Hybrid materials and conical bolts for high-strength bolted joints

Since rotor blades are growing in size, the loads on bolted connections at the blade root or for segmented blades are increasing. Therefore, we have developed high strength bolted connections using 2 technologies. Hybrid materials made of fibre-reinforced plastics combined with steel (fibre-metal-laminate, FML) can substitute conventional laminates at the joint bearings to enhance the strength. Radially and axially pretensioned connections (RAX) use conical bolts and bushings to clamp the laminat at the joint and thereby boost the strength. First results show, that FML and RAX can at least double the joint strength, compared to conventional T-bolts or insert joints.