Identification of elastic and damping properties of sandwich structures based on high resolution modal analysis of point measurements

International audienceA method is proposed to identify the mechanical properties of the skin and core materials of sandwich structures having heterogeneous cores. All the elastic coefficients and loss-factors that matter in the dynamics of such a panel in the thick-plate approximation are identified. To this end, experimental natural modes (i.e. eigenmodes of the damped system) are compared to the numerical modes of large sandwich panels (lx,y/h ≃ 80). The chosen generic model for the visco-elastic behaviour of the materials is E(1 + j ). The numerical modes are computed by means of a Rayleigh-Ritz procedure and their dampings are predicted according to the visco-elastic model. The frequencies and dampings of the natural modes of the panel are estimated experimentally by means of a high-resolution modal analysis technique. An optimisation procedure yields the desired coefficients. A sensitivity analysis assess the reliability of the method. Identification is conducted on two very different kind of sandwich panels to illustrate the method