Identification of honeycomb sandwich properties by high-resolution modal analysis

A method is proposed to identify the mechanical properties of the skin and core materials of honeycomb sandwich. All the elastic coeo,cients and loss-factors that matter in the dynamics of a panel in the thick-plate approximation are identio,fied. To this end, experimental natural modes (i.e. eigenmodes of the damped system) are compared to the numerical modes of a large sandwich panel (l_x,y/h b80). The chosen generic model for the visco-elastic behaviour of the materials is E (1 + jη). 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 coeofficients. A sensitivity analysis assess the reliability of the method.