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The encapsulation of dye solar cells in translucent, structural and lightweight glass fiber-reinforced polymer laminates was investigated with a view to designing multifunctional envelopes for daylit buildings. Small and large integrating sphere experiments and solar radiation experiments were performed to determine the light transmittance of the laminates and the electrical efficiency of the encapsulated cells. An overall cell efficiency of 3.9% (before encapsulation) only decreased to 3.4% after encapsulation below laminates of around 3-mm thickness. Thermal cycle experiments and finite element analysis allowed the thermal performance of the encapsulation for two types of cell substrates (glass and acrylic polymer) to be evaluated. Contrary to glass substrates, no delaminations were observed on acrylic substrates after 300 h of cycles +60/−20℃. A design for integrating dye solar cells into multifunctional sandwich building envelopes is proposed. A light transmittance of around 0.35 was estimated through a sandwich envelope with cell modules occupying 50% of the external face sheet. Research on the manufacturability of cells on polymeric substrates is encouraged. [ABSTRACT FROM AUTHOR]

After 17 and 15 years of use, respectively, a detailed inspection of a pedestrian bridge and a 5-story building structure composed of partly adhesively bonded pultruded glass fiber-reinforced polymer (GFRP) profiles was conducted accompanied by full-scale serviceability and destructive coupon testing on exchangeable profiles. The bridge is exposed to a harsh Alpine climate and the building to a mild plateau climate. The system and material stiffness of the bridge remained unchanged during the 17 years. The material strength of the bridge, however, was significantly affected by combined freeze-thaw cycles and ultraviolet (UV) irradiation. The latter accelerated the strength degradation by uncovering the fibers (fiber blooming) and thus inducing humidity ingress into the material by wicking effects. A large majority of the small-area adhesive bonds in the bridge were intact, although a few small cracks were observed in some joints at the surface. The large-area bonds of the building did not show any damage. Based on results of the inspection of the bridge, the application of an appropriate coating on pultruded GFRP structures exposed to harsh environments is recommended. [ABSTRACT FROM AUTHOR]

This paper demonstrates how the translucency of glass fiber-reinforced polymer (GFRP) laminates allows the derivation of their mechanical properties through optical measurements. Spectrophotometric, goniophotometric and tensile experiments were performed on unidirectional and cross-ply hand lay-up GFRP laminates with fiber volume fractions ranging from 0.15 to 0.45. An analytical model to predict the directional fiber volume fractions—and thus the mechanical properties of GFRP laminates—has been developed based on the total and diffuse transmittance and directional light scattering of the laminates. It is demonstrated that structurally optimized GFRP laminates can meet the requirements for GFRP skylights and the encapsulation of photovoltaic cells into translucent GFRP laminates. [ABSTRACT FROM AUTHOR]

This paper presents experimental and analytical investigations about the creep behaviour of sandwich panels comprising glass-fibre reinforced polymer faces and rigid polyurethane foam core for civil engineering applications. A full-scale sandwich panel was tested in bending for a period of 3600 h, in a simply supported configuration, subjected to a uniformly distributed load corresponding to 20% of the panel’s flexural strength. Additionally, specimens of polyurethane foam core were tested in shear for a period of 1200 h, for three different load levels corresponding to 10%, 20% and 30% of the foam’s shear strength. Experimental results were fitted using Findley’s power law formulation. Creep coefficients, shear modulus reduction factors and time-dependent shear moduli were obtained for the polyurethane foam in shear. A composed creep model is proposed to simulate the sandwich panel’s long-term creep deformations by considering the individual viscoelastic contributions from (1) the core material in shear and (2) the glass-fibre reinforced polymer faces in tension/compression. The composed creep model predictions adequately reproduced the full-scale panel’s experimental results. In addition, a good agreement was found between the composed creep model predictions and the extrapolation of the power law fitting obtained from the full-scale panel test, for a 50-year period. [ABSTRACT FROM AUTHOR]

