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Glass fiber reinforced polymer (GFRP) composite pipes are mostly used in transmission lines of submarine oil, natural gas, and chemical fluids. The alterations in mechanical characteristics of composite pipes used in submarine applications are of great importance to the lifespan of the material. Some important mechanical properties of composite materials are density and hardness value. In this study, the changes in the density and hardness values of GFRP composite pipes which were unexposed to seawater and exposed to seawater for 1, 2 and 3 months were investigated. As a result of the present study, it was deduced that the characteristics of the sample changed with the effect of seawater.

A micro-meso-macro analysis framework based on the multi-scale method was employed to analyse the mechanical behaviour of marine GFRP stiffened panels. The study aims to establish a procedure for assessing the impact of material composition and weave on the ultimate strength of GFRP stiffened panels. The ultimate strength assessment was an essential step in the design process, and the investigation of construction materials has a great benefit to the lightweight design of marine composite structures. The micro- and meso-scale RVE models of components used in GFRP materials are established, and their failure criteria and stiffness degradation models are created using the user-defined material subroutine VUMAT in ABAQUS. The equivalent material properties at the micro-scale (meso-scale) obtained by a homogenisation method are used to define the meso-scale (macro-scale) mechanical properties in the finite element analyses. The multi-scale method assesses the macro-mechanics of composites, and it is shown that the ultimate strength of GFRP stiffened panels is mainly determined by the failure of CSM fibre bundles and WR yarns. Parametric study of the meso-mechanics of composite materials can provide an analysis tool to obtain the optimal macro ultimate strength of the composite stiffened panel.

Background Fatigue failure criteria for fibre reinforced polymer composites used in the design of marine structures are based on the micromechanical behaviour (e.g. stiffness properties) of their constituents. In the literature, there is a lack of information regarding the stiffness degradation of fibres, polymer matrix and fibre/matrix interface regions affected by environmental fatigue. Objective The aim of present study is to characterize the stiffness properties of composite constituents using the nanoindentation technique when fatigue failure of composites is due to the combined effect of sea water exposure and cyclic mechanical loads. Methods In the present study, the nanoindentation technique was used to characterize the stiffness properties of composite constituents where the effects of neighbouring phases, material pile up and viscoplasticity properties of the polymer matrix are corrected by finite element simulation. Results The use of finite element simulation in conjunction with nanoindentation test data, results in more accurate estimation of projected indented area which is required for measuring the properties of composite constituents. In addition, finite element simulation provides a greater understanding of the stress transfer between composite constituents during the nanoindentation process. Conclusions Results of nanoindentation testing on the composite microstructure of environmentally fatigue failed composite test coupons establish a strong link to the stiffness degradation of the fiber/matrix interface regions, verifying the degradation of composite constituents identified by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis.

Purpose Drilling holes in composite materials is a complex and challenging process because of their intrinsic anisotropic characteristics and unevenness compared to conventional metals. Hybridization of composites enhances the strength and hardness of the material but makes it more difficult to drill a hole in it. The purpose of this study is to optimize the drilling to minimize the delamination and taperness of hybrid glass fiber reinforced plastic (GFRP)/Al2O3 composites. Design/methodology/approach The present study investigates the impact of drilling parameters on delamination of the drilled hole and the taperness of the hole on hybrid GFRP/Al2O3. Optimum drilling conditions for minimizing delamination and taperness of the hole are determined to enhance the hole quality. Feed (f), speed (N) and drill diameter (D) are the parameters taken into consideration for drilling operation. By applying Taguchi’s signal-to-noise ratio analysis, process parameters have been optimized to reduce the delamination and taperness of holes on Hybrid GFRP/Al2O3 composites. The effect of process parameters was analyzed using the analysis of variance method. Findings The investigational results confirmed that the delamination is positively affected by speed, drill diameter and feed rate. Also, the taperness of the hole is positively affected by the drill diameter. Regression-based models were developed to predict the delamination and taperness of the hole matched with the experimental results, which are attained with an order of 95% and 97%. Originality/value Minimum delamination was found at the optimum condition of drill diameter 10 mm, feed at 0.225 mm/rev and the speed at 151 rpm and minimum taperness were found at the optimum condition of drill diameter 10 mm, feed at level 0.3 mm/rev and speed at 86 rpm for hybrid laminate composite (S-glass+ GFRP/Al2O3) were evaluated.

In this article, a genetic algorithm (GA) is used for optimizing a metamodel of surface roughness (R_a ) in drilling glass-fibre reinforced plastic (GFRP) composites. A response surface methodology (RSM) based three levels (-1, 0, 1) design of experiments is used for developing the metamodel. Analysis of variance (ANOVA) is undertaken to determine the importance of each process parameter in the developed metamodel. Subsequently, after detailed metamodel adequacy checks, the insignificant terms are dropped to make the established metamodel more rigorous and make accurate predictions. A sensitivity analysis of the independent variables on the output response helps in determining the most influential parameters. It is observed that f is the most crucial parameter, followed by the t and D. The optimization results depict that the R_a increases as the f increases and a minor value of drill diameter is the most appropriate to attain minimum surface roughness. Finally, a robustness test of the predicted GA solution is carried out.

