Experimental and analytical study of natural vibration modes of soft-core sandwich beams

A simple experimental layout consisting of a shaker and a pair of miniature accelerometers was used to investigate the natural vibration modes of a cantilever sandwich beam with a transversely flexible core. The natural vibration frequencies of the sandwich cantilever were measured over a wide range of frequencies, and the anti-symmetric and symmetric natural vibration modes of the soft-core sandwich cantilever were experimentally established. Experiments show that the damping properties of the foam core are manifest most noticeably in the case of the symmetric vibration modes, whereas the influence on the anti-symmetric modes is insignificant. The experimental measurements are shown to be in good agreement with the analytical predictions made with the aid of the higher-order sandwich theory (HSAPT). The quantity of information gained makes the present experimental technique especially attractive in comparison with sophisticated, more expensive full field methods like TV-holography.