Glass Fiber Reinforced Polymer Composites Research Articles

Long-term performance of 15-year-old full-scale RC beams strengthened with EB FRP composites

Despite the well-known advantages of fiber-reinforced polymer (FRP) composites, concerns of the long-term performance of reinforced concrete (RC) structures strengthened with FRP composites have been an obstacle to the growing applications of FRP composites due to the lack of knowledge and scarce test data about long-term performances. Thus, the long-term performance of three 15-year-old full-scale (6.8 m long) RC beams was investigated in this study. A non-strengthened beam was served as a control specimen and two were strengthened with externally bonded (EB) glass FRP (GFRP) laminates. The three beams that had been left outside for exposure to harsh environmental conditions for over 15 years were tested under the typical three-point bending condition. It was found that the EB GFRP-strengthened RC beams were superior to the non-strengthened RC one from the standpoint of load-carrying capacity, initial stiffness, ductility, and toughness (energy absorption capacity), which indicates that the EB GFRP strengthening was still effective even over 15 years. Furthermore, the long-term effective tensile strength reduction of the GFRP composites due to the over 15-year exposure to the harsh environment was calculated to be 26.5 % in comparison with the design tensile strength, which is crucial information for the EB FRP strengthening technique.

Compressive Behavior of Concrete Containing Glass Fibers and Confined with Glass FRP Composites

In this paper, numerous experimental tests were carried out to study the behavior of concrete containing glass fibers and confined with glass fiber-reinforced polymer (GFRP). Concrete specimens containing different fiber percentages ( 0.3 wt.%, 0.6 wt.%, 0.9 wt.% or 1.2 wt.%) and with different strengths of concrete (8.5 MPa, 16 MPa and 25 MPa) and different confinement levels (two, four and six layers of GFRP) were used as research parameters. The samples were tested to failure under pure axial compression. The results imply that the confinement effect with GFRP is relatively higher for concrete samples containing glass fiber (GFCC) with a percentage equal to 0.6 wt.%. The theoretical of stress ratios (fcc/fco) estimated by using existing ultimate strength models are found to be close to the experimental results for high strength of GFCC, but not close to the experimental results for low strength of GFCC.

A Comparative Study On Sliding Wear Behaviour Of Post-Cured Hybrid Reinforced Polymer Composites

<p>This endeavour also entails developing novel materials for composites that are superior to existing composites. Lapox L-12 resin, E glass fibre material, and cerium oxide, which are the rare earth material family member in the periodic table. The combination of these materials was utilised to investigate the wear loss, and surface roughness in a dry sliding wear in two conditions: with and without postcuring (at 100oC for 60 minutes) with process parameters such as percentage of filler material, normal load and sliding speed. The experiments were planned according to L16 orthogonal array based on Taguchi design. Results reveal that wear loss and surface roughness is minimum in post-cured glass fiber reinforced polymer (GFRP) composites compoared to without post-cured specimens. The optimum process parameters level for minimum wear loss of post-cured GFRP composites, optimum process parameters are percentage of filler material is 20%, load is 15N and sliding speed is 0.25 m/s.</p>

Enhancing surface insulation of glass fiber reinforced polymer composites by plasma fluorinating glass fiber

AbstractGlass fiber reinforced polymer (GFRP) is a widely used composite material in industrial production. In this article, glass fiber (GF) was fluorinated by dielectric barrier discharge (DBD), and the GFRP composites made of GF with different fluorination time and various numbers of fluorinated GF layers were prepared to improve the surface insulation property. The effect of plasma fluorination on GF was analyzed by scanning electron microscope (SEM) and X‐ray photoelectron spectroscopy (XPS), including the surface morphology and chemical composition. In addition, the surface electrical properties of the above composites were investigated experimentally. The results show that the flashover voltage of modified GFRP is 29.84% higher than that of the original sample. By analyzing the charge dissipation and trap, it is inferred that plasma fluorination can raise the trap energy level of the composites, therefore suppressing the carrier migration on the surface and increasing the flashover voltage. Furthermore, the internal structure of composites can be improved by increasing the number of fluorinated GF layers, which accelerates the charge dissipation along the body, thus enhancing the surface insulation properties of the composites in both ways.

