Predict Flexural Rigidity of Sandwich Structures Using Mechanical Properties of the Constituents

There has been a great deal of interest in the development of sandwich structures as viable engineering constructions. Sandwich constructions offer many advantages over traditional stiffened shapes including light weight, high strength to weight ratio, high flexural rigidity, high stability, high thermal and acoustical insulation, and relatively ease of manufacture. Recently, an advanced technique was developed to fabricate sandwich structures for high temperature applications at the Center for Advanced Coating Technologies (CACT), Toronto, Canada. In this technique, sandwich sheets are made by depositing alloy 625 skins on Ni foam core using Air Plasma Spraying (APS). Generally, analysis of mechanical behavior is difficult in sandwich constructions because of the complex nonlinear and inelastic behavior of the constituent materials. This study tries to utilize an analytical model to estimate the mechanical performance of sandwich structure based on the mechanical properties of the constituents. To this end, the mechanical properties of the core and skin materials were examined separately. First, the stress-strain curve for the as-received and heat treated foam structure was determined using uniaxial compression testing. Secondly, the stress-strain curve for the as-sprayed and heat treated alloy 625 coating was determined using tensile testing. Finally, the flexural rigidity of the as-fabricated and heat treated sandwich samples were calculated using the elastic moduli of the alloy 625 coating and Ni alloy foam. The model was also used to calculate the flexural rigidity of sandwich samples with different skin thicknesses to check the accuracy of the model and to understand the effect of skin thickness on the predicted mechanical performance of sandwich structures.