XCT inspection in bonded aircraft repairs for composites

Abstract

As bonded composite repairs are gaining importance for modern civil aircraft, it is necessary to investigate such repairs in detail under relevant environmental conditions. In this work, X-ray computed tomography (XCT) was performed on bonded repairs for carbon fiber (CF) reinforced epoxy matrix composites before and after cyclic conditioning between dry/cold and hot/wet conditions. In detail, high resolution XCT scans in absorption contrast (AC) mode as well as Talbot-Lau grating interferometer (TLGI)-XCT scans to obtain additional differential phase contrast (DPC) and dark-field contrast (DFC) modalities were performed. The repair bonds' constituents could be identified by the high resolution XCT scans. Additional information about fiber alignment, at least of the fiber bundles, could be extracted from the TLGI-XCT scans. In order to gain detailed information on certain specimen features, specimen dimensions were reduced for additional high resolution XCT scans.