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• This paper proposes a damage-resistant Hybrid Fiber Reinforced Polymer Composites (HFRP) design method based on the interface properties. • The microscopic interface properties of composites are introduced into the investigation of interlayer interface properties. • The influence of different hybrid interlayer interfaces on the delamination damage behavior of composites is clarified. • The 3D printing technology was used to prepare specimens of the hybrid fiber-reinforced composites. In this work, the poor impact damage resistance of carbon fiber-reinforced plastic (CFRP) composites was improved by mixing carbon fibers with ductile fibers (glass fibers/Kevlar fibers). The damage behavior of five interfaces of the prepared hybrid fiber-reinforced plastic (HFRP) composites was investigated through mode-I and mode-II interlaminar fracture toughness tests and micro-droplet debonding tests. On this basis, a numerical model for predicting the impact damage of HFRP composites was established. Through a comprehensive evaluation of the impact damage resistance indexes obtained from the numerical simulations, the hybrid fiber type, hybrid ratio between different fibers, and hybrid lay-up sequence could be optimized. The specimens with optimized lay-ups were prepared by 3D printing, and the effectiveness of the numerical model was verified through low-velocity impact and compression after impact (CAI) tests. The results show that the introduction of glass fiber layers in CFRP composites can significantly improve the damage resistance of the composites. Compared with CFRP composites, when the volume fraction of the glass fibers is 25%, HFRP composites have a smaller delamination damage area (reduced by 74.08%), furthermore, the pit depth is reduced by 43.01%, the CAI is increased by 17.29%, and the strength retention rate is increased by 31.94%. [ABSTRACT FROM AUTHOR]

Highlights • Detailed numerical analysis of S0/A0 mode conversion phenomenon on the delamination based on spectral element method. • Analysis of wavefield (including S0/A0 mode conversion) distribution through the thickness in the delaminated region. • Implementation of the model for impact damage. • Full wavefield measurements and numerical results show good agreement. Abstract In this paper results of numerical analysis of S0/A0 elastic wave mode conversion at discontinuities in glass fibre reinforced polymer (GFRP) plates are presented. Analysis of S0/A0 mode conversion effect at Teflon inserts simulating delamination (circular Teflon inserts located at a different depth, Teflon inserts with different shapes at the same depth) and impact damage with energies 5 J, 10 J and 15 J is conducted. Numerical analysis is based on spectral element method (SEM) in the time domain. Numerical model includes a composite plate, a piezoelectric transducer and bonding layer for transducer and damage. Numerical model takes also into account the influence of material damping. Numerical results are compared with experimental results based on full wavefield measurements using scanning laser Doppler vibrometry (SLDV). It is shown that based on effects of S0/A0 mode conversion it is possible to detect the damage and determine its shape and size. [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 Fiber reinforced polymer (FRP) composites are commonly used in the chemical industry for storage tanks and pipelines, since most metallic alloys suffer from corrosion and result in costly maintenance and safety hazards. E-glass fiber is commonly used because of its low cost, but it is extremely susceptible to rapid degradation in low-pH environments. C-glass is an acid-resistant substitute, and while not as durable as carbon, it is much cheaper. Nevertheless, durable fibers are not the only key aspect of designing corrosion-resistant composites, as various degradation mechanisms must be considered. In this study, plain-weave laminates of C-glass and amine-cured epoxy are exposed to water and sulfuric acid solutions, and the relationship between diffusion kinetics and strength-loss is discussed. Results show that both solutions attack the fiber surface to some degree, but more importantly sulfuric acid increases the saturation uptake of water in the material, causing high swelling stresses that significantly reduce mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract This paper presents experimental and numerical investigations about the effects of thermal cycles on adhesively bonded joints between pultruded glass fibre reinforced polymer – unsaturated polyester (GFRP) adherends used in civil engineering structural applications. Single lap bonded joints were produced with two commercial polymeric adhesives – epoxy (EP) and polyurethane (PUR) – and exposed to a mild (Mediterranean) range of thermal variations (−5 °C–40 °C) for up to 350 cycles in a dry condition. The mechanical performance of the adhesively bonded joints was assessed by means of single lap shear tests. Regardless of the inherent differences between both adhesives, results obtained show that the global effect of thermal cycles on the load vs. displacement response of EP-GFRP and PUR-GFRP joints was similar. For both adhesives, thermal cycles caused considerable reduction of joint stiffness and strength, with maximum reductions of 18% and 22% for EP-GFRP joints, respectively, and 19% and 11% for PUR-GFRP joints. The degradation of performance was influenced by post-curing effects, more relevant in the PUR adhesive. Before exposure to thermal cycles, both types of specimens exhibited similar failure mechanisms, which generally (80–90% of cases) involved light fibre tear and fibre tear modes, attesting the effectiveness of the adhesion process and material compatibility. Exposure to thermal cycles did not influence the failure modes of the PUR-GFRP joints; however, EP-GFRP joints became more prone to adhesive failure after being subjected to thermal cycles. Three-dimensional finite element models were used to estimate the magnitude of the internal stresses developed during the thermal cycles. For both types of bonded joints, the numerical results showed a relatively low magnitude of both shear and normal stresses developed due to the mismatch of the coefficients of thermal expansion (CTE) of the adherends and the adhesives. Overall, the results obtained indicate that thermal cycles degrade bonded joints between pultruded GFRP adherends and this degradation seems to be due mostly to detrimental effects on the constituent materials, namely the adhesives; however, for the conditions used in this study, this degradation seems to be compatible with the structural use of this type of joints in civil infrastructure. [ABSTRACT FROM AUTHOR]

