Experimental and analytical estimation of loss factors by the power input method

The system loss factor of sandwich panels with different configurations of constrained layer damping treatments is estimated both experimentally and analytically using the power input/injection method over a broad frequency range. Results of the experimental power input method are compared with results from other experimental methods. A new analytical power input method is proposed for evaluating the loss factor of built-up structures, based on a finite element model with assigned properties of the constituents. The new analytical power input method is evaluated by comparison with the commonly used modal strain energy method. Instead of making an approximate correction of the constant material properties, this analytical power input method directly takes into account the frequency-dependent material properties of the viscoelastic material, using the MSC/NASTRAN direct frequency-response solution. Results of experimental and analytical methods are presented, compared, and discussed. It is shown that all three currently available experimental methods yield consistent results and that both the analytical power input method and the modal strain energy method yield results consistent with the experimental power input method.