The effective stiffness of a nanoporous rod

A study was conducted to analyze the influence of surface effects on the elastic characteristics of nanoporous materials. Two models were considered, such as one based on taking into account the surface stresses and the other using the approach of the theory of composite materials. This approach involved taking into account the surface effects due to the surface layer of finite thickness with elastic moduli differing from those of the basic material. The increase or decrease in the rod stiffness depended the relation between the elastic moduli of the surface layer and the matrix. The effective stiffness decreased and increased with decreasing pore radius. A complex model combining both the presence of surface stresses and the surface layer with the properties that differ from those of the matrix was proposed on the basis of these two approaches.