Condition-based Maintenance Plus
Structural Integrity (CBM+SI)
& the Airframe Digital Twin
March 2011
Pamela A. Kobryn & Eric J. Tuegel
Structural Mechanics Branch
Air Vehicles Directorate
Air Force Research Laboratory
88ABW-2011-1428
Distribution Statement A
Approved for public release: distribution is unlimited.
AFRL’s Condition-based Maintenance Plus
Structural Integrity Initiative (CBM+SI)
88ABW-2011-1428
Distribution Statement A
Approved for public release: distribution is unlimited.
2
CBM+SI Technology Focus Areas
Damage
State Awareness
2. Structural
Health
Monitoring
Usage
3. Structural
Teardown
Assessment
4. Loads &
Environment
Characterization
1.E+00
6. Prognostics
&
Risk Analysis
9. Replacement
Concepts
1.E-01
1.E-02
Single Flight Probability of Failure
1. Non-Destructive
Inspection/
Evaluation
1.E-03
1.E-04
1.E-05
1.E-06
1.E-07
1.E-08
1.E-09
1.E-10
1.E-11
1.E-12
1.E-13
1.E-14
0
Legend:
88ABW-2011-1428
Emphasis Area
4000
6000
Flight Hours
7. Life
Enhancement
Concepts
Structural
Modifications
2000
8. Repair
Concepts
8000
10000
12000
5. Characterization,
Modeling
& Testing
Structural
Analysis
Technology Focus Area
Distribution Statement A
Approved for public release: distribution is unlimited.
3
CBM+SI Mid-term Vision
per AFRL Air Vehicles Directorate’s “Vision 2009”
• In ten years, aircraft lifecycle management and maintenance
practices will be completely transformed from an inefficient,
inconsistent, disparate, and labor-intensive state to an
efficient, standardized, integrated, and semi-autonomous state.
• The structural capability of individual airframes will be known
and predictable based on the capability to characterize the
current health status, predict the future health status, and
plan usage and maintenance accordingly.
• Risk of structural failure will be quantified and
safety will be enhanced.
• The inspection and repair burden will be
diminished and cycle times for inspections,
repairs, and modifications will be greatly reduced.
• The remaining useful life of airframes will be extended.
• As a result of all of these improvements, aircraft availability
will be increased and O&S costs will be reduced.
88ABW-2011-1428
Distribution Statement A
Approved for public release: distribution is unlimited.
4
CBM+SI Far-term Vision
per AFRL CBM+SI Workshop - Feb 2009
“Digital Twin”: Real-Time, High-Fidelity Operational Decisions for Individual
Aircraft Enabled by Tail Number Health Awareness
• When physical aircraft is delivered, a Digital Model of the aircraft – specific to that tail
number, including deviations from the nominal design – will be delivered as well.
• The Digital Model will be flown virtually through
the same flight profiles as recorded for the
actual aircraft by its on-board SHM system.
• The modeling results will be compared
to sensor readings recorded by the SHM
system at critical locations to update /
calibrate / validate the model.
• As unanticipated damage is found, it will be added to the Digital Model so that the
model continually reflects the current state of the actual aircraft.
• Prognostics for the airframe will be developed by “flying” the Digital Model through
possible future missions.
• The Digital Model will be used to determine when & where structural damage is likely
to occur, and when to perform maintenance.
88ABW-2011-1428
Distribution Statement A
Approved for public release: distribution is unlimited.
5
Digital Model Functions
Damage from Inspections & SHM
USAGE
, , T, environment
Structural Response
Damage
Progression
PROGNOSIS
 properties,  geometry
FORECAST
88ABW-2011-1428
Repairs, Modifications, Replacements
Distribution Statement A
Approved for public release: distribution is unlimited.
6
Tech Disciplines & Challenges
• Disciplines
• Challenges
– Aerodynamics
– Structures
– Materials and
Manufacturing
– Computer Science
– Information
Management
AFRL POC: Dr. Eric Tuegel,
eric.tuegel@wpafb.af.mil
Upcoming Cross-organization
Discussion Opportunities:
AIAA SDM, AA&S2011,
ICAF2011, ISHM Conference…
88ABW-2011-1428
– Developing parameterized, multi-disciplinary
computational models of appropriate fidelity for the
full-scale aircraft
– Developing high-fidelity computational models of
the relevant capability-controlling phenomena at
physically appropriate length and time scales
– Linking computational models across length/time
scales at varying levels of fidelity
– Understanding and incorporating all influential
sources of uncertainty and variability into the
models at each length/time scale
– Developing analysis techniques for assessing and
optimizing both capability and reliability of the
aircraft
– Integrating materials and manufacturing
phenomena into the aircraft-level digital twin
framework
– Developing technologies and methods to track and
update the state and behavior of both the actual
aircraft and the digital twin based on real-world
experience
Distribution Statement A
Approved for public release: distribution is unlimited.
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