Mixed LW/ESL models for the analysis of sandwich plates with composite faces

In this paper, a new set of models in the framework of Carrera’s Unified Formulation (CUF) is presented for the static analysis of sandwich plates. Concerning the study of multilayered structures, it is important to fulfill the interlaminar continuity conditions for the transverse stresses. For this aim, the CUF has been conceived by allowing to handle in a unified manner many theories that can differ by the order of expansion and the variables description in the thickness direction. This last can be Equivalent-Single-Layer (ESL), if the variables are assumed for the whole laminate, or Layer-Wise (LW), if the variables are described independently for each layer. The models considered in this work are derived from the Reissner Mixed Variational Theorem (RMVT) in order to model a priori the transverse shear and normal stresses. If sandwich plates with composite faces are considered, the transverse stresses are described as LW while the displacements are assumed ESL in the faces and LW at sandwich level (faces + core). This procedure permits to save degrees of freedom, preserving the same accuracy of a full layer-wise description. The new formulation is implemented in the framework of finite element analysis. Comparisons are made with 3D results.