Glass-reinforced Epoxy Research Articles

Fault current limiting HTS transformer with extended fault withstand time

We describe the design, construction, and testing of a proof-of-principle 45 kVA, 450/450 V, single phase superconducting transformer with fault tolerant capability. This small-scale transformer demonstrates extended short circuit withstand time as a result of the high thermal mass of the windings as well as improved recovery under load due to the high heat transfer achieved in subcooled liquid nitrogen with wire coated to optimise boiling heat transfer. Primary and secondary windings consist of 38-turn single layer solenoids wound in helical trenches milled in glass-reinforced epoxy formers. The thermal mass of the 0.4 mm thick brass-laminated conductor provides for adiabatic fault withstand times over 1 s, allowing greater flexibility in the design of protection systems required to isolate faults. Enhanced heat transfer from the windings to the liquid nitrogen coolant allows the transformer to recover from the short circuit event, cooling from around 300 K to return to the superconducting state even while current close to the rated current continues to flow. Two factors contribute to the high heat transfer. Firstly the HTS transformer operates in subcooled liquid nitrogen, at 65 K–66 K at atmospheric pressure, significantly increasing the heat transfer compared to operation at saturated vapour pressure. Secondly, the HTS conductor is coated with solid polymer insulation with optimised thickness, which allows efficient cooling by nucleate boiling to take place over an extended range of conductor temperature.

Rapid fabrication and characterization of PDMS microfluidics device using printed conductive silver ink

Abstract Currently, new fabrication methods for rapid prototyping of microfluidic devices has bring attention among researchers from various fields. The main reason is the use of lithographic equipment in standard fabrication method for master fabrication require trained personnel and high cost disposable materials. In this paper, a new fabrication method via printed conductive silver ink is introduced in order to minimize the current fabrication process through elimination of the photolithography process. As a result, a usable, faster and cost effective prototyping process of a microfluidic based biosensor devices able to be produced. In this method, the conductive silver ink was used to create a master template contains microchannel onto glass-reinforced epoxy laminate sheets (FR-4). Then, Polydimethylsiloxane (PDMS) were used to replicate the structure. Next, the digital microscope was used to obtain images to demonstrate geometry fluidics structure with channel dimension up to 200 µm width. Moreover, a 3D profilometer was used to evaluate their thickness and roughness of the microfluidics structure. The stability test demonstrates the consistency of flow sequence inside the serpentine and separation channel.

Influence of a reactive diluent on curing kinetics, Internal Curing Process, and Mechanical Performance of Filament Wound Glass Fiber‐Reinforced Epoxy Composite Pipes

Nowadays, glass reinforced epoxy (GRE) pipes are industrially manufactured by the filament winding process using internal heating technology. This study deals with the comprehensive evaluation of a strategy aimed to improve the plant productivity by means of physical experiments, mechanical tests, and numerical simulations of the curing process. The reactive system is composed by diglycidyl ether of bisphenol A (DGEBA), methyltetrahydrophtalic anhydride (MTHPA), and benzyltriethyl ammonium chloride (BTEAC) used as initiator. An increase in BTEAC concentration in system formulation leads to a reduction in curing times of GRE pipes. The processing problems associated with this increment are proposed to be solved by the incorporation of a reactive diluent (RD) together with the optimization of the curing cycle. The effects that different amounts of 1,4‐butanedioldiglycidyl ether (DGEBD) added as RD exerts on system viscosity, copolymerization kinetics mechanism, curing process and properties of matrix, laminated composites and GRE pipes are deeply analyzed. Results demonstrate that if a 10 wt% RD is used, not only the strategy turns out to be feasible but also GRE pipes performance is improved. POLYM. ENG. SCI., 59:344–354, 2019. © 2018 Society of Plastics Engineers

Numerical investigation on optimal arrangement of IC chips mounted on a SMPS board cooled under mixed convection

