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Extending the application of fiber-reinforced polymer (FRP) composite materials into the automotive, aerospace and military manufacturing is a significant advance in recent years. However, few extending have been achieved in civil infrastructure and building construction industry. This gap is partly due to (i) the lack of multiphysics and multiscale models unifying degradation-deformation damage phenomena to assess the safety and durability of newly adopted or proposed material and structural systems, and (ii) no available computational models that are succinctly fundamental and directly interactable with other digital files from architecture designer or manufacturer. To begin addressing this gap, this paper presents a structure level multiphysics model that uses the UV and moisture deterioration variables homogenized from a micromechanics model to integrate a nonlocal continuum damage model in a curvilinear coordinate system. This model links the application of analysis to the architecture or manufacturing digital model by enabling more accurate predictions of mechanical performance. An example of the model is presented for analysis of a group of glass fiber-reinforced polymer (GFRP) composite plates in SFMOMA Façade System, the first and largest architectural application of fiber reinforced polymer (FRP) in the United States. [ABSTRACT FROM AUTHOR]

A recent invariant-based theory of composites is re-examined using multidirectional laminates through classical lamination theory applied on experimental data and micromechanical predictions for unidirectional laminates. Initially, the master ply values developed for carbon reinforced polymer composites (CFRP) proved to be inappropriate for aramid and glass reinforced polymer composites (KFRP and GFRP). This led to part the material systems into four classes, According to the type of reinforcing fibre, with dedicated master ply values. By then, GFRP was declared unfit for this theory due to the wide variation of the trace-normalized stiffness parameter with a small variation of longitudinal modulus. Here, the specialization of master ply values for KFRP and GFRP is demonstrated using micromechanical predictions. The invariant-based theory is applied to short beam deflection of multidirectional laminates and cross-ply GFRP laminates. This approach leads to small errors, for all material classes including GFRP. In brief, GFRP composites proved fit for invariant-based theory under the present conditions. [ABSTRACT FROM AUTHOR]

Interfacial mechanical properties of carbon/glass hybrid thermoplastic epoxy composite rods play a crucial role in the determination of the composite strength and fracture behavior. In this study, push-out and push-back tests using three hybrid rods with different carbon/glass ratios were performed to investigate the interfacial shear strength and fracture mechanism. Debonding occurred at the interface between the glass fiber bundles and thermoplastic epoxy. After the onset of debonding, sinusoidal behavior during sliding was observed in the load displacement curve, which was identical with the interface roughness in terms of wavelength. Debonding and sliding strength were considered to be related to the interfacial bonding region between the carbon fiber bundle core and surrounding braided glass fiber bundles. [ABSTRACT FROM AUTHOR]

In this work, the influence of a layer of glass fiber mat (GFM) inserted in a bi-material bonded joint interface is investigated as a toughening mechanism to improve the fracture performance of bonded structures. Composite-to-metal bonded specimens were manufactured by hand lay-up using two different consolidation processes: at room pressure or using vacuum bagging. The fracture behavior was evaluated under quasi-static loadings using the mixed-mode bending (MMB) test. Test results revealed an increase of the fracture toughness with the insertion of an adjacent layer of GFM. The toughening mechanism is associated with a more irregular fracture surface profile. It was verified a relationship between the fracture surface roughness and the fracture toughness. The toughening effect showed to be more evident in higher mode II fracture conditions. The insertion of a layer of GFM and the use of vacuum pressure in the consolidation of the composite increase the fracture performance of composite repairs in metal structures. [ABSTRACT FROM AUTHOR]

• The AET is applied in the damage evolution of a GFRP plate during a bending test. • AE signals were identified by using a proposed algorithm based in a threshold level. • Several global parameters allowed to show different aspects of the damage evolution. The damage process in fiber-reinforced polymers (FRP) has been the subject of continuous studies in recent decades using different approaches. In particular, the acoustic emission technique has been proved to be a powerful tool in the monitoring of structures of this type of material due to the large acoustic activity captured when this material is loaded to rupture. The present work explores several indexes that were calculated from the experimental recording of acoustic emission signals, and their efficiency in describing the failure process in structures. One of these indexes, called c value, is originally proposed, and its sensibility it is compared with other classical parameters that are usually employed in the Acoustic Emission analysis. A 3-point bending test has been performed on a glass fiber reinforced polymer plate. Our own methodology was proposed to identify AE signals in semi-automatic manner. This methodology also allowed a faster analysis of the global parameters during the process data of the AE test. The global parameter evolution obtained from the acoustic emission data during the damage process could be considered as precursors of the more meaningful event and as an aid to understand in which way the structure is going to the collapse. [ABSTRACT FROM AUTHOR]

