Glass-epoxy Composite Material Research Articles

Analysis of Epoxy Fiber Composite Clamp with Variable Slotted Holes for Electric Overhead Crane Mounting

Composite materials offer an excellent solution for structural applications requiring a high strength-to-weight ratio and stiffness-to-weight ratio. This is particularly beneficial in weight-sensitive structures like aircraft and spacecraft, where the cost-effectiveness of composite materials becomes evident. The exploration of composite materials encompasses various aspects, such as manufacturing processes, anisotropy, the elasticity strength of anisotropic materials, and micromechanics. This study focuses on the investigation of a novel glass epoxy composite material as a substitute for expensive, heavy, and corroding metals in applications involving tensile loadings. The objective is to experimentally analyze and employ finite element methods to understand the mechanical behavior of composite components, specifically those featuring slotted holes. Furthermore, the study aims to validate these findings using the finite element analysis (FEA) method.

Inter-fibre failure under biaxial loads in glass–epoxy composite materials: Effect of the presence of a nearby fibre

Fibre-reinforced composite materials are especially prone to transverse failure. It appears at the lamina level following the mechanism known as matrix/inter-fibre failure. This mechanism of damage is associated with the appearance of fibre–matrix debonds (interface cracks), as shown in previous numerical micromechanical studies. After the nucleation, growth and kinking into the matrix, these interface cracks give rise to the final macro-failure.When compared to uniaxial loading, the growth stages of this mechanism of damage (analysed in light of Interfacial Fracture Mechanics) show some alterations under different combinations of biaxial loads. This work gives a step forward and focuses on the micromechanical BEM study of the evolution of an interface crack in the presence of a neighbouring fibre.Thus, after considering a transverse tensile load (nominally responsible for the failure) a secondary transverse load is also applied (tensile or compressive, perpendicular to the primary load). When considering the two-fibre BEM model, the results obtained lead to identifying the neighbouring fibre locations that act as accelerative agents on failure progression and establishing the effect of the biaxial load on them. Specifically, when a secondary tensile load is applied, the presence of the nearby fibre (for most of its positions) confirms the slight inhibition of the mechanism of failure for biaxial tensile loads already referred to in previous single-fibre studies by the authors. As the secondary tensile load increases, it tends to mitigate the effect of the presence of the neighbouring fibre that was previously observed for uniaxial tensile load. The opposite effects are found when a secondary compressive load is considered, which intensifies the alterations of the presence of the neighbouring fibre on the interface crack growth. Experimental evidence on some aspects is provided confirming the associated conclusions derived from the numerical models.

Structural and modal analysis of gas insulated switchgear structure made up of glass-epoxy and carbon-epoxy composite materials for seismic application

Earthquakes cause significant loss of life and infrastructure damage. As a result, there has been a huge increase in the development of technologies and materials to mitigate the effects of earthquakes in the infrastructure sector. Along with the infrastructure industry, the electrical sector is working to design structures that can withstand the effect of an earthquake. The purpose of this study is to develop lightweight frame structure for Gas Insulated Switchgear (GIS) for seismic applications. In the proposed study, GIS frame structure incorporates composite materials such as carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) in addition to traditional materials such as steel. These composite materials are subjected to experimental testing in order to determine their mechanical properties. To select optimal material for the frame structure, the structural and modal performance of these materials is evaluated using finite element simulations for the GIS frame structure under seismic loading as per California Building Code (CBC) and International Building Code (IBC) code.