The paper aims to investigate numerically the mixed convection heat transfer characteristics from seven non-identical IC chips (Aluminium) mounted on a Switch Mode Power Supply (SMPS) board (substrate) made by FR-4 (glass-reinforced epoxy laminate material). The objective is to determine the optimum configuration of these IC chips positioned at different locations on the substrate board. The optimum configuration is proposed by defining a non-dimensional geometric distance parameter (λ) and by employing a hybrid strategy (collaborating Artificial neural network (ANN) and Genetic algorithm (GA)). 3D, steady state numerical simulations are carried out using ANSYS Icepak to determine the temperature distribution of the IC chips. It has been confirmed that, the temperature of the IC chips strongly rely on their shape, size, and location on the substrate board. The hybrid optimization is the most robust technique to predict the arrangement of the IC chips on the substrate board more accurately, as compared to conventional methods.

Morphological and Radio Frequency Characterization of Graphene Composite Films

Graphene is a monolayer of carbon atoms which exhibits remarkable electronic and mechanical properties. Graphene based nano-materials have gained a lot of interest for many applications. In this paper, inks with three different graphene concentrations (12.5, 25, and 33 wt % in graphene) were prepared and deposited by screen printing. A detailed investigation of films’ surface morphology using Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM) revealed that the graphene films present a homogeneous dispersion of the filler with a comparatively lower surface roughness at higher concentrations and negligible agglomerates. The films were then printed between copper electrodes on FR-4 substrate (trade name for glass-reinforced epoxy laminate material), commonly used in Radio Frequency (RF) circuits, and the measured scattering parameters analyzed. Finally, the reflection coefficient of a patch antenna, fabricated on FR-4 substrate with and without a stub loaded by a thin film were measured. The difference of the resonant frequency due to the different interaction between graphene flakes and polymer binders shows attractive features of functionalized graphene films for chemical and bio-sensing applications.

Failure Analysis of Glass-Reinforced Epoxy Pipes Under Internal Hydrostatic Pressure: A Comparison With the Split Disk Test Method

In this paper, the ultimate hoop strength of an industrial (±55 deg)9 filament-wound glass-reinforced epoxy (GRE) pipe as a short-term test is determined according to the ASTM D-1599 standard by performing the internal hydrostatic pressure test. After the test, the failure surface of the pipe is photographed by a high magnification camera, and in addition, the explanations are presented about the type of failure. The main purpose of this study is to compare the results obtained for the ultimate hoop strength and failure mechanisms of the pipe by using the internal hydrostatic pressure test with that by the split disk test method according to the ASTM D-2290 standard in the previous work.

A Performance-testing Platform for a Conduction Micropump with an FR-4 Copper-clad Electrode Plate.

Here, a conduction micropump with symmetric planar electrode pairs prepared on flame-retardant glass-reinforced epoxy (FR-4) copper-clad laminate (CCL) is fabricated. It is used to investigate the influence of chamber dimensions on the performance of a conduction micropump and to determine the reliability of the conduction pump when acetone is used as the working fluid. A testing platform is set up to evaluate conduction micropump performance under different conditions. When the chamber height is 0.2 mm, the pump pressure reaches its peak value.

Impact responses, compressive and burst tests of glass/epoxy (GRE) composite pipes

The paper presents the impact responses, compression and burst tests of glass reinforced epoxy (GRE) composites pipes. Impact loadings of three different energy levels (5 J, 7.5 J, and 10 J) were applied, followed by monotonic burst tests. Uniaxial compressive tests were conducted GRE samples using a universal testing machine in accordance with ASTM D695-10. In addition, the tests were also repeated with samples of different winding angles of ±45 ° and ±55 ° and tested at room temperature, and elevated temperatures of 45 °C and 65 °C. The result shows that the higher the impact energy applied to the pipes, the lower the burst strength of the pipes. The maximum burst strength found decreased with an increase in the impact energy level. The results also indicate that the strength of the GRE pipes significantly decreases with increase in temperature though, they are also found to increase as the winding angles decrease.

