A composite material consists of a rubber filled with gas-filled microspheres. In underwater applications it is compressed hydrostatically by a pressure that may be not insignificant compared with the shear modulus of the rubber, so large strains are produced around each spherical inclusion. When these spherical inclusions scatter an incident acoustic wave, the strained region around an inclusion has had its elastic properties altered by the large static strain. Thales Underwater Systems asked the Study Group to address the question of how this strained region affects the elastic scattering, bearing in mind that the dynamic shear modulus differs from its static value.

Problem presented by
Peter Brazier-Smith, Thales Underwater Systems

Study Group contributors
David Abrahams (University of Manchester)
David Allwright (Smith Institute)
Chris Bell (University of Oxford)
Tamas Bodai (University of Aberdeen)
Philip Bond (University of Oxford)
Andrew Hazel (University of Manchester)
Gareth Jones (University of Oxford)
Roman Novokshanov (University of Oxford)
David Parker (University of Edinburgh)
William Parnell (University of Manchester)
Emmanuel Perrey-Debain (University of Manchester)
Ben Veitch (University of Manchester)