Fiber-reinforced thermoplastic composites offer a high potential for high-volume car body structures. A tailored use of thermoformed and subsequently injection overmolded unidirectional pultruded material in the so-called "skeleton design" is a promising approach towards economical lightweight design. The paper investigates the interlaminar shear strength of pultruded specimens for polyamide 6 and polypropylene as matrices at various temperature degrees. The specimens are made of different ratios of glass and carbon fibers. The results are compared to tape-laid specimens of the same materials to show the influence of the manufacturing technology. The performance is tested using a compression shear device at three testing temperatures −35 °C, +23 °C and +85 °C covering the typical temperature range for automobile structures as well as in conditioned and dry state. The interlaminar shear strength decreases on average by 65% from −35 °C to +85 °C, whereas conditioning reduces interlaminar shear strength by 25% at −35 °C and +23 °C with no influence at −35 °C. The results are analytically described in order to obtain a continuous description of the interlaminar shear strength within the analyzed temperature range. [ABSTRACT FROM AUTHOR]

Pultruded Glass Fiber Reinforced Polymers (PGFRPs) have been increasingly used in the field of engineering construction. In civil engineering structures, mechanical connections such as bolted connections are widely used because they are an easy way to connect the members. However, this kind of connection for PGFRP has low shear strength when the main part of the PGFRPs features unidirectional glass roving, and the shear strength of this part is determined by the shear strength of the matrix. This problem reduces the mechanical performance of the connections. In this study, the strengthening effects of three types of glass fiber sheets (GFSs) (0°/90°, ±45°, and a chopped strand mat (CSM)) on PGFRP connections were experimentally investigated under tensile loads. Based on the experimental results, GFSs could remarkably improve the ultimate loads and stiffness of PGFRP connections. Moreover, simple formulas were proposed to evaluate the ultimate loads of single PGFRP-bolted connection reinforced by multiaxial GFSs. [ABSTRACT FROM AUTHOR]

This paper evaluates the strain-sensing ability of a nanoengineered hierarchical twill weave composite using multiscale numerical simulations. Piezoresistivity is incorporated in such composite by introducing carbon nanotubes (CNT) in the polystyrene (PSS) matrix so as to form a percolating microstructure. The glass fiber twill weave, which itself contains CNT-modified PSS matrix inside the yarns, is coated with thin film of such piezoresistive matrix to obtain the smart composite configuration. The methodology, presented in this paper, captures the hierarchical intricacies at multiple length scales and implements various mechanical damage mechanisms at subsequent interactive length scales as well as consequent electrical responses so as to yield macroscopic electromechanical response. The simulated responses show excellent correlation with experimental observations signifying the efficacy of the simulation methodology. Such a detailed multiscale approach can provide valuable insights towards tuning of structural hierarchies at multiple length scales for efficient design of smart woven laminated composites. [ABSTRACT FROM AUTHOR]

Glass Fiber Reinforced Polymer pipes (GFRP) are used in a variety of industries such as water, oil and gas, aerospace and chemical industries. In the present paper, the creep response of GFRP pipes undergoing compressive transverse loading is analyzed through experimental observations and numerical modeling. Firstly, the long-term creep response of a GFRP pipe is investigated under single-stage loading till more than 400 days. Then, the creep response of another sample from the same pipe is evaluated under multi-stage loading with four 720-h steps (totally 2880 h). Theoretical modeling is performed using a two-level model based on short-term viscoelastic behavior of resin. A procedure is proposed to replace a long-term creep test under a single stage loading with short-term creep tests with multi-stage loading. The proposed procedure is validated through experimental study. The proposed multi-stage creep test scenario is very valuable to reduce the duration of experimental creep test. Utilizing the proposed method during the design process of a GFRP pipe, the creep response of the pipe can be estimated and its long-term properties can be ensured by performing equivalent short-term tests. The proposed procedure is validated through experimental study. [ABSTRACT FROM AUTHOR]

Depending on fiber size and volume fraction, polymer matrix type, processing temperature, injection speed, etc., short fiber reinforced composites produced by injection molding may exhibit complex fiber concentration, orientation and length distributions at different locations, causing large variations in their mechanical properties. In this work, a representative volume element (RVE) scheme is developed to describe the elastic properties of short glass fiber reinforced PA6,6 composites produced by injection molding. In the RVE formulation, fiber length is assumed to follow a two-parameter Weibull distribution, and a new concept, namely preferential angle, is introduced to account for the preferential alignment of fibers at different locations of injection molded composites. A random sequential insertion algorithm is developed to implement the fiber length distribution and fiber preferential alignment, and finite element method (FEM) is employed to analyze the relations of the elastic properties of RVE with three parameters, that is, the mean length, volume fraction and preferential angle of the fibers. Based on the FEM results, quantitative formulas for these relations are obtained. It is found that the variations in the mean length, volume fraction, and preferential angle of the fibers can cause large variations in elastic moduli and elastic anisotropy of the RVE. [ABSTRACT FROM AUTHOR]

Aim of the paper is the evaluation of the bond transfer mechanism and the following cracking behavior for concrete elements reinforced with Glass Fiber Reinforced Polymer (GFRP) bars. At the scope, an experimental survey has been developed on nine 3000 mm long tie-specimens with square cross-section of 150 mm × 150 mm, reinforced with a 4000 mm long GFRP reinforcing bar embedded in the centerline. Besides the reference element, reinforced with conventional steel rebar with diameter equal to 16 mm, nine GFRP bars with the same equivalent diameter and different surface treatments (smooth, sand-coated and helical fiber wrapped surfaces) were taken into account. The specimens were subjected to tensile force and the obtained results have shown how the different surface coating may affect the bond behavior at the concrete – GFRP interface, and the following crack pattern. [ABSTRACT FROM AUTHOR]

