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Sandwich structures with thick soft cores subjected to transverse loads are usually resulting in deformations with various modes, including bending, twisting and compressing. In addition, the compression of the core results in a significant influence of the structural response. All classical plate theories are inadequate in predicting the behavior sandwich structures with thick soft core due to the assumption of no thickness change during deformation. To overcome this issue, a hybrid first/third-order shear deformation hypothesis with consideration of compressive effect is proposed for sandwich structures with thick soft cores. The first-order shear deformation theory is applied to both the top and bottom layers, while a refined third-order shear deformation theory that releases the assumption of no thickness change is developed for the thick soft cores. An eight-node quadrilateral plate element with twelve degrees of freedom including compressible displacements is created for finite element modeling. Based on the proposed refined hybrid first/third-order theory, a finite element model is developed using the Hamilton's principle. The numerical model is first validated by the computational results of sandwich structures using commercial software. Then, the influences of various parameters on static displacements, vibrations and compressive deformations are systematically investigated, including e.g. boundary conditions, thickness of the core and face layers, elastic modulus of the core layer and the plate size. The present finite element modeling approach provides a powerful tool to accurately investigate the mechanical response of sandwich structures. [ABSTRACT FROM AUTHOR]

A finite element formulation using zig-zag hypothesis is developed for sandwich smart structures with partially smart constrained layer damping (SCLD) treatment. In order to achieve higher accuracy, both of the viscoelastic and elastic layers of the sandwich structures are based on the Reissner–Mindlin theory. An eight-node quadrilateral element with seven mechanical degrees of freedom (DOFs) is considered for the finite element (FE) analysis. Using Hamilton's principle, a piezoelectric coupled dynamic FE model is obtained. This FE model is validated by frequency and loss factor analysis of an elastic–viscoelastic–elastic plate. Furthermore, the effects of various parameters on the damping characteristics of the cantilever sandwich smart structures are carried out, e.g. coverage percentage and position of SCLD, thickness of the viscoelastic or piezoelectric layer, curvature of structures, and shear modulus and loss factor of the viscoelastic layer. [ABSTRACT FROM AUTHOR]