Search

Under high temperatures, fiber-reinforced polymers are destroyed, releasing heat, smoke, and harmful volatile substances. Therefore, composite structural elements must have sufficient fire resistance to meet the requirements established by building codes and regulations. Fire resistance of composite materials can be improved by using mineral fillers as flame-retardant additives in resin compositions. This article analyzes the effect of fire-retardant additives on mechanical properties and fire behavior of pultruded composite profiles. Five resin mixtures based on vinyl ester epoxy and on brominated vinyl ester epoxy modified with alumina trihydrate and triphenyl phosphate were prepared for pultrusion of strip profiles of 150 mm × 3.5 mm. A series of tests have been conducted to determine mechanical properties (tensile, flexural, compression, and interlaminar shear) and fire behavior (ignitability, flammability, combustibility, toxicity, smoke generation, and flame spread) of composites. It was found that additives impair mechanical properties of materials, as they the take place of reinforcing fibers and reduce the volume fraction of reinforcing fibers. Profiles based on non-brominated vinyl ester epoxy have higher tensile, compressive, and flexural properties than those based on brominated vinyl ester epoxy by 7%, 30%, and 36%, respectively. Profiles based on non-brominated epoxy resin emit less smoke compared to those based on brominated epoxy resin. Brominated epoxy-based profiles have a flue gas temperature which is seven times lower compared to those based on the non-brominated epoxy. Mineral fillers retard the spread of flame over the composite material surface by as much as 4 times and reduce smoke generation by 30%. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) composite materials are very versatile in use because of their high specific stiffness and high specific strength characteristics. The main limitation of this material is its brittle nature (mainly due to the low stiffness and low fracture toughness of resin) that leads to reduced properties that are matrix dominated, including impact strength, compressive strength, in-plane shear, fracture toughness, and interlaminar strength. One method of overcoming these limitations is using nanoparticles as fillers in an FRP composite. Thereby, this present paper is focused on studying the effect of nanofillers added to glass/epoxy composite materials on mechanical behavior. Multiwall carbon nanotubes (MWCNTs), nano-silica (NS), and nano-iron oxide (NFe) are the nanofillers selected, as they can react with the resin system in the present-case epoxy to contribute a significant improvement to the polymer cross-linking web. Glass/epoxy composites are made with four layers of unidirectional E-glass fiber modified by nanoparticles with four different weight percentages (0.1%, 0.2%, 0.5%, and 1.0%). For reference, a sample without nanoparticles was made. The mechanical characterizations of these samples were completed under tensile, compressive, flexural, and impact loading. To understand the failure mechanism, an SEM analysis was also completed on the fractured surface. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the usability of hybrid sandwich structures as facade panels. The explored sandwich structure was made of mineral-glass fibre reinforced polymer (GFRP) skins and a GFRP truss core, fabricated by means of a novel manufacturing method. The compressive and shear specific strengths of the panels were assessed and compared with a few common lightweight structures to verify that the manufactured truss core had comparable values. Three-point bending tests indicated that the polyurethane foam used (required for the manufacturing process) had negligible mechanical contribution. Full-scale panels were tested under a distributed load. The tests were simulated using the three-dimensional finite element method to predict the pressure at which mineral cracks appeared in order to avoid their occurrence in the design phase. The simulation results exhibited good agreement with experimental data, and the model was validated in terms of deflection and strain responses. The occurrence of cracks and their propagation were numerically reproduced using the concrete-damage plasticity model. The link between the connector and crack positions in the mineral skin was highlighted in this study. [ABSTRACT FROM AUTHOR]

Abstract The aim of this study is to compare two different standardized testing procedures, tensile testing and Mode-I double cantilever beam (DCB) testing, to evaluate a possible correlation between the dominant failure in glass fibre-reinforced plastics and their according acoustic emissions (AE). AE is processed by using a burst collection of all recorded transient signals and is further analysed with the k-means clustering algorithm. To generate damage related AE, a series of experiments for tensile testing and Mode-I DCB testing is performed on 16-layer glass fibre/epoxy specimens with a cross-ply lay-up for tensile and an unidirectional lay-up for Mode-I DCB testing. Three sensors at tensile testing and one sensor at Mode-I DCB testing gather AE data. The results of clustered burst signals show a good accordance between both testing procedures, with a similar weighted peak frequency (WPF) range in each classified cluster. In total, three different clusters are determined. An assignment of these three clusters to the three dominant damage mechanisms, visually observed by microscopy, is suggested. [ABSTRACT FROM AUTHOR]