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]

The paper deals with multiparameter sensitivity analysis of a composite footbridge. A shell-like structure is 14.5 m long shows U-shaped cross-section and inner service dimensions 1.3 × 2.5 m. Glass fiber reinforced polymer GFRP laminate constitutes faces of a sandwich structure while PET foam received from recycled bottle builts a core. The structure was divided into 285 independent areas where the thickness of laminates and stiffness modulus of PET foam were established as design variables. The impact of their variation on variation of state variables was investigated, vertical displacement of structure, longitudinal strain in handrail and transverse strain in deck were addressed here. Sensitivity vector was computed by a semi-analytical method and, subsequently, expressed in a matrix form and next presented graphically in the form of sensitivity areas. The conducted sensitivity analysis exhibits areas that can be strengthened in order to minimize vertical displacement, longitudinal strain in handrail and transverse strain deck, determining the areas where parameters can be reduced without increasing the value of state variables. The obtained results are bound to support the structural design process or to improve the performance of existing structures. [ABSTRACT FROM AUTHOR]

Four reinforced concrete (RC) beam models undamaged, damaged by notches and strengthened by external bonded (EB) glass fiber reinforced polymer (GFRP) strips have been experimentally studied. The paper aims to assess the availability of strengthening with EB GFRP strips in RC beams having a deep localized damage. The behavior of RC beams has been analysed under bending loading until failure. Furthermore, the assessment of RC beam models foresaw nondestructive control of damaged and strengthened models by free vibration tests to obtain frequency values at different damage degree. Damage, artificially obtained by notches with different width, on the midspan section and on the lateral location of beams, has been analysed. The envelope of frequency response functions (FRFs) obtained by dynamic tests was elaborated and changes of natural frequency values are then correlated to damage both to non-strengthened beam with notches and to strengthened beam models. Results of static tests on RC beams strengthened with filled mortar in the notched sections and EB GFRP strips have allowed to validate the strengthening of RC elements with composite material characterized by relatively low elastic modulus; further, it has been assessed maintenance of bond between concrete surface and GFRP strips until failure under bending loading. [ABSTRACT FROM AUTHOR]

The challenge associated with the use of polyvinyl chloride (PVC) plastic pipelines is to improve their structural integrity without increasing their cost. Currently, PVC pipelines are the most cost-effective method of transporting water and sewage drainage. However, their low deterioration and mechanical properties cause significant losses and sacrifice the structural integrity of pipelines. Therefore, this study proposes the glass fiber-reinforced polymer (GFRP) overwrapped system to strengthen the external surface of PVC pipes, which will improve pipes' flexural load-carrying capacities. Accordingly, an extensive experimental program is developed and performed to examine the flexural behavior of GFRP composite overwrapped onto PVC plastic pipes. These phases include the fabrication process and different types of tests for evaluating the structural integrity of the GFRP/PVC pipes. The results showed that the proposed overwrapped system significantly improved the flexural carrying capability. The initial flexural failure load increased significantly, with an improvement from 64 to 1140 N. Also, the ultimate flexural load found to be improved by a factor of nine. The flexural behavior was significantly affected by changes in the fiber orientation angle. The results also revealed that as the pipe diameter increased, the flexural carrying load capacity increased. It is also important to note that the matrix cracking, fiber debonding, and fiber breakage were dominating the failure modes of GFRP/PVC pipes. [ABSTRACT FROM AUTHOR]

In this study, mechanical behavior of multilayer corrugated core laminated composite sandwich panel subjected to quasi-static three-point bending is investigated experimentally as well as numerically. Parameters such as contact force, energy absorption and specific absorbed energy (unit mass energy) for different geometries of corrugated core (rectangular, trapezoidal and triangular) are studied during loading process and failure. Composite plates and corrugated cores have been manually made using ML506 epoxy resin with 15% hardener and 45% volumetric woven glass fibers. Experimental results show that multilayer sandwich composite panels not only strengthen the structure in the quasi-static three-point bending process, but also make the absorbed energy to grow significantly by increasing the contact force and displacement up to the complete failure. The main mechanisms of damage and failure of sandwich panel specimens during load bearing process are matrix cracking, fiber breakage, delamination, local indentation, global bending, crushing and buckling of cell walls and face sheet and core de-bonding. Rectangular geometry of corrugated core, in terms of energy absorption and specific energy exhibits better results in comparison to other shapes. Numerical simulation using ABAQUS FEA package led to results, which are in good agreement with experimental ones and make it possible to use simulation instead of costly tests for analysis and design. [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]

