Elastic-plastic analysis and strength evaluation of adhesive joints in wind turbine blades

The objective of this paper is to investigate the performance of adhesive joints of carbon/epoxy wind turbine blade subjected to combined bending and tension loadings through finite element method. The influence of adhesive material properties and geometrical details including fillet and imperfections was examined in terms of interlaminar stresses in the adhesive layer. The variation of stress intensity with change in adhesive shear modulus has also been investigated, while contour integral method was used for evaluating the stress intensity factors (SIF) at the imperfection tip. Furthermore, the strength of the joint was assessed through the crack initiation and propagation analysis. Results suggested that either adding a fillet or considering the plasticity led to the reduced peak stresses at the edge of the adhesive layer and redistributed the load to low stress regions. Inclusion of imperfections has resulted in high stress concentrations in the adhesive layer and reduction in the strength of the joint. Compared to the filleted adhesive, the strength of the joint reduced 2.4% and 4.8% considering a flat adhesive and filleted adhesive with through-thickness imperfection, respectively. Large shear modulus of the adhesive diminishes the fracture strength with the increased SIF.