One dimensional modeling of ultrasonic characterization of face sheet core debonding in composite sandwich panels

Theoretical models of ultrasonic wave propagation in polymeric composite sandwich panels, deteriorated by various types of face sheet core debonding, are analyzed. All sandwich panels consist of a core of one material and two identical face sheets of a second material. Debonding, either completely or partially, is modeled at either of the face sheet core interfaces. For the constant amplitude input and the corresponding steady state output (both of which are observed at the top surface), all models produce similar output spectra, though each model displays distinctive characteristics. The undamaged sandwich panel can be distinguished from any of the debonded panels by the presence of detectable waves along the unloaded bottom surface, especially at frequencies near the through thickness natural frequencies of the top or bottom face sheet in the corresponding longitudinal or shear wave mode. Distinguishing the top face sheet core debonding or the bottom face sheet core debonding, however, requires detecting narrow secondary peaks in the output spectra, which imposes more challenging demands on experimental measurements.