Abstract The aim of this work to investigate the effect of glass fiber (GF) on the thermal properties of sugar palm (SP)/thermoplastic polyurethane (TPU) hybrid composites. Sugar palm/glass fiber hybrid composites at the different weight fraction of 0/40, 10/30, 20/20 and 30/10 were prepared by using melt-mixing compounding followed by hot pressing machine. Thermal properties of hybrid composites carried out by using Dynamic mechanical analyzer (DMA) and thermo-gravimetric analyzer (TGA). The storage modulus (E′), loss modulus (E″) and damping factor (tan δ) were evaluated as a function of different relative sugar palm/glass fiber weight fraction. Also, the peak height was investigated for tan δ curves. At higher glass fiber loading exhibited the highest storage and loss modulus while the lowest damping factor was observed for higher sugar palm fiber loading. Thermogravimetric analysis (TGA) demonstrated that the amount of residue decreased as the glass fiber loading decreased. Overall, the hybridization of glass fiber with sugar palm/TPU composites enhances the thermal properties of the hybrid composites for automotive applications. [ABSTRACT FROM AUTHOR]

Abstract Glued-in-rods (GiR) represent a class of joints being used in timber engineering that are mostly used to transfer axial loads in structural members with Glass Fibre Reinforced Polymers (G-FRP) increasingly being considered as rod material in substitution for the usually considered metallic rods. The primary objective of the research presented herein was to apply a probabilistic capacity prediction method to timber joints with G-FRP GiR. Necessary secondary objectives were to mechanically characterise the involved components (adhesive, rods, and timber) and to numerically investigate the stress state inside the tested joints. The methodology shall be applied to a recently reported in literature Zhu et al. (2017) that was specific in two ways: firstly, G-FRP rods were bonded into both ends of the timber block with both ends being tested to failure—a deviation from common practice; and secondly, as opposed to most previous studies exhibiting stiff adhesives, a ductile Polyurethane with markedly non-linear behaviour was used. All material characterisation was performed with methods that can be reproduced by any standard laboratory equipment, to provide parameters for the subsequent numerical analyses. Based thereupon, a probabilistic method was used and provided reasonably accurate predictions of the joint capacities of 25 different geometrical GiR configurations. The probabilistic method was extended for realistic estimations of the experimental capacity scattering in form of upper and lower percentiles. [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]

this paper analyses the numerical and experimental results to evaluate the dynamic properties of pultruded GFRP (Glass-Fiber Reinforced Polymers) buckled columns. The profiles are made of glass fiber reinforcement and thermosetting vinylester matrix with thin-walled open or closed cross section. The buckling phenomena of the column with fixed ends were evaluated with a non-destructive method based on experimental modal data through dynamic identification procedure. Numerical analysis has been carried out through Finite Element models calibrated considering two consecutive stages that involve the local and global scale: i) parametric natural frequencies analysis to model the different cross sections taking into account the sti f fness of the rotational constraint between the wall segments of the thin walled pultruded profiles; ii) buckling analysis to identify the inaccuracies in the specimen or in the experimental apparatus through global flexural displacements which increase continuously with the axial load. Experimental, theoretical and numerical results were compared in order to know the wall segment effects of GFRP columns in free vibration field when affected by buckling phenomena. The results allow to investigate the significant role that the manufacturing imperfections of pultruded material play in the structural performance of GFRP buckled columns. [ABSTRACT FROM AUTHOR]

