A Local/global Sandwich Homogenization Procedure for Finite Element Simulation

219-235, ASME winter meeting, Anaheim, CA, Nov. 1998. ABSTRACT A new finite element approach to sandwich shells is proposed. It uses existing shell finite elements formulated for homogeneous shells. The “sandwich” nature of the problem is hidden from the main finite element program. Based on several assumptions the proposed homogenization procedure calculates stress increments in a homogeneous fictitious material, called “equivalent”, which correspond to the strain increments in the equivalent material points. The stresses in the equivalent material are calculated based on the stress and strain fields in the sandwich layers, which are determined from the incoming strain field for the equivalent material. This procedure is most suitable for including strain softening and other material nonlinear behavior. The approach can be combined with shell elements formulated for homogeneous materials, based on Reissner-Mindlin shell theory or with elements based on a higher order shell theory. It avoids the necessity of formulating special shell elements for sandwich constructions, which in most cases, due to their large number of degrees of freedom, significantly decrease the computational efficiency of the finite element analysis. The sandwich homogenization procedure is combined with a composite micromechanics-based model for woven composites to analyze sandwich shells with woven fabric faces.