  We prove existence and uniqueness for solutions to equilibrium problems for
free-standing, traction-free, non homogeneous crystals in the presence of
plastic slips. Moreover we prove that this class of problems is closed under
G-convergence of the operators. In particular the homogenization procedure,
valid for elliptic systems in linear elasticity, depicts the macroscopic
features of a composite material in the presence of plastic deformation.