Highlights • Recycled glass fiber reinforced polymer (GFRP) was used as reinforcement in the mortar. • Fiber-like GFRP shapes replaced fine aggregate in mortar. • Aspect ratios were compared in terms of toughness and strength. • Volumetric percentages of 1 and 3 showed the most successful results. Abstract Glass fiber reinforced polymer (GFRP) panels from retired wind turbines were recycled into discrete structural elements in mortar. Based on 7-day testing, out of Powder, Small, Medium, and Large fiber size groups, the Large group was identified as the optimum size due to the highest modulus of rupture (MR) and toughness index (TI) while maintaining comparable compressive strength (f’ c) relative to control. Implementing the Large group at 1, 3, and 5% replacement of sand resulted in 5, 25 and 35% increases in 90-day MR with significant increases in TI and minimal reductions in f’ c and no expansion due to alkali-silica reaction. [ABSTRACT FROM AUTHOR]

Fiber reinforced polymer (FRP) rebars have recently been gaining popularity in the construction industry all around the world while steel rebars have been widely used so far. FRP bars, which have higher tensile strength compared to steel rebars with the same nominal diameter under normal conditions, are composed of resin matrix and fibers. In this study, mechanical and bonding properties of glass fiber reinforced polymer (GFRP) and steel rebars subjected to elevated temperature effects were investigated throughout a correlative comparison. Axial tensile tests and pull-out tests of these materials were performed subsequent to exposing them into elevated temperature effects in the range of 23–800 °C. Severe effects on the tensile properties of bare steel bars were observed after 600 °C, while this critical limit is 300 °C for bare GFRP bars. Test results show that bond strength degradation is almost linear for both type of rebars, however, 600 °C is also the critical temperature regarding the serious deterioration on concrete. Additionally, an empirical modeling approach on the bond strength degradation of rebars at elevated temperatures was proposed and it was found that comparison results have quite promising consistency based on the modeling process. [ABSTRACT FROM AUTHOR]

This paper aims to present a methodology to predict the anisotropic and non-linear behaviour of glass fibre reinforced plastics using finite element methods. A material model is implemented in order to remedy the need of multiple material definitions, and to control the local plastic behaviour as a function of the fibre orientation. Injection moulding simulations traditionally provide second order orientation tensors, which are considered together with a homogenization scheme to compute local material properties. However, in the present study, fourth order tensors are used in combination with traditional methods to provide more accurate material properties. The elastic and plastic response of the material model is optimized to fit experimental test data, until simulations and experiments overlap. The proposed material model can support design engineers in making more informed decisions, allowing them to create smarter products without the need of excessive safety factors, leading to reduced component weight and environmental impact. [ABSTRACT FROM AUTHOR]

The present investigation deals with an experimental analysis of punching process of Glass Fiber Reinforced Plastics (GFRP) sheets. The process has the potential to dramatically reduce the cycle time; thus, it can be used for industrial applications where large numbers of holes are needed. However, the laminate damage represents the major concern for the employment of hole punching. Thus, a campaign of experimental tests was conducted on thin laminates with varying the punch-die clearance. In addition, drilled holes were performed in order to compare the quality and strength of the holes performed by drilling and punching processes. To assess the influence of the process parameters on the holes quality, mechanical characterization was performed by means of tensile test with central hole and bearing test. Moreover, morphological analysis was conducted to determine the quality of the punched hole and the extension of the delaminated region. According to the achieved results, the damage produced by punching process, especially when small clearances were used, is limited and comparable to that produced by drilling process. [ABSTRACT FROM AUTHOR]

