Transparente Klebstoffe für Glas‐Metall‐Verbindungen

Weller, Bernhard; Wünsch, Jan

doi:10.1002/stab.201390062

“…11). Previous tensile tests on shoulder bars by the Institute of Building Construction, Technische Universität Dresden 15 further suggest that the tensile strength of adhesive A is considerably higher at -20˚C (~ 50 MPa) than at room temperature (~ 10 MPa); tensile tests by Weller and Wünsch [20] on point fixings made of glass and stainless steel before and after various types of artificial aging show good aging resistance of the bonds with DP 610. The 5% fractile values of the residual strength are (except for aging with surfactants) between 2 and 12 MPa.…”

Section: Resultsmentioning

confidence: 91%

The adhesively-bonded glass brick system of the Qaammat Pavilion in Greenland: From research to realization

Oikonomopoulou

¹

,

Bristogianni

²

,

Velden

³

et al. 2022

Archit. Struct. Constr.

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An adhesively bonded, solid-glass brick pavilion has been designed by Konstantin Arkitekter as a landmark within the Aasivissuit – Nipisat UNESCO heritage in Greenland. The sculptural glass structure, measuring approximately 3.2 m in diameter × 2 m in height, faces a diverse set of engineering challenges compared to existing adhesively bonded glass brick structures. Placed in a remote location in the arctic circle, it has to withstand winter temperatures as low as -35 °C, and be built under a limited budget with the aid of the local population. Hence, key for the successful construction of the pavilion is finding an adhesive that satisfies the structural and aesthetic requirements of the project and simultaneously provides a simple and fast construction that spares the need for specialized building crew and sophisticated equipment, and is able to withstand the polar winter temperatures. Applicability and shear tests in (i) lab temperature conditions and (ii)) -5 °C lead to the final selection of: (a) 3M™ Scotch-Weld™ Polyurethane Adhesive DP610, which has a higher shear strength capacity, 1 mm gap filling capacity and is clear in colour, for bonding the bottom rows of the pavilion where higher strength is required due to the reduced overlapping of the bricks; and of (b) DOWSIL Experimental Fast Curing Adhesive developed by Dow Silicones Belgium particularly for this project, with a satisfactory shear strength, 3 mm gap filling capacity and white colour for the rest of the pavilion; its considerably larger gap filling capacity facilitates the ease of assembly as it can accommodate within the joint thickness the anticipated ± 1.5 mm standard size deviations of the soda-lime cast glass solid bricks and the possible accumulated deviations during construction. The paper further describes the application of the adhesive, first on a small-scale prototype, and then on site, and presents the encountered engineering and logistical challenges during the construction of the pavilion in Greenland.

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Water in polyurethane networks: physical and chemical ageing effects and mechanical parameters

Possart

¹

,

Zimmer

²

2022

Continuum Mech. Thermodyn.

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The chemical structure, polymer mobility and mechanical properties are studied for a cross-linked amorphous poly(ether urethane) (PU) from glass transition to rubber elasticity for juvenile dry samples and for water-saturated states after exposure to humid air (r.h. = 29, 67, 95, 100%) at $$60~^\circ \hbox {C}$$ 60 ∘ C during 1 y of ageing. For saturated samples, network chain cleavage is the chemical ageing mechanism, but it is too weak and slow to affect on the physical properties significantly within 1 y. Water acts primarily in a physical manner. Within 1 d, $$\hbox {H}_{{2}}\hbox {O}$$ H 2 O molecules replace part of the weak urethane H-bonds by $$\hbox {H}_{{2}}\hbox {O}$$ H 2 O –urethane H-bonds and reduce all other physical interactions between network chains by solvating hydrophilic segments. Thus, the cooperative polymer mobility strongly amplifies: The gain of specific conformational entropy doubles across the caloric glass transition, which shifts by −17 K. A $$\hbox {H}_{{2}}\hbox {O}$$ H 2 O concentration of only $$\hbox {c}_{{\mathrm{H}_2\mathrm{O}}}~\approx ~(0.4~\ldots ~0.5)~\hbox {c}_{\mathrm{\mathrm{H}_2\mathrm{O},max}}$$ c H 2 O ≈ ( 0.4 … 0.5 ) c H 2 O , max suffices for the major part of these fast rearrangements. Some part of the water slowly forms (during 3–4 months) a finely dispersed water-rich mixed phase with the PU chains. Except the new phase, these molecular processes of physical ageing strongly affect the mechanical properties at damage-free deformation. For dry PU in the glass transition, the shear modulus, $$\mu _{\mathrm{relaxed}}$$ μ relaxed (T), after viscoelastic stress relaxation only depends on the deformation-induced entropy change—like in the rubber elastic state. Within one month, water drastically decreases the viscoelastic response, as expected for plasticisation. However, $$\mu _{\mathrm{relaxed}}$$ μ relaxed (T) slightly grows in wet PU. $$\hbox {H}_{{2}}\hbox {O}$$ H 2 O molecules cause these opposite trends by boosting the cooperative mobility (i.e. extension of the accessible conformational space and entropy by reduction in energy barriers) and by occupation of free volume compartments. Water quickly reduces the fracture parameters by about 50%. We explain that embrittlement by the $$\hbox {H}_{{2}}\hbox {O}$$ H 2 O -induced facilitation of cooperative network chain motions, which let fracture proceed with less energy. In summary, our findings provide a detailed conception of the molecular effects the $$\hbox {H}_{2}\hbox {O}$$ H 2 O molecules have on the PU network, and they explain the consequences for the mechanical properties.

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Elastic lateral-torsional buckling of glass beams with continuous lateral restraints

Sonck

¹

,

Belis

²

2016

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Lateral-torsional buckling is a typical buckling mode for slender members loaded in bending, which is characterized by the lateral and torsional displacement of the cross-section along the complete member length. Structural glass members are often connected to the encompassing structure by means of a silicone sealant joint along the member length, which acts as a partially rigid lateral connector, restraining the movement of this side of the member. While this will increase the lateral-torsional buckling resistance of these members, this is currently not considered during the design. In this paper the behaviour of glass beams with a continuously restrained top edge, loaded by a line load or central point load along this edge, will be investigated by executing a numerical parametric study. In this study, the restraint provided by the silicone sealant joint is modelled by lateral springs along the edge of the beam. The influence of the spring stiffness on the critical load and corresponding eigenmode shape will be determined in an eigenvalue analysis, considering both monolithic and laminated glass beams. The results of this study will give some first insights in the influence of lateral restraints on the lateral-torsional buckling behaviour.

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Transparente Klebstoffe für Glas‐Metall‐Verbindungen

Cited by 3 publications

References 5 publications

The adhesively-bonded glass brick system of the Qaammat Pavilion in Greenland: From research to realization

The adhesively-bonded glass brick system of the Qaammat Pavilion in Greenland: From research to realization

Water in polyurethane networks: physical and chemical ageing effects and mechanical parameters

Elastic lateral-torsional buckling of glass beams with continuous lateral restraints

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