In this study, numerically and experimentally the dynamic characteristics of graphene-reinforced glass fiber–reinforced polymer hybrid uniform and thickness tapered laminated composite beams were investigated. First, the graphene-epoxy nanocomposite solution without and with 0.25, 0.50, and 0.75 wt.% of graphene reinforcement is prepared by the heat shearing technique and then used for the fabrication of glass fiber–reinforced polymer hybrid uniform and thickness tapered composite beams using the hand lay-up method. The elastic properties of the hybrid beams were evaluated using the impulse excitation of vibration technique (ASTM E1876-15) under elevated temperature. Further, the numerical and experimental modal analysis of the hybrid beams with uniform and tapered configurations were conducted with variation in wt.% of graphene particles under fixed-fixed and fixed–free end supports. The results reveal that the natural frequencies of the glass fiber–reinforced polymer hybrid uniform and tapered configurations with 0.25 wt.% of graphene are greater than those of the glass fiber–reinforced polymer beams without graphene reinforcement and observed lesser for 0.5 and 0.75 wt.% of graphene under fixed-fixed and fixed-free end supports, respectively, due to unavoidable agglomeration effects. Furthermore, the parametric study was performed with the influence of weight fraction of graphene and temperature on the transverse response of the tapered composite beam. Hence, it can be concluded that the use of graphene filler in the glass fiber–reinforced polymer composites in the tapered composite beams improves the bending natural frequencies significantly when the weight fraction of the graphene is used lesser as agglomeration is unavoidable in practical condition. Therefore, the comprehensive numerical and experimental work presented in this study will be useful to the designers while using graphene fillers to improve the bending characteristics of the tapered composite beams.

Wind energy is one prominent solution to mitigate the increasing energy demand. Composite materials are exhibiting enormous advantages with their tailor-made properties. With the development of renewable energy power generation, the issue of blade vibration reduction has gotten a lot of technical attention. It has become an essential technique for blade analysis and design. Various attempts were recorded to reduce the vibration of the blade and enhance its natural frequencies. The present work aimed to characterize the mechanical properties of the GFRP composite material and the GFRP composite with 4wt% of the MWCNT filler. Both hybrid and non-hybrid GFRP are subjected to characterization, with the same free vibration analysis of NACA 63-415 wind turbine blades being analyzed. The study results revealed that the hybrid GFRP has more stiffness, which causes it to enhance the free vibrations in all mode shapes.

Adhesively bonded interfaces of glass fiber– reinforced plastics (GFRP) composite to rubber and rubber to propellant were investigated for planar interfacial defects with a spatial resolution of 100 μm. Single-sided low-field nuclear magnetic resonance (NMR) with a magnetic field strength of 0.3 T (12.88 MHz proton frequency) has been used for noninvasive inspection of planar defects in GFRP-based multilayered composite structures. Further, in this paper, the application of low-field NMR for adhesive liner thickness measurement is also demonstrated. The investigation revealed applicability of single-sided low-field NMR for onsite field applications. Results were compared with other nondestructive evaluation (NDE) techniques: acousto-ultrasonic and radiographic testing (RT). It is observed that single-sided low-field NMR is an excellent NDE tool to study adhesive bonds and defects such as debonding, variations in thickness to accuracies ranging from 50 to 200 μm, and degradation. In comparison with the acousto-ultrasonic technique and RT, single-sided low-field NMR is observed to be more sensitive.

Pultruded glass-fibre reinforced polymer (pGFRP) composites are classified as lightweight material, which exhibit high strength-to-weight ratio for structural usage. This composite material has been applied as cross-arm members in transmission towers due to its ability in thermal and electrical insulation. However, the influence of the stacking sequence of pGFRP composite on its mechanical performance has not been fully covered in the literature to explain the long-term durability of the current cross-arm designs. The study expected to evaluate five fiber layers with various stacking sequences in terms of quasi-static and creep tests in a four-point bending mode. The creep test was performed for 1440 h (60 days). These composites were fabricated using the pultrusion process in the form of a square hollow structure. Later, it was cut into composite coupons with various sizes depending on the test conducted. The results showed that nine layers with 0°/45°/0°/−45°/0°/−45°/0°/45°/0° had the ultimate flexural strength. This stacking sequence configurations seemed to be optimally manufactured in continuous roving fibre by alternating between 0° and ±45° fiber orientations. Additionally, the S-9 pGFRP composite sample showed that it had a low-creep deflection with high elastic and apparent creep moduli in 1440 h. In terms of strength reduction factor, this configuration was recorded as the highest. The findings showed that the nine layers of pGFRP composites with alternation of 0° and ±45° fiber orientations were highly suitable for structural application at transmission towers for a long-term operation.

