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Highlights This study investigated the fatigue behavior of glass fiber reinforced polymer composite and the changes in the physical properties and the structure of epoxy due to fatigue loading. Vacuum infusion process (VIP) was used to manufacture the glass fiber biaxial (0°, 90°) reinforced epoxy composite. The tensile strength of the fabricated composite was 420.1 MPa. Tensile‐tensile fatigue test was performed at 70%, 50%, 42%, and 35% of the tensile strength of fabricated composite. Damage mechanisms causing fatigue failure, namely, pull‐out, debonding, delamination, and matrix cracking were examined by scanning electron microscopy (SEM) fractography. Pull‐out of the fibers and debonding were more at the lower load level, while delamination and matrix cracking were more prevalent at the higher load level. Fourier transform infrared spectroscopy (FTIR) analysis revealed changes in the OH and CH stretching aliphatic peaks of the composite after fatigue loading. Decomposition temperature and the glass transition temperature of the epoxy in the composite also decreased due to the applied fatigue loading. Glass fiber reinforced polimer biaxial (0°, 90°) composite was manufactured by VIP technique Tensile‐tensile fatigue test was performed at 70%, 50%, 42% and 35% of the UTS SEM analysis was utilized to investigate fractography of fatigue failure Structural and physical properties in epoxy matrix was studied after fatigue Results showed changes in physical and structural properties of epoxy matrix [ABSTRACT FROM AUTHOR]

When creating lightweight structures to lower the rail vehicle's overall weight, composite materials with fiber reinforcements are the material of choice. Because of its excellent strength, low weight, high durability, stiffness, damping ability, flexural strength, resistance to wear and tear, impact resistance, indentation resistance, and corrosion resistance, composite materials. This study proposes to analyze the load and contact mechanic on the glass fiber reinforced polymers (GFRP) composite structural under tensile and flexural load. Tensile load 17.490 N was applied in 2 model, with Tab and without Tab. The flexural loading 669 N was applied in 6 models with the 3-load types and 2-contact mechanic types. The stress values and locations of the proposed finite elements analysis (FEA) modeling results were verified through experiments for tensile loads and flexural loads. The FEA modeling of GFRP composites under tensile load with tabs and without tabs have same the maximum stress location. The location at the outer surface of the grip splitter line. The stress 107 MPa on the gauge length area of FEA modeling and the experimental are same. FEA modelling under flexural loads, when using bonded contact shows that the location and value of stress concentration is not same as experimental. Using frictionless contact model have the value and location of maximum stress same as experimental. The FEA model 5 with Face load and frictionless mechanical contact has the stress concentration that is closest to the experimental results. By considering the type of load applied to the surface and the frictionless contact mechanics, FEA modeling can be used to predict the behavior of composite structures under bending loads. [ABSTRACT FROM AUTHOR]

The field of application of Glass Fiber Reinforced Polymer expands as well as the size of the component where composite material is applied. Due to the size limitation of the prepreg used, it is difficult to apply 1ply to large parts. Many studies have been reported on the bolt joint that assembles parts and parts for the joint area, butt and overlap design for joining dissimilar materials, and mechanical properties. Although the mechanical properties of the joint areas are important, studies on the microstructure are also needed. In this study, the microstructure was observed by controlling the type of subsidiary materials in the bagging process by applying prepregs of the same composition. It was found that the air and resin flow inside the prepreg acted differently depending on the type of subsidiary material. The flow of resin during curing was inferred from the influence of subsidiary materials and explained by connecting it with the microstructure. The behavior of the resin determined thickness, resin, and void contents of the composite. This flow affects voids in the joint area, causing differences in microstructure and mechanical properties. There was no significant difference in the tensile strength of the laminate specimens manufactured according to the process, but the minimum strength was found in the specimens containing many void contents. The joint specimen showed a decrease in strength as the void content increased. It was discussed that this reduced the adhesive force of the specimen due to the effect of the void generated in the joint area. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Three types of carboxyl‐functionalized multi‐walled carbon nanotubes (MWCNTs) were used to manufacture MWCNT‐modified laminates. The effects of the MWCNTs on the mode I interlaminar fracture toughness and the fracture propagation were investigated experimentally. Fractured surfaces were inspected with SEM micrographs to justify the effects of MWCNTs on the mode I fracture of the laminate. The short‐thin MWCNTs in a weight ratio of 0.3% increases mode I interlaminar fracture resistance of the laminate by about 2 times. The effects of long‐thin and long‐thick MWCNTs are quite low. Polymer crazing is the most important mechanism to improve interlaminar fracture properties. [ABSTRACT FROM AUTHOR]

