Glass Fiber Reinforced Polymer Composites Research Articles

Crack self-sensing capability of glass fiber reinforced polymer composites embedded with magnetostrictive fibers in mixed-mode bending

Glass fiber reinforced polymer (GFRP) composites integrated with sensors have received attention because the composite material can transmit information about the structural condition during operation. This study investigated the crack self-sensing capability of GFRP composites with magnetostrictive Fe–Co fibers under mixed-mode bending. The mixed-mode bending (MMB) test was performed using GFRP composites with a certain number of Fe–Co fibers introduced. Three different mixed-mode I/II ratios for MMB tests were selected and tested. The self-sensing capability of crack propagation was discussed by measuring the magnetic flux density induced by the inverse magnetostrictive effect using Hall probes. The GFRP composites with Fe–Co fibers fabricated in this study are a promising monitoring technology for non-contact sensing.

Enhancement of high-performance structures with sustainable seashell filler-based GFRP composites in static loading

Research on reinforcing airplane structures while reducing their weight by employing sustainable materials is currently challenging. In this study, damage mechanisms, mechanical characteristics, and failure behavior of laminates made of plain-woven glass fiber/epoxy and Glass Fiber Reinforced Polymer (GFRP) with sea shell filler under low-velocity impact static loading conditions are experimentally investigated. The bi-directional GFRP type E-glass laminates with 10 plies and a total thickness of 3.35 mm are created by hand lay-up process using an epoxy matrix. Comparing GFRP with an effective ratio of sea shell filler of 5% under various impact loading, composites are characterized in accordance with ASTM standards to assess the progressive damage and failure of GFRP composite. The findings of the experiment indicate that GFRP with seashell filler composites outperforms GFRP composites in terms of impact strength, outstanding flexural strength, and tensile strength. The findings show that adding seashell filler to GFRP increased the composite’s ability to sustain various impact loads. The sample with seashell infill has a drop weight impact that is 25.26% lower than GFRP. Moreover, the flexural test demonstrated a 59.6% increase in bending over GFRP. Seashell filler outperformed GFRP in the longitudinal strength test by 33.12%, according to the results of the tensile test. Finally, the compression after impact test (CAI) manifested a remarkable increase in transverse strength by 78.23%.

Characterization of material, mechanical, static bending and vibration properties of glass fiber composite panels reinforced with graphene nanofillers

The present study investigates the material, mechanical, static bending and vibration characteristics of glass fiber reinforced polymer (GFRP) composites reinforced with graphene nanofillers. The crystallinity, functional groups, morphology, and tensile and flexural strengths of GFRP and graphene reinforced GFRP composites were examined using a variety of material and mechanical characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and tensile and flexural tests. The first-order shear deformation theory (FSDT) based finite element (FE) model was developed to obtain the static bending and vibration characteristics of the graphene reinforced GFRP composite panels. The validity of the FE model is verified with numerical data published in the literature. Further research is conducted into the effects of the wt% of graphene, end conditions, curvature ratio, and aspect ratio on the static bending and vibration characteristics of graphene reinforced GFRP panels. The findings of this study indicate that graphene reinforced GFRP panels could be utilized in a variety of applications, particularly for parts used in the aerospace and automotive industries.

Structural health monitoring of carbon nanotube-modified glass fiber-reinforced polymer composites by electrical resistance measurements and digital image correlation

A method based on changes of electrical resistance was used to evaluate non-visible damage inflicted to multiscale hierarchical composites subjected to monotonic and cyclic bending loads. The composites comprise glass fiber weaves modified by carbon nanotubes in a vinyl ester matrix. Damage sensing is achieved by placing an array of electrodes close to the surfaces of four-point bending specimens and is correlated to strain fields measured by digital image correlation (DIC). The top (compressive) surface exhibited lower electrical resistance changes than the bottom (tensile) one. Spatial measurements of electrical resistance allowed identification of the most severely damaged zones, which coincided with those pinpointed by DIC. DIC also indicated an important presence of irreversible interlaminar shear strains accumulating close to the supports and/or loading introduction elements, which coincided with the location of delamination. The electrical technique allowed not only the detection of the onset of damage in the form of initial fiber breakage and matrix cracking, but also the detection of damage progression under cyclic loading and low-velocity impact.