Investigation and analysis of the dynamic behavior of composite materials and their failure resistance are essential. The main aim of this study is to investigate the improvement of impact properties of incorporated glass fiber reinforced polymer (GFRP) composite specimens with various loading of nanoclay and nanosilica in a corrosive environment. After fabrication of samples by hand layup method, all of them were immersed in 5 wt. % of sulfuric acid solution for 0, 1 and 3 months. As the immersion time increased, the specimens containing nanosilica absorbed more water than the other samples. The force-displacement, force-time and energy-time diagrams showed the superiority of filled composites with nanoparticles over the pure sample in all immersion periods. Low-velocity impact (LVI) test results of specimens containing nanoclay showed a better behavior and with the addition of 5 wt. % of nanoclay, the impact force increased by 15.72% and the displacement decreased by 5.26%. Also, in these samples, the energy absorption rate decreased by 17.15%, which was associated with a reduction in the damage rate. After immersion of specimens in different times, specimens containing 5 wt. % of nanoclay had better strength than other samples and maintained their superior properties. The obtained results illustrated that the addition of 1 and 3 wt. % of nanosilica had no specific effect on the improvement of impact properties. Finally, incorporated GPRP composites with 3 wt. % of nanoparticles were simulated using LS-DYNA software and the experimental and numerical results were compared to investigate their accordance.

In this paper, we have investigated the damages of glass fiber reinforced plastic (GFRP) composite tubes under the effect of low-velocity impact (LVI) at cryogenic environment conditions and room temperature. A GFRP composite tube consists of 6 layered E-glass/epoxy samples with a ± 55° winding angle, which produced by the filament winding method. Composite tubes either at room temperature or conditioned by liquid nitrogen at different temperature values (273 K, 223 K, 173 K, and 77 K) were impacted at 5, 7.5, and 10 J. Also, force-time and force-displacement graphs were plotted. The damaged regions of the samples were scrutinized. The damage areas of the GFRP composite tubes were smaller as the temperature decreased. However, the energy absorbed at low-temperature conditions was slightly higher than that absorbed in room temperature. Besides, no micro-cracks developed in the composite tubes after cryogenic conditioning.

Millions of tons of glass fiber reinforced polymer (GFRP) waste have been steadily generated from end-of-life wind turbine blades and many other GFRP composites prevalent in everyday life, with limited reuse options. Recycled GFRP (rGFRP) by mechanical processing could be used in mortar and concrete as fibers or fillers. Maintaining the composite nature of rGFRP with a high fiber content is paramount to increased mechanical properties for concrete. In this study, high-modulus rGFRP particles were produced in three small, medium, and large relative sizes by hammer milling and screening. Small and medium rGFRPs were used in 1, 2, 3%, and large rGFRP in 1, 2, 3, 5, and 7% volume replacing sand in mortar. Almost all rGFRP-mortars showed significant improvement in flexural strength with their high modulus. All size groups of rGFRP progressively showed higher fracture toughness at higher amounts. Within the large group, 5 and 7%Vol had flexural toughness of about 2.00J compared with 0.75J of 3%Vol. Large rGFRP at 5 and 7%Vol offered nearly 60% and 70% 28 day equivalent flexural ratio. Micrographs of rGFRP–matrix interfaces from fracture faces showed rGFRP was well embedded within the matrix, provided bridging and deflecting of microcracks, and failed in pullout or rupture modes. Fly ash and silica fume had a positive synergy with 3%Vol large rGFRP and improved its flexural toughness from 0.75J to 1.12 and 1.00J, respectively. The investigated recycling process and sizes of rGFRP shreds showed great promise in this exploratory study and are recommended for further evaluation for highway and bridge concrete.

In this paper, an attempt is made to optimize the control parameters for the minimization of specific energy consumption in turning GFRP composites using particle swarm optimization (PSO).Optimization of specific energy consumption in machining is helpful to evaluate the process energy characteristics and also facilitates choosing the best control parameters for energy saving. The control parameters considered are cutting speed, feed, depth of cut and fiber orientation angle. Experiments are planned and executed according to Taguchi’s L25 orthogonal array in the design of experiments on an all geared lathe with PCD cutting tool insert. A quadratic predictive model was developed for specific energy consumption using RSM and the optimal combinations of control parameters were determined using PSO. The Predicted results from PSO show that there is an improvement in MRR by 46.44% and a reduction in SEC by 33.69%. From the confirmative experimental results, it is observed that PSO algorithm has a powerful global search ability to solve the optimization problem.

Delamination is definitely an important topic in the area of composite structures as it progressively worsens the mechanical performance of fiber-reinforced polymer composite structures in its service period. The detection and severity analysis of delaminations in engineering areas like the aviation industry is vital for safety and economic considerations. The existence of delaminations varies the vibration characteristics such as natural frequencies, mode shapes, etc. of composites and hence this indication can be effectively used for locating and quantifying the delaminations. The changes in vibration characteristics are considered as inputs for the inverse problem to determine the location and size of delaminations. In this paper Artificial Neural Network (ANN) is used for delamination evaluationof glass fiber-reinforced composite beams using natural frequency as typical vibration parameter. The Finite Element Analysis is used for generating the required dataset for ANN. The frequency-based delamination prediction technique is validated by finite element models and experimental modal analysis. The results indicate that the ANN-based back propagation algorithm can predict the location and size of delaminations in composites with good accuracy for numerical natural frequency data but the accuracy is comparitivelyless for experimental natural frequency data.