Glass-fiber-reinforced polymer (GFRP) cell-core sandwiches are composed of outer GFRP face sheets, a foam core, and a grid of GFRP webs integrated into the core to reinforce the shear load capacity. One of the critical failure modes of cell-core sandwich structures is shear wrinkling, a local buckling failure in the sandwich webs because of shear loading. The shear wrinkling behavior of GFRP laminates with different laminate sequences, stabilized by a polyurethane foam core, was experimentally and numerically investigated. Shear wrinkling was simulated by a biaxial compression-tension setup. The results show that an increasing transverse tension load significantly decreases the wrinkling load. The decreasing effect of tension is explained by the lateral contraction because of Poisson's effect, which causes an increase in the initial imperfections and subsequent accelerated bending. [ABSTRACT FROM AUTHOR]

The feasibility of encapsulating solar cells into the glass fiber-reinforced polymer (GFRP) skins of load-bearing and thermally insulating sandwich elements with foam cores has been evaluated. Exposure of the encapsulated cells to artificial sunlight led to a significant temperature increase on the top sandwich surface, which almost reached the glass transition temperature of the resin. Mechanical loading up to serviceability limit loads did not cause any damage to the solar cells. Stresses of less than 20% of the material strength arose in the face sheets due to thermal and mechanical loading up to failure. Composite action through the face sheets with encapsulated cells was maintained and no debonding between face sheets and foam core was observed. Thanks to the superior mechanical and thermal sandwich behavior, thin-film silicon cells are more appropriate than polycrystalline silicon cells for use in multifunctional GFRP sandwich structures, although they are less efficient. [ABSTRACT FROM AUTHOR]

Abstract: The Weibull distribution, used to describe the scaling of strength of materials, has been verified on a wide range of materials and geometries; however, the quality of the fitting tended to be less good towards the upper tail. Based on a previously developed probabilistic strength prediction method for adhesively bonded joints composed of pultruded glass fiber-reinforced polymer (GFRP) adherends, where it was verified that a two-parameter Weibull probabilistic distribution was not able to model accurately the upper tail of a material strength distribution, different improved probabilistic distributions were compared to enhance the quality of strength predictions. The following probabilistic distributions were examined: a two-parameter Weibull (as a reference), -fold Weibull, a Grafted Distribution, a Birnbaum–Saunders Distribution and a Generalized Lambda Distribution. The Generalized Lambda Distribution turned out to be the best analytical approximation for the strength data, providing a good fit to the experimental data, and leading to more accurate joint strength predictions than the original two-parameter Weibull distribution. It was found that a proper modeling of the upper tail leads to a noticeable increase of the quality of the predictions. [Copyright &y& Elsevier]

Abstract: As part of a 15-year railway noise remediation plan, 300km of noise barriers will be installed in Switzerland over the next few years. To enable pultruded glass fiber-reinforced polymer (GFRP) materials to be used for the noise barrier posts, a specification concerning design and installation was prepared for their technical approval. The approval of a first GFRP-post system confirmed that the requirements defined in the specification are reasonable and can be met. A coherent system of design values for strength and stiffness resulted from the process that differentiates between environmental impact (inside or outside the concrete foundation) and short- or long-term loading. The GFRP posts, composed of glass fibers and a polyester matrix with a protective coating, showed that even a small number of scratches in the coating may strongly affect the long-term strength of the GFRP material inside the concrete foundation. The post-foundation system stiffness decreased by only 7% during 12 million fatigue cycles due to concrete cracking and remained below the 10% limit prescribed in the specification. [Copyright &y& Elsevier]

This paper reports on the design and construction of a lightweight glass fiber-reinforced polymer roof structure in Basel, Switzerland. The sandwich construction allowed for an integration of static, building physical and architectural functions that enabled the prefabrication of the entire roof in only four lightweight elements that were easily transported to the site and rapidly installed. Cutting of foam blocks with a computerized numerical control machine and adhesive bonding proved to be advantageous procedures for the fabrication of the complex roof shape, without the use of expensive molds. The factor of safety of the design was adjusted during the design process through experimental verification. Although some of the characteristic material properties were overestimated in the preliminary design, the design properties for the final design were higher than for the preliminary design as it was possible to reduce the resistance factors (according to Eurocode format) after testing by a factor of 2.0. Existing design models and test standards to determine material properties proved to be applicable. [ABSTRACT FROM AUTHOR]

