FORCED RESPONSE OF A SANDWICH PLATE WITH A FLEXIBLE CORE DESCRIBED BYA BLOT-MODEL

There is a great interest in computational models describing the behav iour of coupled acoustic-structural systems. A finite element programm e for acoustics has been developed incorporating a variety of elements including porous material elements described by the Blot-theory and p late elements described by thick plate theory (Reissner-Mindlin). This paper makes up a part of an experimental verification of models incor porating these plate and porous material elements, models which may be used for the prediction of airborne and impact sound transmission in multilayer systems, of which sandwich constructions are an important t ype. Forced response measurements have been performed on sandwich beam s, a 50mm thick polyurethane foam core sandwiched between two aluminiu m plates, 2-3 mm thick. The measured input and transfer mobility data as well as plate vibrational shape have been compared with both 2- and 3-dimensional models of the beam. Due to the complexity of the model description, in particular the porous material, a rather simple SD-mod el was used. However, the fit between measured and calculated data was quite satisfactory indicating that a 3-dimensional model is necessary for better precision particularly in frequency ranges where dilatatio nal motion, or antiphase motion of the skins, is important.