Compact, wideband‐printed quasi‐Yagi antenna using spiral metamaterial resonators

A novel structure for size reduction and bandwidth enhancement of quasi-Yagi antenna using spiral resonator (SR) metamaterials is presented. The basic resonance is produced through excitation of simple quasi-Yagi antenna elements through a microstrip feedline while parasitic SR metamaterials augment bandwidth. The antenna is designed on an glass-reinforced epoxy laminate sheets (FR4) substrate with a dielectric constant of 4.4 and a thickness of 1.6 mm. Compared to original printed quasi-Yagi antennas, the size of the proposed quasi-Yagi antenna is reduced by ∼53%. Simulation results show that the proposed antenna has the impedance characteristics with a frequency bandwidth of 1.43–3.97 GHz (94%) for return loss more than 10 dB and a gain of 3.4–5.2 dBi in the corresponding frequency range. The designed antenna presents an end-fire radiation with a front-to-back ratio >10 dB. The antenna is fabricated, and measurement results demonstrate compactness and wide bandwidth of the antenna.

A Comparison of the Polymer Matrix Behavior and Mechanical Properties of the Glass Reinforced Plastics and Glass Reinforced Epoxy Pipes under Different Oil Field Chemicals

Fiber reinforced composite material is used widely in oil fields for its high specific strength and resistance to corrosion. Glass reinforced plastics (GRP) and Glass reinforced epoxy (GRE) pipe samples were investigated under oil field conditions. The samples were subjected to ultraviolet radiation, moisture and elevated temperature using accelerating weathering machine and then aged in different environments encountered in oil well streams and characterized by using Scanning Electron Microscopy (SEM). The surface morphology was analyzed and the images produced from wet crude and effluent water has shown different degree of deformation of the glass fiber and debonding with the polymer matrix. The tensile and modulus properties were also evaluated and effect of ageing found to be more pronounced in the case of wet crude especially for the GRE. The study revealed some tendency of GRP samples to reform the polymer matrix interface with the glass fiber after weathering. The assessment of physical properties provided information about the structural stability of composite pipes under harsh environments, which in turn can impact their overall performance and service life.

Tension–tension fatigue performance and stiffness degradation of nanosilica-modified glass fiber-reinforced composites

The aim of this study is to investigate the influence of nanosilica on glass-reinforced epoxy composites under static mechanical and tension–tension fatigue loading. The glass-reinforced epoxy composites were manufactured with three different concentrations of nanosilica (6, 7, and 8 wt%). Static mechanical tests include tensile, flexure and short-beam strength. 6 wt% nanosilica composites showed the greatest enhancement in tensile strength, percentage elongation, and inter-laminar shear strength compared to the other concentrations and the control. Extensive tension–tension fatigue tests (R-ratio of 0.1 and frequency 2 Hz) were conducted on the control and 6 wt% nanosilica composites. In load-controlled and constant amplitude tests, a percentage of the ultimate tensile strength was applied to the specimens. Stress applied was from 80% of UTS, and reduced in steps of 10% until specimens survived 1 million cycles. In high-cycle and low-cycle fatigue tests, 6 wt% nanosilica composites showed 10 and 3 times improvement in fatigue life, respectively, compared to the control composites. Stiffness degradation curves were explained with three stages of damage mechanisms. The final failure occurred due to fiber breakage in the third stage. Both the control and 6 wt% nanosilica composites survived 1 million cycles at a maximum stress of 46.6 MPa, but at the end of 1 million cycles, control composites lost 65% modulus compared to 45% modulus loss in the 6 wt% nanosilica composites.

Design and development of a stacked complementary microstrip antenna with a “π”-shaped DGS for UWB, UNII, WLAN, WiMAX, and Radio Astronomy wireless applications