For fillers reinforced polymer composites, the material properties of the composites are affected by the dispersion and orientation of the inclusions. In particular, high aspect ratio inclusions such as glass fibers in the polymer matrix generate the mechanical or thermomechanical anisotropy of the composites that are critical to the dimensional stability, flowability, toughness, and strength of the final products. We investigate the microstructural anisotropy of multiphase polymer composites composed of talcs and glass fibers to characterize the anisotropic thermomechanical properties of the composites. The internal structure of the composites is observed by using an X-ray microtomography to characterize fiber length distributions. The fiber length distributions are fitted to the Weibull distribution statistical function to model the ultimate tensile strength of the composites. A fiber efficiency factor is coupled with the statistical function to understand the effect of the fiber length distributions on the mechanical strength of the composites. The thermomechanical anisotropy is evaluated by using linear thermal expansion coefficients. The flowability of molten polymer composites is evaluated experimentally and numerically to evaluate the role of inclusions on rheological properties and processability of the composites. [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 study provides a fuzzy-based model for predicting the shear contribution of FRP in RC beams strengthened by externally bonded FRP sheets. For this purpose, ultimate strain of FRP, effective depth of FRP, compressive strength of concrete, width and spacing and angle of FRP, shear span to depth ratio, the elastic modulus of FRP and thickness of FRP were considered as input parameters while shear strength of FRP is treated as the target one. After a comprehensive review in existing literature, 89 FRP-strengthened RC beams were selected which had experienced FRP rupture failure mode. The results indicate that the proposed fuzzy-based model could predict the shear contribution of FRP in RC beams strengthened by FRP sheets with a good degree of precision compared with the results obtained directly from the existing guideline equations such as fib-TG9.3, CIDAR, ACI 440.2R-08 and CSA-S806(12). Proposed model provide an accurate and reliable tool than the guidelines equations. [ABSTRACT FROM AUTHOR]

Three dimensional (3D) printing is a technique conventionally used to manufacture prototypes. Commercial desktop 3D printers have become available which produce functional 3D printed parts. The MarkOne by Mark Forged manufactures printed structures reinforced with continuous Carbon, Fiberglass or Kevlar fibers. The aim of this study is to evaluate the elastic properties of the fiber reinforced 3D printed structures and predict elastic properties using an Average Stiffness (VAS) method. Samples evaluated in this study were produced by varying the volume fraction of fibers within the 3D printed structures (4.04, 8.08 and 10.1% respectively). The experimentally determined elastic modulus was found to be 1767.2, 6920.0 and 9001.2 MPa for fiber volume fractions of 4.04, 8.08 and 10.1% respectively. The predicted elastic moduli were found to be 4155.7, 7380.0 and 8992.1 MPa. The model results differed from experiments by 57.5, 6.2 and 0.1% for the 4.04, 8.08 and 10.1% fiber volume fractions. The predictive model allows for the elastic properties of fiber reinforced 3D printed parts. The model presented will allow for designers to predict the elastic properties of fiber reinforced 3D printed parts to be used for functional components which require specific mechanical properties. [ABSTRACT FROM AUTHOR]

An innovative hybrid sandwich slab for the rehabilitation of floors in old masonry buildings was conceived, designed, and tested. This structural system is a lightweight composite floor consisting of bottom skin and shear ribs in Glass Fiber Reinforced Polymer (GFRP), a top layer of Deflection Hardening Cement Composites (DHCC), and Polyurethane foam core. In the first part of this study, the material/structural performance of the panel’s concept was assessed by experimental tests. The second part is now dedicated to the execution of advanced numerical simulations, including parametric studies, for assisting on the optimization of this composite slab system and investigating the influence of the relevant characteristics of GFRP and DHCC components. The influence of considering orthotropic behavior for the GFRP components and linear or nonlinear behavior for the DHCC are also investigated numerically in terms of accomplishing serviceability and ultimate limit state requisites for this structural system. The parametric studies show that the thickness of GFRP rib is the most important parameter to increase the load carrying capacity of this type of slabs. Based on the results of these parametric studies, two slabs are built and tested experimentally, and the obtained results are not only used to demonstrate the effectiveness of the developed structural system, but also to appraise the predictive performance of the constitutive models adopted in the FEM-based simulations. [ABSTRACT FROM AUTHOR]