An experimental investigation is presented into the explosive blast response of fibre-reinforced polymer laminates used in naval ship structures. Blast tests using plastic explosive charges were performed in air on square target plates made of carbon-polyester, glass-polyester, carbon-vinyl ester or glass-vinyl ester laminates, which are composite materials used in naval ships. The laminates were dynamically loaded by shock waves of increasing pressure and impulse, and the deformation, damage and residual mechanical properties were determined. The amount of blast-induced damage and the post-blast mechanical properties depend on both the fibre reinforcement and polymer matrix. E-glass laminates have higher resistance to blast-induced delamination cracking and tow rupture than carbon fibre composites. Furthermore, glass or carbon fibre laminates with a vinyl ester matrix have superior blast damage resistance compared to composites with a polyester matrix. The higher damage resistance is attributed to the higher flexural strain energy capacity and interlaminar fracture toughness properties of laminates containing glass fibres or vinyl ester matrix. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of simultaneous mechanical and environmental loading on the degradation rate of pultruded Glass Fiber Reinforced Polymer (GFRP) composites. The experimental program included testing a large number of GFRP coupons, with vinylester or polyester matrices, conditioned for 1000 or 2000 h under a wide range of sustained stresses and exposed to freshwater or saltwater at an elevated temperature of 60 °C. Mechanical tests, including tensile strength and elastic modulus measurements were performed on the GFRP composites. In addition, glass transition measurements, moisture uptake measurements, scanning electron microscopy, and acoustic emission testing were performed to better understand the synergistic effect of mechanical loading and environmental conditions. [ABSTRACT FROM AUTHOR]

Experimental and statistical analyses are represented considering the impact resistance and mechanical properties of self-compacting concrete reinforced with recycled Glass Fibre Reinforced Polymers (GFRP). Specimens were reinforced with recycled GFRP in three groups, including 0.25%, 0.75%, and 1.25% of fibre volume fractions. An extensive experimental program including two hundred and fifty two specimens were prepared and tested to characterize the impact resistance and mechanical properties of the reinforced self-compacting concrete with glass fibre reinforced polymers. Scanning Electron Microscope images were used to perceive the failure mechanism of recycled glass fibre in the matrix. Then, the relatively large and reliable collected data from the experimental tests was used to start statistical and analytical analysis. The results showed that adding recycled glass fibre reinforced polymers results in improving the impact resistance and mechanical properties of the reinforced self-compacting concrete with glass fibre reinforced polymers. Moreover, the statistical data analysis revealed that the impact resistance and mechanical properties of reinforced self-compacting concrete follow a normal distribution. Furthermore, some equations were developed to correlate the impact resistance of the reinforced self-compacting specimens to the mechanical properties with high values of coefficient of determination. [ABSTRACT FROM AUTHOR]

The effect of moisture on the mechanical properties of glass fiber reinforced polyamide composites was investigated. The composites of short glass fiber/polyamide with different weight percent (0–30 wt%) were prepared. To investigate the effect moisture on mechanical properties of these composites, the specimens were prepared and then immersed in distilled water for a period of 60 days. The weight changes of the specimens were daily measured to determine the amount of moisture absorption of the specimens. Tensile test and flexural test were conducted based on ASTM D638 -02a and ASTM D790 -02, respectively. The effect of moisture on the microstructure of the composites was also investigated. The moisture absorption of the glass fiber reinforced polyamide composites could be divided into four stages: (I) the beginning stage (1–7 days), (II) the second stage (8–24 days), (III) the third stage (25–35 days) and (IV) the saturated stage (36–60 days). Yield strength, ultimate tensile strength and flexural strength of all specimens significantly decreased at the beginning stage of moisture absorption and then these mechanical properties were almost constant. The modulus of elasticity of all specimens decreased at the beginning stage and saturated stage. In addition, ductility (%Elongation) of all specimens did not change at the beginning stage. However, ductility of all specimens significantly decreased in the third stage, and then their ductility were almost constant. Based on the microstructure analysis, the results indicated that the transition of brittle to ductile properties of the glass fiber reinforced polyamide composites after moisture absorption would be attributed to the changes in their mechanical properties. [ABSTRACT FROM AUTHOR]

A series of the long glass fiber–reinforced thermoplastic polyurethane elastomers and acrylonitrile–butadiene–styrene (LGF/TPU/ABS) composites with different content of LGFs were prepared using self-designed impregnation device. Dynamic mechanical properties of the LGF/TPU/ABS composites have been investigated using dynamic mechanical thermal analysis. The results indicated that the content of LGFs and scanning frequency have some effect on the dynamic mechanical properties and glass transition of LGF/TPU/ABS composites. In the meantime, the Arrhenius relationship has been used to calculate the activation energy of α-transition of the LGF/TPU/ABS composites. The thermogravimetric analysis thermograms of the LGF/TPU/ABS composites were found to decrease in two steps. The good dispersion of the LGFs in the matrix resins is obtained from scanning electron micrographs. In addition, effects of the LGF contents on mechanical properties of LGF/TPU/ABS composites were investigated. [ABSTRACT FROM AUTHOR]