Effects of Seawater Environment on the Degradation of GFRP Composites by Molecular Dynamics Method.

Glass fiber-reinforced polymer (GFRP) composites are promising composites often utilized in coastal infrastructure or used as an alternative to steel reinforcement in seawater sea sand concrete due to their excellent corrosion resistance. Understanding the degradation mechanism of GFRP in corrosion environments is significant for improving the long-term performance of GFRP materials. This paper presented the influences of seawater content and temperature on the properties of GFRP composites using the molecular dynamics method. The simulation results were validated by existing experiments on mechanical properties, interlaminar strength, and microstructures of an accelerated aging test of GFRP. The calculation results indicated that when seawater content of the matrix increased from 0% to 9.09% at 298 K, Young’s modulus, shear modulus, and bulk modulus decreased 46.72%, 53.46%, and 41.75%, respectively. The binding energy of GFRP composites with seawater content of 2.15% at 353 K was 26.46% lower than that of unconditioned GFRP at 298 K. It revealed that the higher seawater content and temperature accelerated the degradation of the GFRP composites. The investigation provided a comprehensive understanding of the degradation mechanism of GFRP in seawater environments and provided a basis for the durability design of GFRP composites.

Effect of the fibre length on the mechanical anisotropy of glass fibre–reinforced polymer composites printed by Multi Jet Fusion

ABSTRACT Mechanical anisotropy greatly influences the applications of materials printed by additive manufacturing techniques such as Multi Jet Fusion (MJF) and selective laser sintering. However, the mechanical anisotropy of MJF-printed fibre–reinforced polymer composites has not been well understood. In this work, the effect of the fibre length on the mechanical performance of MJF-printed glass fibre–reinforced polyamide 12 (GF/PA12) composites is systematically investigated. Both experimental and simulation results confirm that longer fibres are in favour of fibre alignment in the powder spreading direction. The composite parts with longer fibres exhibit higher porosity. When GFs with an average length of 226 μm are added, the ultimate tensile strength and tensile modulus of the composites measured in the powder bed spreading direction are remarkably improved by 51% and 326%, respectively, as compared with those of neat PA12 specimens. This work provides guidance for the printing of other high-strength fibre–reinforced polymer composites.

Physical Properties of Glass-Fibre-Reinforced Polymer Filled with Alumina Trihydrate and Calcium Carbonate.

Gutters made of glass-fibre-reinforced polymer (GFRP) are usually produced with a three-millimetre thickness. The fillers are mixed into unsaturated polyester (UP) resin, which is intended to make the composite material more affordable. This study aims to examine the effects of the addition of alumina trihydrate (ATH), calcium carbonate (CC), and a mixture of ATH and CC of 15 and 30 parts per hundredweight of resins (PHR) on the material properties of the three-millimetre-thick three-layered GFRP composites. The properties observed included physical properties, namely, specific gravity and water absorption, chemical properties such as burning rate, and mechanical properties such as hardness, flexural strength, and toughness. The effects of the fillers on the voids and interfacial bond between the reinforcing fibre and matrix were analysed using the flexural fracture observation through scanning electron microscopy (SEM). The results showed that the addition of fillers into the UP resin led to an increase in the density, hardness, flexural strength, modulus of elasticity, and toughness but a decrease in water absorption and burning rate in a horizontal position. This information can be helpful for manufacturers of gutters made of GFRP in selecting the appropriate constituent materials while considering the technical and economic properties.

Investigation of physical, mechanical, and thermal properties of glass fiber reinforced polymer composites strengthened with KH550 and KH570 silane-coated silicon dioxide nanoparticles

