First test NDT Measurement by shearography on a wind turbine blade in 1996 by P. Mäckel, L. Yang, G. Kupfer and A. Tiemich at Kassel University. The object is a special wind rotor blade of a single wing wind turbine energy plant.
Applied loading method: Loading by internal pressure (the blade has been sealed). A manual pump has been used to increase a pressure difference against the surrounding. The fringe images show areas at different locations. The fringes are proportional to the out of plane deformation gradients of the surface, which allows to identify inhomogeneous stiffness of the structure: left — Delamination; right — Axial crack; center ‑Structural change over (different number of glasfiber layers).