Abstract: Adhesively bonded joints are being used increasingly in civil engineering structures, especially for joints comprising pultruded glass fiber reinforced polymer (GFRP) laminates. The layered material architecture, however, leads to a complex delamination failure within the pultruded material, thus necessitating understanding of the progressive failure mechanism of such joints under axial tensile loading. In this work, adhesively bonded joints composed of pultruded GFRP laminates, including double and stepped lap joints, were experimentally investigated. The static strengths of joints were obtained and the failure mechanism was understood. Crack propagation and back face strain gages were successfully employed to identify crack initiation and describe crack propagation, even though the failure mechanism was always sudden and brittle. The dominant failure mode for both types of joints was a fiber-tear-off failure that occurred in the mat layers of the GFRP laminates. The critical strain energy release rate was calculated. Different values were obtained for the two joint types due to different combinations of fracture modes. [Copyright &y& Elsevier]

A durability study was performed on a pultruded glass fiber reinforced polymer (GFRP) compression element of a hybrid GFRP/steel joint for concrete structures. GFRP elements were immersed in alkaline pore water solutions of different temperatures during 18 months. Moisture uptake occurred very quickly, within a few days, mainly through a wicking effect along the fiber/matrix interfaces and matrix cracks. The loss of matrix stiffness due to swelling led to a first rapid and significant drop in element compression strength, because of the loss of matrix resistance against buckling of the compressed fibers. In the second phase, strength reduction due to chemical glass and matrix degradation occurred at a much slower rate. It was found that the Arrhenius rate law could predict the element strength decrease. Due to the less harsh environment in practice, the strength and stiffness decrease was found to be acceptable, thereby making it possible to assure structural safety and serviceability of the hybrid GFRP/steel joint after 70 years of service. [ABSTRACT FROM AUTHOR]

In the summer of 2005, after eight years of use as a temporary bridge during the winter, the Pontresina Bridge for pedestrians was transported to the Swiss Federal Institute of Technology Lausanne for a detailed assessment of the structural safety, serviceability, and long-term durability of the bridge. The assessment included a visual inspection, quasistatic testing identical to that performed in 1997, and detailed investigations of material degradation. The visual inspection showed a variety of different local defects and damage such as local crushing caused by impact, local cracks due to inappropriate storage and lifting of the structure, fiber blooming, degradation of cut surfaces, and damage due to vandalism. Comparisons between load tests performed in 1997 and 2005 showed, however, that the structural safety and serviceability of the bridge have not been affected by these local damages. The stiffness of the pultruded shapes remained unchanged, whereas a slight decrease in strength between 13 and 18% was measured, which, however, is not critical when taking into consideration the high effective safety factors. In view of a further service period of 5 years until the next inspection, the visible damages were repaired. This experience showed that the durability is primarily affected by inappropriate constructive detailing and that pultruded glass fiber-reinforced polymer shapes, if correctly manufactured and processed, can offer good long-term performance and durability. [ABSTRACT FROM AUTHOR]

Axial tension–tension fatigue experiments were performed on pultruded glass fiber reinforced polymer (GFRP) plates in a laboratory environment. Different full-scale specimen shapes were examined: plate strips as-delivered, plate strips with tabs and plates in tapered form. Experiments were performed up to ten million loading cycles with different frequencies up to 12 Hz. It was observed that the specimen temperature could increase during fatigue test. This increase was dependent on the loading frequency and the loading range. S–N fatigue life curves were determined. Tapered specimens showed a higher fatigue life than as-delivered specimens; and as-delivered specimens showed higher fatigue lives than tabbed specimens. A degradation rate of 3–5% of the single-cycle ultimate tension strength (UTS) per decade of fatigue cycles was observed. This observation is not consistent with a characteristic slope of 10% UTS/decade as shown from many previous studies.A loss of specimen stiffness up to 50% during the fatigue experiments was observed and can only be explained by considerable fiber failures. This finding is consistent with results from previous studies showing that fatigue failure of fiber-reinforced polymer composites is basically fiber dominated.The fatigue behavior of the plates was compared with the fatigue behavior of adhesively bonded double-lap joints made from the same plates. Plates and joints showed converging fatigue life curves and the same fatigue limit at approximately 25% of the single-cycle failure load at ten million cycles. [Copyright &y& Elsevier]