Silicon dioxide (SiO2) nanoparticles can be used as reinforcing material for composites due to their favorable characteristics. However, they are commonly subjected to surface treatments with silane coupling agents to achieve fine dispersibility and better mechanical interlocking at interface. In this study, the silane-coated SiO2 nanoparticles (as received) were used as secondary reinforcement without applying additional silane treatment process. KH550 and KH570 silane-coated SiO2 nanoparticles were dispersed, respectively, into polymer matrix, and then the modified matrix was reinforced with glass fibers. Silanized SiO2 filled glass fiber reinforced polymer (GFRP) nanocomposites were investigated for physical, mechanical, morphological, and thermal properties. Depending on the nanoparticles' ratio and silane coating, the increments were obtained till 10% for tensile strength, between 18.40% and 75.26% for flexural strength, and till 81% for impact strength. SEM confirmed that the enhancements could be attributed to the improved interfacial adhesion between the modified matrix and fiber reinforcements. The void contents within the polymer nanocomposites decreased by 38%–54% compared to a pure one. DSC and TGA examinations revealed that silanized SiO2 nanoparticles provided a better curing behavior (10% increase in Tg for 3 wt.% KH550-SiO2) and improved thermal stability for the GFRP composites (increase in Tend values by 50–70°C). Generally, KH550 silane-coated SiO2 has provided enhanced interface strengthening, leading to better characteristics for GFRP composites since the amino functional groups contained in KH550 have more favorable integration with epoxy matrix.

Effect of the Fiber Orientation of Glass Fiber Reinforced Polymer Composites on Mechanical Properties

Fiber reinforced polymer (FRP) composites possess excellent specific strength, specific stiffness and controlled anisotropy for which these are extensively used in various engineering applications, like automobile industries, aerospace industries, marine industries, space industries, electronics industries and many more. Glass fibers (GF), carbon fibers (CF) and aramid fibers (AF) are common reinforcements for polymer matrix composites (PMCs). High mechanical properties and wear resistance behaviour of glass fiber reinforced composites are the premises for the current experimental research on the effect of fiber orientation on the tensile strength of the polymeric composite materials. The glass fiber reinforced epoxy resin composite was prepared by wet lay-up method, followed by thermal treatment.

Full scale promoted convolution neural network for intelligent terahertz 3D characterization of GFRP delamination

Damage detection of composite materials is crucial to monitor the component condition over the life cycle for the maintenance management and possible replacement. Delamination damage, as a common damage form in glass-fiber reinforced polymer (GFRP) composites, may occur during the manufacturing and service process due to the mechanical and thermal loads. Terahertz (THz) NDT technique, as a novel characterization approach, can provide promising alternatives to fulfill the 3D characterization of delamination defects in multi-layer GFRP composites. During THz testing, in order to attain adequate discrimination in depth direction, complex signal processing and prior knowledge of the undamaged stratigraphy are usually required to suppress confounding effects from noise, overlap, and dispersion of THz signal, which hinders the realization of automatic defect detection. Therefore, here we propose an effective, reliable, and end-to-end 3D THz characterization system based on deep learning methods to fulfill the automatic localization and imaging of delamination defects in GFRP composites without any additional signal processing or prior knowledge. In the localization process, the full-scale promoted convolution neural network (FSP–CNN) is developed by integrating dual mechanisms of the full-scale feature learning and the promoted classifier. In the imaging process, the class encoding strategy is employed to obtain the 2D and 3D information of delamination defects based on the classification results. Finally, a series of experiments validate the effectiveness of the system for automatic localization and imaging of delamination defects in GFRP composites, which provides a novel and efficient paradigm for the intelligent and automatic THz 3D characterization of hidden delamination defects in composites.

Influence of tool parameters on ultrasonic assisted drilling of GFRP composites

Glass fiber reinforced polymer (GFRP) composites are widely used in aviation, aerospace, sports and special vehicles because of their light weight, high wear resistance, good fatigue resistance and low thermal expansion coefficient. However, the anisotropy and low interlaminar strength easily lead to defects such as wire drawing, delamination and tearing during drilling process, which seriously restricts the development of GFRP composites. In this study, the effects of drilling tool material and geometrical parameters on the machining quality of GFRP composites in ultrasonic-assisted drilling are revealed through single-factor experiment. Unidirectional laminated GFRP epoxy plates of 80 × 50 × 5 mm are used in the experiment, and the thrust in the machining process is collected by a dynamometer. An industrial camera is used to record the exit morphology of the hole, and then MATLAB is used for image processing to convert it into a greyscale map. Finally, the size of the delamination factor Fd is obtained according to the equation. The experiment results indicate that using the carbide drilling bit with a diameter of 4 mm and a point angle of 120° is beneficial to reduce the thrust and suppress the machining defects.

