Inferring viscoelastic dynamic material properties from finite element and experimental studies of constrained layer damping systems

Viscoelastic materials are often used to add damping to metal structures, usually via the constrained layer damping method. The added damping is strongly dependent on material temperature and frequency, as are the underlying material properties of the viscoelastomer. Several standardized test methods are available to characterize the dynamic material properties of viscoelastomers. However, they rely on limited test data which is extrapolated using the time-temperature superposition technique. The authors have found that the different testing methods typically produce significantly different material properties. A new approach to inferring viscoelastomer material properties is suggested here. Several metal bars are treated using constrained layer damping. Experimental modal analyses are conducted on the bars at different temperatures to produce sets of system resonance frequencies and loss factors. Corresponding finite element (FE) models of the treated bars are analyzed using assumed viscoelastomer material properties. The properties are adjusted by trial and error until the FE-simulated system loss factors match those of the measurements.