APPLICATION OF A MULTI-DIRECTOR DISPLACEMENT FIELD APPROACH FOR SANDWICH SHELL STRUCTURE-ANALYSIS

Sandwich shells are layered constructions where a thick lightweight core is positioned between comparatively thin, dense face sheets to give optimized structural configurations which impart higher specific stiffnesses to a structure. The multilayered shell is 'kinematically inhomogeneous' through the thickness. Hence, reliable estimates of all the stresses within layers, including the effects of transverse normal and transverse shear stresses, are difficult to obtain through the usual higher order theories. As an improvement, the kinematic formulation should account for displacement gradients that vary significantly between layers and are discontinuous at layer interfaces. The formulation should represent individual layer material characteristics and account for the transverse warping of a cross-section due to the shear deformation and fibre compressibility of each layer resulting from transverse normal stresses. The multi-director displacement field approach of Pinsky and Kim is used with soft-core sandwich structure analysis. Here the concept of a multi-director field defined over a reference surface is employed to describe the geometry of the multi-layered sandwich shell. The linear theory assumes three-dimensional constitutive relations, and the finite element method is used to evaluate the stresses and displacements in the layers. Results are compared with a higher order shear deformation theory, and the analytical results and efficiency of a multi-director formulation in reproducing sandwich behaviour are demonstrated.