Dynamic Mechanical Thermal Analysis of EVA and PVB Polymeric Interlayers in Low Temperatures

Abstract

Many examples of glass load bearing structures such as beams, panes, balustrades, columns or even stairs can be found in a current architecture. These members are usually made of laminated glass panels. Glass plies of a laminated panel are bonded with polymeric interlayer significantly influencing shear forces transfer between them. It principally depends on a polymer shear stiffness which is affected by an ambient temperature and load duration. There is still general lack of knowledge regarding shear stiffness of most polymeric interlayers. Civil engineers thus design laminated glass members with excessive caution neglecting positive shear coupling of the glass plies provided by the interlayer. This approach leads to uneconomical and over-sized glass bearing structures profoundly preventing an extensive use of laminated glass in civil engineering. There are many polymer interlayers of different chemical composition available on the market. Mechanical properties of most of them are unfortunately not available for civil engineers dealing with laminated glass constructions design. This paper is focused on dynamic shear modulus of EVA (ethylene-vinyl acetate) and PVB (polyvinylbutyral) interlayer and their experimental investigation as a function of temperature and loading ratio. One possible way of determining this modulus is a shear dynamical thermal analysis (DMTA) which further enables to derive time and temperature dependent shear stiffness of EVA and PVB. This experimentally investigated property helps engineers design safer and cheaper glass constructions, possibly extending the use of laminated glass in a current architecture.