An accurate material representation of polymeric interlayers in laminated glass panes has proved fundamental for a reliable prediction of their response in both static and dynamic loading regimes. ...This issue is addressed in the present contribution by examining the time-temperature sensitivity of the shear stiffness of two widely used interlayers made of polyvinyl butyral (TROSIFOL BG R20) and ethylene-vinyl acetate (EVALAM 80-120). To that end, an experimental program has been executed to compare the applicability of two experimental techniques, (i) dynamic torsional tests and (ii) dynamic single-lap shear tests, in providing data needed in a subsequent calibration of a suitable material model. Herein, attention is limited to the identification of material parameters of the generalized Maxwell chain model through the combination of linear regression and the Nelder-Mead method. The choice of the viscoelastic material model has also been supported experimentally. The resulting model parameters confirmed a strong material variability of both interlayers with temperature and time. While higher initial shear stiffness was observed for the polyvinyl butyral interlayer in general, the ethylene-vinyl acetate interlayer exhibited a less pronounced decay of stiffness over time and a stiffer response in long-term loading.
Para-aramid fibers (Kolon) are high performance polymeric fibers characterized by their high tenacity and impact resistance. They are used for the soft body armor structures in ballistics. In this ...study, the testing specimens were made from multilayered Kolon fabrics impregnated with epoxy resin where silicon carbide (SiC) microparticles or SiC nanofibers were added as reinforcement. The laminated composite samples were fabricated by hot compression and curing of epoxy resin.
The tensile and impact strengths of the untreated specimens were compared with the ones that underwent water absorption in duration of 72 h (immersion or humidity) followed by desorption. The immersion of the specimens in water and exposure to high humidity (70%) were performed according to the ISO 62 standard while the tensile test was carried out in accordance with the ASTM D 3039 standard. In the end, the tensile test simulation of the laminated composite by using software Abaqus® was accomplished.
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•Kolon/еpoxy composites reinforced by SiC microparticles or SiC nanofibers.•The immersion of the Kolon specimens in water and exposure to high humidity (70%).•The impact of water absorption on the tensile and impact properties.•Tensile test simulation of the laminated composite by using software Abaqus®.
The determination of the load bearing capacity of masonry in existing structures is not an easy task, even for experienced surveyors. For its assessment, it is necessary to know the compressive ...strength of the masonry units and mortar. Relatively good destructive and non-destructive methods were developed for the determination of the compressive strength of masonry units. However, mortar compressive strength determination is currently closer to a rough estimation rather than a deterministic approach. All of the currently used methods are either complicated, have a limited application, or are based on the surveyor’s experience only. Influence of the human factor on the results of testing is significant. The paper introduces the development of a new non-destructive method, which eliminates the influence of the human factor. The method is supposed to work as quickly and as easily as the Schmidt hammer used for concrete structure surveys. The new instrument was created where the compressive strength of mortar is assessed by hammering a steel bar into a joint with constant energy, while the depth of penetration is measured. The impact energy is provided by a steel spring with a prescribed stiffness, and the loading is provided by an automatic system similar to those used in air-soft guns.
Rooftop solar modules are usually held in place by racks or frames that are mechanically attached to a roof structure and/or by heavyweight, ballasted footing mounts. These mounts ensure that the ...panel system remains in position against wind load. However, mechanical connectors create penetrations into the water-resistant layer of the roof, whereas ballasted footing mounts cause a significant additional load on the load-bearing structure of roof. For these reasons, adhesive connection seems to be a beneficial solution. Acrylic adhesive tapes, marked as VHBTM, may provide sufficient strength, and they have no need for mechanical fasteners or ballast. Acrylic adhesive tapes also provide a comfortable, fast, and efficient bonding process with no curing compared to liquid adhesives. On the other hand, resistance to water at load-bearing joints has not been sufficiently studied yet and could be critical for connections exposed to the outdoor environment. The present study aims at the determination of water resistance and durability of the VHBTM tapes from the GPH series, which are typically used to bond a variety of substrates including many metals. The mechanical properties and failure modes are compared for the specimens before and after a 21-day immersion in water. A significant reduction in strength was observed, depending on the substrate material. The study of chemical changes in the acrylic tape and in its leachate through infrared spectroscopy (FT-IR), X-ray fluorescence, and X-ray diffraction analyses clarified the reduction in mechanical properties. The selected VHBTM tape demonstrated strong resistance to the effects of water. However, the overall strength of the joint after immersion was significantly impacted by the decrease in adhesion to a specific substrate.
Kevlar fibers are widely used for industrial and military purposes due to their remarkable mechanical properties, such as their high tenacity and high strength-to-weight ratio. In this study, ...two-layered Kevlar composite specimens were impregnated with 10 wt.% poly (vinyl butyral)/ethanol solution which contained TiO2 nanoparticles as reinforcement. The concentrations of the nanoparticles were 1 wt.% or 2 wt.% with respect to the poly (vinyl butyral), PVB. The single-axial tensile test and three-point bending test of the Kevlar/PVB composites have been performed according to the ASTM D 3039 and ASTM D 790-03 standards, respectively. The tensile and bending properties of the dry and wet Kevlar/PVB composite specimens after a 56-day immersion are examined in this work. Upon the addition of the 2 wt.% TiO2 nanoparticles, the tensile strength and modulus of the dry specimens without reinforcement were increased by 39.8% and 24.3%, respectively. All the submerged specimens’ tensile and flexural property values were lower than those of the dry specimens. After comparing the wet composite specimens to their dry counterparts, the percentage decrease in tensile strength was approximately 20%. The wet Kevlar/PVB specimens with no TiO2 reinforcement showed the greatest reduction in bending strength, 61.4% less than for the dry Kevlar/PVB specimens, due to the degradation of the PVB matrix. In addition, a numerical simulation of the three-point bending test was carried out in Abaqus.
