A previous model [Phys. Fluids31, 658 (1988)] has been generalized and modified to describe ion beam interaction with planar foils in which the energy absorption region is composed of two materials. The model provides a unified description of foils with thicknesses larger and smaller than the ion range (super‐range and subrange foils). The hydrodynamic efficiency of the unheated part of the foil, the payload, is studied for different foil structures and a set of parameters that determine the dynamics of the interaction is found.