An experimental program has been carried out to investigate the structural behavior of adhesively bonded glass fiber reinforced plastic (GFRP) sandwich girders. The girders, conceivable for main spans up to 20 m, are composed of translucent double sandwich element webs and adhesively bonded pultruded shape flanges. The continuous adhesive connections between web and flanges are loaded in a highly favorable manner without peeling stresses. Despite the complex load-carrying and failure behavior of the girders, simple calculation models can be applied. The successful girder experiments allowed for the development of a material-adapted construction method for new GFRP bridges and buildings. The integration of architectural aspects such as transparency, translucency, lighting, and color, as well as building physical aspects for buildings such as thermal insulation, substantially increases the overall value of the proposed constructions. Together with the lower life-cycle costs, this further justifies these new materials’ higher initial costs as compared with traditional materials. [ABSTRACT FROM AUTHOR]

Bending-active elastica beam is a structural configuration that is based on the elastic deformation of an initially straight beam. This deformation occurs when horizontal displacements are applied to a sliding support, causing the beam to bend into an arched shape. Previous research has focused on the stability of small-scale bending-active structures, thus not considering material strength, which is crucial in real-scale applications and structural design. This paper investigates the short-term structural behavior of bending-active elastica beams using pultruded glass fiber-polymer composite profiles, as used in real-scale structures. A series of short-term bending and service load application experiments were performed considering different bending degrees and loading scenarios. These results were used to validate finite element modeling. They demonstrated that steeper bent beams experience material failure, while shallower ones exhibit snap-through buckling. Material failure initiates on the tensile side of the beams, with cracks initiating at locations of maximum curvature. Higher bending degrees and symmetric loading result in higher maximum loads than lower bending degrees and asymmetric loading. A strain-based failure criterion, which can serve for structural design, is derived. [ABSTRACT FROM AUTHOR]

Abstract The compressive kinking behavior of non-slender unidirectional glass fiber-reinforced polymer (GFRP) specimens has been analyzed by finite element (FE) models. The experimentally observed imperfections, including the initial fiber waviness throughout the entire specimen volume and the scattered resin/interface defects, were taken into account in the FE models. The birth-and-death method was employed to simulate the progressive damage to the material. The consideration of the coexistence of initial fiber waviness and initial resin/interface defects was found to be essential for accurate modeling of the kinking failure process. Kinking was initiated due to the disproportional increase of the fiber microbuckling at the locations of initial defects. The numerically obtained peak load, fiber microbuckling amplitudes, kink band angle and width, and compressive strain concentrations at the kink band edges were well predicted compared to the experimental results. The number of defects was less significant than the fact that defects existed that served as initiation points of the kink band formation. [ABSTRACT FROM AUTHOR]

Highlights • The 2D delamination behavior of composites laminates was studied. • A new design and experimental set-up for GFRP/epoxy plates was developed. • Quasi-static out-of-plane opening loading has been applied. • Stiffening and softening mechanisms were activated during the loading process. • All the stiffness-related mechanisms were reflected in the compliance. Abstract The 2D delamination behavior of composite laminates under quasi-static out-of-plane opening loading has been experimentally investigated. A circular embedded pre-crack was introduced in the center and at the midplane of the laminates. To investigate the effect of the fiber architecture on the fracture behavior, six different types of fabrics were selected. Increasing load–displacement curves were obtained due to the increasing crack front length during propagation. During the loading process, stiffening and softening mechanisms were activated. The stretching of the laminates, constituted the main stiffening mechanism that appeared and increased as the plate opened. Once the crack started growing, a corresponding softening due to crack propagation occurred together with a secondary stiffening mechanism, fiber bridging. These stiffness-related mechanisms were reflected in the compliance and clearly differentiate 2D- from 1D-delamination. [ABSTRACT FROM AUTHOR]

The rotational behavior of the web-flange junctions (WFJs) of a pultruded glass fiber-reinforced polymer (GFRP) bridge deck system with trapezoidal cell cross-sectional geometry was investigated. The rotational response of three WFJ types, in two bending moment directions each, was characterized. An experimental procedure based on three-point bending and cantilever experiments conducted on the web elements and simple analytical models was used. The WFJs generally exhibited non-rigid and nonlinear behavior. The overall moment-rotation relationships, rotational stiffness, strength and failure modes differed depending on the web type, the location of the WFJ within the deck profile, the existing initial imperfections and the direction of the bending moment applied. This evidenced the relevance of separately characterizing the response of all WFJ types in the two possible bending directions. Simplified expressions to model the WFJ rotational behavior were derived. The validity of the experimental and idealized rotational responses was assessed by means of numerical simulations of full-scale experiments conducted on the GFRP deck. [ABSTRACT FROM AUTHOR]