This work investigates the effect of hydrothermal ageing on the mechanical and thermo-mechanical properties of glass fiber reinforced cyanate ester composites. A large test campaign was realized to this direction. Coupons from in-house autoclave manufactured plates were immersed in distilled water at four different temperatures 40, 60, 75 and 90 °C for up to 61 days. Moisture absorption measurements followed by dynamic mechanical analysis as well as a series of mechanical tests were conducted at regular intervals during the ageing process. In addition, scanning electron microscopy was utilized in order to identify the exact degradation mechanisms that are active and dominant in the different ageing scenarios. The analysis of the results outlines the degradation behavior of the material properties and the accelerating effect of temperature elevation on the activation and acceleration of certain degradation mechanisms. Based on the existing literature this is probably the first thorough experimental study regarding the hydrothermal ageing of cyanate ester glass fiber reinforced composites. [ABSTRACT FROM AUTHOR]

Glass fiber composites (GFRP) are common in civil engineering projects, but not in marine structures. One reason is that seawater effects degrade GFRP composites mechanical properties and interlaminar shear strength (ILSS). Here, influence of seawater environment is studied to determine the best composite materials for marine civil engineer applications, studying the influence of several factors in their mechanical properties. This is to determine safety factors to use in the design of structural calculations for marine applications. Glass/epoxy composites are the safest materials to use in marine civil structures as mechanical properties degradation becomes stabilized after moisture saturation level. UV and water cyclic analysis must be done to determine affection to transversal strength. Only vinylester GFRP has problems with biodegradation. GFRP fatigue performance is not influenced by seawater environment. [ABSTRACT FROM AUTHOR]

Fiber Reinforced Polymer (FRP) composites are widely used for strengthening and conservation of historic masonry, even if research problems are still open. The mechanical behavior of masonry columns having a circular cross section, confined with glass and basalt FRP systems was studied in this paper. An extended experimental investigation is presented in order to show the results of axial compression tests on circular masonry columns built with natural blocks (calcareous stone). Active confinement was also studied by using a novel technique that employs Shape Memory Alloys (SMA). Totally twenty-four masonry columns were built, instrumented and tested. Different fibers, strengthening schemes and matrix/adhesive were used for the confinement of the columns. Unstrengthened columns were tested as reference specimens. Axial strain of the columns and tensile strain of the fibers in the direction perpendicular to the primary axis of the columns were measured with the applied load. Experimental results revealed the effectiveness of the FRP-confinement for masonry columns. Active confinement was found to be effective at early loading stages since an increased stiffness of the SMA/GFRP-confined columns was measured. A prediction of the compressive strength was obtained by using the model of the Italian guidelines CNR DT 200 (National Research Council) in order to compare the experimental results with the design approach, also for new types of fiber like basalt which were not included in the technical codes. Finally, the experimental results were compared with theoretical values calculated according with to two existing analytical models in order to test their effectiveness for the analyzed configurations. [ABSTRACT FROM AUTHOR]

Highlights: [•] For first time, mechanical behavior of GFRP panels is computed directly as a function of their constituents. [•] A set of experiments is performed on constituents of the GFRP sandwich panels: skin and fiber insertion. [•] The resulting constitutive relationships are used in a nonlinear finite element model. [•] The models can predict the behavior of GFRP sandwich panels beyond their elastic limits. [•] A parametric study is performed to optimize the effects of skin and panel thickness, and fiber pattern. [Copyright &y& Elsevier]

Bond behavior of sand-coated deformed glass fiber reinforced polymer rebars was experimentally investigated in this study. A total of 84 specimens, including 30 beam specimens, 48 Losberg pullout specimens, and six RILEM/CEB/FIP pullout specimens, were constructed and tested under monotonic loading. Two failure modes including pullout failure and splitting failure were observed. The pullout failure occurred when the embedment length of specimens was less than 5 times glass fiber reinforced polymer rebar diameter, while the splitting failure occurred when embedment length was more than 5 times rebar diameter. The specimens with the embedment length of 5 times bar diameter failed either by glass fiber reinforced polymer rebars pulling out or by concrete splitting. The results also showed that bond strength of sand-coated deformed glass fiber reinforced polymer rebars was, on average, 59–127% that of the deformed steel rebars. With higher concrete strength, higher bond strength of sand-coated deformed glass fiber reinforced polymer rebars was obtained. When rebar diameter or embedment length increased, bond strength of sand-coated deformed glass fiber reinforced polymer rebars decreased. Based on these results, formulas for the bond strength and the development length of glass fiber reinforced polymer rebars were proposed, considering the effects of concrete strength, bar diameter, embedment length, and rebar outer surface. [ABSTRACT FROM AUTHOR]

