The present disclosure relates to a method for detecting a fibre misalignment in an elongated structure, such as a wind turbine blade component. The elongated structure has a length along a longitudinal direction and comprises a plurality of stacked reinforcing fibre layers. The plurality of fibre layers comprises fibres having an orientation aligned, unidirectionally, substantially in the longitudinal direction. The method comprises scanning the elongated structure along at least a part of the length by emitting an x-ray beam in an angle compared to the orientation of the fibres. The method comprises detecting scattered rays, and determining an intensity of the detected scattered rays. The method comprises estimating a size of the fibre misalignment based on the determined intensity.