Similarly to the post-buckling behavior of steel girder webs, the post-wrinkling behavior of glass fiber-reinforced polymer (GFRP) cell-core sandwich webs can increase their ultimate shear strength. Post-wrinkling is, however, different from post-buckling since wrinkling is a local buckling instability mode that can occur in any part of the web. Furthermore, all the previously presented theories or models have been limited to isotropic web plates, while the fiber architecture of orthotropic plates can greatly influence post-wrinkling behavior. Based on biaxial compression–tension experiments on GFRP web-core sandwich panels, the redistribution of the strain field during post-wrinkling was examined for two different fiber architectures, [90/0] and [±45] stacking sequences. The results proved that fiber architecture greatly influences the wrinkling loads and wrinkling mode as well as post-wrinkling behavior. During post-wrinkling, the ultimate shear strength of the sandwich structure and the redundancy of the system can be increased, thus enhancing the safety, functionality and reliability level of this type of structure. [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 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]

Abstract: The effect of loading sequence on the fatigue behavior of adhesively-bonded pultruded GFRP double-lap joints was experimentally investigated by applying different tensile and compressive block loading patterns. The observed failure modes were consistent with failure modes under constant amplitude loading. A significant load sequence effect was observed for both tensile and compressive loading. Under tensile loading the transition from low to high load cycles in a two-block loading was more damaging than the high to low sequence. The inverse was observed for compression loading. This behavior was associated with the crack propagation rates and their dependence on loading type. The effect of the number of load transitions in a multi-block loading spectrum was also studied by using different loading sequences. The influence of this loading parameter was found to be more dominant than the sequence effect, which is diminished by increasing the number of transitions. [Copyright &y& Elsevier]

Abstract: The fracture behavior of adhesively-bonded double- and stepped-lap joints composed of pultruded glass fiber-reinforced polymer composite laminates and subjected to axial tension was experimentally investigated and numerically modeled. Two methods were used for the calculation of the strain energy release rate: the experimental compliance method and the virtual crack closure technique. Their results showed good agreement for stepped-lap joints, while significant deviations were observed for double-lap joints due to small stiffness changes. The experimental compliance method results were sensitive to these small changes and the virtual crack closure technique accuracy was affected by the inability of the finite element analysis to accurately model the behavior before visual crack initiation. The dominant fracture mode changed from Mode I to Mode II in the case of stepped-lap joints, while an almost constant mode ratio was retained for double-lap joints in the applied loading range. A non-convex mixed-mode fracture criterion was established for crack initiation and propagation based on the virtual crack closure technique results. Both the experimental compliance method and the virtual crack closure technique proved applicable for the interpretation of the fracture mechanics data of the structural joints examined, provided that stiffness degradation can be accurately described. [ABSTRACT FROM AUTHOR]

Abstract: The fracture behavior of adhesively-bonded structural joints under tensile constant amplitude fatigue has been investigated. Double-lap joints (DLJs) and stepped-lap joints (SLJs) composed of pultruded GFRP laminates and an epoxy adhesive were examined. Both joint types exhibited a fiber-tear failure with cracks that initiated at the joint edges in the adhesive–laminate interface and then propagated in the laminates’ mat layers. A linear trend of crack growth and compliance was observed for the DLJs whereas a sigmoid trend was found for SLJs. The experimental compliance method was used for the calculation of the maximum strain energy release rate, G max, and the incremental polynomial method for the calculation of the crack propagation rate, da/dN. Fatigue crack growth (FCG) curves established for both joint types showed that empirical constants are dependent on the joint configuration. Based on this fatigue life modeling, design allowables that correlate the developed damage with fatigue life were derived. [Copyright &y& Elsevier]

