Ultrasonic propagation and damage sensing in a bonded PMC/SiC-Foam

The nondestructive evaluation of hybrid material systems is a challenging problem, where very different materials are often combined to enhance performance. In the present application, the bondline integrity of a sandwich structure is of interest, where two polymer matrix composite (PMC) facesheets are bonded to an insulating silicon carbide (SiC) foam interior. The propagation of ultrasound within the PMC-SiC Foam sandwich structure was studied using bonded PZT ultrasound sensing and scanning laser vibrometry, where wave propagation and scattering processes were evaluated for damaged and non-damaged SiC foam cases. The material system included two, 1-millimeter thick PMC facesheets bonded to a 14-millimeter thick SiC foam, where the sample had been subjected to a 4-point bend experiment, which generated a localized 45-degree crack in the SiC foam and a fracture of the PMC-SiC foam interface. The scanning laser vibrometry measurements were taken along the side profile of the layered material system, which permitted the visualization and study of propagating elastic wave energy through the thickness of the PMC-SiC-foam material system.