An indicator device for detecting a delamination of a composite material, including detecting a delamination of a composite material of a wind turbine or a wind turbine rotor blade is provided. The indicator device includes: A first part, a second part and an electric circuit. Therein, the first part comprises at least a part of a lower part of the electric circuit. The second part comprises at least a part of an upper part of the electric circuit. And the lower part and the upper part are electrically connected to each other at a predetermined breaking point forming the electric circuit in such a manner, that when the indicator device is in use in a composite material, if a delamination of the respective composite material occurs, the electric connection between the lower part and the upper part breaks at the predetermined breaking point, thus cutting the electric circuit.