Abstract: Modelling physical and mechanical properties of fibrous materials requires a relevant description of their microstructures, e.g. the descriptors of fibres and fibre–fibre contacts. In this work, a method is proposed to identify fibres with complex cross sections and their contacts from 3D images of disordered fibrous media, obtained from X-ray microtomography. The image analysis procedure first consists in obtaining a map of the local fibre orientation. Fibres are then detected by deleting regions of high local orientation gradients. Therewith, dilatation operations using slender orientated structuring elements are performed to retrieve deleted fibre parts. The procedure thus provides 3D images with labelled fibres and fibre–fibre contacts. Its relevance is assessed by analysing the microstructures of three typical fibrous media used in short fibre reinforced polymer composites or as paper materials: mats of (i) mono-disperse copper fibres with circular cross sections, (ii) glass fibres bundles, (iii) wood fibres. [Copyright &y& Elsevier]

Stella Job, Knowledge Exchange Expert for the Materials Knowledge Transfer Network (KTN), UK, discusses the issues surrounding the recycling of glass fibre reinforced plastics (GRP), and reviews some of the options available today. [ABSTRACT FROM AUTHOR]

Abstract: A multi-scale numerical fatigue modelling methodology is proposed for the characterization of axial tension–tension fatigue behaviour of unidirectional Glass Fibre Reinforced Polymer (GFRP) composites. The methodology is developed to link the dominant fibre failure mechanism to composite fatigue properties, by a three-step geometrical up-scaling process. This study aims to provide composite fatigue predictions by only using the material properties of fibres and matrix. Compared to the experimental results, the fatigue model over-predicts fatigue lives and gives reasonable estimations of axial stiffness degradation curves of the unidirectional GFRP composite dog-bone specimens. [Copyright &y& Elsevier]

Abstract: This paper presents the test results of an experimental study carried out to investigate the residual tensile properties of new generation of GFRP bars after being subjected to several harsh environmental conditions for different periods. The bars were exposed to ten different environmental conditions for 6, 12, and 18months. In addition to a control laboratory condition, the environments included exposure to ordinary tap water and sea water at two temperatures (room and 50°C), sea water dry/wet, alkaline solution, and hot-dry condition at 50°C. Furthermore, the environments included two typical harsh field conditions of the Kingdom of Saudi Arabia. The performance of the GFRP bars was evaluated by conducting tensile tests on the bars after different exposure periods. Scanning electron microscope was used to investigate the degradation mechanism of the bars. After 18months of exposure, the test results showed that at 50°C the tap water and alkaline solution had the maximum harmful effect on the tensile strength of the tested GFRP bars. The two field conditions considered in the present study did not show any significant effect on the tensile properties of the bars. The test results also showed that the GFRP bars tested in this study had better resistance to alkalinity and water compared to most of the GFRP bars in the literature. [Copyright &y& Elsevier]

Textile glass fiber reinforced particle-filled polymer composite beams which have different weight fractions of glass fibers were produced with varying notch-to-depth ratios. The mechanical properties of specimens were found. The specimens were investigated in Mode I and Mode III fracture behavior using three-point bending (TPB) tests. Textile glass fiber contents used were 1, 2 and 3%, and polyester content was 16.5% of the total weight of the polymer composite system. The critical stress intensity factor was determined by using a compliance technique, the initial notch depth method and the J-integral method. Effects of crack angles on fracture behavior were also studied. The specimens, which have an inclined crack at an angle θ to the axis of the specimens, were used to carry out the tests. The specimens were tested with inclination angles 30°, 45°, 60° and 75°. The results are compared with the values of KIC obtained using conventional (θ = 90°) specimens. In addition, J-integrals were also determined. [ABSTRACT FROM AUTHOR]