Energetically weak points in thermally insulated building envelopes are formed by thermal breaks that are implemented to structurally connect external balconies to internal slabs. Current thermal breaks comprise stainless steel bars that penetrate the insulation layer and thus cause significant thermal losses. A new thermal break composed of highly insulating aramid and glass fiber-reinforced polymer (AFRP and GFRP) components and aerogel granulate insulation materials was developed and the first prototypes of the load-bearing components were experimentally investigated. The use of AFRP leads to an excellent thermal performance with linear thermal transmittance values of below 0.15 W/m K. The experimental prototype investigations confirmed the targeted ductile failure mode through concrete crushing in the component–concrete interfaces. The serviceability limit state conditions are met for a targeted balcony cantilever span of 4.0 m. The material-tailored components can be manufactured by fully automated processes such as filament and tape winding and pultrusion to economically produce large quantities within a short time. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to simulate long-term hydrostatic tests on Glass Fiber Reinforced Plastic (GFRP) pipes. An experimental procedure for obtaining pressure class of GFRP pipes on the basis of long-term behavior is very time consuming and costly that sometimes take about 2 years for collecting required data. Then, obtained results are extrapolated to 50 years. In this work, a theoretical modeling procedure is developed to obtain residual strength of pipes after 50 years taking into account creep phenomenon. Developed progressive modeling consists of creep modeling, stress analysis and failure evaluation. An integrated modeling procedure is developed reporting time-to-failure at any desired internal pressure. As a case study and also validation purpose, the developed modeling procedure is conducted for predicting long-term behavior of a specific GFRP pipe subjected to internal pressure. A comparison between real experimental data and theoretical modeling is presented. A very good agreement between predicted 50-year hydrostatic pressure and experimental data implies on the proficiency of the developed modeling. Since the developed modeling is just in need of short-term experimental data on pure resin, it could be used as an appropriate engineering tool for industrial centers. [ABSTRACT FROM AUTHOR]

The kink behavior of non-slender glass fiber-reinforced epoxy prismatic specimens of variable length and fiber volume fraction at temperatures ranging from 25 °C to 125 °C was investigated. Splitting failure occurred at the glassy state while kinking failure was observed at the glass transition state and buckling with subsequent post-peak kinking at the rubbery state. Kink initiation was caused by the initial imperfections, i.e. the waviness of the unidirectional fibers. Initiation occurred through fiber microbuckling caused by combined compressive and shear stresses at the glass transition state and predominant shear stresses at the rubbery state due to the preceding buckling. The kink band width was narrow at the glass transition state due to the significant compressive stresses and corresponded to the wavelength of the initial fiber waviness. The kink band width at the rubbery state was much wider and corresponded to the band width of the maximum shear stresses at the inflexion points of the buckling shape. The kink band angle depended on the ratio of compressive to shear stresses. The different specimen slendernesses and fiber volume fractions did not influence the kink initiation and kink band formation mechanisms. [ABSTRACT FROM AUTHOR]

The failure mechanism of non-slender glass fiber-reinforced epoxy prismatic specimens subjected to axial compression and different temperatures was investigated. Digital image correlation was used to map and derive the failure modes. The failure mode changed from splitting failure at ambient temperature to kinking at the onset of the glass transition temperature. The kink initiation mechanism could be clearly observed. Based on the initial waviness of the fibers, the wave amplitude disproportionally increased at one specific location up to fiber microbuckling and surrounding matrix failure; the wavelength of the initial imperfection was thereby maintained. The kink band then rapidly propagated through alternating horizontal and inclined segments leading to an overall inclined kink band of 31° on average. The kink band width doubled from around three to six times the average wavelength of the initial imperfection. [ABSTRACT FROM AUTHOR]