Low-Velocity Impact Resistance of Glass Laminate Aluminium Reinforced Epoxy (GLARE) Composite

This study intends to determine the behavior of glass laminate aluminum-reinforced epoxy (GLARE) and glass fiber-reinforced polymer (GFRP) composites under a low-velocity impact test. Experimental tests and numerical simulations are considered for this investigation. All samples are made by the hand lay-up method. Moreover, specimens are produced with a 7075-T6 aluminium sheet with a 0.5 mm thickness, resin 3001, and E-glass fiber. The drop weight test performs the low-velocity impact at 6.7 J and 10 J impact energy levels and the heights of 1.0 m and 1.5 m. Numerical simulation is also conducted by ANSYS software to compare the results obtained by the experimental tests. Generally, results show that maximum deflections of the GLARE samples are significantly lower as compared to GFRP ones by 87% and 83.5% for 1.0 m and 1.5 m drop heights, respectively. Experimental results demonstrate that although aluminum sheets prevent damage to the fibers in GFRP, delamination and fractures between layers are observed in GFRP samples. An appropriate agreement is also obtained between the FE results and experimental data.

Ultra-high performance concrete reinforced with macro fibres recycled from waste GFRP composites

Ultra-high-performance concrete (UHPC) is a promising cementitious composite to produce lightweight and high-performance structures. Steel fibres are an essential constituting material of UHPC to prevent the brittle failure of UHPC, but the high cost steel fibres impedes the wider application of UHPC to some extent. This paper proposes a concept to produce UHPC reinforced with macro fibres processed from waste glass-fibre-reinforced polymer (GFRP) composites, therefore addressing two issues of the high cost of UHPC as well as the difficulty in disposal of waste GFRP simultaneously. A series of tests have been carried out to investigate the effect of adding macro fibres on the properties of UHPC. The test results show that the incorporation of macro fibres leads to a loss of the workability and a reduction of up to 21.8 % in the compressive strength, but improves the flexural strength and flexural toughness greatly by up to 27.9 % and 46.9 times, respectively. The tensile constitutive relationship has been converted from the results of the bending tests through inverse analyses. The proposed concept of producing UHPC with recycled macro fibres contributes to lowering the price of UHPC, whose properties are comparable to that of UHPC with steel fibres, and establishing an effective routine to valorise the waste GFRP.

Compression strength analysis of glass fibre polymer composites filled with brown algae powder compared to glass fibre reinforced polymer composite

The current investigation intends to compare the compression strength analysis of glass fiber composites filled with brown algae filler. The material involved in this work is a glass fibre composite filled with and without brown algae filler. 40 specimens were tested by using selected parameters using the universal testing machine. In this work, the control group was a glass fiber epoxy composite and the experimental group was a brown algae-filled glass fiber-reinforced polymer. The mean compressive strength obtained for the brown algae-filled glass fibre reinforced polymer is, whereas it is for the Glass fibre reinforced polymer with the significant value is 0.018 (p<0.05). Within the scope of this investigation, experimental data reveals that strength in compression is high when the glass fiber-reinforced composite is filled with brown algae powder.

A comprehensive investigation of the low-velocity impact response of enhanced GFRP composites with single and hybrid loading of various types of nanoparticles

This study investigates the effects of incorporating various types of nanoparticles, both singularly and in hybrid form, on the low-velocity impact (LVI) response of glass fiber reinforced polymer (GFRP) composites. GFRP composites were fabricated using the hand lay-up method and different weight percentages (wt. %) of multi-walled carbon nanotubes (MWCNT), clay, TiO2, and CuO nanoparticles were added into the matrix of composites. To test the LVI response, 14 types of specimens were fabricated with single and hybrid nanoparticle loadings, and LVI tests were conducted using 5 and 10-cm span dimensions at two levels of subjected energy. The experimental results reveal that specimens with a single loading of MWCNT or nano-clay have a lower maximum contact force compared to pure specimens with fully rebounding behavior. This indicates that neither 5 nor 10 cm spans result in severe damages during the impact tests. Furthermore, incorporating more MWCNTs results in stiffer behavior and more brittleness. The study also explores the synergetic effect of adding hybrid nanoparticles in the fabricated composites and discusses the calculated results for absorbed energy. Finally, scanning electron microscopy (SEM) images are analyzed to evaluate the enhancement mechanisms resulting from the addition of nanoparticles to GFRP composite specimens.