The proposed research paper presents the design, development, and experimental testing of a broadband stacked complementary microstrip antenna for ultra-wideband (UWB) (5.28–5.85 GHz), Unlicensed National Information Infrastructure band (UNII) (5.25–5.825 GHz), wireless local area networks (WLAN, IEEE802.11a, 5.15–5.35 GHz), and IEEE 802.11b (5.75–5.85 GHz), Worldwide Interoperability for Microwave Access band (5.25–5.85 GHz), and Radio Astronomy band (6.6–6.75 GHz) wireless applications. The main aim of this paper is to obtain an UWB behavior from the combined effect of two resonances exhibited by the driven and parasitic patches of a stacked complementary antenna geometry. Circularly polarized radiations are also emitted by the antenna by the addition of an orthogonal stub to its feed line. The proposed three-layered antenna structure (without air gap) is fabricated on commercially available glass-reinforced epoxy laminate, FR4 substrate. The topmost layer of FR4 has a square-shaped patch parasitic patch printed over it; this patch has a square slot etched out from it. The middle layer of the antenna has a square-shaped driven patch of approximately the same dimensions as that of the slot in parasitic patch. The antenna is fed using aperture-coupled feeding mechanism. Therefore the lowermost layer of FR4 has a ground plane on its top with a “π”-shaped slot etched from it and a feed line with an orthogonal stub at its bottom forming a “T”-shaped geometry. The antenna is fed by the electromagnetic coupling between the antenna layers .The proposed antenna has a compact structure with overall volumetric dimensions of 4.7 × 3.82 × 0.483 cm3. The antenna design and simulations are carried out using CSTMWSV'10 with perfect boundary (electric and magnetic) estimations. This designed antenna shows an UWB behavior from 5.14 to 5.85 GHz with an impedance bandwidth of 710 MHZ and a fractional bandwidth of 12.62% at the center frequency of band at 5.5 GHz. The radiating antenna also possesses a good gain of 4.59 dBi at the central frequency of 5.50 GHz and a 1 dB axial ratio bandwidth of 820 MHz from 5.16 to 5.98 GHz. The validation of results is done by fabrication and experimental testing of the antenna using a vector network analyzer and placing the antenna in an anechoic chamber for gain measurements. The measured results show close matching with the simulated ones and this makes the antenna well suited for the proposed wireless applications of interest, specifically in small handheld wireless communication devices.

Piezoresistive performance characterization of strain sensitive multi-walled carbon nanotube-epoxy nanocomposites

Carbon nanotubes polymer nanocomposites have attracted a significant research, which provide interesting aspects for the realization of cost effective, highly sensitive piezoresistive strain sensors. Here, we report on an extensive piezoresistive performance investigation of multi-walled carbon nanotubes (MWCNTs)/epoxy nanocomposite under uniaxial cyclic tensile and compressive loading in low strain range. Dispersion quality of MWCNTs in the epoxy polymer matrix was monitored by scanning electron microscopy. MWCNTs/epoxy nanocomposite was deposited directly on a glass-reinforced epoxy cantilever beam on the same axis with a commercial metallic strain gauge. The strain sensitive nanocomposite presents high-performance properties, including gauge factor up to 78, good stability of ±0.26% for 10h and durability of −0.08% after cyclic loading and unloading. Furthermore, MWCNTs/epoxy nanocomposites show quite small creep up to ±0.26%, fast response and recovery times, low hysteresis under cyclic tensile and compressive loadings and temperature response make the proposed nanocomposites suitable in various potential strain sensor applications including structural health monitoring.

Effects of elevated temperatures on glass-reinforced epoxy pipes under multi-axial loadings

The effects of elevated temperatures on the performance of glass-reinforced epoxy (GRE) pipes under multi-axial loadings were investigated. Finite element software was used to develop the layers of the winding angle on GRE composite pipes. The simulations of the closed-ended pipes’ performance under internal pressure loadings of various hoop to axial stress interactions were observed, then the failure strength was illustrated in the form of a failure envelope. Five different stress ratios ranging from pure axial loading 0:1, 1:1, 2:1, 4:1 and pure hoop 1:0 were tested at elevated temperatures (room temperature (RT), 65°C and 95°C) respectively. The first ply failure (FPF) for GRE pipes was predicted based on Tsai–Wu failure criteria. The results show that the highest temperature reduced the strength of the GRE pipes since the hoop and axial stress decreased with increasing temperature and thus the mechanical properties of the GRE pipes were degraded with the increase of temperature. Both showed a strong dependence on the stress ratio and test temperatures. Moreover, as the temperature increases, the glass fibres become more ductile and cause the failure envelopes to shrink towards the origin and become slightly narrower to accommodate the increase in strength of the composite pipes. It is shown that the initial failure stress based failure envelope at elevated temperatures generally degraded, except for the 2:1 loading where the initial failure stress increased.

