Influence of core density, core thickness, and rigid inserts on dynamic characteristics of sandwich panels with polyurethane foam as core

The growth in practical applications of sandwich constructions in high performance vehicles, aerospace, marine, automobile, and electronic packaging industries needs a thorough investigation of all vibration modes of the structure. This is to ensure that debonding between facings and core in the through-thickness vibration mode does not occur during service. In the present work, experimental modal analysis on sandwich panels of different densities and core thicknesses have been carried out under three different boundary conditions. The influence of rigid inserts of different volume fractions on the dynamic behavior has also been examined. A non-dimensional parameter representing the ratio of core density and core thickness to face density and face thickness has been established, which correlates excellently with measured fundamental natural frequency. The corresponding mode shapes and modal damping have also been evaluated.