The fiber reinforced polymer (FRP) bars are used in hollow concrete columns (HCCs) to alleviate the steel-reinforcement corrosion problem and to make an efficient and lightweight structure. The presented study has endeavored to numerically and theoretically explore the structural behavior of hollow concrete columns (HCCs) reinforced with glass fiber reinforced polymer (GFRP) bars and spirals. Six HCCs were simulated in a commercial finite element software ABAQUS 6.14. The control finite element model (FEM) was calibrated for various variables of HCCs using the previous experimental testing results. The complex nonlinear behavior of concrete was defined using the concrete damaged plastic model (CDPM) and the behavior of GFRP bars was considered as linear elastic. The proposed FEM portrayed a close correlation with the testing results of HCCs. Moreover, the different empirical models were proposed for predicting the two-peak loading behavior of FRP-reinforced HCCs based on a large database constructed from the previous research.

Hole making is an important phase in composite machining as structural applications of composites require assemblage. To do so, abrasive waterjet machining (AWM) is recommended by several fabricato...

Whereas most previous studies have focused on improving the penetration resistance of Shear Thickening Fluids (STFs) treated composites, in this study, the dynamic compressive response of single and multi-ply 3 D E-Glass Fiber Reinforced Polymer (GFRP) composites with the STF matrix was investigated by using a drop-weight low-velocity impact test. The experimental results revealed the STF improved the compressive and cushioning performance of the composites such that with increasing its concentration, further improvement was observed. The five-ply composite containing the STF of 30 wt% silica nanoparticles and 1 wt% carbon nanotubes (CNTs) reduced the applied peak force by 56% and 26% compared to a steel plate and five-ply neat samples, respectively. A series of repeated impacts was performed, and it was found that the performance of high-concentration composites is further decreased under this type of loading.

Glass fiber reinforced polymer composites were prepared by different manufacturing technology and are extensively used for various applications. In recent times more research is carried out on glass fiber reinforced composites owing to their excellent mechanical properties. This study deals with the analysis of glass fiber reinforced polymer composites manufactured by different types of glasses, Matrix materials prepared using different production technologies. Glass fibers possesses good properties such as high strength, flexibility, stiffness, durability etc. With an increase in the content of glass fiber volume the properties of GFRP composites were improved. The mechanical & thermal attributes of various polymer composites reinforced by glass fiber when subjected to mechanical loading have been studied and reported.

Mechanical fastening technique plays a vital role in aerospace and automotive industries because of their ability to make large assemblies in composite materials. However, it is challenging to drill holes in composite materials which are free of defects. Thus, the paper investigates the influence of glass fiber content within the GFRP composites during the drilling operation. Different hole quality parameters such as roundness deviation, delamination, fiber pull-out, taper angle were observed as they contribute to better machinability and improved surface quality while drilling. A radial drilling machine was used to perform the drilling process on the composites keeping a constant rotational speed and feed rate. Only fiber weight percentages were varied. The experimental results exhibited that the drilled surface quality is closely related to the percentage of the fiber content of the specimens. In terms of roundness deviation, delamination, fiber pull-out, and taper angle, a better result is achieved for the composite specimen having comparatively lower glass fiber content.

In this experimental investigation, internal scarf repaired composite laminate with a scarf angle ranging from 10° to 18° were examined under low velocity impact. The comparison between simulation and experiment was analyzed based on parameters like maximum contact force, maximum absorbed energy, maximum displacement, depth, damage area, and impact time duration. The residual tensile strength revealed that when the scarf angle was large, it performed best with less absorbed energy and less damage, the reasons for it could be attributed to less material removal from the parent laminate. Furthermore, it was observed that repaired composite with 18° scarf angle recovered 95.71% of the initial tensile strength. Thus it is safely concluded that increasing the scarf angle increases the residual tensile load bearing capacity.

The aerospace and automobile sectors are widely utilized the polymer composites. The composite materials, like unidirectional glass fiber reinforced polymer (UD-GFRP), is difficult to machine due to its anisotropic that is non-homogeneous character and such material requires special cutting tools. The proposed work is going to examine the tool wear, quality of the surface and forces generated in the various stages of inputs given to the machining of unidirectional glass fiber reinforced polymer (UD-GFRP) composites. The assessment of the machining incorporates tool wear investigations, surface roughness investigations and quality of material by varying input parameters. The Taguchi optimization technique with experimental design of L9 orthogonal array employed. The parameters range identified by trail runs and observations of conducted machining utilized for optimization. The Turning process parameters of cutting velocity or speed, rate of tool movement or feed rate and cutting depth on composite part or depth of cut were considered. The other factors, like tool material i.e., Poly-Crystalline Diamond (PCD) tool, its cutting regime (dry), profile of cutting tool are considered as constant parameters. The responses, like tool wear, surface finish, and cutting force, were measured against various input parameters, while machining the composite (UD-GFRP) composite part. The objective of this research is to establish relationship among various operating parameters to achieve desired results. That is major focus of the work on the economic condition for getting better values based on setting of input parameters.