Looking at a current architecture, there are many examples of glass load bearing structures such as beams, panes, balustrades, columns or even stairs. These elements are mostly made of laminated ...glass panels. Panels are bonded together with polymer interlayer significantly influencing a shear forces transfer between them. There is still overall lack of knowledge in the task of shear forces transfer between these panels. It principally depends on the polymer stiffness, which is affected by an ambient temperature, humidity and load duration. Civil engineers currently tend to design laminated glass members on the safe side, generally not taking laminated panels interaction provided by the interlayer into account. This approach leads to uneconomical and robust glass bearing members significantly preventing the use of laminated glass more extensively. There are many polymer interlayers made for structural laminated glass applications available on a market. Most of them differ in stiffness and other important properties therefore these must be experimentally examined to design safer and more economical laminated glass members. This paper is focused on the shear modulus of PVB (polyvinyl-buthyral) and SentryGlasÒ (ionoplast) experimental investigations as a function of temperature and loading ratio. It is possible to find out these functions by static creep or relaxation tests as well as by dynamic mechanical thermal analysis-DMTA. A lot of DMTA experiments in shear with the aforementioned interlayers in various loading conditions have been performed in order to determine their shear stiffness. It also enables to identify their Prony parameters as a part of the next survey. Experimentally verified common polymer interlayer stiffness helps engineers to design safer and cheaper glass constructions. This is the way how to extend the use of laminated glass in a current architecture.
There are many examples of glass load bearing structures used in a contemporary architecture, such as panes, balustrades, and even stairs. For safety reasons, these structural elements are made of ...laminated glass which is a composition of glass plies bonded with polymeric interlayer. The distribution of stress in a perpendicularly loaded laminated glass panel depends on the shear stiffness of the used interlayer. There are various interlayers for laminated glass applications available on the market with wide variety of shear stiffness. To correctly evaluate the shear coupling provided by the interlayer, great research efforts have been made followed by appropriate national Standards and Codes for laminated glass in bending in recent years. Polymeric interlayers are viscoelastic materials and their stiffness is time and temperature dependent, which makes the reliable design of laminated glass panel in bending rather complicated. This paper is focused on experimental investigation of six polymeric interlayers (Trosifol® BG R20; Trosifol® Extra Strong; Evalam® 80/120; Evasafe®; SentryGlas® 5000; Krystalflex® PE399) loaded in displacement-controlled shear test in various temperatures and loading rates. The experiments showed nonlinear stress–strain dependence and confirmed the viscoelastic behaviour of presented interlayers. In addition, the values of their initial shear stiffness are listed and failure modes of testing specimens are presented. Results obtained in this study can be used for the estimation of the rate of glass plies interaction in short-term loaded laminated glass structures. All experiments were performed in Klokner Institute CTU.
The continuous welded rail (CWR) is nowadays standardly used on almost all modern railway bridges. However, its placement results in an interaction between CWR and the structure, which brings not ...only longitudinal forces on the substructure, but also significant additional stresses in the rail. These stresses can result either in the rail break, or in a track buckling. Unfortunately, input parameters for performing a numerical analysis are hardly accessible and they vary significantly in different sources. Because of that, an extensive long-time monitoring of the rail–bridge interaction was performed on a bridge with an unusual combination of ballasted track, direct fastening and a barrier in the ballast. The paper presents the results of the monitoring and shows the analysis and evaluation of formulas, defining the fastening nonlinear stiffness of track to the bridge connection. The influence of the temperature on the ballast stiffness is also analysed.
•Long term monitoring of the interaction between the steel railway bridge and continuous welded rail•Establishing an interaction functions between the bridge and the track•Comparison of the ballasted bed and direct fastening track behaviour•Impact of the temperature to the longitudinal resistance of the ballasted bed track
The shear interaction of laminated glass belongs to the essential characteristics of this material. The impact of the increased temperature on deformation properties was tested within investigation ...of basic mechanical properties of laminated glass panes. The specimens of laminated glass with the size of 120 x 1100 mm loaded by four-point bending load were exposed to the effect of the gradually increasing temperature up to approximately 65 °C in a thermal chamber. The progress of the deformation was continuously monitored by a measuring device during both temperature rise and subsequent cooling. Four kinds of interlayers were tested in total. In this paper the obtained experimental results are compared to numerical FE analysis and also the degree of an interaction of particular interlayer is evaluated.
In recent years, the field of structure monitoring has been making increasing use of systems based on fiber-optic technologies. Fiber-optic technology offers many advantages, including higher quality ...measurements, greater reliability, easier installation and maintenance, insensitivity to the environment (mainly to the electromagnetic field), corrosion resistance, safety in explosive and flammable environments, the possibility of long-term monitoring and lower cost per lifetime. We have used SOFO fibre-optic strain gauges to perform measurements to check the overall relative deformation of a real reinforced concrete structure. Long-term monitoring of the structure revealed that the measurement readings obtained from these fibre-optic strain gauges differed from each other. Greater attention was therefore paid to the calibration of the fibre-optic strain gauges, and to determining their measurement accuracy. The experimental results show that it is necessary to calibrate SOFO strain gauges before they are used, and to determine their calibration constant.
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