Stresses in mixture theory

The foundations of mixture theory are formulated using a geometrical approach. In order to model diffusion, configurations of mixtures are allowed in which the various constituents may occupy different regions in space in addition to the usual relaxation of the impenetrability axiom. Forces on a mixture are defined as continuous linear functional on the space of virtual displacements of the mixture. This implies the existence of partial stresses without any further assumptions. The notions of the total force and the total stress are critically reviewed and introduced through the definition of a simple body model of a mixture. Some examples of such models are given.