Buckling of hybrid laminated composite sandwich panels with transversely flexible cores

The structural performance of sandwich panels made with hybrid laminated faces and a transversely flexible core can be optimised by varying the mechanical and geometrical parameters characterising both the faces and the core, taking into account also the whole cost. In particular the hybridisation technique applied to the faces seems to be a very attractive solution, giving an improvement from both a mechanical and economical point of view. However, because of the out of plane flexibility of the core and the great slenderness of these structures, instability problems assume a relevant role from a static point of view, becoming a complex phenomenon as well. In this paper a modified first order shear deformation theory has been used, which treats the displacement field of the sandwich panels as a combination of different buckling modes. Buckling loads are finally obtained as a solution of an eigenvalue problem by means of an energetic algorithm solved by the Rayleigh-Ritz method. The influence of mechanical and geometrical parameters, characterising the composite laminated faces and the core, on buckling phenomena were investigated for different in plane load conditions. A numerical FEM approach was also employed; comparisons between FEM and analytical results, in which some key parameters were varied, show the effectiveness of the analytical model. (C) 2003 IoM Communications Ltd.