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

Sandwich shells are layered constructions where a thick lightweight co re is positioned between comparatively thin, dense face sheets to give optimized structural configurations which impart higher specific stif fnesses to a structure. The multilayered shell is 'kinematically inhom ogeneous' 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 sh ould account for displacement gradients that vary significantly betwee n layers and are discontinuous at layer interfaces. The formulation sh ould represent individual layer material characteristics and account f or the transverse warping of a cross-section due to the shear deformat ion and fibre compressibility of each layer resulting from transverse normal stresses. The multi-director displacement field approach of Pin sky and Kim is used with soft-core sandwich structure analysis. Here t he concept of a multi-director field defined over a reference surface is employed to describe the geometry of the multi-layered sandwich she ll. The linear theory assumes three-dimensional constitutive relations , and the finite element method is used to evaluate the stresses and d isplacements in the layers. Results are compared with a higher order s hear deformation theory, and the analytical results and efficiency of a multi-director formulation in reproducing sandwich behaviour are dem onstrated.