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.