Abstract: The friction and wear of short glass fiber reinforced polyamide 12 (PA12) were investigated. The behavior of the fibers on a sliding surface and their effect on the friction and wear were studied in terms of the amount and orientation of the fibers in the composite. Results showed that the friction level and wear resistance were strongly affected by the fiber content, and glass fiber patches produced on the sliding surface played important roles in the wear resistance of the composite. The optimum fiber content for the best wear resistance of the PA12 composite was approximately 30wt.% and higher fiber contents had no added effect on the wear amount. The applied load also strongly affected the wear resistance due to the increase in temperature at the sliding interface, and an increase in rapid wear was observed when the interface temperature increased above the glass transition temperature of PA12. On the other hand, the fiber orientation had less effect on the friction and wear of the composite compared to the fiber content and applied load. Based on the behavior of glass fibers on the sliding surface and wear debris analysis, the wear mechanism of the PA12 composite is discussed. [Copyright &y& Elsevier]

Abstract: Polymer matrix composites are widely used in the automotive industry and undergo fatigue loadings. The investigation of the nonlinear cyclic behaviour of such materials is a required preliminary work for a confident fatigue design, but has not involved many publications in the literature. This paper presents an extensive experimental study conducted on a polyamide 66 reinforced with 35wt% of short glass fibres (PA66 GF35), at room temperature. The material was tested in two conditions: dry-as-moulded (DAM) and at the equilibrium with air containing 50% of relative humidity (RH50). An exhaustive experimental campaign in tensile mode has been carried out, including various strain or stress rates, complex mechanical histories and local thermo-mechanical recordings. Such an extended database allowed us to highlight several complex physical phenomena: viscoelastic effects at different time scales, irrecoverable mechanisms, non-linear kinematic hardening, non-linear viscous flow rule, cyclic softening. Taking into account this advanced analysis, a constitutive model describing the cyclic behaviour is proposed. As the experimental database only includes uniaxial tensile tests, the general 3D anisotropic frame is reduced to an uniaxial model valid for a specific orientation distribution. The robust identification process is based on tests which enable the uncoupling between the underlined mechanical features. This strategy leads to a model which accurately predicts the cyclic behaviour of conditioned as well as dry materials under complex tensile loadings. [Copyright &y& Elsevier]

Abstract: New perspectives have arisen on basalt fibre applications due to the potential low cost of this material together with its good mechanical performance, in particular at high temperature. The idea to fill these fibres into a polymer matrix is relatively recent and could offer very interesting perspectives that have not yet been sufficiently investigated. In this work, with the principal aim of evaluating the possibility to replace glass fibres in most of their applications, mechanical tests were carried out on comparable E-glass and basalt fibre reinforced plastic laminates. The latter were cut by square plates fabricated through vacuum bag technology. The results obtained on the two laminates were compared showing a high performance of the basalt material in terms of young modulus, compressive and bending strength, impact force and energy. These good properties suggest possible applications of basalt fibres in fields where glass composites are nowadays largely applied. The short-beam strength tests confirmed what above said by denoting an interfacial adhesion similar to that between E-glass and epoxy matrix. [Copyright &y& Elsevier]

The interest in fibre-reinforced polymer composites is growing rapidly due to its high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost, and low density. The development of composite materials based on the reinforcement of two or more fibre types in a matrix leads to the production of hybrid composites. In the present work, woven coir-glass hybrid polyester composites were developed and their mechanical properties were evaluated for different stacking sequences. Scanning electron micrographs of fractured surfaces were used for a qualitative evaluation of interfacial properties of woven coir-glass hybrid polyester composites. These results indicated that coir-glass hybrid composites offered the merits of both natural and synthetic fibres. [ABSTRACT FROM AUTHOR]

Abstract: Drilling of glass fibre reinforced plastic (GFRP) composite is substantially different from metallic materials due to its mechanical properties. The drilling of this material may generate delamination of drilled holes on workpiece. The purpose of this paper is to investigate the influence of the cutting parameters, such as cutting speed and feed rate, and point angle on delamination produced when drilling a GFRP composite. The damage generated associated with drilling GFRP composites were observed, both at the entrance and the exit during the drilling. Hence it is essential to obtain optimum cutting parameters minimizing delamination at drilling of GFRP composites. Moreover, this paper presents the application of Taguchi method and analysis of variance (ANOVA) for minimization of delamination influenced by drilling parameters and drill point angle. The optimum drilling parameter combination was obtained by using the analysis of signal-to-noise ratio. The conclusion revealed that feed rate and cutting speed were the most influential factor on the delamination, respectively. The best results of the delamination were obtained at lower cutting speeds and feed rates. [Copyright &y& Elsevier]