The objective of this article was to experimentally evaluate timber–concrete composite beams in two different situations – with and without glass fiber reinforced polymer (GFRP). Four full-scale composite beams (5.4 m in length) were produced, two of which had reinforcement (nominal thickness of 10 mm) and two with no reinforcement. The fiberglass reinforcement was formed from the impregnation of unidirectional fiberglass cloth – effective thickness of 0.5 mm – with epoxy resin. The connection system consisted of steel hooks inclined at 45 degrees, bonded with epoxy adhesive to the holes previously drilled on the wood, whose apparent density at 12% moisture content was 0.79 g/cm 3 . The reinforced timber–concrete composite beams tested had performance efficiency of 79% and average rupture strength of 142.5 kN. Finally, the reinforced timber–concrete composite beams were analytically evaluated using the proposed method in Eurocode5, showing reasonable agreement with the experimental results. [ABSTRACT FROM AUTHOR]

A novel method using microwaves is proposed to detect and evaluate defects in glass fiber reinforced plastic (GFRP) laminates. A thin circular plastic film simulating delamination was inserted in GFRP laminates and was detected using microwave reflectometry. A focusing mirror sensor consisting of a horn antenna and two metal mirrors was used to improve the measurement resolution. In addition, the thickness of the film was calculated using a proposed model based on microwave propagation theory. Measuring the variation in the amplitude of the microwave reflectivity, a 7.5-μm-thick film was successfully detected in a 3-mm-thick GFRP laminate. Moreover, the calculated results of the inserted film thickness had a high degree of accuracy. [ABSTRACT FROM AUTHOR]

Pultruded glass fibre reinforced polymer (GFRP) composite wide flange (WF) beams were fabricated with mid-span splice joints. The joints comprised: two or six GFRP plates bolted to the flanges. The bolts were torqued to 3, 20 and 30 Nm. The 2.9 m span simply supported spliced beams were tested in symmetric three-point flexure. Each beam was subjected to three load – unload cycles and loads, mid-span deflections, support rotations and splice plate surface strains were shown to be linear and repeatable. Spliced beam transverse stiffnesses were quantified as functions of bolt torque for both splice plate configurations and were shown to increase linearly as the bolt torque increased. Transverse stiffnesses of unspliced and six-plate bolted/bonded splice jointed beams were compared and the stiffness of the splice bonded beam was shown to be about 47% stiffer than the splice bolted beam with a bolt torque of 3 Nm. [ABSTRACT FROM AUTHOR]

This study is focused on the finite element analysis of the hygro-elastic stresses experienced by unidirectional composite structures instrumented by Fiber Bragg Grating (FBG) sensors. One of the significant advantages of this method is that by taking into account the complex geometry of elaborated specimen and their different constituents with heterogeneous hygroscopic and mechanical properties. In the first time, the obtained results were compared with the results obtained owing to an analytical solution deduced from the simplified concentric cylinders approach. This comparison allows us to evaluate the reliability of the concentric cylinders approach which cannot account for every aspects of the actual geometry of the studied samples. Besides the numerical results were compared to the experimental characterization of the mechanical states deduced from the Fiber Bragg Grating measurements. [ABSTRACT FROM AUTHOR]

Abstract: In the automotive industry, more and more engineered parts are shifting from metals to engineering plastics. However localised impact loading and long term ageing effects of under-the-hood plastic components is not well understood. In this paper, localised low velocity impact experiments and simulations were conducted on glass fibre-reinforced polyamide sump to investigate typical flying stones impact scenarios. Complete components were manufactured by injection moulding techniques for the experimental samples. The samples were then subjected to a range of low velocity impact using drop weight tower and flying projectiles from an air gun. Damage assessments were then performed following the experiments. In parallel, finite element analysis using LS DYNA was carried out to virtually benchmark and to predict the strength and fracture behaviour of stressed plastic parts. This has permitted to perform numerous impact tests in different situations with varying parameters. The study results show the significant contribution of the design in terms of shock absorption. The specific sump design with a protective ribbing combined with a superior material increases considerably the impact resistance. The paper will provided detailed discussions and results from both the experiments and finite element analysis investigations. [Copyright &y& Elsevier]

