Experimental validation of a novel hybrid plywood/steel load frame design for sub-component testing of wind turbine blades

Wind turbine rotor blade full-scale tests typically utilize plywood load frames to introduce forces normal to the length of the blade. Plywood frames are low cost and easily milled to the unique profile of a rotor blade. A sub-component
test supplements full-scale tests by focusing on a region exposed to specific loading scenarios. However, these tests require an alternative load introduction frame, capable of introducing both axial forces and bending moments. There-
fore, novel plywood/steel load frames were designed and glued to the fiber reinforced polymer structure of the blade. The axial loads are thus transferred via a shear-loaded adhesive layer. The paper describes the integrity analysis using the design resistance from a representative experiment and taking into account thermal residual stress. The design model was finally validated in a non-destructive blade sub-component experiment using an acoustic emission system.