Experimental estimation of the damping ratio of metallic foam sandwich panels with sand intrusions

The interest to use steel foam sandwich structures is expanding in various industrial applications, and more attention is paid to improve the properties of these materials. However, liquid and solid intrusions can severely hamper their useful characteristics. This study aims to provide an experimental investigation on the potential of steel foam (hollow sphere) sandwich specimens to operate as passive dampers in flexural vibration and to preserve their capabilities when affected by the intrusion of external particles. The authors utilized two different experimental examinations, random noise (white noise) and impact (hammer) tests. The specimens consist of a hollow sphere foam core sandwiched between two mild steel sheets, bonded with a thermosetting epoxy resin. To simulate the intrusions of granular materials in operating conditions, the metallic foam cores of the samples were partially filled with different percentages of quartz sand particles. The two-phase specimens were then compared to the pristine (single-phase) ones. The resulting estimates of the vibrational damping ratio for single and double-phase metallic foam specimens were used to calibrate the respective Finite Element models, which proved to be suitable for replicating the damping characteristics of the specimens.