Stress states investigation of adhesive bonded joint between spar cap and shear webs of a large wind turbine rotor blade

Abstract

The debonding failure at the adhesive bonded joints between spar caps and shear webs is one of failure modes of the wind turbine rotor blades. To avoid such a failure, the numerical investigation of stress states at the adhesive bonded joints is important to assess the structural integrity of a rotor blade subjected to the extreme bending moments. In this paper, the simplified stress state calculation method was derived based on the multiaxial stress states of shear webs computed from the linear elastic composite analysis from ANSYS 19.2. From the close investigation of a small blade and a large blade, it turned out that the care must be taken evaluating stresses of a large blade with double shear webs than a small one with a single web. In case of a large blade, the adhesive structure between spar cap and a shear web close to an aft shear web (ASW) showed higher stresses compared to the adhesive part located to a forward shear web (FSW). Especially, the out-of-plane stresses of the adhesive at ASW were increased toward the outboard region of a blade, while the stress level of the adhesive at FSW was almost constant along the blade length, which is similar to a single shear web case of a small blade (< 25 m). It indicates the higher peeling failure possibility at the interface between the adhesive and an ASW when blade size is increased.