Theoretical and experimental investigation of a double-lap adhesive joint with glass fiber reinforced polymer to plywood interface

Wind turbine rotor blade full-scale tests 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 upgraded load introduction frame capable of introducing axial forces and bending moments. To develop such a frame structure, a generic small-scale load introduction frame was designed and proved as a concept in this work. The specimen was a double-lap shear adhesive joint bonding a glass fiber reinforced polymer composite, representing the blade, to plywood, representing the frame, tested under uni-axial tension. The bond line of the specimen was modeled analytically and numerically. A digital image correlation system recorded the experimental full-field strain. Furthermore, a validation of the models was performed.