This paper presents the results of an experimental study that investigates the compression behavior of concrete and evaluates the effect of hybrid reinforcement by multiple geometries, and total and partial confinement, using CFRP and GFRP composite materials. A total of nine (09) variants of concrete cylindrical specimens, including one (01) variant of unconfined concrete and eight (08) variants of confined concrete with different geometries were subjected to axial load compression. The objectives of this study were to verify the applicability and effectiveness of partial and total confinement to improve the behavior of concrete, evaluate the effect of the hybrid confinement used, and obtain a typical reinforced model. The results obtained clearly show the effectiveness of the hybrid confinement and partially confined concrete in improving the compressive strength and deformation of the concrete, so it is possible to replace CFRP total confinement by partially confined concrete with two CFRP layers or by a hybrid confinement with a CFRP layer in the central zone and GFRP layers on the top and bottom of the specimen.

In this paper, the size effect in unidirectional (UD) laminated glass-fibre reinforced plastic (GFRP) composites subjected to quasi-static bending loading was investigated: the sensitivity of a specimen’s mechanical behaviour and failure mechanism to its geometry was studied. Composite beams with different numbers of 0° unidirectional plies were tested and their post-deformation structures were analysed microscopically. In the subsequent simulations, the intraply damage was modelled using continuum damage mechanics, implemented as a user-defined VUMAT subroutine in ABAQUS/Explicit, while cohesive zone elements were employed to characterize the delamination between different plies. It was observed that the flexural failure triggered the multiple delaminations; their location was studied. The influence of the size effect on the bending response of the UD composite beams was analysed in depth. The findings of the current study can be used to design modern structures made of composite materials.

The effects of outdoor ageing on various compositions of glass fibre reinforced plastic (GFRP) composites were studied. Changes in the interlaminar shear strength (ILSS) of hand-laid samples with 50–60 wt.% of fibre were determined by three-point bending and glass transition temperature (Tg) measurements. SEM analysis was carried out for exploring the mode of failure. The moisture ingress rate and extent were concentration-dependent at first, but became increasingly dependent on the fibre-matrix interfacial area. The ILSS initially fluctuated and then showed a decreasing trend with time, especially for the higher fibre concentrations. ILSS variations were zigzag initially and showed a lowering trend after the initial periods. Rate of lowering of ILSS was the highest for samples with the highest fraction reinforcement. Weight fraction reinforcement didn’t have any significant effect on the Tg variations. SEM fractograph revealed excessive fracture and fragmentation for the composite samples with the highest weight percentage reinforcement.

Fatigue of structural adhesives has been investigated through joints and a little number of works investigate bulk adhesive behaviour itself. Aerospace and automotive engineering focuses more on joint configuration studies, which are correlated with practical applications. Previous works showed that for thin adhesive joints, material properties measured by bulk adhesive testing and joint testing are similar despite the triaxial stress states developing in the adhesive bondlines. However, with the introduction of structural adhesives in construction industry, thicker bondlines have emerged where the bulk adhesive material dominates the joint behaviour. This review work summarises works on the fatigue of bulk structural adhesives used mainly in the construction industry investigating structural adhesives fatigue behaviour either through experiment on joints or on bulk adhesive specimens. The work focuses on thick adhesive bondlines in joints, and discusses the controversy that is over whether adhesive properties from joints or from bulk material should be used.

There are different process parameters of bonding joints in the literature. The main objective of the paper was to investigate the effects of bonding angle, composite lay-up sequences and adherend thickness on failure load of adhesively bonded joints under tensile load. For this aim, the joint has four types of the bonding angles 30°, 45°, 60° and 75°. Composite materials have three different lay-up sequences and various thicknesses. The bonding angle, adherend thickness and composite lay-up sequences lead to an increase of the failure load. Moreover, artificial neural network that utilized Levenberg-Marquardt algorithm model was used to predict failure load of bonding joints. Mean square error was put into account to evaluate productivity of ANN estimation model. Experimental results have been consistent with the predicted results obtained with ANN for training, validation and testing data set at a rate of 0.998, 0.997 and 0.998 respectively.

Fiber reinforced polymer composites have paved the way for the evolution of the engineering materials. Glass fiber reinforced polymer (GFRP) has become one of the most promising materials among the novel composites due to its low price and high performance. Here, the GFRP composite in investigated by fill atomistic molecular dynamics, which contains the epoxy matrix and amorphous silica substrate. The degradation in chloride environment is revealed through the interfacial interactions, the structural changes of the epoxy matrix and hydrogen bonding in the composites. Compared to dry and aqueous environment, the simulation results show that chloride environment leads to the worst deterioration of interfacial adhesion, which correlates with structural and mechanical degradation of bonded interface, as indicated by the decreased epoxy density close to interface. It is indicated by examining the nano-structures of the interface during the pulling process that the chloride environment hinders the formation of intramolecular and intermolecular hydrogen bonds in the GFRP composites. These findings indicate the deterioration towards bond and matrix is critical in the presence of the chloride environment, which provides the fundamental insight for designing and predicting performance degradation of macroscopic GFRP composites in the marine application.