Abrasive water jet machining of glass fibre reinforced polymer composite: experimental investigation, modelling and optimization

Abrasive water jet machining of glass fibre reinforced polymer composite: experimental investigation, modelling and optimization

Indentation, finite element modeling and artificial neural network studies on mechanical behavior of GFRP composites in an acidic environment

In this study, the indentation tests are performed with various forces using the Vickers indenter to investigate the mechanical properties, including the elastic modulus, hardness, and the plasticity index of pure, and incorporated glass fiber reinforced polymer (GFRP) composites with nanosilica and nanoclay. To study the effect of adding different nanoparticles on reducing the mechanical properties of immersed specimens in acid for 0, 1 and 3 months, incorporated composite specimens with 3 wt percent (wt. %) of nanoparticles were fabricated using hand lay-up method. Accordingly, the reduction in mechanical properties and increase in plasticity index was attributed to the penetration of acid into composite specimens during the immersion period, which resulted in the failure of matrix and fiber following increased moisture penetration. Adding the nanoparticles especially nanoclay, has alleviated the trend of drop in mechanical properties. In fact, for the incorporated composite specimen with nanoclay, the hardness and elastic modulus of the immersed samples in acid for 0 and 3 months indicated a decrease of 10.55 and 7.88%, respectively on grounds of hydrophobic nature of nanoclay. Conversely, incorporating nanosilica increased the plasticity index leading to higher rate of degradation, which was even more than pure sample, yet the pure sample had the lowest mechanical properties after 3 months of immersion. In addition, Finite element modeling (FEM) and artificial neural network (ANN) were used to respectively predict the indentation behavior of fabricated composite specimens and study the effects of immersion time in an acidic environment.

Optimization of CO2 laser drilling process parameters of GFRP/Al2O3/perlite composites

Glass Fiber Reinforced Polymer (GFRP) composites have excellent mechanical characteristics and are extensively used in aerospace and marine applications. Drilling GFRP composite through conventional methods leads to delamination and taperness, causing quality loss and imprecision. CO2 laser drilling, an unconventional method to drill GFRP composites, is adopted in this study to reduce the delamination and taperness. This work aims at optimizing the process parameters of CO2 laser drilling. Hybrid S-glass/Al2O3/Perlite powder composite is used in this study. Laser drilling parameters: laser power (P), cutting speed (N), focal length (L), and hole diameter(d) were studied to reduce the hole delamination and hole taperness. These results were achieved through mathematical modelling and optimization using Response Surface Methodology (RSM) and Multi-Objective Genetic Algorithm (MOGA). The optimum process parameters were found by minimizing the objective function upon considering the drilled holes economic features, deposition efficiency, geometric features, and hole diameter at larger and smaller sides. The most critical output factors, delamination and taper responses, had a deviation from the objective by less than 3%. The optimum process parameters laser power, cutting speed, and focal length is found to be 80.795 W, 7.9089 mm/sec, and − 1.9641 m respectively. From the experimental confirmation study, the optimum process parameters effectively reduced the hole delamination and taperness.

Hygrothermal aging effects on the diffusion-degradation process of GFRP composite: Experimental study and numerical simulation

The durability performance of glass fiber reinforced polymer (GFRP) has attracted wide attention, but conventional experimental methods for durability prediction are time-consuming, labor-intensive and not applicable to members with different sizes or geometries. To address this issue, a new modeling approach is developed in this study to simulate the diffusion-degradation process of GFRP composite in a moist environment. Taking a GFRP rebar as an example, the water diffusivity of composite is firstly obtained from a finite element model with the assumption of hexagonal fiber arrangement. With test results on the degradation of single coated fibers in the wet environment, and the simulated water front from the diffusion analysis, the strength retention at each location over the rebar section can be derived. The time-dependent degradation of tensile strength can hence be obtained from integration. To account for the defects (including matrix cracking, fiber erosion and fiber/matrix debonding) which can affect the water diffusivity, a refined diffusion model was also performed with increased water diffusivity (from 4.0 × 10-6 mm2/s to 4.5 × 10-6 mm2/s) and presence of interfacial crevices in the corroded region. While the refined model can lead to faster water diffusion and tensile strength degradation, the difference with the original model is within 10%. More importantly, both models are able to correctly predict the GFRP tensile strength degradation measured in the laboratory over a 12-month period. As the diffusion-degradation framework proposed in this study is applicable to any member size and geometry, it supplies engineers with an evaluation method to quickly predict the long-term tensile performance of GFRP structures.

