Improving aircraft composite inspections using optimized reference standards Page: 4 of 13
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very large and unmanageable. Inspection
characterizations and equipment responses have been
used to determine the important variables needed in a
composite reference standard thus eliminating
unnecessary standard configurations.
The advantages of industry-wide accepted
composite standards include: 1) providing a consistent
approach to composite inspection thus helping to
minimize false calls, 2) reducing standard procurement
costs, and 3) aiding the assessment of composite
inspection technologies. Through the active participation
of the OEM's, this project represents a harmonized
approach by aircraft manufacturers.
The goal of this project is to develop standards
that will allow for repeatable, accurate inspections.
Many composite inspections are performed by visual
inspections and tap tests. Composite inspection
requirements are increasing and may soon surpass the
capabilities of the tap test. This effort will aid the
composite inspection process through the use of
engineered reference standards and the utilization of
more sensitive NDT equipment. The following
discussion describes the activities completed thus far to
develop composite laminate and composite honeycomb
SIN TO CORE DISBONDS
TASK 1: COMPOSITE HONEYCOMB TASK
Determining Key Factors Affecting Inspection
DEVELOPING APPROPRIATE RANGE OF
HONEYCOMB SPECIMENS - A set of 64 honeycomb
specimens were fabricated to isolate the effects of the
following variables (construction materials and flaw type)
and bounding conditions on NDT: 1) laminate material
(carbon; fiberglass), 2) honeycomb core material
(Nomex; fiberglass), 3) laminate thickness (3 plies; 12
plies), 4) honeycomb core thickness (0.25"; 2"), 5)
honeycomb cell size (0.125"; 0.25"), 6) honeycomb core
density (2-8 lb/ft3), and 7) disbond and delamination
flaws. The bounding conditions on each parameter,
shown in parenthesis, represent the extreme values
found in aircraft construction. The goal of this approach
is to allow the results from this program to be applied to
aircraft from all manufacturers. Figure 1 shows the
design of the composite honeycomb panels used in this
parametric study. Sixteen panels contained four
different construction types (four quadrants) and isolated
the effects of each of the variables listed above (2
extremes, 6 variables creates 28 = 64 different
specimens). NDI was applied to the specimens in order
to assess the difficulties presented by the engineered
MACHINED CORE DISBONDS
3,6 9 AND 12PLY CARBON
Figure 1: Design Drawing of Composite Honeycomb Panel Containing
Four Different Construction Types and Engineered Flaws
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Roach, D.; Dorrell, L.; Kollgaard, J. & Dreher, T. Improving aircraft composite inspections using optimized reference standards, article, October 1, 1998; United States. (https://digital.library.unt.edu/ark:/67531/metadc711418/m1/4/: accessed April 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.