The fiber-matrix interphase in composites is defined as the
intersection region between fibers and the matrix material. It shows
altered matrix material properties. In dependency of the matrix material
or the fiber coating, this phase is created by interdiffusion processes
at the macromolecular scale driven by thermodynamic forces. Especially
for FE simulations of composites and the validation of multi-scale
material modeling approaches, the information about the existing
interphase becomes important.