Torsional behavior of glass fiber-reinforced polymer composite: polymer matrix effect and acoustic emission signal analysis

Torsional behavior of glass fiber-reinforced polymer composite: polymer matrix effect and acoustic emission signal analysis

Non-destructive detection of thin micro-defects in glass reinforced polymer composites using a terahertz electro–magnetic wave based on a convolution neural network

This study presents a non-destructive evaluation (NDE) method that utilizes a convolutional neural network (CNN) based terahertz (THz) signal processing to quantitively distinguish overlapping signals from micro-defects in glass fiber reinforced polymer (GFRP) composites. Theoretical electro–magnetic wave propagation models for describing the propagation of the THz signal into the GFRP composite were devised considering the interaction of THz with the micro-defects in the GFRP composite. THz signals were simulated with respect to the thickness of the defects, and transformed into two-dimensional (2D) spectrograms using a short-term Fourier transform (STFT). The converted 2D-STFT images were used to train the CNN deep learning model to classify the size and thickness of the defects. A probability map of the classification of the defect thickness was derived from the trained CNN deep learning model. Using the probability map based on the CNN model, the depth and size of the micro-defects thinner than 20 μm inside the GFRP composites could be successfully differentiated with 95% accuracy. This research proposes a promising approach for analyzing micro-defects in composite materials by quantitatively evaluating the extent of signal overlap, going beyond the traditional approach of training the model based solely on the signal.

New Anchorage Technique for GFRP Flexural Strengthening of Concrete Beams Using Bolts-End Anchoring System

The concept of external glass FRP composite confinement is a current process for strengthening concrete beams subjected to static loads. End anchorage glass FRP composites of 80 mm width and 90–130 mm length with different thicknesses (2.4 and 4.8 mm) have been fixed at the bottom of beams with bolts of various diameters (6 and 10 mm). For this purpose, the behavior of beams strengthened with bolt-end anchoring glass fiber polymer composites (BEGFPC) has been analyzed. It is concluded that the load capacity of the BEGFPC beams is improved by increasing the end-anchorage glass FRP composite thickness (about 98–188%). In addition, the BEGFPC system with bolts of 6 mm diameter has significantly improved the flexibility of beams. In contrast, the 10 mm bolts in diameter give a high ultimate load, whatever their quantity. Therefore, combining bolts with diameters of 6 and 10 mm would be the best solution for increasing the ultimate load and ductility of the retrofitted beams. Depending on the number and bolts' arrangement, there is also an enhancement in the crack patterns by changing from intermediate flexural failure to shear failure in beams.

Effects of vacuum infusion configuration on homogeneity of glass fiber reinforced polymer composites for automotive components

In this study, the effects of vacuum infusion configuration on the homogeneities of glass fiber reinforced vinyl ester composites have been evaluated. Three different sizes of samples (100x100, 500x500, and 1000x1000 mm) were fabricated. Three different configurations were used to fabricate the samples. The first two configurations had one inlet, while the third configuration had two inlets for resin infusion. Thickness variations and hardness (Shore D) measurements were performed to determine the homogeneities of the samples. The results revealed that, for small size samples, the configurations have no obvious effect on the homogeneity of the samples, both in terms of thickness variations and hardness values. However, for larger samples, the configuration where the resin is introduced into the preform in the center of the component showed better homogeneity than other configurations. Even a better distribution is assessed with the introduction of the resin in the center of the sample, although this configuration also resulted in thickness swellings in the central areas of the sample. The thickness swellings were observed around the inlet areas for all configurations. The study shows that the resin flow in the center of the component is preferable but thickness swelling must be considered when dimensional tolerances are critical.

An embedded non-intrusive graphene/epoxy broadband nanocomposite sensor co-cured with GFRP for in situ structural health monitoring

Glass fiber-reinforced polymer (GFRP) composites degrade continuously through service, entailing effective health monitoring to ensure structural integrity. We develop a new type of GFRP structure, with the embedded non-intrusive sensors for in situ structural health monitoring (SHM). Piezoresistive nanocomposite sensors – a pre-cured hybrid of graphene nanoplatelet (GNP) and epoxy, are molded in the second lamina of GFRP prepreg with epoxy matrix during lay-up to laminate process and then co-cured with GFRP composite, keeping the continuity at the interface between the composite. The GNP/epoxy sensor successfully captures the structural response from static strain to a high frequency ultrasonic wave up to 600 kHz with a gauge factor up to 26, which is the first ever nonintrusive GNP/epoxy piezoresistive sensor with an ultra-wide frequency response to mechanical deformation. Furthermore, the mechanical properties of host composite show negligible signs of intrusion testified with tensile and bending tests. GFRP with embedded sensor features merits of high strength from GFRP as well as high-sensitivity sensing capability from the nanocomposite sensors, opening up a new avenue to in situ health monitoring of composites.

