Evaluation of X-ray target materials to improve CT-based measurement of fiber orientations inside CF-SMC components

Carbon fiber sheet molding compounds (CF-SMC) are increasingly used in automotive and aerospace industries. The accuracy of fiber orientation measurement depends on the quality of the computed tomography (CT) results. This is significantly influenced by signal and contrast obtained when imaging the low absorption materials. Using standard tungsten X-ray targets as available in most commercially available microfocus CT scanners appears to be a compromise in terms of contrast and flux. The authors compare the X-ray spectra and imaging properties achieved using tungsten, copper, and silver X-ray targets. Projections and volume data sets obtained from scanning a CF-SMC sample component using different X-ray targets are compared and evaluated using common quantities like grey value distribution and signal-to-noise ratio. Finally, the different volumes are analyzed by using a common software module and fiber orientation tensors are compared.