Modal characterisation on recyclable foam sandwich panels: a preliminary study

The reduction of the mass of a structure is an important issue in the engineering field since it leads to reduced emissions and operating costs. On the other hand, weight saving often leads to an increase of vibration/noise transmission. For this reason, in the last years the dynamic design of lightweight structures has received more emphasis, particularly in engineering transport applications, where dynamic loads can produce high amplitudes of vibration. At the same time, the research has been also focussed on the use of “green materials” with the intention to satisfy both weight and sound insulation/vibration suppression requirements using environmentally friendly materials. This paper presents the results of an experimental campaign performed on sandwich panels manufactured by using recyclable foam core and face sheets made from natural and plastic fibres combined with recyclable resin. In order to evaluate the vibrational characteristics, the mode shapes, natural frequencies and damping ratio of the sandwich panels were identified experimentally. The tests were performed by adopting the so-called roving hammer technique. Experimental results were compared with numerical ones, obtained by means of a finite element model. The structural loss factor of these panels was measured using the reverberation time method.