Stiffened graphite/epoxy composite panels with box and T-sections representative of aircraft, naval and automotive structural sub-elements were fabricated in-house. The panels were subjected to baseline nondestructive evaluation (NDE) using ultrasonics and vibration techniques. Acoustical properties of the composite panels were measured using ASTM C522-87. The panels were subjected to room temperature static compression tests in conjunction with in-situ acoustic emission (AE) monitoring. The ultrasonic reflected pulse amplitudes were found to be very sensitive to skin-to-core interface conditions; a profile of amplitude measurements provided exact locations of bond weaknesses. From vibration tests, it was seen that following compression testing, the damping ratio value of the box-section panel exhibited nearly 50 % increase due to the accumulated damage in the panel. Acoustical airflow resistance of the box-section was significantly higher than the T-section stiffened panel; exhibiting better acoustical properties for the box-section composites. From AE parameters, major failure mechanisms due to compression loading, such as shearing of the box section, local microbuckling, fiber fracture and matrix macrocracking were identified.
Compression behavior and nondestructive evaluation of stiffened panels
Druckverhalten und zerstörungsfreie Bewertung von versteiften Paneelen
1995
11 Seiten, 14 Bilder, 2 Tabellen, 9 Quellen
Conference paper
English
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