Machine learning based thermal imaging damage detection in glass-epoxy composite materials

Machine learning (ML) based fatigue damage detection from thermal imaging in glass-epoxy composites is an important component of remote structural health monitoring used for safety assessment and optimization of composite structures and components. However, accurate characterization of fatigue damage hotspots in terms of size, shape, location, hysteretic heat, and local temperature deep inside the material using surface thermal images remains a challenge to date. This work aims at evaluating the theoretical accuracy level of hotspot characterization by training a ML model with artificially generated thermal images from 3D finite element models with increasing complexity. Modelling the fatigue damage as an intrinsic heat source allowed to significantly reduce the influence of thermal image noise and other uncertainties related to heat transfer. It is shown that ML can indeed accurately recover the heat influx, depth, and geometry of the heat source from the original thermal images of the composite materials with prediction accuracies in the range 85%–99%. The effect of training set size and image resolution on the prediction error is also presented. The findings reported in this work contribute to the advancement of accurate and efficient remote fatigue damage detection methods for fibre composite materials.

Tribological behaviour of SiC and AL2O3 filled glass-epoxy composite

Metal glass fibre reinforced composites which are considered as advanced composite materials play a significant role in aerospace, marine and automotive industries. In the current study, an attempt has been made to examine the tribological characteristics of glass fibre reinforced plastic (GFRP) composite filled with aluminium oxide (Al2O3) and silicon carbide (SiC) powder particles. Experiments were performed on pin-on-disc tribometer to evaluate the friction and wear rate as a function of normal load and sliding velocity under different conditions. For each composition of glass-epoxy composite filled with and without fillers, sliding tests were performed with normal load (20 N, 40 N, 60 N, 80 N 100 N) and sliding velocity (2.62 m/s, 4.18 m/s, 5.23 m/s, 6.85 m/s, 7.85 m/s) respectively. The metal GFRP composites were fabricated using hand-lay-up technique. The filler content (SiC & Al2O3) in epoxy-glass composite were varied. SiC was varied from 0 to 10% while Al2O3 was kept constant at 5%. To study the worn surface of glass-epoxy composite material scanning electronic microscopy is used. Before and after the experiment, weights of the composites (pin specimens) were studied on digital balance for wear loss. The present studies reported that the fabricated metal epoxy-fibre composite has performed excellent wear resistance when compared with epoxy-fibre composite without metal powders. The present work findings offer new insights into reinforcement in epoxy-glass composites with metal powders.

Finite element analysis of tensile behaviour of glass fibre composites under varying strain rates

Glass-epoxy Composite materials are extensively used in the complex engineering applications due to their better strength to weight ratio, corrosion and fatigue resistant properties. However, to achieve an efficient material for its adequate use, its behaviour at various strain rates is to be well understood, which could be best achieved by carrying out numerical simulations. The present study is made to understand the strain rate sensitivity with various orientations of the fibres in 6 layered, [0]6, [0/90/0] s and [0/30/60] s, laminates. FEM simulations are carried out for a strain rate range of 10−3 to 103 s−1 for tensile loading. L S DYNA software is used to understand the stress–strain behaviour of the composite material for the various strain rates, which have been compared with the experimental results. It is observed that the tensile properties like the Young’s modulus, tensile strength and toughness increase with increase in the strain rates of the glass epoxy composites for different orientations of the plies. The simulation results are in good agreement with the experimental results and in line with the results available in literature.

NUMERICAL INVESTIGATION OF FATIGUE BEHAVIOURS OF NON-PATCHED AND PATCHED ALUMINIUM PIPES

In this study, the fatigue behaviors of non-patched and patched aluminum pipes were investigated numerically. The Finite Element Method was used for fatigue analysis in the study. Finite Element Method was implemented with Ansys Workbench (15.0) program. Al 6063 type aluminum pipe, DP-460 type adhesive and [0/90]2 reinforced angled glass-epoxy composite patch material were used in the analyzes. As a result of the numerical study, it was observed that patch size is an effective parameter in fatigue strength and that quarter-circle and semi-circular composite patches increase the fatigue life. It was also observed in the analyzes that the quarter-circle patched aluminum pipes achieved higher fatigue strength.

