Nomenclature of Cambrian lithostratigraphy of the Skryje-Týřovice Basin

Ecuador Debate es una publicación periódica electrónica dependiente del Centro Andino de Acción Popular (CAAP), que cubre diversos temas de la actualidad local y Latinoamericana. Centrada especialmente en asuntos económicos y políticos del Ecuador, la publicación también incluye importantes secciones dedicadas a la cultura (crítica literaria), el mundo agrario, social-urbano, y los temas de conflictividad social. Estos últimos son analizados desde un punto de vista de sociológico y cuantitat..

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

Bond strength of hot – dip galvanized reinforcement (B500B) with concrete

This paper evaluates the effect of initial corrosion damage to the surface of the hot - dip galvanized steel coating in fresh concrete on its final bond strength. The tests were performed on uncoated and hot-dip galvanized ribbed reinforcements. The measurement of bond stress (τ_m) according to the standard procedure (ASTM C234; ČSN 73 1328) revealed decreased bond strength of the coated reinforcement. Both types of reinforcement exhibit similar values of maximum shear stress (τ). To make some general conclusion, the bond strength also needs to be verified on smooth profiles

Viscoelastic properties of EVA interlayer used in laminated glass structures

Abstract Laminated glass is getting used more extensively in a current architecture due to its transparency, aesthetic impression, and post-breakage behaviour. Examples of such structures are balustrades, stairs, or facade panels. These are usually loaded in bending. Polymeric interlayer embedded between glass plies has no flexural stiffness, but it can itself transfer shear stress. The rate of this transfer depends on the shear stiffness of interlayer which is time and temperature dependent parameter. Producers of interlayers often do not specify this quantity thus engineers rather neglect the shear interaction of glass plies in perpendicularly loaded laminated glass panels. This paper provides the values of shear stiffness modulus of common interlayer EVASAFE® by BridgestoneTM in time and temperature domain. This shear stiffness is expressed through Maxwell model whose parameters are based on the series of Dynamic mechanical thermal analysis (DMTA) performed on single lap small-scale specimens in Klokner institute CTU in Prague. Results show that shear stiffness of this interlayer is able to provide significant shear coupling of glass plies in broad temperature range of short-term perpendicularly loaded laminated glass structures.</jats:p

Durability of structural adhesive joints for facade applications exposed to the extended cataplasm test

The effects of exposure to humid conditions in the extended cataplasm ageing test, based on ISO 9142, Procedure E2 on the mechanical properties of adhesively bonded joints, were investigated as a part of a comprehensive study on the ageing of an acrylate adhesive and a Silane-terminated polymer (STP) adhesive. The adhesives were applied in aluminium and Zn-electroplated steel substrates with various surface treatments (a smooth surface, a roughened surface, and anodized and blank aluminium) to observe the effect of ageing on joints with various substrates. The predominant effect of high relative humidity in the cataplasm test was compared with the results of immersion in water according to ETAG 002