The polyamide-based composite materials are widely employed in various industrial domains. Along with the numerous advantages of these engineering materials, an important sensitivity to hygrothermal conditions represents a major drawback. Hence, this study aims to thoroughly evaluate the variation of physical and mechanical properties in moist and thermal environments of three stacking sequences. An extensive tensile testing campaign is performed in order to create a rich experimental database. It is therefore preceded by a proper establishment of desiccation/absorption protocol for the composite material. The results demonstrate that the humid ageing parameters are highly affected by the temperature. The mechanical response is dependent on the glass transition temperature, or T g - T criterion, due to the occurring material plasticisation as a result of absorbed moisture. The shear modulus, the shear yield stress and strength deteriorate with the increase of temperature and moisture content. The changes of properties for the longitudinal and transversal orientations are not considerably pronounced. [ABSTRACT FROM AUTHOR]

In this paper, a new type of concrete-filled Glass Fiber Reinforced Polymer (GFRP) tubular hollow composite column is tested and analyzed by finite element analysis. The axial pressure test of 27 concrete-filled GFRP tubular hollow composite columns is made to investigate the compressive properties of the specimens, including the failure mode, ultimate bearing capacity under axial compression, load-strain relationship and load-displacement relationship. The effects of the three parameters of hollow ratio, diameter-to-thickness ratio of GFRP tube and concrete strength grade on the axial compressive properties of concrete-filled GFRP tubular hollow composite columns are studied, and some key principles of designing concrete-filled GFRP tubular hollow composite columns are presented. The parameters of hollow ratio, diameter-to-thickness ratio of GFRP tube, and concrete strength grade are analyzed by using the verified finite element model. An ultimate bearing capacity adjustment coefficient is proposed, which takes into consideration the influence of hollow sections. A recommended formula is given for the axial bearing capacity of concrete-filled GFRP tubular hollow composite columns. [ABSTRACT FROM AUTHOR]

This paper deals with strengthening statically indeterminate reinforced concrete (RC) beams with carbon and glass Fiber Reinforced Polymers (FRP) rods by using the Near Surface Mounted (NSM) technique. The test program consisted of six two-span beams; one control beam, which had exploited for comparison purposes, and five others initially strengthened in flexure with NSM-FRP rods in both hogging and sagging regions. The main test parameters were type, ratio and length of the FRP bars as well as characteristics of the filling material. The study presents and discusses their impacts on the global flexural behavior of continuous RC beam that mainly includes investigating the overall capacity, failure mode, moment redistribution and ductility state. All NSM-FRP strengthened beams displayed higher overall capacity than the control beam; the test results showed that implementing the NSM technique in an appropriate way could significantly improve the yielding capacity and load-carrying capacity of RC beams without large decrease in the ductility index or the moment redistribution degree despite the non-conventional failure mode. The beam failure was primary affected by the strengthening length; terminating the FRP bars before the zero moment point caused to change the failure mode from pull out of the FRP bars to premature peeling off of the concrete cover. On the other hand, moment redistribution and ductility of the NSM-FRP beams were negatively affected by: (I) Increasing the FRP reinforcement, (II) Decreasing the FRP length or (III) Using mortar as a filling material instead of epoxy-resin. Adopting a nonlinear analysis of the cross-sections could accurately quantify the moment–curvature and the ultimate load of the NSM-FRP continuous beams. [ABSTRACT FROM AUTHOR]

The failure analysis of cracked steel pipe repaired by glass fiber reinforced polymer (GFRP) was investigated in this study.3-dimensional elastic-plastic finite element method (FEM) was used to examine the GFRP composite patch with different orientation of fiber, [0°] 8s and [0°/90°] 4s. The development of various inclined stationary cracks under static and cyclic internal pressures in steel pipe was simulated using Extended-FEM. The findings showed that the path of inclined crack changed to be pure mode I crack. The crack path is not affected by fiber orientation. However, crack initiation pressure is affected by fiber orientation. [0°] 8s fiber orientation showed the best orientation for arresting crack in pipelines subjected to inner pressure. The reductions in the values of J -integral, crack mouth opening displacement, and monotonic plastic zone Δ m of stationary crack were observed in GFRP composite repaired steel pipes. It was found that these reductions in GFRP composite repaired steel pipe are mainly dependent on the fibers orientation, the length and the angle of stationary crack [ABSTRACT FROM AUTHOR]

Due to its induction heating mechanisms, eddy current pulsed thermography (ECPT) is always used as Non-destructive testing (NDT) technique only for conductive materials. This work explores the feasibility of ECPT to detect subsurface defects in glass fiber-reinforced polymer (GFRP) composites, a typical non-conductive material. The proposed method introduces a metal part as the heat-generating component to generate the induction heat. Then the induction heat in the metal part can be transferred to GFRP, which makes it possible to detect subsurface defects in GFRP. The detection mechanism of the proposed method is firstly investigated, and the influence factor analysis is then performed to obtain the optimal test condition. Experiments were finally performed on GFRP specimens with various subsurface defects to verify the effectiveness of the method. The results demonstrate that the proposed method is effective in subsurface defects detection of GFRP, which provides a promising way to extend the application of ECPT to non-conductive materials. [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]

