1. Structural Integrity of Hybrid Metal Composite Structures in a Fighter Aircraft
Presented at Flygteknik 2010 – Stockholm, October 18-19, 2010

2. NFFP – Structural Assessment of Hybrid Structures
Research programme aiming to develop the required methodology and data to certify complex metal/composite hybrid assemblages subjected
to in-flight coupled thermo-mechanical load spectra.
Focused on test verification techniques to cover the significant effects of:
Thermal induced stresses
- dissimilar thermal expansion
- heat transfer into structure
- speed & altitude
- surrounding temperature
Load sequences
- rare high peak loads
- frequent small load ranges

3. Wing – Fuselage Attachment
A/B/C/D - versions
E/F - versions

4. Full-scale fatigue test of complete airframe
and sub assemblages

5. Coupled thermo-mechanical load cases
syFlight
sxTemp
txyFlight
P high LT
txyFlight
syFlight
syTemp
P low LT

6. Typical temperatures (MIL-STD-1530C)
85oC
100oC
Gripen E/F – temperatures for static loads
Sustained – through all structure: -40oC g +94oC

7. Example – Super Sonic Fighter Sweep

8. Flight and temperature loads
Stagnation
Temperature To
Heat
transfer
syFlight
sxTemp
txyFlight
P LT

9. Detailed FE-analysis of complete wing

10. Fatigue testing of specimens exposed to heating
156 20 32
228 16 64
D = 8 10
Aluminium
9,4
2 x composite 20 32 16 36
160 70 50
228
232
D = 8

11. Dissimilar failure mechanisms – metal / composite
Load sequence effects – retardation / accelerations
Metal
predominating singel crack
Composites
matrix cracking
delamination
fiber breakage
interfacial debonding

12. Fatigue test verification of metal and composite structure
Truncation or extension of high loads
composites (to verify life also for aircraft exposed to rare high loads)
metals (to verify life also for aircraft not exposed to
rare high loads)
Load ranges
Elimination of insignificant
load cycles
Mean maneuver load spectra for
one service life e.g. 8,000 hrs.
composites
metals
Log number of cycles

13. Participants – NFFP project
Zlatan Kapidzik
Lars Djärv
Martin Ekström
Hans Ellström
Jonas Wahlbäck
Hans Ansell
Joakim Schön
Rolf Jarlås
Anders Blom
Börje Andersson