Tank measurements of elastic scattering by a resin-filled fiberglass spherical shell

Abstract

Acoustic elastic scattering measurements were conducted in a tank on a 6cm radius fibreglass spherical shell filled with a low-shear-speed epoxy resin. Preliminary measurements were conducted also on the void shell before filling and on a solid sphere of the same material of the filler, in order to estimate the constituent material parameters via acoustic inversion. The objects were measured in the backscatter direction, suspended at mid water, and insonified by a broadband directional transducer. From the inspection of the response of the solid-filled shell it was possible to detect and characterize inhomogeneities of the interior (air inter-layers), the presence of which were later confirmed by CT scan and ultrasound measurements. Elastic wave analysis and analytical modeling tools supported the physical interpretation of the measured responses.