An Homogenization Procedure for Cardboard and Stitched Sandwiches using Respectively Analytical and Numerical Simulation

The interest of the use of sandwich structures is not any more to show. Their performances go from pairs with their complexities. The structural analysis using this type of materials becomes very quickly expensive (mesh, CPU). The idea used through this study consists: working out a procedure of homogenization to obtain an equivalent homogeneous material and then reproduce the mechanical behaviours of these structures by simulation. Two types of sandwich structures were studied: corrugated cardboard and a stitched sandwich with PU core and whose skins are out of woven glass. The method of homogenization of these structures differs according to studied material. For corrugated cardboard, the procedure consists to discretize the unit cell and apply to it the theory of the stratification and to go up to the global rigidities [1]. For stitched sandwich, the analytical model consists in determining the global rigidity starting from the basic rigidities of the components [2]. In each configuration, two new elements were developed the DMTS and the SFR [3]. The 3-node multilayered shell element DMTS has 6 dof per node. It’s obtained by combining the membrane element CST and a bending/shear plate element DDMT (Displacement Discrete Mindlin Triangle). The new 8-node solid element SFR, is based on kinematical concept based on the rotation of a space fibre. This concept allows to improve the accuracy of the displacement field ·U× and to get a higher element with comparison to the 20-node quadratic hexahedral element. Results of the two finite element approaches are compared with experiments related to the corrugated cardboard structures and the stitched sandwiches