Material Properties of Polymeric Interlayers under Static and Dynamic Loading with Respect to the Temperature

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

Four-point bending tests of PVB double laminated glass panels – experiments and numerical analysis

Current architecture uses glass even for load bearing structural elements. Typical example is perpendicularly loadedlaminated glass panel as a part of balustrade, staircase, or canopy. Laminated glass is a composition of two or more glassplies bonded by polymeric interlayer which enables the shear transfer between the individual plies in a laminated panel.The shear transfer depends on the shear stiffness of a certain interlayer as a time and temperature dependent parameter.Shear stiffness in time and temperature domain can be numerically described by a discrete Maxwell model whose Pronyparameters may be obtained by Dynamic mechanical thermal analysis (DMTA) of a particular interlayer. There arevarious techniques of DMTA as well as various Prony parameters fitting methods. As soon as shear stiffness given byMaxwell model is quantified, it is desirable to verify its credibility by experiment. This paper compares the experimentaldata from displacement-controlled four-point bending tests in various loading rates and from four point bending longtermcreep experiment of double laminated glass panels with PVB interlayer Trosifol BG-R20® to the numerical analysisperformed in ANSYS® 18.0. The interlayer was modelled as a viscoelastic material by two discrete Maxwell models.Prony parameters of the first Maxwell model were based on DMTA results performed on small scale specimens in singlelap shear mode and Prony parameters of the second Maxwell model were based on DMTA results performed on smallscale specimens in single lap shear mode and torsion mode. Results show that Maxwell model based only on single lapshear tests enabled to describe the long-term response of a panel while that based on single lap shear and torsion testswas more precise in task of displacement-controlled test. All experiments and analyses were performed at CTU in Prague

Hybridní konstrukce ze dřeva a skla

Dřevo i sklo jsou materiály, které vynikají svými estetickými vlastnostmi. V současné architektuře je sklo, stejně tak jako dřevo, stále častěji používáno na pohledově exponované nosné konstrukce. Protože sklo je křehký materiál, jsou vyvíjeny různé druhy hybridních konstrukcí, kde je sklo kombinováno s jinými materiály (např. beton, dřevo, ocel, hliník apod.) s cílem zvýšit únosnost prvku, dosáhnout bezpečného chování při porušení skla a současně zachovat vysokou míru transparentnosti. Výzkumem sklo-dřevěných konstrukcí se v současné době zabývá několik evropských univerzit, proto se tento článek zabývá touto problematikou

Nosné konstrukce ze skla a dřeva

Rostoucí zájem o sklo jako konstrukční materiál vede k jeho uplatnění mimo jiné i v dřevěných konstrukcích, např. pro vnější fasádní prvky nebo sloupy či nosníky uvnitř budovy. Sklo je křehký materiál, ale dosahuje až šestkrát vyšší tuhosti než dřevo. Vhodnou kombinací obou těchto materiálů lze vytvořit takový kompozitní prvek, kde slabé vlastnosti jednoho materiálu (např. křehkost skla a nízká pevnost v tahu) lze vhodně doplnit vlastnostmi druhého materiálu (např. pevností dřeva v ohybu a duktilitou v tlaku)

Teretron : první SPIN-OFF projekt univerzitního centra UCEEB

Příspěvek představuje jeden z prvních českých „SPIN-OFF“ projektů, který si klade za cíl nejen představení výhod takového typu projektu, který je v posledních letech populární na vyspělých trzích, například ve Velké Británii a USA, ale zároveň vkládá naděje do úspěchu nového, zajímavého projektu. Projekt je realizován ve spolupráci Univerzitního centra UCEEB a britské společnosti The Rope Effect Ltd vyvíjející výpočetní software Teretron. Projekt je ve fázi beta testování a brzy bude připraven pro český trh.

Material properties of adhesives for shear bonded connections of structural glass

Thanks to intensive research in the field of polymer adhesives in the last few years, there is a possibility of using a glued joint with a real load bearing role. The reliability of adhesive in the connection during the lifetime of a structure is affected by many factors, but the initial choice of a proper adhesive material is the most crucial one. The article deals with the experimental analysis focused on the determination of material characteristics of adhesives in planar connections, it describes the effect of various factors on the behavior of an adhesive joint under increasing loads, its ultimate bearing capacity and its failure modes. The main investigated factors are the type of adhesive, the type of connected materials (material of substrate), surface treatment and the thickness of the adhesive layer. A special part of the article describes numerical models of a glued joint with respect to different types of adhesive

Environmental durability of Kevlar composites reinforced with TiO2 nanoparticles

In this research, the testing specimens were made from the Kevlar fabrics impregnated with 10 wt.% poly (vinyl butyral)/ethanol solution but with the addition of the TiO2 nanoparticles. The tensile and bending properties of the dry specimens were compared with the ones that had been immersed in a water bath filled with distilled water (40°C) in the period of 8 weeks. The PVB/fabric weight ratio for the impregnation of the woven Kevlar fabric was 20 wt.%. The Kevlar/PVB fabric composites were reinforced with the TiO2 nanoparticles in different concentrations (1 wt.% or 2 wt.% of reinforcement regarding poly (vinyl butyral), PVB). The two layers of composite fabrics were hot-pressed by using the digital press at a temperature of 170 °C for 30 minutes. The immersion of the square Kevlar/PVB composite specimens for the water weight gain measurements was performed according to the ISO 62 standard. The Kevlar/PVB specimens were tested in accordance with the ASTM D 3039 standard for the tensile properties and ASTM D 790-03 standard for the flexural properties. During the tensile and the flexural test, the complete fracture of the specimens did not occur. The addition of 2 wt.% TiO2 nanoparticles produced 39.8% and 24.3% improvement in the tensile strength and tensile modulus, respectively, compared to the dry Kevlar/PVB specimens without reinforcement. The tensile properties of all the immersed Kevlar/PVB composite specimens had decreased values compared to the ones of their dry specimens. Unlike the tensile test results, the best flexural properties (strength and modulus) were achieved with the dry specimens with no particles due to the better bonding between their two impregnated fabric layers since the presence of TiO2 nanoparticles reduced the shear connection between the layers. However, there was not such a decline in the properties of the wet specimens with nanoparticles which even made some improvement in the bending strength compared to the wet Kevlar/PVB specimens

Degradation Effect of Moisture on Mechanical Properties of Kevlar/PVB Composites with TiO₂ Nanoparticles

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

Effects of Water Immersion on Mechanical Properties of Kevlar Composites Reinforced with ZnO Nanoparticles

The Kevlar fabric composites have a wide range of applications in the body armor and lightweight vehicle-armor structures. Nanoparticles are one of the most common nanofillers for these structures. In this research, the testing specimens have been made from the Kevlar fabrics impregnated with the poly (vinyl butyral)/ethanol solution which had been reinforced with the ZnO nanoparticles. The two-layered composite samples have been fabricated by means of hot compression. The immersion of the square Kevlar/PVB specimens for the water uptake measurements has been performed according to the ISO 62 standard. The specimens have been immersed in a water bath filled with the distilled water (40 °C) in the period of 8 weeks. The Kevlar/PVB specimens have been tested in accordance with the ASTM D 3039 standard for the tensile properties and the ASTM D 790– 03 standard for the flexural properties. The tensile and bending characteristics of the dry specimens have been compared with the ones that had undergone the water immersion