Experimental and numerical evaluation of the mechanical behaviour of GFRP sandwich panels

This work deals with the analysis of the mechanical behaviour of a class of sandwich structures widely employed in marine constructions, constituted by fiber-glass laminate skins over PVC foam or polyester mat cores. In detail, a systematic experimental study and numerical simulations have shown that the theoretical prediction of the strength and the actual failure mechanism of these sandwich structures can be affected by significant errors, specially in the presence of prevalent shear loading. Moreover, because of the low shear stiffness and the elastic constants mismatch of the skins and core material, failure modes and strength are strongly influenced by eventual stresses orthogonal to the middle plane of the sandwich. In particular, for the sandwich structures with a PVC foam core, such a stress interaction leads to early skin–core delamination failure, whereas for those with a polyester core it leads to core shear-cohesive failure. By means of accurate non-linear simulations, accurate failure criteria, that can be used at the design stage in the presence of complex loading, have also been developed.