Abstract: The tensile behavior of adhesively-bonded double-lap joints composed of pultruded glass fiber-reinforced adherends and an epoxy adhesive was investigated under temperatures ranging between −35°C and 60°C. The load–elongation response was influenced primarily by the thermomechanical behavior of the adhesive and much less so by that of the adherends. For temperatures above the adhesive glass transition temperature, strength and stiffness decreased with the former being less affected than the latter. The failure mechanism changed with increasing temperature from fiber-tear to adhesive failure. The crack initiation loads were unaffected as long as the temperature remained below the adhesive glass transition temperature. However, the crack propagation rate was higher at low temperatures. Critical strain energy release rates for crack initiation and propagation consistently rose as temperature increased. Modeling results obtained using existing empirical models and FEA compared well to the experimental data in the examined temperature range. [Copyright &y& Elsevier]

A numerical investigation was carried out in order to simulate experimental results previously obtained concerning two-dimensional (2D) in-plane crack propagation in laminated glass fiber-reinforced polymer (GFRP) plates. The laminated plates were designed with an embedded circular pre-crack and subjected to quasi-static out-of-plane loads. In order to study the transition from standard fracture mechanics tests, where the crack propagates only in one dimension (1D), to 2D scenarios, additional double cantilever beam (DCB) experiments were carried out on the same material system. Three-dimensional finite element models were developed for the simulation of the experimental fracture responses and cohesive elements were used to take into account the fracture mechanisms acting on the fracture process zone. Compared to the 1D DCB specimens, a much higher value of the total strain energy release rate (SERR) was obtained for the 2D plates, which was correlated to their higher flexural stiffness and to the stress stiffening effect caused by the stretching of their deformed part. Furthermore, and based on the numerical results, it was proved that the area of the fully developed fiber-bridging in the plates can be directly obtained from the experimental compliance vs crack area curves. [ABSTRACT FROM AUTHOR]

Abstract: The span limits of two glass fiber-reinforced polymer (GFRP) bridge concepts involving GFRP-balsa sandwich plates are discussed. The sandwich plates were either used directly as slab bridges or as decks of a hybrid sandwich-steel girder bridges. In the latter case, the potential of the sandwich decks to replace reinforced concrete (RC) decks was also evaluated. Taking the limits of manufacturing into account (800mm slab thickness), maximum bridge spans of approximately 19m can be reached with FRP-balsa sandwich slab bridges, if a carbon-FRP (CFRP) arch is integrated into the balsa core. Above this limit, hybrid sandwich-steel girder bridges can be used up to spans of 30m. RC deck replacement requires timber and steel plate inserts into the balsa core above the steel girders. GFRP-balsa sandwich slabs or decks exhibit full composite action between lower and upper face sheets. Stress concentrations occur at the joints between balsa core and timber inserts which however can effectively be reduced by changing from butt to scarf joints. [Copyright &y& Elsevier]

This paper aims to present an experimental investigation on the behavior of web-flange junctions (WFJs) rotational stiffness of pultruded fiber-reinforced polymer composites (FRP). Channels and I-sections were tested using a simple set-up, which was developed in order to experimentally characterize the junctions in a direct manner. The Digital Image Correlation (DIC) technique was used, allowing overall deflections and relative rotations between web and flange to be monitored. The WFJs' imperfections were analyzed through an optical microscope and correlated with the cracks' formation. Further, damage thresholds are identified using available stress equations for curved composite members and lower bound functions are proposed to simulate the junction stiffness retention. Finally, two Equations are developed in order to analytically predict pultruded junctions' rotational stiffness per unit of width. In general, the theoretical and experimental results agreed fairly well, with a maximum difference of 24% for I-sections and 38% for channels. [ABSTRACT FROM AUTHOR]

Abstract: The temperature-dependent thermo-physical and mechanical properties of a pultruded E-glass fiber-reinforced polyester (GFRP) composite are investigated in this paper. Fitting of theoretical models of the material properties to results of TGA, DSC, hot disk, and DMA experiments demonstrated good agreements. The constants for an Arrhenius representation of the decomposition mass-loss were determined using multi-curves methods. The effective specific heat capacity for the virgin material was found to increase during the decomposition process. A series model based on component volume fraction during decomposition provided an accurate description of the thermal conductivity as a function of temperature as measured by hot disk. Models based on the kinetic theory can describe the material degradation during glass transition as indicated by DMA results, while the parameters still need to be accurately identified. This paper provides a full set of temperature-dependent physical properties of a polyester matrix composite and demonstrates the applicability of theoretical models to represent the experimental results. [Copyright &y& Elsevier]