Strain-based theoretical fatigue damage model of woven glass-epoxy fabric composite material

Strain-based theoretical fatigue damage model is developed by utilizing internal variable theory of thermodynamics of continuum damage mechanics approach related to woven glass fabric composite material. Based on the laminate theory of composite engineering, a phenomenological fatigue damage model under decomposition of Helmholtz Free Energy (HFE) is carried out to demonstrate the stiffness degradation, decrease in the Young's modulus of elasticity), damage development corresponding to normalized life, its accumulation, strain evolution, loss in strength and stress reduction. Investigational data from the tensile fatigue test from different literatures were employed to verify the model and the results show that model can describe strain-based theoretical fatigue damage of woven glass fabric epoxy composite material.

Detection of damages on biaxial GFRP composite material using non-destructive technique

This exploratory research work presents a non-destructive evaluation (NDE) method based on optical metrology and ultrasonic C-scan technique. The Optical metrology technique has a 7 MW He–Ne laser, as the source, which is used to perform NDE of biaxial glass–epoxy composite material. This methodology acquires the images of the healthy and the tested samples (tensile, compression, three point and impact). Further, it is post-processed to yield their respective contours and thereby the damaged regions are identified by their pixel intensity values represented in yellow colour code. The second technique, ultrasonic C-scan used for the present study is of immersion pulse-echo method. Using this, the damaged regions are characterized by means of variations in their amplitude signals. C-scan gives more information about the cracks in the fibre and delamination in the composite by means of whitish blue colour code. Further failure analysis is also studied, using Abaqus software, and the results obtained from the analysis are compared with optical metrology and ultrasonic C-scan results. It is found that the results obtained from all three methodologies are indistinguishable from each other. Due to the high-resolution capability aspects, the optical metrology technique may be considered as an efficient tool for the detection of damaged area. Using these techniques, various damages such as interlaminar voids, porosity, resin rich areas and resin starvation, delamination, fibre fracture and matrix cracking are identified and analysed. Therefore, NDE techniques (C-scan, optical metrology) serve as an effective and reliable tool for the assessment and evaluation of extent of damages in the composite material.

Fatigue damage model of woven glass-epoxy fabric composite materials

Based on the Stiffness degradation rule of woven glass fiber composite under fatigue loading, a phenomenological fatigue damage model containing two material parameters in which first is directly proportional to the fatigue life and second is inversely proportional to fatigue loading level is presented in this paper by analyzing damage development effects with very nice result as fatigue modulus is inversely proportional to fatigue strain. Experimental data from Tensile Fatigue Test were employed to verify the model, and the results show that the model can describe the damage evolution of woven glass-epoxy composite laminates under different fatigue loading by verifying the predicted fatigue life of composites. Degradation of Young’s Modulus at different loading cycles, damage development corresponding to Normalized life, its accumulation subjected to constant amplitude fatigue loading including its verifications are well discussed.

Numerical and experimental evaluations of a glass-epoxy composite material under high velocity oblique impacts

Composite materials are used as alternatives to conventional metallics in a multitude of applications including military ground vehicles, aircraft, space launch and re-entry vehicles and even personnel protection where weight savings are critical. In application, these materials are susceptible to high velocity impacts from various threats and it is essential that the response of these materials, under relevant conditions, be understood in order to provide optimized effective designs. This work details an on-going effort to validate the anisotropic multiple constituent model (MCM) within the CTH hydrocode. Within the CTH framework, the anisotropic MCM model is coupled with an equation of state (EOS) and provides continuum averaged stress and strain fields for each constituents (fiber and resin) of a composite microstructure from which progressive damage evaluations can be performed. In this paper we focus on recent validation efforts where woven S2/SC15 (glass/epoxy) composite panels were impacted with steel spheres at various impact velocities and angles of obliquity. The experimental testing was performed at the Shock Thermodynamics Applied Research (STAR) Facility at Sandia National Laboratories to provide data for further validation of the MCM model under oblique impact conditions. Oblique impacts result in stress fields which exercise the anisotropy of the strength model and the EOS coupling of the MCM model more robustly. Results are presented for both the CTH MCM model predictions and the experimental testing. The primary comparison metrics evaluated are the predicted and observed damage extent, overall damage pattern, and residual velocity of the projectile.

