Influence of ANO3 and ANO3·nH2O Nitrates on the Deformation Properties of Aluminosilicate Adhesives for Wood Products and Structures

As a result of the research, the deformation properties of aluminosilicate adhesives modified with nitrate salts and intended for gluing wooden products and structures made of pine, beech and oak wood at different stages of their hardening were determined. Considering that pine is the most common wood in the manufacture of products and structures, then in order to reduce the numerical values of the elastic modulus in glued materials, it is advisable to add ammonium, lithium and sodium nitrates in an amount of 0.5%, potassium nitrate in an amount of 1% into the composition of an aluminosilicate adhesive. which will ensure the approximation of the elastic modulus values to the values of the unmodified aluminosilicate adhesive and will significantly affect the water resistance of the glue joint and the depth of penetration of the adhesive into the wood structure. For gluing beech wood products to reduce the elasticity modulus, it is advisable to introduce 0.5% ammonium and potassium nitrates and 1% lithium and sodium nitrates, which will reduce the numerical values of the elastic modulus in glued materials by 1.18 and 1.53 times compared with the values of the elastic modulus of the unmodified aluminosilicate adhesive. For gluing oak wood products to reduce the elasticity modulus, it is advisable to introduce 0.5% potassium nitrate and 1.5% sodium nitrate, which will reduce the numerical values of the elastic modulus in glued materials by 1.4 and 2.83 times compared to the values modulus of elasticity of unmodified aluminosilicate adhesive.

Technology development for automobile glass assembly

The analysis of glass assembly technology and impact of different factors upon strength and accuracy of glass positioning is presented. The modeling of residual stresses after manufacturing as a result of technological impact has shown the presence of residual stresses of stretching along the edges. To the stresses there are summed up assembly stresses caused by shrinkage processes in the glue joint. It is defined that at the minimum width of the glue roll during dry-out a discontinuity of the glue joint along the contour is possible and at the maximum layer width the additional technological stresses in glass arise.

The use of coffee bean post-extraction residues as a filler in plywood technology

The use of coffee bean post-extraction residues as a filler in plywood technology. The aim of the research was to determine the influence of post-extraction coffee beans used as a glue mass filler for the plywood glue joint on their selected mechanical and physical features. In the scope of the research the plywood of different content of post-extraction coffee beans in glue mass have been produced in laboratory conditions, as well, as reference material, the plywood with wheat flour as a glue mass filler have been made. The investigated material has been tested according to different features, including measurement of the plywood density profile, static bending strength and modulus of elasticity, shear strength, water absorption, as well as resistance to axial removal of screws. The significant reduction of bending strength, modulus of elasticity when bending, shear strength, as well as resistance to axial removal of screws has been found for samples with coffee bean residues, when referred to reference plywood. Also, decreasing penetration depth of coffee residues filled glue mass has been noted, with the coffee bean post-extraction residues content raise.

The formation of residual stresses in the bonding of automotive glass

This article discusses the formation of residual stresses during the assembly of automotive glass. The influence of various parameters of the adhesive bead on the spatial deviations of glasses during their installation is shown. Currently, the glass assembly technology involves filling the gap between the automotive glass and the car body with a glue roller. It has been established that the formation of residual stresses is influenced by the width and thickness of the glue roll, with a minimum width of the glue roll during drying, a discontinuity of the glue joint along the contour is possible, and with a maximum width, unacceptable residual deformations occur in the glass, which lead to cracks.

Numerical and Experimental Research on Delamination of Glulam Elements

The paper presents numerical and experimental research on glulam delamination in a double lap connection with predominant shear stresses. Laboratory tests and wide literature survey enabled to determine timber and glue joint parameters. Cohesive zone theory, generally used for epoxy matrix and fiber reinforced composites, was adopted to modelling glue layer delamination in glulam elements. Numerical models were validated with laboratory tests.

The phenomenon for the wood creep in the reinforced glued wooden structures

For the composite structures based on wood, that include reinforced wooden structures, allowance for the influence of wood specific features as a building material allows us to evaluate its structural design as accurately as possible and ensure the required reliability and durability. Creep that causes wood deformations evolving in time can be referred to the specific properties of wood to a greater extent affecting the operation of the reinforced wooden structures. Taking into account the state of the issue to determine the effect of the long-acting loads on the stress-strain state of the reinforced glued wooden structures, the article considers the application of the theory of elastic heredity as the most applicable to assess the deformability of wooden structures in time. The conducted experimental and theoretical investigations and the reinforced glued wooden structures observations during the operational process have shown that their stress-strain state changes significantly under the load over time. Glue compositions used to connect reinforcement with wood ensure their reliable joint operation, however, as the result of the wood creep where wood is the basic material, the redistribution of forces between the reinforcement and wood occurs there on and off. At the same time normal stresses in the reinforcement and the glue joint “reinforcement - wood” increase in the calculated cross sections while they decrease in the wood, which is caused by a change (decrease) in the wood elastic modulus. Allowance for the wood creep in the design of the reinforced wooden structures will allow to determine the stress - strain state of the structure in the design more precisely. Therefore, when developing the reinforced wooden structures design standards, this factor must be taken into account.

Some properties of LVL composed of poplar and beech veneer and possibilities of their application for window frames

The subject of this paper was a research of physical and mechanical properties of LVL composed of peeled poplar veneers in core layers and only outer layers of beech peeled veneers, so as the examination of window frame glue joint strength produced of this material. LVL boards have been hot pressed in industrial conditions, using appropriate phenol formaldehyde (PP) adhesive. Samples for corner window frame glue joint strength testing were glued with PVAc D4 class adhesive. Statistical analysis showed that there were significant differences both in moisture content and density of LVL boards regarding their thickness, while in the case of hardness this difference did not exist. Examinations of LVL glue line shear strength showed that both phenol formaldehyde (PP) and PVAc D4 class adhesives fulfilled standard requirements. The results of corner window frame double tenon glue joint strength produced from combined poplar-beech veneer LVL indicated that such material could be used to produce window frame corner joint, strong enough to withstand the additional load, without an increase of the cross section.

Environmental Conditions Effect for Adhesive Connections in Glass Structures

Load-bearing joints of glass structures belong to the one of new applications of adhesive connections in civil engineering. They provide several important benefits particularly even stress distribution along the contact depending on geometry and stiffness of the glue joint, which is crucial for brittle glass. There is a lack of knowledge about semi-flexible or semi-rigid adhesive connections in the structural glass field and durability is one of the essential properties that have to be assessed during design-process of bonded connection. An extensive research focused on shear glued joints in glass structures was performed at CTU in Prague, which also comprised environmental effect simulation on the glued specimens in laboratory accelerated conditions. The paper is dedicated to impact of ageing to the specimens and their mechanical properties together with brief overview of available laboratory ageing methods.

Fracture Resistance of Bended Glued Timber Elements with Flaws

The test results for deriving of the dependencies of critical stress intensity factors on significant agents are presented for glued laminated timber. The dependencies of critical stress intensity factors on moisture content, width of cross section for I and II forms of fracture are investigated. For the second fracture form the influence of glue joint thickness within the limits of 0.07 - 0.35 mm was estimated. The influence on critical stress intensity factor was estimated also for the moisture content of wood within the limits of 12-35%, for crack front width within the limits of 30 - 140 mm, for loading velocity within the limits of 16 - 32 kN/min, for the form of crack tip, and the location of crack - in glue joint or in wood.