Pultruded Fiber-Reinforced Polymers (FRP) are innovative structural elements that are experiencing a steady increase in use for different structural applications. Due to their appealing properties that set them apart from traditional construction materials, such as magnetic transparency and excellent strength-to-weight ratio, numerous experimental and numerical studies have been performed in the last decades to assess their performance as structural components. The description of the micro- and macro-scale mechanical features of FRP elements requires multiple levels of information to be accurately characterized to predict their strength, and as a result, researchers have developed computational models with varying levels of complexity to parametrize their response and investigate design parameters through numerical simulations. This paper presents a critical review of the current state-of-the-art in numerical modeling of structural fiber-reinforced polymeric elements for the prediction of their mechanical behavior under serviceability and failure limit state conditions, with particular attention devoted to pultruded Glass Fiber Reinforced Polymers (GFRP), and their use as load-bearing structural elements. The most commonly adopted numerical methods for the solution of this set of problems range from classical Finite Element Method (FEM) approaches to eXtended Finite Element Method (XFEM), Virtual Crack Closure Technique (VCCT), Cohesive Zone Modeling (CZM), Multiscale Reduced Order Modeling (ROM), as well as Random Lattice Modeling (RLM) techniques recently developed by the co-authors. Each one of these methods has its own distinctive features and brings specific challenges and capabilities that will be presented and discussed in detail in the manuscript. This paper, therefore, aims at illustrating the reliability of existing numerical models for the simulation of FRP structural elements and draw conclusions and recommendations for future research, discussing 160 references from the available literature. [ABSTRACT FROM AUTHOR]

Abstract: Due to the mechanical properties of fibre reinforced polymer (FRP) bars, deflections often drive the design of FRP reinforced concrete (RC) flexural members. This has led to an increasing number of studies focused on the analysis of short-term deflections of FRP RC beams. However, investigations and experimental data focused on long-term deflections are scarce. The time-dependent deflection in RC beams is a function of member geometry, material properties and loading characteristics. Maximum service loads, as well as repeated loading, affect the deflections under sustained loads. This paper presents the results and discussion of an experimental programme concerning eight glass FRP RC beams tested at service load, and subsequently subjected to sustained loading for 250days. Two reinforcement ratios and two levels of sustained load were considered. The experimental results revealed an effect of the loading–unloading processes and the reinforcement ratio on short and time-dependent deflections. No significant influence of the sustained load level was observed. Moreover, the theoretical predictions obtained with different models have been compared with the experimental results. The modified time-dependent factor presented in ACI 440.1R-06, together with the modified Bischoff’s equation to compute the immediate deflections due to sustained load, give the best agreement with experimental deflections. [Copyright &y& Elsevier]

Abstract: Glass fiber reinforced polymer (GFRP) composites are used extensively to strengthen and/or to rehabilitate infrastructures. The current study focuses on the use of GFRP for enhancing local buckling behaviour of wide flange steel beams. The study is conducted numerically using a nonlinear finite element model developed in-house. In the numerical model, consistent shell elements are used to simulate the flanges and web of the steel beams as well as the GFRP plates. The interface between the steel and GFRP plates is simulated using a set of continuous linear spring systems representing both the shear and peel stiffness of the adhesive based on values obtained from a previous experimental study. The numerical model is validated using test results and numerical predictions available in literature. Various failure modes, including GFRP rupture, adhesive shear failure, and local buckling of the flanges of beams are included in the model. The effect of geometric imperfection and residual stresses are also included. The model is then used to conduct a parametric study to assess the effect of bonding GFRP plates on enhancing the local buckling behaviour of wide flange steel beams. The results reveal that the effectiveness of this approach especially for the case of slender beams. [Copyright &y& Elsevier]

Abstract: In the last decades, FRP composites have been widely used for constructing entire civil structures. One of the challenging issues for building with pultruded FRP composites is understanding the behaviour of bolted joints. In this paper, the results of a numerical analysis performed on different types of bolted composite joints with different geometry and subjected to tensile loads are reported. The aim of this study is to examine the distribution of shear stresses among the different bolts by varying the number of rows of bolts as well as the number of bolts per row. The study also considers the presence of variable diameter washers and their influence on the bearing stresses of composites with different fibre orientations. For verification of the validity of the analytical models, numerical results are compared to experimental results reported elsewhere. The results of this study showed that in multi-bolt joints, the load is not distributed equally due to varying bolt position, bolt-hole clearance, bolt-torque or tightening of the bolt, friction between member plates and at washer-plate interface. The results also indicated that in the presence of washers, the stress distributions in the fibre direction, varying fibre inclinations, are decreasing for each value of washer pressure. [Copyright &y& Elsevier]

