A Comparison of Different Methodologies for PVB Interlayer Modulus Characterization

Abstract

The proper measurement and interpretation of modulus data for glass laminate interlayers can be quite complex. The development of master curves using different deformation modes and the preparation of the samples for measurement can significantly affect the results. International standard ISO 6721, determination of dynamic mechanical properties, uses modulus as a primary criterion for method selection. The shear modulus of polyvinylbutyral (PVB) materials varies to a great extent, e.g. 1 – 400 MPa, over the temperatures and durations encountered for glass laminates in a building. We have evaluated the use of tensile and plate-plate geometries for a regular and a high rigidity (“structural”) PVB interlayer material, as well as torsion geometry for a structural PVB interlayer material. In some cases, datasets from different sources have been compared. This paper will discuss the results we obtained using different methodologies, and explore the effect with regards to positioning of the interlayers in the “stiffness families” and the associated shear transfer coefficients as in draft European norms prEN 16612 and prEN 16613.