This paper aims to analyze the multi-effects of the glass fiber reinforced polymer (GFRP) composite patch to repair the inclined cracked 2420-T3 aluminum plate. Three-dimensional finite element method (FEM) was used to study the effect of GFRP composite patch with different stacking composite laminate sequence, [0°]4, [90o]4, [45o]4, [0o/45o]2s and [0°/90°]4s on the crack driving force, J-integral, of inclined cracked 2420-T3 aluminum plate. Furthermore, the effects of patch geometry, number of layers, single or double side patch and crack incline angle are described. The present results show that the patch has a high effect in case of a crack in pure mode I. Furthermore, the effectiveness of the composite patch is increasing with the crack length increases. Moreover, the efficiency of the composite patch has a high effect by changing the fiber orientation, the number of layers, and the single or double side patch.

The present work deals with temperature effects and parametric optimization in the drilling of continuous glass fiber reinforced epoxy composite. Drilling ability was examined operating a drilling system with different drill bits, feed rate, and spindle speed parameters. The investigation was performed by changing the tool and composite interface. Drilling experiments were carried out under the dry condition. Thrust force and drilling temperatures were measured using dynamometer and thermal camera. Peel-up and push-out delamination were evaluated using an image analyzing tool. Results show that the tribo-mechanical behavior of the drilling operation is affected at different levels by tool coating. This behavior is related to the intrinsic friction properties of coating nature. Response surface methodology was used in the evaluation of experiment results. The feed rate of 0.13 mm/rev, spindle speed of 2425 rpm and HSS-TiN drill bit are found as an optimum drilling parameters and drill type.

Glass fiber-reinforced epoxy composite pipes are used in submarine applications, natural gas, and oil transportation lines, transfer of chemical liquids. Especially in the transport of pressurized fluids, changes in the strength of the pipes are important. The corrosive effect of seawater has an important impact on the mechanical properties of the composite material. In particular, the alteration in hoop tensile strength is one of the issues to be investigated. In this experimental study, glass fiber-reinforced epoxy resin composite pipes were exposed to the seawater aging process for different time periods (1, 2 and 3 months) in order to determine the effects of seawater absorption behavior on hoop tensile strength. Hoop tensile strength test was realized in accordance with ASTM D2290 Procedure A. As a result of this work, the average tensile strength values of the composite pipes decreased as the waiting times in seawater increased.

In this study, a new low-velocity shear impact test was introduced to carefully investigate the resistance of 3D E-glass fiber reinforced polymer composites with shear thickening fluid matrix. The shear thickening fluids were prepared by dispersing silica nano-particles in polyethylene glycol. Pure shear thickening fluid was modified by treating the silica surface with (3-Aminopropyl) triethoxysilane. Despite the low-velocity shear impact test, various experimental tests such as yarn pull-out, quasi-static puncture, flexibility and thickness tests were carried out to study the mechanical behavior of the composites. Results revealed the treated shear thickening fluid up to 60 wt% improves the performance of the impregnated samples against the yarn pull-out and puncture tests by 353% and 45%, respectively, and their shear impact resistance by 130% compared to the neat cases without noticeably affecting the fabric flexibility.

Low-velocity impact performance of notched glass fiber reinforced plastic composites repaired by bonding external composite patches was investigated by experimental and numerical methods. Various patches of different fiber materials such as carbon and glass fiber and thickness were considered under different impact energy levels. The continuum damage mechanics based on a dynamic progressive damage model was using to build the finite element model and cohesive elements were used between the composite patch and notched composite plate. Five different failure criteria based on three-dimensional Hashin damage models were implemented by the explicit finite element subroutine ABAQUS-VUMAT with degradation model and used to compare experimental damage areas. The experimental contact force, kinetic energy histories, and experimental damage areas were calculated and compared the numerical ones. While the experimental data confirm the efficiency of the proposed model, they show consistent results with the numerical model. Finally, using the composite patch is succeeded to avoid impact damage. This research provides fundamental support for the appropriate selection of external composite patch type and use of the degradation model with different failure model to achieve high-efficiency simulation under impact loading.

