The explicit dependence of material properties on the basic space-time parametrization
of continuum mechanics is a most interesting departure from standard behavior. The
best framework to formally place these effects in evidence is the so-called
material mechanics of materials advocated by the late G.Herrmann. Among the
manifestations of these dependencies, material inhomogeneity is the most obvious
and frequent one, but others such as volumetric growth or ageing also occur
naturally, not to speak of artificial situations where one tries to build dynamic
materials whose parts purposefully react differently in space and time at the will
of the designer. These different cases are briefly sketched out first on the
basis of a Lagrangian formulation and then in the general framework of
thermomechanics.
