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: aoki.yuichiro@jaxa.jp

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!

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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

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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

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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

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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

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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

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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

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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.

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(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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