Mechanical behavior of a sandwich with corrugated GRP core: numerical modeling and experimental validation

In this work the mechanical behaviour of a core reinforced composite sandwich structure is
studied. The sandwich employs a Glass Reinforced Polymer (GRP) orthotropic material for both the two
external skins and the inner core web. In particular, the core is designed in order to cooperate with the GRP
skins in membrane and flexural properties by means of the addition of a corrugated laminate into the foam
core. An analytical model has been developed to replace a unit cell of this structure with an orthotropic
equivalent thick plate that reproduces the in plane and out of plane behaviour of the original geometry.
Different validation procedures have been implemented to verify the quality of the proposed method. At first a
comparison has been performed between the analytical model and the original unit cell modelled with a Finite
Element mesh. Elementary loading conditions are reproduced and results are compared. Once the reliability of
the analytical model was assessed, this homogenised model was implemented within the formulation of a shell
finite element. The goal of this step is to simplify the FE analysis of complex structures made of corrugated
core sandwiches; in fact, by using the homogenised element, the global response of a real structure can be
investigated only with the discretization of its mid-surface. Advantages are mainly in terms of time to solution
saving and CAD modelling simplification. Last step is then the comparison between this FE model and
experiments made on sandwich beams and panels whose skins and corrugated cores are made of orthotropic
cross-ply GRP laminates. Good agreement between experimental and numerical results confirms the validity of
the proposed model.