Inserting FRP rods into grooves using the NSM technique has been demonstrated to be a suitable method for repairing reinforced concrete (RC) beams. There is limited experience with the use of GFRP in the strengthening of RC elements due to low Young's modulus of glass fibers. The aim of the paper is to analyse the static and dynamic behaviour of RC beams damaged and strengthened by glass fiber reinforced polymer (GFRP) rods utilizing the near surface method (NSM). Undamaged and damaged three RC beams have been experimentally tested under bending loading with and without strengthening by GFRP rods. For a beam, damage has been represented firstly by notches on concrete cover. The beam has been successively strengthened by epoxy resin and NSM GFRP rod and then subjected to bending tests. Vibration tests have been adopted as nondestructive method of control during the experiments to assess the response of RC beams at different damage steps of concrete or due to decrease of bond of GFRP rod. Vibration tests foresaw two boundary conditions, respectively, free-free and hinged ends. Experimental static and vibration results are below shown; discussion and comments on the strengthening bond of NSM GFRP rod have been developed. [ABSTRACT FROM AUTHOR]

The present study developed a new and original strengthening method to enhance the shear capacity and ductility of unreinforced masonry (URM) walls based on the unbonded prestressed units using steel bars and glass fiber (GF) grids. The strengthening efficiency was validated through the experimental analyses including the failure mode, the lateral load-displacement relationship, shear capacity, and work damage indicator measured from four specimens subjected to a constant axial load and cyclic lateral loads. In addition, new design equations for the shear capacity of masonry walls were derived based on the regression analysis of 172 datasets. In particular, the proposed equations considered the shear enhancement by the axial stresses created due to the prestressed strengthening materials. The test results showed that shear capacity of the masonry walls strengthened with diagonal steel bars and GF grids increased by 4.2 times when compared with that of the companion URM walls. The proposed design equations for shear capacity of masonry walls also exhibited superior accuracy to FEMA 306 and EC 6 models. [ABSTRACT FROM AUTHOR]

In the presented investigation composites consisting of carbon and glass fiber reinforced plastics in combination with steel and elastomer layers are subjected to experimental drop-weight impact tests and compression after impact tests. The objective is to study the low-velocity impact behaviour, damage resistance and residual strength of composite laminates dependent on position and proportion of additional layers. In continuation of earlier studies two additional laminate configurations containing thin steel layers and two elastomer layers are tested. Impact damage and damage tolerance are determined respecting the aspect of differing bending stiffnesses and structure densities. It is found that concerning the elastomer addition the damage area, which mainly depends on the elastomer layer position, is an essential influencing factor on the residual strength. The steel addition leads to wide delaminations but high residual strengths. [ABSTRACT FROM AUTHOR]

Combining seawater, recycled coarse aggregate (RCA), and glass fiber reinforced polymer (GFRP) reinforcement in concrete is potentially advantageous from a sustainability perspective. This paper reports on the results of an experimental study on the short-term flexural performance of seawater-mixed recycled-aggregate concrete beams with GFRP bars. Twelve medium-scale reinforced concrete (RC) beams (150 × 260 × 2200 mm) were tested under four-point loading. The test variables included the mixing water (seawater/freshwater), aggregate type (conventional/recycled), and reinforcement material (black steel/GFRP). A wide range of flexural properties, including failure mode, cracking behavior, load-carrying capacity, deformation, energy absorption, and ductility were characterized and compared among the beam specimens. The results suggest that the use of seawater and RCA in concrete has insignificant effects on the flexural capacity of RC beams, especially if concrete strength is preserved by adjusting the mixture design. Altering reinforcement material had a strong influence on the flexural capacity and performance of the tested specimens: the GFRP-RC beams exhibited higher load-carrying capacities (on average 25%) but inferior deformational characteristics as compared to their steel-reinforced counterparts. Theoretical predictions were obtained for the flexural capacity, crack width, and deflection of steel- and GFRP-RC beams based on their corresponding design guides, and compared with the experimental results. [ABSTRACT FROM AUTHOR]

Arranging a hybrid combination of longitudinal fiber reinforced polymer (FRP) bars and longitudinal steel bars in the tensile zone of a concrete beam is able to sufficiently exploit the superior properties of both FRP and steel materials to achieve a satisfactory ductility level. As the foundation of analysis and design of hybrid FRP-steel reinforced concrete (RC) members, study of tensile behavior of concrete chords with FRP-steel reinforcement is essential and necessary. In this paper, the average crack spacing of hybrid (Glass Fiber Reinforced Polymer-GFRP and steel) RC chords is analytically estimated. Subsequently, the Tension Chord Model (TCM) is extended to predict the tensile behavior of hybrid GFRP-steel RC chords. Finally, the presented models are effectively validated by experimental results of concrete chords reinforced with GFRP bars and steel bars in different combinations available in the literature, and detailed discussions about analytical and experimental results are also performed. [ABSTRACT FROM AUTHOR]

