Design and structural responses of a 38-meter sectional wind turbine blade under extreme static loads

The structural reliability of large sectional blades has always been a challenging issue with regard to the mild cost increment incurred compared with corresponding non-segmented blades. The use of excellent connection configurations and optimized composite layouts are cost-efficient approaches to achieve this goal as well as better understanding of the structural responses of sectional blades under extreme loads. This work presents the design and fabrication of a sectional blade, based on a 38-meter typical commercial wind turbine blade, with unique connections and a composite layout. The prototype blade is experimentally studied under extreme static loads according to international standards. The strains of the spar caps, sandwich structures, and shear webs are collected, and the contact status of adjacent segments and bolt loads are also monitored as well. The results revealed that the sectional blade successfully sustained the extremely static loads with only a moderate manufacturing cost increment compared with the corresponding non-segmented blade. The advantages of the proposed strategies are validated for sectional blades. Regarding the structural integrity of the sectional blade, blade buckling, composite failure and residual deflection were not observed. Flap-wise loads are more critical for the bolted joint of segment connections than edge-wise loads, as detrimental bolt load increases tend to occur due to the prying effect at the leading and trailing edges. An improved analysis based on the load factor from multi-bolted joint box-beam models and experiments could predict the bolt loads of segmented connections with desirable accuracy and could be suitable for the multi-bolted joint design of sectional blades.