Static and dynamic analysis of soft core sandwich panels with through-thickness deformation

Sandwich plates represent an efficient structural element, providing a high stiffness/weight ratio characteristic. Moreover, when using this structural element, different design configurations and materials in the core can be adopted in order to obtain desired properties. From high dissipation elastomers to light and stiff honeycombs, several core materials may be applied, looking for high damping ratios or simply to obtain an high flexural stiffness/weight ratio.Despite the huge interest on the sandwich structures, its numerical modeling requires special attention in the representation of the skin/core interrelation. This aspect assumes an important role when dealing with soft cores. In fact, regardless the difficulties arising from the high skin/core modulus ratio, which requires a representative displacement field descriptor, the numerical model should take into consideration the permissible deformation along the thickness direction to which the core may be submitted to. Currently, the modeling of such behavior requires the application of layerwise models accomplishing for a complete 3D spatial field description, which lead usually to a high computational cost during the simulation of sandwich panels.In this paper, to trim down the computational cost, it is proposed a simple and cost-effective layerwise model based on a two-dimensional displacement field descriptor. This finite element is formulated using a plate finite element to represent the in-plane and out-plane deformation field of each layer, and a set of bar finite elements to describe the stiffness related to the nodal normal displacement degree-of-freedom. The proposed finite element formulation and numerical implementation are assessed by comparison with results obtained from other modeling methodologies. Furthermore, the finite element model is also validated through the correlation analysis between the numerical results and the experimental data obtained from a dynamic analysis conducted on representative specimens.