Carbon fiber laminate composites provide good strength to weight ratio for aerospace applications. Manufacturing imperfections and impact during the operation and servicing of the aircraft can lead to barely visible and difficult to detect damage. Impact can lead to delaminations and matrix or fiber cracks, reducing the load carrying capacity of the structure. Both ultrasonic and X-ray techniques have a good track record for the nondestructive testing of composite structures. Immersion ultrasonic C-scans were performed to measure the delamination extent for impact damage in a cross-ply composite specimen. Guided ultrasonic waves propagating along composite plates were employed for defect imaging. The first antisymmetric A0 Lamb wave mode was excited experimentally using piezoelectric transducers and measured using a laser vibrometer. X-ray imaging was used for the detailed visualization of the damages in the composite material. Application examples include carbon fiber composite plates with barely visible impact damage and manufacturing defects. The composite specimens and damage were characterized using ultrasonic measurements. Guided ultrasonic wave and X-ray imaging were used and the respective sensitivity for damage detection in composite panels is discussed.
P. Fromme, P. Fromme,
"Composite structures defect imaging", Proc. SPIE 10600, Health Monitoring of Structural and Biological Systems XII, 106000C (27 March 2018); doi: 10.1117/12.2294522; https://doi.org/10.1117/12.2294522