  The propagation of an adhesive crack through an anisotropic heterogeneous
interface is considered. Tuning the local toughness distribution function and
spatial correlation is numerically shown to induce a transition between weak to
strong pinning conditions. While the macroscopic effective toughness is given
by the mean local toughness in case of weak pinning, a systematic toughness
enhancement is observed for strong pinning (the critical point of the depinning
transition). A self-consistent approximation is shown to account very
accurately for this evolution, without any free parameter.