Effect of Geopolymer filler in Glass Reinforced Epoxy (GRE) Pipe for Piping Application: Mechanical Properties

The present work is aimed to carry out the effect of geopolymer material which is fly ash as filler in the glass reinforced epoxy pipe on the micro structure of fly ash geopolymer, compression properties, and bulk density using the filament winding method. Conventional glass reinforced epoxy pipes has its own disadvantages such as high corrosion resistance at acidic environment and low strength which can be replaced by the composite pipes. Geopolymer is a type of amorphous alumino-silicate and can be synthesized by geopolymerization process. A series of glass reinforced epoxy pipe and glass reinforced epoxy pipe filled with 10 - 40 weight percentage geopolymer filler which is fly ash with 4 Molarity were prepared. Morphology of the raw material fly ash and fly ash based-geopolymer surface was characterized using scanning electron microscopy. It was found that the additions of fly ash at the beginning with 10 wt% are showing higher compressive strength than glass reinforced epoxy pipe without fly ash geopolymer filler. The compressive test of these series of samples was determined using Instron Universal Testing under compression mode. It was found that compressive strength for samples fly ash based-geopolymer filler are higher as compared to glass reinforced epoxy pipe without geopolymer filler. However, the compressive strength of glass reinforced epoxy pipe with fly ash geopolymer filler continues to decline when added to 20 wt% - 40 wt% of geopolymer filler loading. The results showed that the mixing of geopolymer materials in epoxy system can be obtained in this study.

Image Processing for Measuring Damage and Delamination in Glass Reinforced Epoxy

This work proposed an image processing method for the measurement of damage and delamination in layered materials. Measurement of the damage and delamination area in composite materials has a significant importance as it provides an estimate of factors for implementation of fracture mechanics formulation. It is not always easy to measure delamination as it usually exists inter laminar. In this method, an image of the damaged composite material was processed by commercially available software and the delamination area was estimated within each layer. A strong back light was used for capturing images with prominent damaged areas and clear demarcation of such areas. This method proved itself simple, efficient, and cost effective. It has many advantages over simpler techniques like post experiment visual inspection. At the same time, it is cost effective for composites where standard non-destructive techniques may cost many folds more than the cost of the specimen. The results obtained for damage and delamination in cylindrical glass reinforced epoxy specimen were presented. Buckingham pi theorem was employed to develop a scale model consisting of four scales. Damage and delamination growth rate collapsed onto the same trend when scaled with the factors of n3 and n4, respectively. Accuracy and confidence in the measurement of delamination area reduced as the number of layers increased; however, overall damage area can be estimated precisely. This technique was used for in situ measurements while specimens were subjected to load, which provided damage and delamination growth rate, too.

Effect of Glass Reinforced Epoxy (GRE) pipe filled with Geopolymer Materials for Piping Application: Compression Properties

The aim of this paper is to achieve the highest compressive strength of glass reinforced epoxy pipe with the geopolymer filler content of weight percentage that were used in glass reinforced epoxy pipe. The samples were prepared by using the filament winding method. The effect of weight percentage of geopolymer materials in epoxy hardener was studied under mechanical testing, which is using the compression test. A series of glass reinforced epoxy pipe and glass reinforced epoxy pipe filled with 10 – 40 weight percentage geopolymer filler which is white clay were prepared. The compression strength of the glass reinforced epoxy pipe filled geopolymer materials is determined using Instron Universal Testing under compression mode. It was found that compressive strength for samples with white clay geopolymer filler are much higher compare to glass reinforced epoxy pipe without geopolymer filler. Moreover, the compressive strength of glass reinforced epoxy pipe filled with white clay geopolymer filler was increased from 10 wt% to 30 wt% of geopolymer content. However, the compressive strength of glass reinforced epoxy pipe with white clay geopolymer filler suddenly decreased when added to 40 wt%. The results indicated that the blending of geopolymer materials in epoxy system can be obtained in this study.