This work presents the experimental and finite element analysis (FEA) study of the bond behavior of a continuous glass fiber-reinforced thermoplastic composite rod (3D-Tow)/over-molded long chopped glass fiber-reinforced thermoplastic (LFT) composite. To obtain the interfacial bond strength between the 3D-Tow and LFT of the composite, pull-out tests were performed according to over-molding conditions of the LFT material to investigate the bond-property changes with respect to the process parameters. From the experiment results, the traction–displacement behavior of the 3D-Tow/LFT interface was derived based on the cohesive zone model (CZM). The obtained bond properties were applied to a structural simulation, which accurately predicted the mechanical behavior of a prototype front bumper assemble component made of the 3D-Tow/LFT composite. [ABSTRACT FROM AUTHOR]

The pultrusion of large-diameter glass fiber reinforced epoxy rods at high pulling speed is often accompanied by the formation of cracks at the surface of a profile, leading to product rejection. In this study, we investigate the causes of crack formation based on numerical simulations of manufacturing process mechanics, including the temperature distribution, degree of polymerization, and residual stresses. Based on the built model, we solve the problem of temperature condition optimization for maximizing pulling speed. The results show that up to 27% increases in pulling speed are possible provided that the following conditions are met: thermal destruction of the material is avoided; a profile is cooled sufficiently quickly before cut-off; a high degree of polymerization is achieved in a final product; and there are no cracks in a profile. [ABSTRACT FROM AUTHOR]

Multifunctional composite structure with unique mechanical and physical characteristics is essential for the lightweight design of engineering structures. Here, we develop a multifunctional sandwich structure for both effective loadbearing and customizable microwave absorption by employing glass fiber reinforced plastic, polyvinyl chloride foam, carbon fiber reinforced plastic, and frequency selective surfaces. The resultant sandwich structures are endowed with effective specific flexure stiffness (up to 130 N/mm), benefiting from the efficiency in material distribution configuration. Moreover, the proposed structures also show highly customizable microwave absorbing capacity in both bandwidth (from 2 GHz to 18 GHz) and band depth (from −10 dB to −15 dB), due to the flexible design ability of multiple interfaces, electromagnetic loss artificial film. The optimized structures highlight a tradeoff among microwave absorption, flexure stiffness, and surface density and thus are promising a smart stage on which high-performance customizable properties can be envisaged. [ABSTRACT FROM AUTHOR]

In this paper, six concrete beams reinforced with a combination of GFRP (glass fiber reinforced polymer) bars and steel bars, and three concrete beams reinforced only with steel bars were designed and tested. Several flexural behaviors of the tested beams were analyzed and compared with theoretical models. The experimental and analytical results showed that under the designed service loads, the crack width and deflection that appeared in the GFRP-steel reinforced concrete beams developed faster than those shown by the steel-reinforced concrete beams. With the same total reinforcement amount of GFRP and steel bars, the ultimate flexural capacity of GFRP-steel reinforced concrete beams was nearly 91–97% of that of steel-reinforced concrete beams, but the deflection and maximum crack width were obviously larger than those of steel-reinforced concrete beams under the same service load levels. The beam deformability coefficient approximately decreased with increasing nominal reinforcement ratio ρ nom,F. The area ratio of GFRP bars to steel bars A f / A s had a great influence on the flexural behaviors of GFRP-steel reinforced concrete beams. Comparisons showed that the data obtained for flexural capacity, deflection, deformability and crack width of GFRP-steel reinforced concrete beams were consistent with the predictions calculated by the proposed models. [ABSTRACT FROM AUTHOR]

In this study, stiff stab-resistant materials for riot shields were developed by using fiber reinforced polymer composites (FRPs) made of three different types of fibers: carbon, glass and p-aramid. The stab resistance of the FRPs were investigated with respect to the thickness and types of reinforced fibers according to the U.S.A. National Institute of Justice (NIJ) standard. Hybrid composites were then developed to compensate for the weaknesses of each FRP, and the stacking sequences were optimized. The mechanisms of the stab resistance and the blade penetration for each FRP were investigated via static stab compressive tests. Additionally, the failure mode and fracture topography after the stab resistance tests were obtained using a micro-CT scanner. [ABSTRACT FROM AUTHOR]

• The depth effect of NSM grooves of strengthened beams was studied. • The effect of horizontal distance between two NSM grooves was studied. • An analytical model is proposed to predict the above effects. In this paper, the effect of interaction between near surface mounted (NSM) strips and internal reinforcement on the structural behavior of upgrading RC beams has been studied. The position, arrangement and area of NSM glass fiber reinforced polymer (GFRP) strips have been examined experimentally. Six strengthened beams in addition to one control beam were tested in flexural until failure. The load carrying capacity, deflections and the mode of failure of strengthened beams were recorded. The experimental results showed that the installed NSM GFRP side by side has a lower interfacial stress than those installed separated. This improvement is more obvious in the case of NSM strips installed near the internal reinforcement. Furthermore, the installed NSM strips in deep groove experienced higher load carrying capacity than those installed in shallow groove for both patterns. The installation of the NSM GFRP strips in deep grooves using epoxy may be delay or prevent the peeling/debonding failure. The ultimate load of the beam upgraded with one NSM strip adjacent to the stirrups (in deeper groove) is about 1.5 times that of one NSM strip installed near the bottom surface of the beam. This ratio decreased with increasing the area of NSM GFRP strips. [ABSTRACT FROM AUTHOR]

