Assessment of the apparent bending stiffness and damping of multilayer plates; modelling and experiment

Abstract

In the context of aeronautics, automotive and construction applications, the design of light multilayer plates with optimized vibroacoustical damping and isolation performances remains a major industrial challenge and a hot topic of research. This paper focuses on the vibrational behavior of three-layered sandwich composite plates in a broad-band frequency range. Several aspects are studied through measurement techniques and analytical modelling of a steel/polymer/steel plate sandwich system. A contactless measurement of the velocity field of plates using a scanning laser vibrometer is performed, from which the equivalent single layer complex rigidity (apparent bending stiffness and apparent damping) in the mid/high frequency ranges is estimated. The results are combined with low/mid frequency estimations obtained with a high-resolution modal analysis method so that the frequency dependent equivalent Young's modulus and equivalent loss factor of the composite plate are identified for the whole [40 Hz-20 kHz] frequency band. The results are in very good agreement with an equivalent single layer analytical modelling based on wave propagation analysis (model of Guyader). The comparison with this model allows identifying the frequency dependent complex modulus of the polymer core layer through inverse Article published in Journal of Sound and Vibration resolution. Dynamical mechanical analysis measurements are also performed on the polymer layer alone and compared with the values obtained through the inverse method. Again, a good agreement between these two estimations over the broad-band frequency range demonstrates the validity of the approach.

Vibro-Acoustic Characterization of a Composite Structure Featuring an Innovative Phenolic Foam Core

“…The solution procedure described in detail in [36] uses three equations to determine the dynamic parameters of the beam along the entire frequency range, but other fitting approaches have been explored in the literature, such as writing frequency as an explicit function of the bending stiffness and minimizing the error in frequency [37]. As pointed out in Ege et al [38], at increasing frequencies the damping increases, resonances are less pronounced, the modes overlap and the frequency response tends to smooth out, thus, this modal identification method can normally be used in a limited frequency range depending on the material. In case of extremely flexible or small specimens, this range could be rather short and other identification methods should be considered.…”

Spatial Patterning of the Viscoelastic Core Layer of a Hybrid Sandwich Composite Material to Trigger Its Vibro-Acoustic Performances

“…[11,12]. In brief, the Guyader model allows for the determination of the equivalent (or "apparent") single layer plate complex bending stiffness (D * ) as a function of the loading frequency (f):…”

On the structural dynamics of laminated composite plates and sandwich structures; a new perspective on damping identification

“…Different experimental procedures exist for the characterisation of multilayer structures. At high frequencies, where modal analysis approaches become unpractical because of the increased modal density [13], other techniques based on vibration field analysis have demonstrated their efficiency, as detailed by Ege et al [14]. Among them, the IWC (Inhomogeneous Wave Correlation) method stands out, which is basically a wave fitting approach used by Berthaut [15] on ribbed panels and by Cherif et al [16] on honeycomb sandwich structures.…”