Test methodMethod to characterize the damping behavior of thin passively constrained layer laminates using dynamic mechanical analysis (DMA) in shear mode

In order to characterize the damping behavior of thin passively constrained layer damping (CLD) loudspeaker membranes, usually the whole loudspeaker has to be built. Therefore, a method was established to characterize the damping performance of these membranes with thicknesses below 50 μm at the film level using dynamic mechanical analysis (DMA).Since in the CLD design damping is provided via shear deformation of the middle damping layer, a test was set up to determine the mechanical loss factor tan δ (f,T) in DMA shear mode. Subsequently, results from 1-200 Hz were extrapolated to application-relevant frequencies of up to 1000 Hz via time-temperature superposition. Finally, the damping behavior was rated by the frequency dependent integrated average of the mechanical loss factor tA¯.Furthermore, in experiments with different constraining and damping layers, it was found that the damping performance was maintained as long as the adhesion between them was sufficiently strong.