Mode mixity for the fracture toughness obtained by climbing drum peel tests

Wind turbine blades include numerous interfaces, which are known to be critical regions for early failure. Thus, reliable testing of interfaces and a solid understanding of the tests used are of utmost importance. The climbing drum peel (CDP) test is a standardized test for characterization of adhesively bonded interfaces, which in literature has been referred to as a possible simple alternative to mode I double cantilever beam testing of composites. The current work uses finite element modeling of the CDP setup to show that it is actually a mixed mode test, and therefore one cannot use it to obtain the mode I fracture toughness. It can, however, be used to compare different interfaces, keeping in mind that the comparison is done for a mode mixity of approximately 40°, and that one adherend has to be thin (around 0.5mm).