This paper focuses on the study of interlaminar fracture of composite materials in mode III using the Modified Split Cantilever Beam (MSCB) test. MSCB test is applied to investigate the dependency of the mode III energy release rate on geometric parameters (specimen width, and thickness), initial crack length, loading condition and crack front material layup. A non perforated release film is introduced to create delamination at the mid-plane of the tested specimens. Three sets of samples (a total of 56 samples) are fabricated and tested from Unidirectional Glass fibers. The length of the specimens is 154 mm. The first set of tests is conducted for three different widths (35 mm, 20 mm, 12 mm) to select the most appropriate width that leads to a crack initiation prior to specimen failure. The remaining sets of tests are conducted with different loading conditions, different thickness, different initial crack length, and different lay up orientations at the crack front (0/0, +45/−45, 0/45, and 0/90). Results show that both width selection and load configuration are of extreme importance for the success of the test. The energy release rate (G IIIc) increases with increasing thickness and width. The stacking orientation at the crack front shows minor influence on G IIIc. [ABSTRACT FROM AUTHOR]

This study aims to introduce a new pipeline joining technique using fiber-reinforced (FRP) composites. To this end, a comprehensive experimental program has been carried out to evaluate the new technique. The experimental program consists of four phases. In phase 1, a fabrication process in which aluminum pipes were employed for both types of joining (i.e., welding and joining by FRP is presented and discussed. Two types of welding have been used to study their effect on the pipe's mechanical behavior. These are V welding and standard faced butt-welding techniques. For FRP joining, there are three types of fibers used. These are Kevlar fiber/epoxy (KFRP), carbon fiber/epoxy (CFRP), and glass fibers/epoxy (GFRP). Effect of fiber orientation angles of the joining system under three-point bending has been taken place in phase 2. The results showed that 00/900 orientation recorded the highest flexural load. In phase 3, the evaluation of welding types and fiber types effects on the bending behavior of joined pipes have been carried out. For the impact of welding types, V-welded pipes showed higher mechanical performance than normal faced butt-welded pipes. In addition, CFRP and KFRP joining system showed a higher value of flexural load than welding techniques, while the GFRP showed similar flexural load to welding techniques. Phase 4 involves assessment of FRP hybridization systems on bending behavior of joined metallic pipes. The improvement in the mechanical performance of pipes joined with four layers of hybrid FRP were found to be insignificant compared to four layers of non-hybrid FRP type. However, increasing the number of hybrid FRP layers to eight resulted in significant improvement in flexural loads compared to four layers of single FRP type. The overall results revealed that using FRP composites in pipes joining showing a promising future for the pipeline. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer (GFRP) bars represent a valid solution as internal reinforcement of concrete members for some particular applications. GFRP reinforcing bars (rebars) have a high-strength-to-weight ratio and good resistance to corrosion. However, they may suffer of degradation when exposed to specific aggressive environments and when subjected to long-term sustained stress. To increase their durability, design guidelines available in the literature limit the stress level in the rebar. However, such limitations are based on few experimental results and represent conservative estimations of the bar long-term behavior. In this paper, the results of 9 short-term tensile tests and 17 long-term tensile tests on GFRP bars are presented. The long-term tests included relaxation and creep tests for 1000 and 2000 h considering five different initial applied stress levels. The results obtained are described by two new relaxation and creep functions able to reproduce the bar behavior from the application of the initial applied stress. The functions proposed allow for obtaining the long-term relaxation losses of the reinforcing bars for different stress levels. [ABSTRACT FROM AUTHOR]

The objective of this work is to investigate the effect of glass fibre addition and benzoylation treatment on the dynamic mechanical, impact and post-impact properties of sugar palm composites. The hybrid composites were prepared using hand lay-up method with different volume fractions of sugar palm fibre and glass fibre. Dynamic mechanical analysis (DMA) results show that EP/30TSPF/70GF composites exhibited the highest loss and storage modulus compared to EP/UTSPF composites. For the low-velocity impact testing, the experimental results show that the impact energy displayed an excellent relationship with the impact response. The ultrasonic C-scan images show that the damaged area is increasing as the impact energy increasing. From the compression after impact (CAI) studies, it could be resolved that the impact damage exhibited outstanding connection with the impact response and compressive strength of the EP/30TSPF/70GF composite decreased as the impact energy increasing. Overall, it can be concluded that the benzoylation treatment and glass fibre addition on the sugar palm composites enhances the dynamic mechanical, impact and post-impact properties of sugar palm composites. [ABSTRACT FROM AUTHOR]

