Delamination is one of the most common defects in FRP and occurs due to low interlaminar strength. Such defects are difficult to detect and lead often to catastrophic failure of the composite. In this work a new approach of a multi-functional FML for structural applications is investigated. The interlaminar fracture toughness is determined and the capacitance change between the metal plies during crack propagation is measured in-situ. The metal sheet component undergoes a chemical pre-treatment by nanoscale sculpturing before manufacturing by resin transfer moulding, to prevent adhesive failure of the interfacial metal/matrix bond. The experimental test results show high potential for detecting defects in FMLs. Delamination, which occurs between the glass fibre/matrix interface, can be electrically detected using the capacitance measurement. The fracture surface of the pre-treated metal sheet demonstrates that the adhesive bond between the cubical hook-like surface structure of the aluminium and the matrix remains intact.