Abstract: The flexural behaviour of a new generation composite sandwich beams made up of glass fibre-reinforced polymer skins and modified phenolic core material was investigated. The composite sandwich beams were subjected to 4-point static bending test to determine their strength and failure mechanisms in the flatwise and the edgewise positions. The results of the experimental investigation showed that the composite sandwich beams tested in the edgewise position failed at a higher load with less deflection compared to specimens tested in the flatwise position. Under flexural loading, the composite sandwich beams in the edgewise position failed due to progressive failure of the skin while failure in the flatwise position is in a brittle manner due to either shear failure of the core or compressive failure of the skin followed by debonding between the skin and the core. The results of the analytical predictions and numerical simulations are in good agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: There are various ways to connect a GFRP deck and girder which have been adopted as systems worldwide such as connection systems that use shear connectors and mechanical connection systems that use bolts or clamps, and recently there has been a study on a system to connect GFRP deck and steel girder using a bonding agent. In this study, an attempt was made to review and analyze the composite level of GFRP decking and a girder bolt connection system using the already proposed GFRP deck shape. In addition, an attempt was made to estimate the decreased rate of the composite level at various bolt connection intervals using the calculated strain and deflection, and also the analytical values of the composite level were compared with prior test results. [Copyright &y& Elsevier]

Abstract: This paper focus on the design of a GFRP truss-like structure for dismountable bridges with maximum span of 30m. The bridge structure is composed of a deck supported by prestressed trussed beams which are mounted by assembling GFRP tubular profiles and steel joints with bearing type connections. Experimental tests were carried out on short profiles to determine their compressive strength at the connections and on two 1:2.3 reduced models of the trussed beam structure: a short 1.3m span cantilever beam and a 13.0m span simple supported beam. The main results obtained from the performed experimental tests on short profiles and on the cantilever beam are presented herein. It is shown that a non-linear behaviour can be generated on the trussed cantilever beam by decompression of tubular members and that collapses are induced by buckling of diagonal members. [Copyright &y& Elsevier]

Abstract: This paper presents the results of compressive tests on pultruded glass fibre reinforced plastics (GRP) channel columns, buckling about both the minor and major axis of the cross-section, at ambient and elevated temperatures. Accompanying mechanical tests of short specimens (30mm) were also carried out to obtain compressive strengths of the GRP material at elevated temperatures. The Southwell plot technique was performed on some of the long column tests, for which the load–lateral deflection curves were available, to obtain the Euler buckling loads, thereby the Young’s modulus values, of the GRP section at ambient and 60°C. Because results of the Southwell plot analysis confirm close correlation between the Euler buckling load with the experimental peak load for the long columns at ambient temperature and 60°C, the experimental peak loads of the long columns at 90°C and 120°C were used to determine the Young’s modulus values of the GRP section at these temperatures. The main conclusions are: [(1)] Pultruded GRP columns may be used in panel walls in low-rise construction exposed to fire because the temperatures in most parts of a GRP section would be much lower than 120°C. At temperatures not exceeding 120°C, the GRP columns can retain substantial proportions of the GRP column strength at ambient temperature. [(2)] Pultruded GRP sections can develop quite high compressive stresses at temperatures below the heat distortion temperature (HDT) of the resin. But at temperatures higher than the resin HDT, the compressive stress of the GRP section is low. [(3)] Pultruded GRP sections retain very high Young’s modulus at elevated temperatures not exceeding 120°C. [Copyright &y& Elsevier]

Abstract: The design of GFRP beams is often governed by deflection limits in service, hence it becomes crucial to evaluate accurately their flexural stiffness. In this work, the flexural stiffness of GFRP pultruded profiles is evaluated experimentally, numerically and analytically. A procedure that simultaneously yields the flexural and the shear modulus of GFRP pultruded profiles directly from 3-point bending tests is applied. Direct tension and 3-point bending tests on coupons extracted from these profiles were also conducted. The TBT and the FEM were applied to analyze the profiles under bending, using material properties estimated by CLT. Comparisons of numerical, analytical and experimental results are presented and discussed at the end. [Copyright &y& Elsevier]