Local stress concentration occurs when faults are present in pipelines under pressure. An example of such defects is the problem of corrosion caused by the environment in the field of pipeline installation. In the first part of this paper, we attempt to model the corrosion in the hemi-ellipsoidal form in order to study the locations of stress concentration in the specimens by several experimental cases and their influence on the stress resistance. The Gurson-Tvergaard-Needleman (GTN) mesoscopic damage model is used to simulate the specimens with good accuracy. In the second part, the investigation is extended to a pipe under static pressure with and without the presence of a glass fibre reinforced polymer (GFRP) composite patch. The maximum stress and percent stress reduction in a defected pipe with a hemi-ellipsoidal defect are determined using a 3D finite element model. This part examines the impact of the geometry of the composite patches on the percentage reduction of the maximum stresses in a section of pipeline subjected to static pressure. In the third part, the stresses and the percentage reduction in the maximum stresses are predicted using an artificial neural network (ANN). An inverse problem using ANN and Jaya algorithm is proposed to predict the group level of different sizes of defects under composite patches based on the maximum stress and percentage reduction of stress that the pipe withstands. The new method relates directly to real-world pipeline construction and repair applications. It could be also used for structural safety monitoring.

The article presents the results of experimental studies determining the influence of the type of adhesive on the static strength properties of the Glass Fiber Reinforced Polymer (GFRP) composite joint determined on the basis of the T-peel test. As part of the static tests on peeling joints, a comparison of peak load and stiffness for individual joints was made. The fracture surfaces were also analyzed, showing various failure mechanisms. It was shown that the variant of joints made with the Enguard BP72A polyester adhesive was characterized by the highest strength properties with a mean peak load of 836.73 N.

The paper proposes to present the results of the evaluation of glass fiber reinforced plastics (GFRP) used in the construction of wind turbine blades. In a wind turbine, the blades are the most exposed to damages and the defects which appear are various and are connected with the type of manufacture, simple/complex loading, environmental conditions etc. In order to increase the lifetime span and to analyze the degradation phenomena during the materials functioning, destructive evaluation tests are performed to determine the mechanical property, by testing pure shear on specimens Iosipescu, from GFRP with woven reinforcement at [± 45°] and [0°/90°], with the shear fixture, endowment of Technical University Gh.Asachi Iasi.

A comparative study on the tribological properties of GFRP laminated composites containing MWCNTs, graphene and graphene-MWCNT mixture under different conditions is presented. The samples comprised of neat GFRP laminates and GFRP laminates further filled with0.1 wt. % graphene, 0.1 wt. % MWCNT and hybrid 0.05 wt. % graphene and 0.05 wt. % MWCNT mixture. The tests were conducted under three different applied loads of 40, 80 and 120N and sliding velocities of 0.98 and 1.96 m/s. Weight of specimen was taken before and after the experiments and to calculate the wear in terms of weight loss. The experiments showed that graphene filled GFRP composite has lowest coefficient of friction value, whereas the MWCNT reinforced GFRP laminate has the highest resistance against wear

Aerospace structural components are made by adhesively bonded layers of different materials for achieving specific properties for industrial applications. One such advanced structural material is made of glass fibre reinforced plastic (GFRP) composite. This is a layered engineered material with composite adhesively bonded to rubber to one of the surfaces. Such engineered materials can withstand structural, thermal and corrosive environments. GFRP composite have to be bonded with rubber using rubber solution or other adhesive to keep them structurally bonded. Any separation of these two layers will make the engineered structure redundant. In this paper, we report application of various NDE methods for evaluating bonded interfaces of engineered structural composite materials. Conventional methods such as X-ray radiography and ultrasonic (acousto-ultrasonic) methods were experimentally verified for identifying defects at the adhesively bonded interfaces. Disadvantages of these conventional methods were overcome by using advanced single sided nuclear magnetic resonance (NMR) technique. The use of low frequency single sided portable NMR for characterising defects at the adhesively bonded interfaces is discussed. In addition to the defect detection, application of NMR for measuring thickness of adhesive layers coated over rubber is also presented. Advantages of using NMR technique over other conventional methods is discussed.

The goal of this analysis is to establish an insubstantial, rising performance and rising firmness of glass fiber reinforced plastic (GFRP) composite and perform the boring operation with an inside breadth of 8 mm on the fabricated GFRP composite plate with cryogenically treated contort drill geometry instrument and untreated curve drill geometry apparatus. The reaction acquired is the delamination factor with the guide of digital representation investigation. The results reveal that penetrating the produced GFRP composite with a cryogenically treated tool demonstrated the optimal outcome.

This paper demonstrates the effect of small ply angle variation in tensile and compressive strength of woven Glass Fiber Reinforced Polymer (GFRP) composites. Four different plies of (0/90)4, (±5°)4, (±10°)4, (±15°)4 manufactured by hand lay-up followed by the press molding machine. Samples for the tensile and compressive tests were prepared according to ASTM D3039 and ASTM D3410 standards. Three samples of each laminate were tested on a Universal Testing Machine (UTM) at a steady crosshead speed of 1 mm/min. A digital microscope was used for tracking the sample damage pattern. It was observed that fiber orientation in laminates affects the tensile and compressive strength. Fibers ruptured during tensile testing of specimens and in compressive testing, samples failed due to the separation of longitudinal fibers. The experimental results showed that (0/90)4 ply showed the maximum tensile strength and compressive strength followed by (±5°)4, (±10°)4, (±15°)4. Weibull distribution analysis was used for statistical estimation of the tensile and compressive life of specimens.

