Discretely tailored multi-zone bondline for fail-safe structural repair

A repair patch for reworking an inconsistent area of a composite structure, comprising:

• a patch body adapted to cover the inconsistent area and having a first patch region, a first separation zone outside the first patch region, a second patch region outside the first separation zone, a second separation zone outside the second patch region, a third patch region outside the second separation zone and a third separation zone outside the third patch region, with the first patch region, the first separation zone, the second patch region, the second separation zone, the third patch region and the third separation zone having increasing interlaminar fracture toughness from a center to an edge of the patch body, and the first separation zone, the second patch region, the second separation zone, the third patch region, and the third separation zone all being substantially concentric rings surrounding the first patch region, the first patch region being centrally located relative to all of the first separation zone, the second patch region, the second separation zone, the third patch region, and the third separation zone;
• and
• a layer of adhesive for bonding the patch body to the composite structure.