The structural integrity and damage tolerance of typical composite T-joints found in ships constructed from glass fibre reinforced plastic was the subject of this investigation. The effect of the geometry of the T-joint on the strain distribution was investigated using finite element (FE) analysis. The results, reported in this paper, showed that the critical strains were significantly affected by the joint geometry. Results of the FE analysis conducted to investigate the effect of disbonds between the filler and overlaminate are also reported. This showed that particular defects led to large changes in the strains in the T-joint structure, which would encourage disbond progression. The FE model was validated by mechanical tests on a representative T-joint, instrumented with surface strain gauges and displacement transducers, into which a range of defects was progressively introduced. [Copyright &y& Elsevier]

Pultrude glass fiber reinforced polymer (GFRP) sections have gained increasing acceptance in building and construction industries considering their promising physical and mechanical properties. However, they are prone to premature web crippling failure due to their orthotropic nature and relatively low interlaminar shear strength and modulus when subjected to transverse bearing load. This paper presents a study on the effect of bearing length on web crippling behavior of pultruded GFRP channel sections. Four channel sections with different sectional dimensions were selected for web crippling testing. Two loading conditions including end-two-flange (ETF) and interior-two-flange (ITF) were adopted. Transverse loading was applied through bearing plates with five different lengths of 20 mm, 50 mm, 100 mm, 150 mm and 200 mm. Failure modes, load–displacement curves and web crippling capacities were reported and discussed associated with the effect of bearing length. Mechanism based design equations which were able to consider effect of bearing length were proposed, and the predicted web crippling capacities agreed well with experimental results. [ABSTRACT FROM AUTHOR]

A glass fiber shell (GFS) and carbon fiber core (CFC) hybrid rod (HFRP) was produced through pultrusion technology for an alternative to traditional steel sucker rod for petroleum production. The mechanical properties of a really used HFRP rod closed to the ground (25 °C exposed temperature, 0.5 MPa hydraulic pressure and ~70 kN cyclic loading) and in the deep oil-well up to 2600 m (90 °C exposed temperature, 18 MPa hydraulic pressure and ~50 kN cyclic loading) were investigated as a function of service time as long as 553 days. The mechanical, thermal properties and microanalysis tests of HFRP rods were conducted to obtain the long-term evolution of HFRP rods under the above service environments. Exposure closed to the ground caused a maximum degradation rate of short beam shear strength (SBSS) up to 18.92%. Meanwhile, the maximum degradation rates of interface shear strength (ISS) were 28.24% for carbon fiber/resin, 16.88% for glass fiber/resin and 36.07% for CFC/GFS interface. In comparison, exposure in the deep oil-well brought in an extra degradation rate from 4.34% to 11.11% for ISS, and the higher cyclic loading (~70 kN) played an insignificant effect on the degradation. The degradation mechanism of mechanical properties for HFRP rods was attributed to plenty of bound water combined with the resin through the hydrogen bond and brought about the hydrolysis of resin and the increase of pore volume content (~5%), leading to the debonding of fiber/resin. The long-term prediction of interface shear strength shows the degradations of CFC and CFC/GFS were more sensitive to the cyclic load (70 kN) compared to no cyclic load (0 kN), and an extra degradation rate up to 31.3% was observed compared to the no load condition, and the accelerated degradation was weakened with the increase of service temperature and hydraulic pressure. In addition, the exposure at the increased service temperature and hydraulic pressure in the deep oil-well led to an additional degradation rate of ISS in comparison to the ground exposure: 10.70% (CFC), 13.25% (CFC/GFS) and 4.81% (GFS). [ABSTRACT FROM AUTHOR]

Timber is one of the materials widely used in construction and industry all over the world. In this paper, the behavior of strengthened timber beams made of beech wood (Fagus orientalis) were investigated experimentally. The composite timber beams were reinforced with flat, U-shaped, and L-shaped pultruded Glass Fiber Reinforced Polymer (GFRP) profiles. The GFRPs were attached to tensile or both tensile and compressive surfaces of beams. Altogether, 24 specimens, including 20 strengthened beams and 4 un-strengthened (control) beams, were tested under three-point bending test. Flexural behavior of specimens was evaluated through their load versus mid-span displacement curves, ultimate load carrying capacity, stiffness, displacement ductility, and capacity of energy absorption. The experimental results indicated that the mean value of modulus of rupture, flexural rigidity, ductility, and energy absorption of strengthened beams increased by up to 61, 59, 79, and 209% in comparison to control specimens, respectively. Finally, an analytical calculation has been conducted in order to predict the test data. There was a reasonable agreement between the test results and the results of numerical model. [ABSTRACT FROM AUTHOR]