This study is dedicated to develop a mixed interpolated formulation for nonlinear analysis of plates and shells. Using Equivalent Single Layer (ESL) theory and the rule of the mixture scheme, the authors present a formulation for analyzing Functionally Graded (FG) sandwich structures. To incorporate large displacements and rotations, and alleviate the shear and membrane locking phenomena, a mixed interpolation of strain fields, including in-plane and shear strains, is utilized. Analyses are based on an isoparamertic 6-node triangular shell element. There are five degrees of freedom, including three displacements and two rotations at each node of this element. In order to validate the proposed formulation, some well-known benchmark problems are solved. Besides, the obtained responses are compared to the other available solutions, separately. Moreover, two other practical structures, including FG-sandwich plate and curved shallow panel, are considered to indicate the accuracy and high performance of the authors’ approach.

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