On the USAF ‘risk of failure’ approach and its applicability to composite repairs to metal airframes
File(s)
Accepted version
Author(s)
Hu, W
Barter, S
Wang, J
Jones, R
Kinloch, AJ
Type
Journal Article
Abstract
The USAF report on the risk analysis of aging aircraft fleets notes that the operational life of
individual airframes is seldom equal to the design life of the fleet and that the life of an
aircraft fleet t
ends to be determined more by its inherent operational capability and
maintenance costs rather than by the number of flight hours specified at the design stage. As
such this paper focuses on whether the USAF approach to risk assessment can be used for
airf
rames repaired with a composite patch/doubler. To this end the present paper describes a
test program designed to study the effect of adhesively
-bonded composite repairs to fatigue
cracks that, prior to repair, have grown from small naturally
-occurring mat
erials
discontinuities. This study reveals that crack growth in composite repairs conforms to the
exponential growth equation used in the USAF approach to assessing the risk of failure.
Furthermore, the exponent, ω, in the exponential growth law can be de
termined from the
crack growth history associated with the unrepaired specimens and the simple reduction in
the stress due to the application of the composite patch/doubler, using the ‘cubic rule’ that
was previously used to assess crack growth in the RAAF
F/A
-18 (Hornet) fleet.
individual airframes is seldom equal to the design life of the fleet and that the life of an
aircraft fleet t
ends to be determined more by its inherent operational capability and
maintenance costs rather than by the number of flight hours specified at the design stage. As
such this paper focuses on whether the USAF approach to risk assessment can be used for
airf
rames repaired with a composite patch/doubler. To this end the present paper describes a
test program designed to study the effect of adhesively
-bonded composite repairs to fatigue
cracks that, prior to repair, have grown from small naturally
-occurring mat
erials
discontinuities. This study reveals that crack growth in composite repairs conforms to the
exponential growth equation used in the USAF approach to assessing the risk of failure.
Furthermore, the exponent, ω, in the exponential growth law can be de
termined from the
crack growth history associated with the unrepaired specimens and the simple reduction in
the stress due to the application of the composite patch/doubler, using the ‘cubic rule’ that
was previously used to assess crack growth in the RAAF
F/A
-18 (Hornet) fleet.
Date Issued
2017-02-01
Date Acceptance
2017-01-30
Citation
Composite Structures, 2017, 167, pp.103-111
ISSN
0263-8223
Publisher
Elsevier
Start Page
103
End Page
111
Journal / Book Title
Composite Structures
Volume
167
Copyright Statement
© 2017 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Subjects
Science & Technology
Technology
Materials Science, Composites
Materials Science
Bonded composite repairs
Fatigue
Small crack
USAF risk of failure
Fibre bridging
FATIGUE-CRACK GROWTH
LIFE DETERMINATION
AIRCRAFT
Materials
09 Engineering
Publication Status
Published