Speckle-based directional dark-field tomography on carbon fibre composites

Speckle-based imaging (SBI) uses a wavefront marker to create a randomly patterned illumination. Refraction and small-angle scattering by a sample then results in a shift or blur of this pattern. In this experiment, we will use SBI to retrieve 3D dark-field information for evaluating microstructural damage to carbon-fiber-reinforced polymer samples. We have expanded our SBI image retrieval software to model dark-field as anisotropic blurring, allowing us to retrieve directional dark-field projections from SBI data. We will then extract directional, volumetric scattering data, similar to X-ray tensor tomography. This signal is especially useful for materials with a strongly directional microstructure. The experiment will demonstrate the feasibility of retrieving directional 3D dark-field data with SBI, and showcase the method’s experimental advantages for directional dark-field measurements.