Experimental investigation of the scaling laws in laterally indented filament wound tubes supported with V shaped cradles

This experimental work is focused on understanding behavior of thin walled filament wound cylindrical Glass Reinforced Epoxy (GRE) tubes subjected to lateral indentation. These tubes are supported by V shaped cradles at each end. Scaling factors are established by using Buckingham Pi theorem for input parameters including geometric dimensions of the specimens, indenter, V shaped supports and indentation speed. Indentation tests are carried out to understand compliance of output parameters including force, energy and damage. Damage growth is recorded throughout the test by video camera and growth rate is calculated by using post experiment image processing. This work presents experimental results including slope of the force–displacement relation, energy absorbed and permanent deformation experienced by each specimen. Damage initiation and growth with respect to indentation displacement, force, energy and time is plotted and scaled to understand compliance with the scaling law. The force displacement, energy displacement and damage growth rate is compared with the existing results from the literature. Some interesting comparisons are observed between the current and existing results in the literature for a study even not meant for scaling analysis. Damage growth rate for all specimens collapse on same trend when data is scaled with non-dimensional factor n3.

Novel Miniaturized Antenna Designs for In-traffic Air-coupled Ground Penetrating Radar Systems

Ground penetrating radar (GPR) antennas are key elements for the operation of air-coupled, compact, low-cost systems that can be operated at road speeds to map subsurface defects such as corroded rebar, trapped moisture, voids, and pavement layers. This paper presents requirements and tradeoffs for such antennas, as well as a brief methodology for the design process to frame the context and boundary conditions of the antenna problem. Furthermore, the paper discusses a number of planar antennas that have been designed in printed circuit board (PCB) technology using low-cost, glass-reinforced epoxy laminate sheets such as FR4.The ultra-wide-band operation of antennas, along with other key parameters such as gain and beam width, is very important in the design of a useful GPR antenna for air-coupled operation. The interconnected relationship between antenna parameters limits the designs and constrains the upper bounds of the performance that can be achieved. Regulatory specifications such as FCC compliance create additional burden on the specifications and requirements.A rounded bowtie antenna, a slotted bowtie antenna and two types of Vivaldi antenna are designed, simulated, fabricated, and characterized. All are intended to operate within the 1.1–3.5 GHz frequency band and benefit from compact size while providing high gain to allow for the detection of pavement layers and rebar in bridge decks to a depth of up to 2 feet. In-field measurements of the antennas, together with the GPR system, are presented for static testing scenarios such as buried rebar in a sand box and concrete slab. The antenna testing over the sandbox and concrete slab demonstrates the great potential of utilizing the proposed antennas in air-coupled GPR systems, especially the compact rounded bowtie and slotted bowtie antennas.

Slot loaded rectangular patch antenna for dual-band operations on glass-reinforced epoxy laminated inexpensive substrate

This paper presents a straightforward design and analysis of rectangular radiating patch with narrow slots and microstrip line fed patch antenna for dual band operations. A parametric analysis has been carried on during the design process for finding the desired resonant frequencies. The final design concept of the antenna has been validated through fabricating the antenna prototype and then measuring its characteristics. The proposed antenna is implemented by using cost effective FR4 substrate, which comprises of vertical narrow slots on the radiating element and partial ground plane. The experimental results of the antenna prototype show the impedance bandwidth ($$<-10$$<-10 dB reflection coefficient, S11) 396.4 MHz (286.9---683.3 MHz) and 310 MHz (4.28---4.59 GHz) with center resonant frequency 460 MHz and 4.5 GHz respectively. The proposed antenna has achieved 6.6 dBi average gain with 85 % average radiation efficiency for lower band and 9.7 dBi average gain with 88 % radiation efficiency for upper band. The bandwidths of the antenna are broader enough to cover medical telemetry communications, UHF wireless communications and terrestrial communications services.