Preliminary tests were conducted using frequency response (FR) characteristics to determine damage initiation and
growth in a honeycomb sandwich graphite/epoxy curved panel. This investigation was part of a more general study
investigating the damage tolerance characteristics of several such panels subjected to quasi-static internal pressurization
combined with hoop and axial loading. The panels were tested at the Full-Scale Aircraft Structural Test Evaluation and
Research (FASTER) facility located at the Federal Aviation Administration William J. Hughes Technical Center in
Atlantic City, NJ. The overall program objective was to investigate the damage tolerance characteristics of full-scale
composite curved aircraft fuselage panels and the evolution of damage under quasi-static loading up to failure. This
paper focuses on one aspect of this comprehensive investigation: the effect of state-of-damage on the characteristics of
the frequency response of the subject material. The results presented herein show that recording the frequency response
could be used for real-time monitoring of damage growth and in determining damage severity in full-scale composites
fuselage aircraft structures.
KEYWORDS: Sensors, Composites, Acoustic emission, Photogrammetry, Signal generators, Nondestructive evaluation, Inspection, Picture Archiving and Communication System, Data acquisition boards, Research facilities
Acoustic emission (AE) was monitored in notched full-scale honeycomb sandwich composite curved fuselage panels
during loading. The purpose of the study was to evaluate the AE technique as a tool for detecting notch tip damage
initiation and evaluating damage severity in such structures. This evaluation was a part of a more general study on the
damage tolerance of six honeycomb sandwich composite curved panels, each containing a different damage scenario.
The overall program objective was to investigate the effects of holes and notches on residual strength. The investigation
was conducted using the Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility located at the
Federal Aviation Administration William J. Hughes Technical Center, Atlantic City International Airport, NJ. This
paper reports on the AE results recorded during the loading to failure of two selected panels. The results show that
damage initiation at the tips of the notches, and its progression along the panel, could be detected and located. These AE
results were correlated with the deformation and strain fields measured through strain photogrammetry, throughout
loading, at the vicinity of these notches. This correlation aided in interpreting the AE results. While the fretting among
the newly created fracture surfaces generated a large number of
low-intensity AE signals, the high-intensity signals
generated at high load levels provided a good measure for anticipating incipient fracture. Further, the AE results located
internal disbonding caused during panel fabrication. The large number of low-intensity AE signals generated from the
disbonded regions was associated with the fretting among the disbonded surfaces.
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