Abstract: Fiber metal laminates (FMLs) are layered materials based on stacked arrangements of aluminum alloy layers and fiber reinforced plastic (FRP) layers. FMLs have benefits over both aluminum and fiber reinforced composites. In this work, glass fibers and Kevlar fibers are used together and effect of fibers orientation on tensile behavior of this novel material is investigated. A modified classical laminate theory (CLT), which considers the elastic–plastic behavior of the aluminum sheets, and a numerical simulation method based on finite element modeling (FEM) are used to predict the stress–strain response of FMLs. Specimens were made and mechanical testing was performed to determine in-plane tensile properties of this type of FMLs. Good agreement is obtained between the models predictions and experimental results. Test results show that fiber sheets with zero orientation in laminate improve modulus of elasticity, yield stress and ultimate tensile stress considerably. Statistical analysis of data is done and an estimated response surface of ultimate tensile strength of the specimens as a function of fiber orientation in each layer is obtained. Also, the effect of the independent variables and interactions with their relative significance on the tensile behavior is specified. It is shown that Kevlar fiber orientation is the most important parameter between all variables and their interactions. [Copyright &y& Elsevier]

Abstract: This paper presents an experimental investigation of the durability of the bond between GFRP bars and concrete, specifically as it relates to degradation of the GFRP-bar surface and behavior of the bar–concrete interface. The GFRP bars were embedded in concrete and exposed to tap water at 23°C, 40°C, and 50°C to accelerate potential degradation. The bond strengths before and after exposure were considered as a measure of the durability of the bond between the GFRP bars and concrete. In addition, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used to characterize how bar aging affected the bond between the GFRP bars and the concrete. The results showed that aging did not significantly affect the durability of the bar–concrete interface under the conditions used in this study. [Copyright &y& Elsevier]

Abstract: This paper investigates the performance of a glass fiber-reinforced polymer (GFRP) bridge deck under static and fatigue load cycles. The bridge deck has a sandwich panel configuration, consisting of two stiff face shells separated by a light-weight honeycomb core. The deck was manufactured using a hand lay-up technique. In this study, a full-size panel that had the same design as an actual bridge deck was tested. The experimental data are analyzed and compared to the results of finite element analysis. The data obtained have indicated that the failure of the system is governed by the delamination of the face shells from the honeycomb core, and the failure behavior is pseudo-ductile even though the material itself is brittle. Hence, the design of such a deck panel should be based on the shear strength of the face–core interface. However, the shear strength can depend significantly on the workmanship in the fabrication process. For design, if the interface shear strength can be reliably identified, the maximum shear stress should be no greater than 15% of the shear strength to avoid fatigue damage under the service load condition. [Copyright &y& Elsevier]

Abstract: Drilling induced damage in fiber reinforced plastic laminates results in high rate of parts rejection and also affects the in-service performance of the composite products with drilled holes. The tensile testing of composite laminates with drilled holes is necessary to render them satisfactory for application. The present research endeavor is an attempt to develop a generic finite element model in order to investigate to failure of uni-directional glass fiber reinforced plastics (UD-GFRP) composite laminates with drilled hole under uni-axial tensile testing. The results have been compared with the experimental work done earlier and are found to be in good agreement. [Copyright &y& Elsevier]

This article reports the mechanical characterization and sliding wear behavior of glass fiber-reinforced vinyl ester resins of varying acid values, based on epoxy-novalocs in the presence of three different comonomers (styrene, methyl acrylate and butyl acrylate) as reactive diluents. It presents a special account of the optimization of fabrication techniques of glass fiber-reinforced vinyl ester resin composites. It outlines optimum reaction conditions such as temperature, time, monomer type and initiator concentration. The experimental plan consisted of preparation of vinyl ester resin followed by the composite samples. Mechanical characterization was done and a comparison was made between the different samples. It was found that these composites have fairly good tensile and flexural properties. The composites with styrene and butyl acrylate as co-monomers had similar tensile strength which was higher than that of the composite with methyl acrylate. Hardness values of the three composites were almost the same without any significant effect of the comonomer type. Volumetric wear rate was estimated for these samples under various test conditions. A steady wear rate regime after certain amount of sliding was observed all the three cases. [ABSTRACT FROM AUTHOR]