Provided is a method of forming a thru-hole through a composite structure having a plurality of internal compartments. An insert ring is connected to the composite structure to create a protective layer around the periphery of a penetration formed within the composite structure. An adhesive is disposed between the composite structure and the insert ring to create a fluid-tight seal between the insert ring and the internal compartments. In this regard, the fluid-tight seal mitigates fluid flow between the internal compartments.