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This paper presents a robust method to estimate polymers’ damping, based on modal identification methods on frequency functions. The proposed method presents great advantages compared to other traditional methods such as the HPB method for polymeric materials where high damping or noise levels can limit their use. Specifically, this new method is applied on an experimental transmissibility function measured in a composite cantilever beam and the complex modulus is determined as a function of frequency. From this, a regenerated function is obtained based on the Euler–Bernoulli beam theory, and it is compared with experimental data. It can be concluded that the best way to apply the curve-fitting method for further testing of polymeric materials is when it is used with the whole frequency range by means of the MDOF method considering the residuals. In addition, this has the added advantage that the number of experimental tests to be carried out is much lower compared to using the SDOF method.

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This paper is aimed at investigating the influence of nonviscous modes on the vibrational response of viscoelastic systems. Thus, exponential damping models are considered. Provided that nonviscous modes disappear with time, they have influence on only the transient response of the system. Thus, the system response is obtained by means of modal superposition in order to examine the contribution of each mode. The analysis is carried out on two lumped parameter systems; systems involving a single degree and three degrees of freedom are studied. For the former, the analytic solution is derived via modal superposition and Laplace transformation. For the latter, the analytic response is contrasted with that provided via two numerical direct methods. From this investigation, it can be concluded that the system may present no oscillations, even if elastic modes are underdamped modes.