Composite material is a well-known structural material which is increasingly adopted as an engineering structure material. Glass fiber reinforced polymer offers the lightweight and high strength characteristics that is required for the modern industry, such as aviation, automotive, wind power, and marine technology. One of the important mechanical characteristics of the composite materials are the tensile properties, because it is well known as the material strength. Therefore, the investigation of mechanical response on the glass fiber reinforced polymer (GFRP) tensile test using numerical analysis is important for the estimation of structural response of the GFRP complex structure, such as boat construction. The objective of this research is to assess and estimate the mechanical response of the GFRP composite material subjected to tension load using finite element method. The linear transversely isotropic model is developed to estimate the unidirectional glass fiber GFRP with the configuration of fiber orientation angles of 0°, 30°, 45°, 60° and 90°. The results show that FE simulation are capable to detect the specimen response during the tensile test. The maximum discrepancy of the estimated stress strain diagram is about 16.5% to 32% compared to experimental data. The larger orientation angle has shown the larger discrepancy value. It is found that the increment of discrepancy value is generated by the nonlinearity behavior of the material due to the domination of polymer material behavior on the large orientation angle. Otherwise, the FE models have estimated accurately the ultimate strength, maximum displacement and fracture load. It can be concluded that the linear transversely isotropic model is adequately accepted as the estimation method of the GFRP composite structure response. [ABSTRACT FROM AUTHOR]

This paper reports the influence of woven (0°/90°) and (±45°) lamina position interchanging about the midplane in an eight-layered quasi-isotropic glass fibre reinforced polymer (GFRP) composite under low velocity impact (LVI). In order to fabricate GFRP composite, two lamina orientations as (0°/90°) (referred as 'a') and (±45°) (referred as 'c') arranged in different stacking sequences. Three number of sample groups as (i) sandwiched ([aacc]S and [ccaa]S) (ii) intercalated ([acca]S and [caac]S) and (iii) alternate ([acac]S and [caca]S) resulted in six number of stacking sequences. The drop weight impact tests are performed at two incident velocities as 1.5 and 4 m/s. The corresponding impact energies generated are 11.39 and 81.05 J, respectively. The impact velocity 1.5 m/s created the barely visible impact damage (BVID) in the GFRP composite, while the impact velocity 4 m/s perforated the GFRP composite. The experimental results showed that the intercalated laminate design with four mismatching interfaces (i.e., [acca]S), offered better impact resistance than two other designs with two and six angle mismatching interfaces. It is also perceived that the impact response (maximum peak load, maximum impact energy and minimum impactor displacement) was independent of the number of angles of mismatching interfaces. Moreover, low velocity impact response of a quasi-isotropic GFRP composite depends on the balanced lamina position about the midplane in the laminate. Experimental results for maximum peak load, maximum energy absorption and laminate displacement proved the significance of conventional designing methodology. Further, the impactor displacement value at maximum peak load and the landing displacement value of the descending portion of the force-displacement curve after reaching the maximum peak load proved to be a practical approach along with the use of determinant of the bending stiffness matrix in determining the better performing stacking sequences for a quasi-isotropic GFRP composite made of (0°/90°) and (±45°) plies under LVI. [ABSTRACT FROM AUTHOR]

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.

