The effect of buffer-layer on the steady-state energy release rate of a tunneling crack in a wind turbine blade joint

The effect of a buffer-layer on the steady-state energy release rate of a tunneling crack in the adhesive layer of a wind turbine blade joint, loaded in tension, is investigated using a parametric 2D tri-material finite element model. The idea of embedding a buffer-layer in-between the adhesive and the basis glass fiber laminate to improve the existing joint design is novel, but the implications hereof need to be addressed.The results show that it is advantageous to embed a buffer-layer near the adhesive with controllable thickness-and stiffness properties in order to improve the joint design against propagation of tunneling cracks.

However, for wind turbine blade relevant material combinations it is found more effective to reduce the thickness of the adhesive layer since the stiffness mismatch between the existing laminate and the adhesive is already high. The effect of material orthotropy was found to be relatively small for the blade relevant materials.