A simple microstructure model is used to describe a fluid-tilled open-cell
foam. In the simplest case it consists of parallel elastic plates with gaps
between them, which are filled with a Newtonian fluid. We assume that the
load applied to this model material is uniaxial. The constitutive equation
is formulated with the pressure of the fluid as an inner variable. The mode
l yields an evolutional equation for the fluid pressure which itself is a h
eld equation, that is a partial differential equation in time and space coo
rdinates. This differential equation is solved for an instantaneously appli
ed constant load and for a harmonically oscillating load. The solution of t
he differential equation, in combination with the constitutive equation lea
ds to a relation between mean applied load and global strain of the test sp
ecimen. Finally, we obtain the creep compliance and the complex modulus of
the foam material, respectively. The influence of different geometries of t
he foam and of different material behaviour of the matrix and fluid on the
creep compliance and the complex modulus is discussed.