In-Situ Ultrasonic C-Scanner

Monitoring damage growth in composite materials during axial fatigue tests, without removing the specimen from the loading machine, is normally achieved using techniques such as shadow moire fringe, X-radiography, thermography or residual stiffness measurements. All except the last method provide an indication of the extent of damage. However none of these techniques provide information on the through-the-thickness location of the damage. For detailed inspection, the specimen would normally be removed from the testing machine and C-scanned using an immersion scanning system. This Technical Report describes an in-situ C-scanning apparatus, based on the time-of-flight C- scanning technique developed at DSTO-ARL, for monitoring damage growth whilst the specimen is still located in the testing machine. This system uses a semi- impervious membrane and water couplant which allows the specimen to be scanned without full immersion of the specimen and the probe. Set-up procedures and operational details are also described. Comparisons of in-situ C-scans with immersion tank C-scans and optical macrographs of cross-sectioned specimens were undertaken, in order to validate the new system.... Ultrasonic scanners, Composite materials, C. Scans, Axial loads, Fatigue damage, Crack propagation.