Effect of Core Material Stiffness on Sandwich Panel Behavior Beyond the Yield Limit

Sandwich panels attracted designer's interest due to its light weight, excellent corrosion characteristics and rapid installation capabilities. Sandwich panels have been implemented in many industrial applications such as aerospace, marine, architectural and transportation industry. Sandwich panels consist of two face sheets and core. The core is usually made of material softer than the face sheets. Most of the previous work deals with sandwich panel in the elastic range. However the current investigation unveils the effect of the core material stiffness on sandwich panel beyond the yield limit of core material. The modulus of elasticity ratio of the core (Foam) to face (sheet metal) is investigated by applying univariate search optimization technique. The load has been increased in steps in quasi static manner till face sheets reach the yield point. The panel is modeled using a finite element analysis package. Simply supported boundary conditions are applied on all sides of the panel. The model has been validated against numerical and experimental cases that are available in the literature. In addition, experimental investigation has been carried out to validate the finite element model and to verify some selected cases. The finite element model shows very good agreement with the previous work and the experimental investigation. It is proved in this study that the load carrying capacity of the panel increases as the core material goes beyond the yield point. Load transmitted to the face sheets gets higher as the core stiffness gets softer. The stiffer the core material is, the closer the sandwich panel behavior gets to isotopic plate, i.e., face sheets are going to yield before core material.