Properties of PVB Interlayer Used in Laminated Glass

A thin elastomeric interlayer called polyvinyl butyral (PVB) is used to bond two or more thin glass plates to form a composite commonly called a laminated glass unit. Even though experiments have been performed to determine the load‐deformation characteristics, efforts to create a mathematical model for the stress analysis fall short of the nonlinear shear stress‐strain behavior of the PVB interlayer. Specially made laminated‐glass specimens $50\mathrm{mm}\times 50\mathrm{mm}\times 9.5\mathrm{mm}\text{,}$ with two interlayer thicknesses, 0.76 mm and 1.52 mm, are tested in a direct shear box testing apparatus. The average shear stress versus average shear strain are plotted. Variations of tangent and secant modulii are also plotted as a function of average shear strain. All tests are performed at very low strain rates, because the objective was to study the static behavior of laminated‐glass units.