Determination of anisotropic mechanical properties of G-10 composite via Direct Strain Imaging

The mechanical properties of the glass-epoxy composite material known as “G-10,” which is primarily used for electrical insulation purposes in electromechanical systems, have long been a topic of uncertainty and controversy. In the present paper, we demonstrate the application of an experimental methodology that exploits the Direct Strain Imaging (DSI) full field method to fully assess the elastic anisotropic mechanical properties of G-10. Tension and compression experiments were conducted for three distinct inclinations of the specimen orthotropic axes relative to the loading directions, while strain and displacement were monitored at relevant locations on the specimens via digital image capturing and subsequent application of DSI. Based on these experiments, we present the stress-strain experimental data, the associated data post processing, the engineering properties, the anisotropic compliance matrix and the ultimate strength properties of the G-10 composite material. Confidence bounds on the material properties based on the results from repeated tests on identical specimens are also reported.

English

English

Size effect in uncracked and pre-cracked reinforced concrete beams shear-strengthened with composite jackets

The paper deals with the size effect on shear behaviour of reinforced concrete beams strengthened with fiber reinforced polymer jackets. Continuous U-jackets were made of glass or carbon fiber fabrics and epoxy composite materials. Twelve uncracked or pre-cracked strengthened reinforced concrete beams and six beams without strengthening, all of them in 6 different sizes, were tested. The results indicate that fabric-epoxy continuous U-jackets have reduced the brittleness of the shear failure of beams, tensile strains in stirrups, and, in a significant way, also the width of shear cracks at the failure state. Although similar strengthening was used for both, uncracked and pre-cracked beams, activation of jackets significantly differed. While jacket strains and their strengthening effectiveness were affected by the sizes of uncracked, retrofitted beams, they remained almost constant in pre-cracked, repaired beams of varying sizes. In contrast to repaired beams, stirrups in retrofitted beams did not yield at failure. Degree of strengthening, defined as the ratio of strengthened-to-unstrengthened beam shear capacities, was studied. It was found out that consideration of the degree of strengthening would provide relations reflecting real behaviour of reinforced concrete beams strengthened with fiber reinforced polymer U-jackets or U-jacketed strips.

Micromechanical fracture analysis of laminated glass-epoxy composite material tested by bending

The object and purpose of this work is the micromechanical analysis of failures caused by mechanical tests of laminate glass-epoxy composite material in bending. The structure of glass-epoxy composite material is a glass fabric 280 g / m2, 'twill weave', width 100 cm, type - Interglas 92125 and epoxy resin type MGS L-135. Samples are shaped manual method with 35% volume fraction of fibers. Previous mechanical tests were obtained relevant data on tensile and flexural mechanical properties. By analyzing the images of fracture surfaces of larger magnification with a scanning electron microscope (SEM) will be performed micromechanical analysis that will lead to the knowledge of the mechanisms of damage and crack growth to final fracture in action bending loads.

Numerical Simulation on Damage Mode Evolution in Composite Laminate

The present work follows numerous numerical simulation on the stress field analysis in a cracked cross-ply laminate. These results lead us to elaborate an energy criterion. This criterion is based on the computation of the partial strain energy release rate associated with all the three damage types: transverse cracking, longitudinal cracking and delamination. The related criterion, linear fracture based approach, is used to predict and describe the initiation of the different damage mechanisms. With this approach the influence of the nature of the material constituent on the damage mechanism is computed. We also give an assessment of the strain energy release rates associated with each damage mode. This criterion checked on glass-epoxy and graphite-epoxy composite materials will now be used in future research on new bio-based composite in the laboratory.

