Modelling the supermodulus effect in metallic multilayers

Abstract

To change the elastic moduli of a material by several hundred per cent is a noteworthy achievement. In metallic multilayer thin film structures, this phenomenon, 'the supermodulus effect', can be selectively incorporated. To date, this effect has only been observed in man-made structures fabricated with an artificial one-dimensional composition modulation. It has not yet been found in naturally occurring systems. To truly understand the cause of the supermodulus effect will prove useful, in concept, in elaborating the inter-relation between microstructure and physical properties and, in application, in the search for structures as yet unidentified. Some insight into the cause of this effect has been obtained for single unbounded layers using a rather practical 'coherency strain' model. This approach will be expanded upon in this paper to model the effect in the actual multilayer systems measured experimentally. The role of the interface in these materials of nanometric-scaled periodic structures will be seen to play a key role in understanding and modelling the supermodulus effect.