl ester composites when compared to solid glass (E glass) fiber reinforced vinylester composites. Applications: Be a light weight and high strength materials, Hollow glass reinforced vinyl ester polymer composite can be used in various engineering applications particularly aircraft industry.

Application of self-healing technique to fibre reinforced polymer wind turbine blade

This paper presents a novel concept of healing some of the damages in wind turbine blades (WTBs) such as cracks and delamination. This is achieved through an inherent functioning autonomous repairing system. Such wind turbine blades have the benefit of reduced maintenance cost and increased operational period. Previous techniques of developing autonomous healing systems uses hollow glass fibres (HGFs) to deliver repairing fluids to damaged sites. HGFs have been reported with some limitations like, failure to fracture, which undermines their further usage. The self-healing technique described in this paper represents an advancement in the engineering of the delivery mechanism of a self-healing system. It is analogous to the HGF system but without the HGFs, which are replaced by multiple hollow channels created within the composite, inherently in the FRP matrix at fabrication. An in-house fabricated NACA 4412 WTB incorporating this array of network hollow channels was damaged in flexure and then autonomously repaired using the vascular channels. The blade was re-tested under flexure to ascertain the efficiency of the recovered mechanical properties.

Experimental Investigation on the Behavior of Hollow GFRP Pipes Subjected to Transverse Impact

As oil &amp; gas exploration and production is moving increasingly towards offshore and deeper water, and then the demand for lighter and stronger material for deep water structures is growing. Fibre reinforced plastic (FRP) is a potential alternate. However, such application has low tolerance for accidental impact loads. This paper presents an experimental investigation on the behaviour of hollow glass fibre reinforced plastic (GFRP) pipes subjected to transverse impact. Drop weight impact tests were adopted. The GFRP pipe specimens were simply supported at two ends. The variations of strain, deflection and impact force were recorded. Different failure modes were observed and the critical factors affecting the damage of GFRP pipes were discussed. Their structural performance under transverse impact was assessed.

Enhanced Sensitivity of Raman Spectroscopy for Tritium Gas Analysis Using a Metal-Lined Hollow Glass Fiber

The precise compositional analysis of tritium-containing gases is of high interest for tritium accountancy, e.g. in future fusion power plants. Raman spectroscopy provides a fast and contact-free gas analysis procedure with high precision, thus being an advantageous tool for the named purpose. In this paper, it is shown that the sensitivity achieved with conventional Raman systems (in 90° or forward/backward configurations) can be enhanced by at least one order of magnitude by using a metal-lined hollow glass fiber as the Raman cell. This leads to the ability to detect low partial pressures of tritium within short measurement intervals (< 0.5 mbar in < 0.5 s).

Trace gas and dynamic process monitoring by Raman spectroscopy in metal-coated hollow glass fibres

Quantitative capillary Raman spectroscopy measurements are described, in which improved speed and sensitivity for atmospheric trace gas analysis and real-time monitoring of catalytic hydrogen-exchange reactions were demonstrated.