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. [ABSTRACT FROM AUTHOR]

The effect of long term immersion in seawater at different temperatures on the properties of pultruded glass fibre reinforced polymer (GFRP) composite rebar was investigated. Samples were conditioned in seawater and in dry at 23, 55 and 75 °C for 0, 8, 20, 30 and 36 months to analyse the changes in shear properties such as transverse shear strength (TSS) and short beam shear strength (SBSS). Both TSS and SBSS increased after conditioning in dry at 55 and 75 °C; on the other hand, TSS decreased gradually due to conditioning in seawater at 23, 55 and 75 °C, whereas SBSS decreased due to conditioning in seawater only at 75 °C. Microscopic analysis specified that the shear strength decreased due to fibre/matrix interfacial failure as a result of de-bonding and fibre pull-out. Compared to the short beam shear test, the transverse shear test was found to be a sensitive technique to measure the durability of pultruded GFRP rebar. FT-IR analysis indicated superficial hydrolysis reaction of polymer matrix occurred when the sample was conditioned at 75 °C. A reversible change in glass transition temperature (Tg) and in viscoelastic property of the polymer matrix was observed due to conditioning in seawater at 23 and 55 °C. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer (CETP) composite materials are new and important engineering materials due to their superior properties. Due to their mechanical properties, rigidity / weight ratio, they are indispensable structural materials, especially in engineering structures where lightness is required. Therefore, GFRP composite materials are commonly used in industry. Drilling is an important process for obtaining the holes which is necessary for the assemblies of GFRP in industry. In addition to drilling parameters, the impact of drill geometry on the hole quality should be considered. In this paper, drilling process was carried out with different cutting parameters (cutting speed, feed rate) and drill geometries (different diameters). The obtained the results of thrust force and deformation factor for exit/entrance surface. Taguchi method and analyze of variance (ANOVA) was also applied to determine the effects of cutting parameters on experimental results. L9(313) orthogonal experimental design was selected for analysis of Taguchi and response Tables was used. Besides the cutting parameters, the impact of drill geometry on the results are also discussed. It is obtained that feed rate governs the thrust force and exit deformation factor; however, the entrance deformation is driven by the drill bit diameter. The results show that this approach has been demonstrated can be used effectively for drilling of GFRP composite materials. [ABSTRACT FROM AUTHOR]

This paper deals with the study of effect of machining parameters on burr height and fibre pullout while drilling on hybrid Fibre Reinforced Polymer (FRP) composite materials. Hybrid composite materials composed of Glass Fibre Reinforced Polymer (GFRP) with liquid silicone rubber and fine silica powder. Laminates of hybrid GFRP are prepared at process parameters like pressure of 100 kgf, temperature of 50 °C and time of 40 min by compression molding technique. The main objective of this study the influence of fiber volume fraction with liquid silicone rubber and fine silica powder on the burr height and fibre pullout in drilling of hybrid FRP composite. The effect of drilling parameters such as cutting speed, feed rate, drill point angle and tool material on drilling hybrid GFRP is studied and optimized by making use of Taguchi design and ANOVA analysis. The results are analyzed by making use of L9 Orthogonal Array (OA) and signal to noise ratio (S/N ratio). The obtained result shows that, very small burr height (0.08 mm and 0.07 mm) was observed in both the materials having matrix weight ratio 60:40 and 50:50. It is almost same burr height in both the materials. Whereas small fibre pullout of 1.01 mm is noticed in material having matrix weight ratio 50:50 than fibre pullout of 2.9 mm in material having matrix weight ratio 60:40. The results are validated by conducting confirmation test. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Polimery is the property of Industrial Chemistry Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To study the axial compressive performance of glass fiber-reinforced plastic (GFRP) composite structure, a full-scale axial compression experiment was conducted on GFRP composite bushing (GFRP-CB) column specimens. The axial compressive mechanical properties, failure mode, and load–displacement curves were obtained and analyzed. It is found that brittle fracture occurs in the GFRP-CB column specimens. Diagonal cracks as the main failure mode appear in the upper part of the GFRP pipe. Moreover, the maximum stress in specimens is less than the compressive strength of the GFRP composite material. The steel casing remains in the elastic state during the entire loading process. Based on the strength theory of transversely orthotropic material, the finite element method was used to scrutinize the influence of eccentricity and diameter–thickness ratios on strength of specimens. Numerical results prove that the ultimate bearing capacity of the eccentric compression specimens decreases with the eccentricity ratio. Reduction in diameter–thickness ratio can improve the ultimate bearing capacity of the specimens. As the diameter–thickness ratio decreases by 20%, the ultimate bearing capacity increases by 20%. Finally, an equation for calculating the ultimate bearing capacity of the GFRP-CB column is proposed according to test results. The calculated and test results are fairly consistent, which indicates the effectiveness and accuracy of the proposed equation. [ABSTRACT FROM AUTHOR]

