Numerical and Experimental Modal Analysis of Laminated Glass Beams

This paper presents a numerical and experimental modal analysis of laminated glass beams, i.e. a multilayer composite structure made of glass panes bonded to an interlayer foil. These polymer foils provide shear coupling of glass layers, damping of vibrations, and play a key role in post-breakage performance. In this contribution, three-layer beams with ethylene-vinyl acetate interlayer are investigated. Using a finite element discretization and the Newton method, we solve numerically a complex eigenvalue problem which is nonlinear due to the frequency/ temperature-sensitive viscoelastic behavior of the interlayer. In our experimental investigations, a roving hammer test was carried out to identify the mode shapes, natural frequencies, and modal damping. The validation shows that there is a good agreement between the numerical predictions and experimental data in natural frequencies. However, the errors in loss factors can be high, because these values are very sensitive to the material properties of polymer, frequency, temperature, and boundary conditions. These effects are discussed in the concluding part of our study.