  Unlike nonlocal models, there is no need to introduce an internal length in
the constitutive law for lattice model at the mesoscopic scale. Actually, the
internal length is not explicitly introduced but rather governed by the
mesostructure characteristics themselves. The influence of the mesostructure on
the width of the fracture process zone which is assumed to be correlated to the
characteristic length of the homogenized quasi-brittle material is studied. The
influence of the ligament size (a structural parameter) is also investigated.
This analysis provides recommendations/warnings when extracting an internal
length required for nonlocal damage models from the material mesostructure
