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Durability and Damage Tolerance Evaluation of VaRTM Wing Structure
Yuichiro Aoki, Yutaka Iwahori, Sunao Sugimoto, Yosuke Nagao and Takeshi Ohnuki
Japan Aerospace Exploration Agency, Tokyo, JapanE-mail: [email protected]
Backgroundg• VaRTM benefits
– Single-sided molding without autoclave⇒Simple and low cost toolingg g p g– Integrated structure⇒Parts count and weight reductions– Applicable to larger, complex part production– High fiber volume panel achievable
More cost-efficient manufacturing method for aircraft it th t l d !
Vacuum bag
composites than autoclaved prepreg!
Dry preformDistribution medium
Resin Vacuum
Mold
Vacuum assisted resin transfer molding2
Background (cont’d)g ( )
JAXA Low-Cost Composite Wing Development Project Project goal
– 20% Cost reduction in comparison with present composite structure– 20% Weight reduction in comparison with present aluminum structure
ChallengesMore stable fabrication process with high quality– More stable fabrication process with high quality
– More integrated structure with high performance– More efficient inspection and maintenance techniques– Accumulate fundamental knowledge and establish a guideline for type
certification as a primary aircraft structure
Schedule Schedule– 1st phase: 2003-2008, Fabrication, Manufacturing and Static performance– 2nd phase: 2008-2010, Durability and Damage tolerance, Repair
Ongoing!
3
Material
Stringers & Reinforcing elements :Multi-axial NCF (IMS5131)Multi axial NCF (IMS5131)
Skin: UD fabric (T800SC)Skin: UD fabric (T800SC)
Resin: XNR6809/XNH6809(Nagase ChemteX Corporation )
C re Temp 120 deg CCure Temp.: 120 deg C4
Project overview
Process i i i
Demonstrator, Full-scale structureYear 2003‐2004 2004‐2006 2007‐2008
optimization qualification
Evaluation
Design Optimization
Structural test
0 m 0.5 m 2 m 6 m
5
Full-scale static test in March 2008
✓
✓
✓
✓
✓
✓
✓
Fabrication, Manufacturing and Static performance were successfully demonstrated throughout the building block approach 6
Durability and Damage tolerance evaluation
Starts from January 2009
Focus on higher structural levels of building block i e
NumericalTest
levels of building block, i.e. element, sub component, full-scale
7
Test articles for D and DT evaluationTo be started in November 2010
Upper panel1.5m
Upper panel
6m
Full-scale wing box2 12.1m
0.5m
Lower panelElement8
Test panel
Test panel: sub-component of lower panel Size: 2.1m long x 0.9m wideg Critical area: Stringer run-outs and maintenance hole
Evaluation areaEvaluation area(0.9m x 0.9m)
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Test preparation Steel fixtures are attached to both end of the panel 2,500kN hydraulic testing machine with hydraulic grip 76 ch Strain gages 76 ch Strain gages Optical 3D deformation measurement system
10
Test plan
DSO: Design service objectiveDSO: Design service objectiveLEF: Load enhancement factorDLL: Design limit load 11
Fatigue spectrumSpectrum:Mini-TWIST* (The Transport WIng STandard load program)
(*: NLR-TR73029, NLR-MP79018)GeneralGeneralStandard flight-load for aircraft wing10 flight types (A~J)4 000flights (58 442 cycles) = 1 block4,000flights (58,442 cycles) = 1 block
Test condition1 DSO: 40 000 flights(584 420 cycles)1 DSO: 40,000 flights(584,420 cycles)Mean load level: +1.0G Load range -0.6G ~ +2.6G Example of most critical flight: A-flight
12
Preliminarily analysisFEM d ABAQUS V 6 8 G i l li i id d FEM code: ABAQUS Ver. 6.8, Geometrical nonlinearity was considered
4-node shell elements with equivalent elastic properties Most critical area: Stringer run-outs
L l t f l d f ti d b t i it t i t Local out-of-plane deformation caused by eccentricity near stringer run-outs Implies a potential for disbonding of skin/stringer due to peel force
Peel
Disbonding
Out-of-plane displacement Principal strain13
Initial strain survey results –deformation Out-of-plane displacement of outer surface was measured by 3D optical measurement system
Evaluated area(900 900 )(900mm x 900mm)
ExperimentalA l i ltat 600kN Analysis result
Local deformation at stringer run-out tips 14
Deformation of run-out area during fatigue spectrum
Subcomponent of lower panelSubcomponent of lower panel
15
Summary of 1 DSO fatigue test (durability) Inspection res lts(e er 10% of DSO) Inspection results(every 10% of DSO)
Visual: No detrimental deformation or damage NDI: Disbonding of stringer run-out shows slow growth tendency but growth rate
tends to be smaller with the fatigue duration increasestends to be smaller with the fatigue duration increases 100% DLL Verification after 1 DSO fatigue test
Survived without detrimental permanent deformation
2nd DSO
After 50% of 1DSO
25mm
35mm
Aft 2DSO
After 1DSO
25mm After 2DSO
1st DSO
Initial16
Impact test Simulate FOD damage (Tool drop, Runway debris, Hailstorm, etc...) Consider repair scenario
ID Location Energy Impactor CategoryImpact 1 Skin/stringer 1200 in-lbs Hemisphere BVIDImpact 2 Skin/stringer 1200 in lbs Sharp edge VIDImpact 2 Skin/stringer 1200 in-lbs Sharp edge VIDImpact 3 Skin 600 in-lbs Hemisphere BVIDImpact4 Stringer web 200 in-lbs Hemisphere BVIDp g p
Hemisphere(1 in. Dia.)
Sharp edge17
Impact test overview
15kg
18
Impact test results200in-lbs, stringer web, g
Dia.= 30mm
1200in-lbs, VID
Dia.= 30mmDia.= 25mm600in-lbs, BVID
1200in-lbs,VID 19
Evaluation of impact damage growth Any impact damages did not grow during 1 DSO fatigue testing
because the structure is a part of lower wing. ⇒Tensile load was dominant in present case which did not cause any local deformationdominant in present case, which did not cause any local deformation near impact points.
The size and shape of impact damages did not change.
Impact 1
Impact 3
Initial After 1 DSO
Impact 2
Initial After 1 DSO
Impact 4 20
Ultimate load test
Disbonding of stringer run-out shows small growth. But the structure withstands 150% of design limit loading But the structure withstands 150% of design limit loading
for 3 seconds without detrimental permanent deformation.
Before 150%DLL test After 150%DLL testBefore 150%DLL test After 150%DLL test21
Summary
Capability on durability and damage tolerance of lower wing subcomponent panel was demonstratedlower wing subcomponent panel was demonstrated.
The structure sustains sufficient strength throughout the operational design service objective.
Although stringer run-out disbonding occurred and Although stringer run-out disbonding occurred and shows slow growth tendency, structural residual strength was not affectedstrength was not affected.
22
(Additional information) D and DT tests for Full scale wing box structureD and DT tests for Full scale wing box structure
The test has started in January 2010 and is going on. 1 DSO has completed without any damage and degradation 1 DSO has completed without any damage and degradation. The vicinity of stringer run-out shows local out-of-plane deformation, but
disbonding has not occurred because strain levels are comparatively ll th b tsmaller than subcomponent.
Inspection by fiber scope camera during test
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