Fiber nonlinear predictive model for combined bending-compression loading of an orthogonal plane weave composite laminate structure

To increase understanding of damage evolution in advanced composite material systems, a series of large deflection bending-compression experiments and model predictions have been performed for a woven glass-epoxy composite material system. Theoretical developments employing both small and large deformation models and computational studies are performed. Results (a) show that the Euler–Bernoulli beam theory for small deformations is adequate to describe the shape and deformations when the axial and transverse displacement are quite small, (b) show that a modified Drucker's equation effectively extends the theory prediction to the large deformation region, providing an accurate estimate for the buckling load, the post-buckling axial load-axial displacement response of the specimen and the axial strain along the beam centerline, even in the presence of observed anticlastic (double) specimen curvature near mid-length for all fiber angles (that is not modeled), and (c) for the first time the quantities σeff – ɛeff are shown to be appropriate parameters to correlate the material response on both the compression and tension surfaces of a beam-compression specimen in the range 0 ≤ ɛeff < 0.005 as the specimen undergoes combined bending-compression loading. In addition, computational studies indicate that the experimental σeff – ɛeff results are in reasonable quantitative agreement with unwoven laminate finite element simulation predictions in the range 0 ≤ ɛeff < 0.010, with the effect of the woven structure appearing to provide the key constraint for various fiber angles that leads to the observed consistency in the experimental σeff – ɛeff results on both surfaces.

Tension mechanical properties of recycled glass-epoxy composite material

The significance of composite materials and their applications are mainly due to their good properties. This imposes the need for their recycling, thus extending their lifetime. Once used composite material will be disposed as a waste at the end of it service life. After recycling, this kind of waste can be used as raw materials for the production of same material, which raises their applicability. This indicates a great importance of recycling as a method of the renowal of composite materials. This study represents a contribution to the field of mechanical properties of the recycled composite materials. The tension mechanical properties (tensile strength and modulus of elasticity) of once used and disposed glass-epoxy composite material were compared before and after the recycling. The obtained results from mechanical tests confirmed that the applied recycling method was suitable for glass-epoxy composite materials. In respect to the tensile strength and modulus of elasticity it can be further assessed the possibility of use of recycled glass-epoxy composite materials.

Experimental Investigations on Some Aspects of Machinability in Drilling of Glass Epoxy Polymer Composites

The glass epoxy polymer composites are extensively used for a wide variety of applications in aerospace, automotive, and chemical industries due to an excellent property profile. Even though these composites are produced as near net shapes, the machining has to be performed in the final stage of production. Drilling is one of the most common machining processes used to install the fasteners for assembly of laminates. However, the drilling of these composites is rather a difficult task due to the highly abrasive nature of reinforcement and hence there is a need to study the machining performance. An attempt has been made in this article to investigate the effects of spindle speed and feed on machinability aspects, namely, thrust force, hole surface roughness, and specific cutting coefficient during drilling of glass epoxy composites. The drilling experiments were performed as per full factorial design for both glass epoxy composites and silicon carbide-filled glass epoxy composite materials. The response surface methodology based mathematical models were developed for analyzing the effects of cutting conditions on machinability characteristics. The parametric analysis reveals that the silicon carbide-filled glass epoxy composite material provides better machinability compared to glass epoxy composite without the addition of filler.

Hybridization of carbon–glass epoxy composites: An approach to achieve low coefficient of thermal expansion at cryogenic temperatures

The paper is based on a study to develop carbon–glass epoxy hybrid composites with desirable thermal properties for applications at cryogenic temperatures. It analyzes the coefficient of thermal expansion of carbon–epoxy and glass–epoxy composite materials and compares it with the properties of carbon–glass epoxy hybrid composites in the temperature range 300 K to 125 K. Urethane modified epoxy matrix system is used to make the composite specimens suitable for use even for temperatures as low as 20 K. It is noted that the lay-up with 80% of carbon fibers in the total volume fraction of fibers oriented at 30° and 20% of glass fibers oriented at 0° yields near to zero coefficient of thermal expansion as the temperature is lowered from ambient to 125 K.