Subcomponent development for sandwich composite wind turbine blade bonded joints analysis

In the sector of wind energy, the trend to increasing turbine size is ongoing and it will continue to do so. This research focuses explicitly on a particular aspect of structural design which is reported to be very critical in many designs of wind turbine blade wing box structures, namely the connection between the spar web and the spar cap, which are usually built up with sandwich materials. A pyramid structured approach is developed which links local phenomena of stress transfer and failure in the adhesive connection to overall loads on the entire machine. This paper focuses on the subcomponent level of the pyramid scheme and it shows the relevance of investigations and experiments on this level. A specific test structure is designed and manufactured as a C-beam to reproduce load transfer phenomena as they occur in real blades. An experimental test campaign is conducted using different data acquisition principles and sensors to monitor structural behaviour. Results from a finite element model are compared to experimental results and satisfactory results are obtained.