VISCOELASTIC PROPERTIES OF SELECTED PVB INTERLAYERS FOR LAMINATED GLASS

Year 2020, Volume: 4 Issue: 4, 37 - 42, 23.10.2020

Miroslav Vokáč , Tomáš Hána Klára V. Machalická Martina Eliášová

Abstract

In contemporary
architecture, laminated glass panes are widely used for structural elements loaded
perpendicularly to its surface such as floors, roofing, facades etc. It is
sought-after for its transparency and smooth reflective surface. In this case,
it is advisable to consider the interaction of the individual glass panes in
the cross-section. A conservative approach, that does not take into account the
shear interaction of glass panes, is uneconomical. Various commercial products
based on PVB (polyvinyl butyral), EVA (ethylene vinyl acetate), ionomer, or
thermoplastic polyurethane (TPU) are used. Stiffness of polymers depends on
temperature and duration of a load. Interlayers exhibit the viscoelastic
properties and temperature dependency is usually described by the generalized
Maxwell model and WLF model (Williams-Landel-Ferry). Parameters of these models
are most effectively determined by Dynamic Mechanical Thermal Analysis (DMTA),
where the material is cyclically loaded at different frequencies and
temperatures. Two types of PVB interlayers (Trosifol® Extra
Strong and Trosifol® BG-R-20) were investigated using DMTA in the
research carried out at Klokner Institute, CTU in Prague. In addition,
experimental quasi-static loading tests were performed in shear at various loading
rates and temperatures. The testing arrangement was as single lap shear test in
both cases. The experimental stress-strain diagrams from static tests were
compared with the theoretical diagrams derived from material parameters based
on DMTA testing. Although both materials are PVB-based, shear stiffness and
temperature dependence are considerably different due to additives added to the
PVB feedstock. These differences in material behavior are important because the
actual material properties have to be taken into account in the design of laminated
glass structure.

Keywords

laminated glass, polymeric interlayer, shear-coupling, Maxwell model, WLF model, DMTA

Supporting Institution

MPO ČR

Project Number

FV10295

Thanks

This contribution was prepared with support of the project MPO ČR No. FV10295.

References

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