The static tensile properties in the form of ultimate failure stress, ultimate failure strain and Young’s modulus of a cross-ply glass fiber-reinforced polymer (GFRP) composite laminate [904, 04]s and an unconventional angle-ply GFRP composite laminate [+67.54, -67.54]s were investigated using the netting analysis, the laminate mixture rule (Hart-Smith 10% rule) and the classical laminate theory (CLT). The findings were then compared to experimental results to determine the accuracy of each analytical technique. It was found that the netting analysis was the best overall method for estimating the cross-ply laminate tensile properties, whereas neither the CLT nor the 10% rule were appropriate for estimating the tensile properties of the unconventional ply angle laminate.

Abstract Structural Health Monitoring (SHM) systems allow early detection of damage which allows maintenance planning and reduces the maintenance cost.Several researchers have proposed use of Neutral Axis (NA) location as a damage sensitive feature. It has been shown that through proper signal processing, NA location is insensitive to measurement noise and ambient temperature changes. This paper presents a methodology for successful NA tracking under changing axial loading conditions. The novel methodology is validated using numerical data as well as experimental results. This paper demonstrates the development of a Kalman Filter (KF) based NA tracking strategy under different loading conditions. The methodology was employed on a composite beam instrumented with fiber optic strain sensors. The stable NA tracking under changing loading conditions allows the application of the NA as a damage sensitive feature. The change in NA location is used to detect delamination in the beam. The method has been validated through a numerical model and experiments. The results show that the novel formulation of the KF for NA tracking allows more robust use of NA location as a damage sensitive feature in a wider range of applications. [ABSTRACT FROM AUTHOR]

This paper presents the fatigue behavior of Glass Fiber Reinforced Polymer (GFRP) composites at constant amplitude tension-tension loading conditions. A two parameter residual strength and fatigue life model has been proposed by accounting the effect of stress ratio when the structure undergoes continuous loading. A model is also developed to predict the fatigue life of GFRP composites based on fatigue endurance limit. Experiments were conducted on GFRP composite specimens to predict fatigue life and residual strength at various stress levels. Tests were also conducted to gain an understanding of the tensile behavior of GFRP composite specimens under different quasistatic strain rates. The lowest tensile strength resulting from strain rate studies has been used ultimately for conducting fatigue life and residual strength tests. Reliability of the proposed models has been verified with experimental results and with the models seen in literature. [ABSTRACT FROM AUTHOR]

GFRP composites are used in fairings, passenger compartments, and storage room doors due to their high mechanical properties. High speed machining (HSM) is an outstanding technology capable of improving productivity and lowering production costs in manufacturing companies. But, machining of GFRP composites is more complex when compared with metallic materials. These materials are bad conductors of heat and hence they do not dissipate the heat generated during machining. This causes increase in temperatures, which may degrade the work material as well as tool materials. During the GFRP drilling process, the most important factor affecting the cutting tool performance and workpiece properties is the cutting temperature generated between drill bit and chip. The thermal effects may interfere with the dimensional accuracy, and can also change the mechanisms at the cutting edge. The attempt in this study is to present the influence of the cutting conditions, viz. the spindle speed, feed rate, drill bit diameter and drill bit configuration on temperature generated during drilling. Results indicate that lower spindle speeds, drill diameters and higher drill bit point angles reduce the temperature at drilling zone. No clear trend is identified for the influence of feed rate on temperature. [ABSTRACT FROM AUTHOR]

