Experimental investigation of temperature and loading rate effects on the initial shear stiffness of polymeric interlayers

There are many examples of glass load bearing structures used in a contemporary architecture, such as panes, balustrades, and even stairs. For safety reasons, these structural elements are made of laminated glass which is a composition of glass plies bonded with polymeric interlayer. The distribution of stress in a perpendicularly loaded laminated glass panel depends on the shear stiffness of the used interlayer. There are various interlayers for laminated glass applications available on the market with wide variety of shear stiffness. To correctly evaluate the shear coupling provided by the interlayer, great research efforts have been made followed by appropriate national Standards and Codes for laminated glass in bending in recent years. Polymeric interlayers are viscoelastic materials and their stiffness is time and temperature dependent, which makes the reliable design of laminated glass panel in bending rather complicated. This paper is focused on experimental investigation of six polymeric interlayers (Trosifol® BG R20; Trosifol® Extra Strong; Evalam® 80/120; Evasafe®; SentryGlas® 5000; Krystalflex® PE399) loaded in displacement-controlled shear test in various temperatures and loading rates. The experiments showed nonlinear stress–strain dependence and confirmed the viscoelastic behaviour of presented interlayers. In addition, the values of their initial shear stiffness are listed and failure modes of testing specimens are presented. Results obtained in this study can be used for the estimation of the rate of glass plies interaction in short-term loaded laminated glass structures. All experiments were performed in Klokner Institute CTU.