Abrasive water jet machining (AWJM) is a non-conventional machining process, which is employed for difficult-to-machining of thin, hard and brittle materials. This experimental study reports the influence of process parameters on the surface roughness and dimensional accuracy when drilling of GFRP composites using abrasive water jet technique. In particular, investigated the effects of abrasive flow rate, pressure, standoff distance and fiber orientation on hole quality were examined. Experimental results revealed that standoff distance and fiber orientation has major effect on surface roughness and dimensional accuracy.

This study is based on the water absorption characteristics of Fiberglass reinforced and waste plastics filled hybrid polymer Composites. The fiberglass reinforced polymer Composites are mostly used in the making of boats making, car bodies, etc. As it is subjected to be in contact with water and salty atmosphere for the most of the days, it must have an enhanced water repulsive nature. Moisture absorption property is affected by the addition of fillers and reinforcement materials. This study reveals the optimized selection and composition of the reinforcements and fillers at which the composite exhibits a better water repulsive characteristics. For the making of composite, spray layup process is followed and the moisture absorption nature of the specimens are tested as per the ASTM standards. For optimization MINITAB17 software is utilized and the specimens are produced as per the L9 orthogonal array design in Taguchi method. The results were then optimized to get the minimum moisture absorption property. The optimized results show that the specimen with E type glass fibre, 55 wt℅ of glass fibre composition and 25 wt℅ of plastic waste particulate fillers and remaining binders have minimal water absorption characteristics. The results reveal that the selection of the glass fibre and percentage of the fillers added has more influence on the moisture absorption property of the composites

This paper presents two techniques of active thermography i.e. the pulsed thermography technique and the step heating technique. The aim of this article is to compare these two techniques and present the possibilities, advantages and limitations of their use in the context of non-destructive testing of composite materials. The experimental section presents the results of tests carried out on samples of the polymer composites reinforced with glass fiber.

In this research, the influence of the drilling process parameters; three cutters (end mill) of different diameters, three of cutting speeds and five of feed rates on the process responses, i.e. the surface roughness ( ) and the delamination factor ( ) of the drilled hole are studied. The two types of the used composites are GFRP and AL/SiCp. From the analysis of the results, the feed rate and the cutter diameter are had a large effect on surface roughness and delamination factor, while both of them are increased with the increase of cutter diameter and the used feed rates. The results of surface roughness and the delamination factor when drilling GFRP composite are bigger than that values of AL/SiCp composite at all used cutters, cutting speeds and all used feed rates. Also, from the results, using of cutting speed (2500 rpm), end mill of the small diameter ϕ 8mm and low feed rate (10mm/min) are suitable for drilling GFRP and AL/SiCp to get a better surface roughness of the resulted.

The surface roughness and the delamination are important difficulties in any drilling operation of (GFRP) composite materials. Both two elements cause structural integrity reduction and poor assembly as well as the potential for long-term performance deterioration. In this research, the optimization of drilling parameters using Taguchi technique, to obtain minimum both surface roughness (Ra) and the delamination factor (df). In addition, ANOVA uses to analyze the data obtained from the experiments and determine the optimal parameters in the drilling of GFRP composite materials. The results revealed that the delamination factor (df) increases with the increase of drilling speed (2250rpm-2750rpm) and increases with the increase of the feed rate (100mm/min to 125mm/min). Increasing the drilling speed and reducing feed rate can reduce the delamination factor (df) and the use of high feed rate and high spindle speed can be increasing the delamination factor (df) within the limits of specified speed and feed rates. The feed rate is the more influential factor on delamination than the other parameters. The results for very low feed rate i.e. 25mm/min and high drilling speed 2750 rpm show a clear decrease in surface roughness (Ra). Feed rate and drilling speed are the more influential factors on surface roughness (Ra) than the other parameters.

This paper presented a systematic approach toward localized failure inspection of internally pressurized laminated ellipsoidal woven composite domes. The domes were made of thin glass fiber reinforced polymer (GFRP) woven composite layups [0,0,0], [0,30,0], [0,45,0], and [0,75,0]. The analytical results demonstrated that the circumferential regions near meridian φ = 45° in prolate ellipsoidal domes and near meridian φ = 90° in oblate ellipsoidal domes sustain the highest deformation under internal pressure. This observation was then confirmed by the numerical and experimental results. In addition, the numerical and experimental results showed localized rather than uniform failure in those regions, irrespective of changes in laminate stacking sequence. It was observed that localized failure occurs since the woven fibers configuration in some areas of woven remains in initial geometry (square shape), while the rests are deformed into the rhombic shape. In other words, by moving along the circumferential direction from the area close to θ = 0° to θ = 45° and θ = 45° to θ = 90°, the shape of woven fibers gradually changes from square (strong area) to rhombic (weak area), and rhombic to square, respectively. Thus, to minimize failure pressure, the meridian region vulnerable to failure must initially be identified. Afterwards, the rhombic regions in the circumference corresponding to that meridian must be strengthened.