Strengthening of Beam Using Glass Fibre Reinforced Polymer

Abstract: Glass fibers reinforced polymer composites have been prepared by various manufacturing technology and are widely used for various applications. Initially, ancient Egyptians made containers by glass fibers drawn from heat softened glass. Continues glass fibers were first manufactured in the 1930s for high-temperature electrical application. Nowadays, it has been used in electronics, aviation and automobile application etc. Glass fibers are having excellent properties like high strength, flexibility, stiffness and resistance to chemical harm. It may be in the form of roving’s, chopped strand, yarns, fabrics and mats. Each type of glass fibers have unique properties and are used for various applications in the form of polymer composites. The mechanical, tribological, thermal, water absorption and vibrational properties of various glass fiber reinforced polymer composites were reported.

Dielectric Analysis of Single Walled Carbon Nanotubes Loaded SMC Composites Depending on Resin Type

This paper investigates effect of different industrial resins including vinyl ester and unsaturated polyester produced by sheet moulding compound (SMC) method on conductivity and dielectric properties of single walled carbon nanotubes (SWCNT) modified glass fiber reinforced polymer composites (GFRP), comparatively. Alternating current (AC) conductivities, complex dielectric permittivity, dissipation factor (DF), electric modulus of unsaturated polyester and vinyl ester resin-based composites was examined by impedance analyzer depending on frequency range from 10-2 Hz to 107 Hz at room temperature. Cole–Cole approach was used to describe the impedance characteristics of tested samples. In order to clearly understand the effect of resin type, the glass fiber and carbon nanotube filling ratios in the produced materials were kept constant. AC conductivity results showed that VE composite exhibited better performance than UP composite in all frequency. The theoretical models including Power Law and Linear Regression (LR) algorithm also confirmed the experimental results about the conductivity of the composites. A comparison of the dielectric characteristics between SWCNT/VE and SWCNT/UP binary composites indicated that VE based composite exhibited superior dielectric properties compared to the UP based sample. In addition, scanning electron microscopy (SEM) images have been taken to observe distribution and organization of fillers in polymer composites.

Intralaminar crack propagation of glass fiber reinforced composite laminate

The intralaminar crack propagation of unidirectional glass fiber reinforced polymer composite (GFRP) laminate has been investigated by quasi-static tensile/compression experiment and complemented by finite element analysis (FEA). The FEA was conducted using a progressive damage model (PDM) -which was executed by the implicit user material (UMAT) and explicit user material (VUMAT) subroutines. Additionally, based on the UMAT implicit algorithm, the intralaminar crack propagation was predicted by the extended finite element method (XFEM). Finally, XFEM was used to simulate the microscopic crack propagation of representative volume element (RVE). The experimental results showed that the intralaminar crack propagation was accompanied by fiber bridging, which was further observed by scanning electron microscopy (SEM). Besides, multi-crack propagation occurred on the specimens without pre-existing crack. The calculated value of intralaminar fracture toughness in stable state was approximately 4.5 N/mm. The PDM revealed the damage status around crack path, stress field at crack tip and the progressive damage mechanical behavior. However, the predicted crack path did not fully agree with those obtained by experiments due to the element delete method. Although the crack propagation process obtained by XFEM was consistent with the experimental result, the damage status could not be observed. The XFEM predictions of the crack state in the RVE was in good agreement with the SEM results; this suggests that crack propagation underpins matrix cracking, interfacial debonding, fiber pulling out, and fiber fracture. In conclusion, using a blended approach by combining the PDM and RVE with XFEM could be a step forward to simulating the intralaminar crack propagation phenomenon in order to gain deeper insights into the micro–macro failure mechanism.

Environmental degradation and mechanical behavior of glass fiber reinforced polymer nanocomposites used in offshore applications

