Modal characterisation of recyclable foam sandwich panels

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 and noise transmission. For this reason, in the last years, the dynamic design of lightweight structures has received more emphasis, particularly in engineering 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 comfort requirements. This paper presents the results of an experimental campaign performed on two ecologically friendly sandwich panels. All the investigated panels present a recyclable core, while the face sheets are made of natural or plastic fibres combined with recyclable resin. In order to evaluate the vibrational characteristics, the mode shapes, the natural frequencies and the damping ratio of the sandwich panels are identified experimentally through modal tests, adopting the roving hammer technique. The structural loss factor is also measured using the reverberation time method. Experimental results, in terms of modal parameters, are compared with numerical ones, obtained through a finite element model.