Effects of alkaline concentration and saline contents on degradation of tensile properties, microstructure and chemical characterization of glass fiber reinforced polymer (GFRP) rebars

Glass fiber reinforced polymer (GFRP) rebar has attracted widespread attention in construction industries to mitigate steel corrosion problems which significantly affect the engineering sustainability. However, GFRP tensile strength may degrade under exposure to alkaline/saline environments, and the inherent quantitative relationship between tensile strength degradation and exposure conditions is still unclear. In this study, the tensile strength retention of GFRP rebars was found to drop to 45.9%, 47.2%, 44.2%, 41.1%, 27.6%, 30.3% and 31.9% in distilled water (DW, pH = 7), seawater (SW, pH = 8.2), sodium hydroxide solutions (NaOH, pH = 11, 12 or 13), simulated normal concrete (NC, pH = 13.6) and seawater sea-sand concrete pore solutions (SSC, pH = 13.6), respectively, after 12 months of exposure at 60 °C. Both the residual tensile strength retention and activation energy in the Arrhenius equation were found to decrease with pH in a descending quadratic parabola form. The underlying degradation mechanism was then revealed by relating the macroscopic tensile strength degradation to the water/ion diffusion and fiber/matrix deterioration at the microscopic level. The pH level rather than saline ions was uncovered to be the major influence factor for GFRP degradation. The findings of this study supply engineers with a comprehensive database on GFRP tensile strength degradation, suggesting that lowering the exposure pH rather than the saline content is critical for enhancing the durability of GFRP composites.

Investigating the Wear Behaviors of Silane Coated Silica Filled Glass/Epoxy Nanocomposites

Wear behaviors of silane coated silica (SiO2) nanoparticle-filled glass fiber reinforced polymer composites were investigated depending on the type of silane coating (KH550: -Aminopropyl-triethoxy-silane and KH570: -Methacryloxypropyl-trimethoxy-silane) and nanoparticle percentages within the polymer matrix. Unlike the cases given in most research studies, the silanized silica nanoparticles were used as received. Therefore, the synergistic effects of silanization and nanoparticle reinforcement were successfully applied since the silanization process was eliminated. The matrix modification with the nanoparticles was carried out using an ultrasound homogenizer, and then the modified matrix was reinforced with glass fibers. Scanned electron microscopy revealed the disperse ability of silanized silica nanoparticles within the glass/epoxy composites. The wear behaviors of the developed composites were investigated via a ball-on-disc tribology device. Wear track profiles were obtained depending on the width and depth of the wear. The length of wear track and wear mechanisms were determined by a stereomicroscope. The findings have shown that both types of silane coating and silica nanofiller percentages significantly affected the wear rate of the composite structures.

Enhancement in Mechanical Properties of Glass/Epoxy Composites by a Hybrid Combination of Multi-Walled Carbon Nanotubes and Graphene Nanoparticles

In this work, an attempt was made to improve the mechanical performance of glass fibre-reinforced polymer composites by adding multi-walled carbon nanotubes (MWCNT) and graphene nanoparticles (GNP) and their hybrid combination at different weight fractions (0.1 to 0.3%). Composite laminates with three different configurations (unidirectional [0°]12, cross-ply [0°/90°]3s, and angle-ply [±45°]3s) were manufactured using the compression moulding method. Characterisation tests such as quasistatic compression, flexural, and interlaminar shear strength properties were carried out per ASTM standards. Failure analysis was carried out through optical and scanning electron microscopy (SEM). The experimental results showed a substantial enhancement with the 0.2% hybrid combination of MWCNTs, and GNPs showed 80% and 74% in the compressive strength and compressive modulus, respectively. Similarly, flexural strength, modulus, and interlaminar shear strength (ILSS) increased by 62%, 205%, and 298%, respectively, compared to neat glass/epoxy resin composite. Beyond the 0.2% of fillers, the properties started to degrade due to the agglomeration of MWCNTs/GNPs. The order of layups per mechanical performance was UD, followed by CP and AP.