Present study aims at the variation of mechanical properties of glass fiber/epoxy composite under the effect of temperature, alkalinity, and rate of loading. Glass fiber reinforced polymer (GFRP) with plain epoxy and GFRP with 1–2% variation of Nanoclay were utilized for experimentation. Flexural testing of specimen at optimum percentage of Nanoclay in GFRP and epoxy was performed and after that pre-stretching of GFRP with plain epoxy and GFRP with optimum percentage of Nanoclay was conducted. Combined effect of moisture, alkali, and temperature on the degradation behavior of glass fiber reinforced polymers in different environments was studied. The macroscopic and microscopic behavior of the GFRP composite specimen and pure epoxy and Nanoclay reinforced epoxy exposed to varying hygrothermal loads has also been analyzed. Scanning electron microscope (SEM) was used to study the microscopic behavior of GFRP composites. X-Ray diffraction analysis of epoxy with 1%, 2%, and 3% Nanoclay addition was also performed. Tensile and flexural testing of specimen at different orientations such as 0°, 30°, 45°, 60°, and 90° were also studied. At 0° orientation, maximum average flexural strength of 295.04 MPa and 481.69 MPa was observed for plain glass fiber reinforced polymer and 2% Nanoclay/glass fiber reinforced polymer before hygrothermal loading. At 20% and 50% loading conditions the maximum flexural strength of 46.7 MPa for plain glass fiber reinforced polymer and 147.52 MPa for 2% Nanoclay/glass fiber reinforced polymer was observed before hygrothermal conditions. Maximum degradation in tensile strength (384.78 MPa at 50% loading) for 2% Nanoclay/glass fiber reinforced polymer after hygrothermal loading was observed in NaCl environment. Lower tensile strength observed for 1% of Nanoclay addition in pure epoxy as compared to the 0% and 2% mixing. There is decrease in tensile strength for specimen with 2% of Nanoclay in pure epoxy as compared to the 0% and 1% mixing. Tensile strength changed by moisture as well as mechanical loading of the glass composites. There is lesser degradation and significant increase in tensile strength of glass fiber reinforced polymer nanocomposite was observed when it exposed for lesser time period while tensile strength significantly reduced when specimen was exposed for longer time (3000 hr). After degradation in four different environments (four tanks) for 30 days intervals, SEM analysis of glass fiber reinforced polymer nanocomposite at pre-stretching of 20% and 50% loading was observed. At 20% loading there is lesser damage of glass fiber reinforced polymer nanocomposite with the formation of small irregular lumps were observed while at 50% loading there is significant damage of glass fiber reinforced polymer nanocomposite with the formation of voids of epoxy was clearly observed during SEM analysis.

A Novel Z Profile of Pultruded Glass-Fibre-Reinforced Polymer Beams for Purlins

Purlins made from galvanised steel in fertiliser warehouses have often been considered less efficient, necessitating a new purlin made using corrosion-resistant material to increase building efficiency. This study was an attempt to design a nine-metre purlin from glass-fibre-reinforced polymer (GFRP) composite material for a new fertiliser warehouse in Bontang-East Kalimantan, Indonesia. The purlin design selected in this study was the Z profile of pultruded beams from GFRP composite material that met the criteria of an efficient purlin, such as corrosion resistance, compact stacking, and ability to withstand technical loads. In particular, the Z profile becomes compact when stacked, and the GFRP material used is corrosion-resistant yet affordable. The primary materials for GFRP composites consist of long yarn glass fibre bundles for reinforcement and unsaturated polyester resin (UPR) for the matrix. Material strength modelling was based on analytical and finite element approaches. The analysis shows that the most considerable normal stress of “64.41 MPa” occurred at the two fixed end supports, while the most significant deflection of “45.9 mm” occurred at the mid-span of the purlin structure. The purlin structure was considered safe, as the strength and deflection were below the threshold. Thus, the Z profile of the pultruded purlin beams built using the GFRP composite material meets the technical criteria.

Predicting the Erosion Rate of Uni-Directional Glass Fiber Reinforced Polymer Composites Using Machine-Learning Algorithms

Abstract The wind turbine and helicopter rotor blades when exposed to dust borne environment are subjected to leading edge erosion because of the impact of dust particles. These blades are manufactured from fiber reinforced polymer (FRP) composites and therefore, it is important to predict the erosion rate of FRP composites. In this paper, the main aim is to accurately predict the erosion rate of uni-directional FRP composites using machine-learning algorithms like artificial neural networks (ANNs) and extreme gradient boosting (XGB) and compare between the algorithms. The model uses input parameters like erodent impact angle, velocity of erodent particle, fiber orientation, and fiber volume fraction as the input and erosion rate as the output variable. The total dataset considered for training and testing the model is obtained from two parts. The first part of the dataset is obtained from the literature and the other part is collected from performing in-house experiments on uni-directional glass fiber reinforced polymer (GFRP) composites. The crater profiles of the tested specimens are characterized using 3D Alicona imaging microscopy. The machine-learning models considered in this study provide accurate results on the dataset. However, the XGB method is more robust, reliable, and faster to train and more accurate than the ANN model in the case of an unknown dataset (dataset not used for training). The feature importance from the XGB model suggests that impact particle velocity, impact angle, and fiber orientation are the most important input features. The model predictions by taking into account the three input features provide accurate results without affecting the accuracy of the model.

