The hollow profile of a wind turbine blade is subject to high levels of deformation when under the crushing pressure that is induced by flapwise loading. The load bearing box girder will ovalize under the pressure like forces and the shear sandwich webs and monolithic composite flanges are critical components whose failure may cause overall blade failure. This paper addresses the underlying causes of failure for these two parts by performing individual representative mechanical testing on them, and using digital image correlation (DIC) and acoustic emissions (AE) monitoring. Results show that the strength of the flange is primarily determined by the tensile strength of a relatively thin biaxial layer in this complex design. The buckling tests performed on sandwich material show that DIC is useful in determining the causes of failure, whilst AE monitoring has potential for in-situ monitoring of these structures, and is able to provide important data about the damage inside a blade.

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