The glass fiber reinforced polymer (GRFP) bars have advantages in corrosion resistance and high load bearing capacity. They can be used as reinforcements in concrete protective structures to replace the steel bars. In this paper, the GRFP bar reinforced concrete beams (GRCBs) were designed, casted and tested. As a reference, the steel bar reinforced concrete beams (SRCBs) having the same flexural rigidity with the GRCBs were also designed, casted and tested. Under close-in explosions, the GRCBs have smaller displacement than the SRCBs, because the GFRP bars are still in elastic state while the steel bars enter into plastic deformation. Cracks, spalling and cratering are the main damage modes of the concrete beams. Through the quasi-static four-point-bending experiments, the residual load capacity of each beam has been evaluated, which quantitatively reveals the damage degree of the exploded concrete beams. In current research the explosion produces negligible damage to the GRCBs, while the load capacity the SRCBs reduces at a level of 28% at the most. The research proves that the GRCB has greater blast-resistance. [ABSTRACT FROM AUTHOR]

The test and evaluation method of dynamic scaling for crude oil transportation pipeline under oil field environment has been presented based on self-developed dynamic scaling testing device, by which the dynamic cyclic fouling experiments of GFRP pipeline under transportation condition have been conducted, and the dynamic amount of scale has been obtained under different temperatures, fluid velocities, exposure times and metal ions. Secondly, the effects of temperature, fluid velocity and exposure time on dynamic scaling rate of GFRP pipeline have been analyzed from macroscopic perspective by using grey correlation method, by which the correlations between dynamic scaling rate of GFRP pipeline and those factors are obtained. Thirdly, SEM and XRD are used to investigate surface morphology, composition and structure of scale from microscopic perspective, by which the effect of metal ion on the scaling mechanism has been analyzed qualitatively. Finally, based on experimental results, the structure model of Ca 6−x Mg x (CO 3) 6 and Ca 6−x Fe x (CO 3) 6 has been established by using materials studio, and the elastic property parameters of different structure model have been calculated, by which the effect of metal ions on scaling mechanism has been investigated quantificationally. Dynamic scaling mechanism of GFRP pipeline is revealed and the corresponding anti-scaling measure is presented. [ABSTRACT FROM AUTHOR]

Lateral torsional buckling (LTB) and local section distortion of pultruded glass fiber reinforced polymer (GFRP) I-sections subject to flexure are investigated. LTB behavior will dominate longitudinally slender beams having low flange slenderness. However, as the flange becomes more slender and/or the beam shorter, the effects of local section distortion (LSD) become significant, reducing the LTB capacity of the member. Using the energy method, an analytical study was conducted and explicit equations for predicting the critical LTB buckling moments of GFRP I-sections accounting for the effects of LSD are proposed. The proposed LTB equation was validated using experimental results and finite element analysis. Excellent agreement was observed between the proposed LTB equation and experimental results for sections expected to be dominated by LTB behavior. Extending the study using the same approach, an equation predicting LTB capacity as it is affected by LSD was also validated using experimental results. It is found that the proposed LTB equation captures the capacity reduction due to LSD and therefore, provides more accurate predictions for sections expected to be dominated by LSD behavior; those having small slenderness ratios and large flange slenderness ratios. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the performance of pultruded glass fiber reinforced polymer (pGFRP) I-section columns subject to short-term concentric compression, bringing up a discussion on the relevant parameters affecting their local buckling behavior and the interpretation of tests results. An experimental program was carried out, including a detailed material characterization and twenty-nine compression tests on short I-columns made of either polyester or vinyl ester matrices, with variable flange width-to-section depth ratios (b f / d), column lengths and local end conditions. The theoretical critical loads predicted using generalized beam theory (GBT) and finite element method (FEM) were compared to experimental results obtained by Southwell and Koiter techniques, with better agreements obtained for the latter. It is shown that, besides the length and local end conditions for loaded edges, post-buckling with associated non-linear elastic strains distribution throughout the cross-section and damage prior to buckling have relevant influence on the measured critical loads. On the other hand, the influence of the rotational stiffness of web-flange junctions were considered small for the material and cross-sections studied. Finally, results have shown that the usual boundary condition adopted in literature approaches a clamped condition instead of simply-supported one. [ABSTRACT FROM AUTHOR]

This experimental work presents results on the effect of different concrete types on the flexural behavior and deflection of beams reinforced with Glass Fiber Reinforced Polymer (GFRP) bars. Four different types of concretes namely; ordinary Portland concrete (OPCC), fiber reinforced concrete (FRC), geopolymer concrete (GPC), and fiber reinforced geopolymer concrete (FRGC) were used. A total of eight beams were subjected to four-point static bending tests. The parameters studied were load capacities, deflection, and strain development in concrete and rebars, while cracking patterns and failure modes were also observed. All tested beams exhibit comparable flexural and deflection characteristics. The results indicate that GPC and FRGC beams were more effective for a GFRP reinforced system than ordinary concrete. The ACI 440-R1-06 equations gave conservative estimates for both the flexural capacity and the deflection of the members and therefore may be used irrespective of the concrete type. Finally, results from flexural capacities normalized for concrete strength, cross-section and reinforcement ratio of GFRP (ρ f / ρ b) indicate that increase in the ρ f / ρ b ratio does not proportionally increase the flexural strength of the beams. [ABSTRACT FROM AUTHOR]