Effect of simulated hygrothermal environment on the flexural and interlaminar shear strength of particulate-filled epoxy-coated GFRP composites

The application of glass fiber-reinforced polymer (GFRP) composites in civil engineering and construction has gained significant interest in the last decade. Such applications require information on the long-term performance and durability of fiber composite materials because these materials are directly exposed to aggressive environments. This comparative study evaluated the effect of a simulated hygrothermal environment on the durability of GFRP composite laminates with and without a particulate-filled epoxy coating. The three-point bending test was conducted to characterize the degradation of interlaminar shear strength and flexural properties of GFRP composites before and after conditioning at combined high moisture and temperature for 0, 1000, 2000, or 3000 h. Dynamic mechanical analysis was also conducted to characterize the changes in the thermomechanical properties of the composite laminates. The results show that hygrothermal conditioning had a negative impact on the flexural and interlaminar shear strength of uncoated GFRP laminates, but this could be efficiently minimized with the use of a particulate-filled polymer-epoxy coating.

Void Content Reduction in 3D Printed Glass Fiber-Reinforced Polymer Composites through Temperature and Pressure Consolidation

To improve the properties of additively manufactured parts to be used in high-end applications, intrinsic defects occurring during the printing process need to be minimized. Defects such as void can significantly degrade the mechanical properties of the resulted parts. The presence of void is more evident in composite printed parts due to the inhomogeneity of the specimen. In this study, composite rectangular coupons printed with a Markforged Mark Two printer were manufactured with different fiber orientations and stacking sequences. A void content reduction/consolidation process, consisting of applying pressure at different temperature levels, was developed and implemented to remove the voids in form of air bubbles trapped in the specimen. A two-part mold with female and male components with the same dimensions as the rectangular specimen was designed and machined to be used in a hot press process. The success of the approach was evaluated by calculating the density of the specimen pre- and post-consolidation. The void content reduction results were highly dependent on fiber orientation; however, the density increased for all tested specimens, confirming the reduction in porosity.

Effect of Graphene Nanoplatelets on Mechanical Performance of GFRP Composites

The carbonaceous nanofillers such as graphene nanoplatelets (GN) due to their unique properties have been increasingly used as nanofillers to improve the mechanical properties of FRP composites. In the present study, unidirectional glass fiber reinforced polymer (GFRP) composites and GFRP composites with graphene nanoplatelets (GN-GFRP) are fabricated using vacuum bag process and hand layup method. The percentage of GN added in GN-GFRP composites is 0.1% and 0.5% in case of hand layup method and 0.5% in case of vacuum bag process. The specimens are tested under uniaxial tension and three-point bending to study the effect of GN on the tensile and flexural performance of GFRP composites. In case of composites fabricated using hand layup method, the tensile strength of GFRP composites increased by 35.8% and 40.4% with the addition of 0.1% and 0.5% GN respectively. The tensile modulus of GN-GFRP composites with 0.5% GN decreased by 11.8% compared to GFRP composites. The flexural strength of GN-GFRP composites with 0.1% and 0.5% GN are found to have increased by 6.5% and 5.3% respectively compared to GFRP composites. The flexural modulus of GN-GFRP with 0.1% GN increased by 11% and the same for GN-GFRP with 0.5% decreased by 8.2% compared to GFRP composites. The tensile strength and modulus of GN-GFRP composites fabricated using vacuum bag process decreased by 24.4% and 7.7% respectively compared to GFRP composites. Scanning Electron Microscope (SEM) investigation reveals that poor adhesion of resin with the fibers caused delamination in GN-GFRP composites fabricated using vacuum bag process resulting in reduction of tensile properties.