Structural Health Monitoring (SHM) systems allow early detection of damage which allows maintenance planning and reduces the maintenance cost. The SHM system should be low cost, suitable for continuous monitoring, able to detect small levels of damage, and insensitive to ambient loading, changes in ambient temperature, and measurement noise. Neutral Axis (NA) location is a function of the condition of the structure alone and may be used as a damage sensitive feature. It has been shown that through proper signal processing, NA location is insensitive to measurement noise and ambient temperature changes. This paper aims at validating the use of NA as a damage sensitive feature through experimental study. This paper demonstrates the use of multi-rate Kalman Filter (KF) for accurate estimation of NA under different loading conditions. The methodology was employed on a composite beam instrumented with fiber optic strain sensors. Delamination was introduced in the beam and then progressively increased. The beam was subjected to different loading and temperature conditions for the different damage scenarios. The measured strains were then used for NA tracking. The results show that indeed the NA location may be used as a damage sensitive feature. Some of the loading scenarios were difficult to realise in the laboratory, so these loading scenarios were applied on a validated Finite Element (FE) model of the composite beam. The results indicate that under these dynamic loading scenarios, NA may be used for SHM. Based on the results it can be concluded that KF based NA tracking may be applied to structures for in-service SHM. [ABSTRACT FROM AUTHOR]

The paper presents an attempt to evaluate the technically important properties of epoxy resin modified alternatively with multi-walled carbon nanotubes and flaked graphene. It is a presentation of experimental results supported by extensive referring to the professional literature. The nano-components were added in the amount which was economically justified and provides hope for a significant improvement of some of the properties of pure resin. Flowability, glass wettability, curing process and gelation time and curing shrinkage of the resin were evaluated. After the resin was cured, inner and outer hardness, thermal conductivity, flexural strength and impact resistance were measured. Glass fibre-reinforced laminates were also prepared with use of the nano-modified resin. The mechanical properties, interlaminar shear strength and flexural strength of the laminates, were evaluated for them. The obtained results showed either no effect or only technically slight effect of the nano-modification on the evaluated properties. Noticeable improvement in interlaminar shear strength and impact resistance for laminates containing resin filled with graphene can predestine this kind of modification as a method of increasing the delamination resistance of laminates. [ABSTRACT FROM AUTHOR]

• Aluminum/glass hybrid composite tubes were fabricated by filament winding method. • Three different stacking sequences [±45 2 /Al], [90/±45 2 /Al], and [±45 2 /90/Al] wound on a 6063-T5 aluminum tube are considered. • The damage process contained two phases in hybrid specimens with 90° layers. It is known that aluminum/composite hybrid tubes of aluminum tube wrapped with a composite material on the outside can offer remarkable performance. This study systematically investigates the effect of stacking sequence on the torque capacity of holed aluminum/composite hybrid tubes. The stacked specimens manufactured by the filament winding method, [±45 2 /Al], [90/±45 2 /Al], and [±45 2 /90/Al], are considered in experimental studies. The tubes were tested for torsional characteristics at a constant angular rotational speed. The experimental studies indicated that although monotonic crack propagation was observed in the aluminum tube with the damage starting from the hole wall at an angle of approximately 45° concerning the specimen axis, the damage in hybrid tubes containing a 90° layer occurs in two phases. This causes a step-like formation in the torque–angle curves. Although the ± 45° reinforcement has a profound effect on torque-carrying, it has been observed that the presence of the 90° composite on the aluminum tube in the reinforced tube improves the effectiveness (torque capacity and stiffness) of the subsequent reinforcement. Accordingly, it is understood that the hybrid structure increases the torque-carrying capacity up to 2.6 times compared to the aluminum tube, corresponding to a 20% increase in specific torque value. The stress components that play an important role in the deformation of the hole wall and damage formation processes have been successfully determined by the finite element method. It was found that there was a consistent relationship between the effect of the stacking sequence on the stress distribution and the experimental results. The results of the study are expected to be useful in terms of providing light and sufficient torque performance in case of possible hole-like discontinuity in-service conditions. [ABSTRACT FROM AUTHOR]