Improved design of large wind turbine blades of fibre composites (Phase 2) - Summary Report

The major results of Phase 2 of a project concerning the development of new design methods for wind turbine blades are summarised. Finite element models were used for studying the buckling behaviour of a box girder, tested to failure in Phase 1 of this project. The deformation behaviour of a box girder section subjected to transverse forces was investigated experimentally and by modelling.

Buckling-driven delamination of planar specimens was studied on experimentally and by modelling. A novel approach was proposed for the determination of mixed mode cohesive laws for large-scale crack bridging problems. The normal and shear stresses of the cohesive laws were obtained from data of the fracture resistance and the normal and tangential displacements of the cohesive zone.

Delamination of a thin layer bonded to an elastic substrate close to corners and edges was also analysed. Results for the shape of the interface crack front and critical stress for steadystate delamination were obtained.