Abschlussworkshop CFK-Rumpf NG

Leitprojekt CFK Rumpf NG

15.02.2011 von 09:00 Uhr – 17:00 Uhr Golden Tulip Hamburg

Abschlussworkshop CFK-Rumpf NG

Infusion Technology for Bonded CFRP Repairs (for Aircraft Primary Structures)

Dr. Christian Hühne, Dirk Holzhüter, B. Kujak, Arne Hindersmann, Jens Bölke, Olaf Steffen

2Leitprojekt CFK Rumpf NG

Topics

Repair Environment

State-of-the Art CFRP-Patch Repair

Repair ConceptsDesign and Automation Infusion Repair

Summary

Outlook

Boeing Demonstration of Patch

Repair

Damage

by

Lightning

Strike


Repair EnvironmentTemporary Conservation

Protection

of damaged

structure

against

moisture. Application

of waterproof

cover

immediately

after

detection

Only

temporary!

Repair with Temporary Life Time: „Field Repair“Structural

recovery

for

full

use

of part. This

repair

has to be

redone

at every

major

maintenance

check!

Permanent Repair: „Depot Repair“Full Repair

of Structure. Structure

is

equivalent

to original one

(Level of Equivalent

Safety)

http://www.martinaire.com/Hangar1.jpg

http://aviationdave.files.wordpress.com/

http://www.aviation.technomuses.ca

(Repair

Level) [nach Baker und Raymond]

http://aviationdave.files.wordpress.com/

http://www.aviation.technomuses.ca/


Repair Environment (EASA)Primary Structure

Safety

relevant, Failure

causes

total losse.g. Centre Wing

Box, VTP Bearings, Rudder, Fuselage

Secondary StructureStructure

relevant for

normal operation, Failure

does

not

cause total Losse.g. aerodynamic

Fairings

/ Flaps, Slats

Tertiary StructureReimaing

Structure, Failure

has low

impact

on operatione. g.Maintenance

covers

Repaired by OEM or certified Company

Redesign

and Certification

of Repair

necessarrye. g. new

Framecoupling

Repaired by OperatorBy

Structural Repair Manual (SRM)

No immediate Repair necessaryPart may

be

temporarily

removedFailure

Cascade

has to be

prevented

5Institute of Composite Structures and Apaptive Systems

State-of-the-art (Bolted Repair)

Bolted

Repair

•

Bypass

of Original Load

Path

by

Riveting

of One or

Two

Doublers

Advantage•

Good Recovery

of Strength•

Slight•

Fast Application•

Easy Certification

because

of Fail-Safe-Concept

Disadvantage•

Minimum Skin Thickness

necessary•

Steps

in Aerodynamic

Shape•

Complex

at edges

and pressure

vessels•

High Weight, Two

Sided Access necessarry

Examples•

Thick

aircraft

structures

(>3mm)

1. Damage Detection by NDT

2. Removal of Damage (Drilling, Grinding, Milling)

3. Riveting of Doublers

4. NDT

6Institute of Composite Structures and Apaptive Systems

State-of-the-Art CFRP-Patch Repair

Scarf

Repair

•

NDT, Removal of Damage, Manual Grinding

of Scarf, Cocuring

of Wet

Prepreg

Layup

or

conbonding

of Hard Patch

(separate Tooling

necessary), Prepreg

Technology favoured.•

Ramp

of Scarf

1:20 –

1:40

Adavantage•

Original Structural

behaviour

nearly

restored•

Flushrepair•

Excellent

mechanical

Performance

Disadvantage•

Extremely

complex

and time consuming•

Qualitymanagement

complex

(Travellorcoupons)•

A lot of healthy

Material has to be

removed

by

the

scarf

Weakening

of Structure? Examples•

Repair

of Flaps (A320)

1. Damage Detection by NDT

2. Removal of Damage by Grinding or Milling

3. Filmadhesive and Filler Plies cobonded or bonding of Hard Patch

4. NDT


DLR - Concepts

ChallengesReduction

of Maintenance

Time

Reduction

of Maintenance

CostsCertification

of Bonded

Repairs

Reproducibility

/ Human FactorStructural

Performance

AimDepot Repair

Method

for

Primary

Structures

SolutionsAutomated

Repair

Process

Robust Repair

ProcessFail-Safe

Repair

Process

Repairs

done

todayRepairs

done

tomorrowDemonstration of Boeing 787 Repair


DLR - Concepts

Machining

of Scarf

-

Laserscanning

of Surface- Surface

Reconstruction

of Real-Geometry- Design of Scarf- Generation of Machining

Data- Milling

of Scarf

(3-Axis or

7-Axis)

Design and Machining

Concept

Advantages

-

Digitized

Geometry

for

Automation

of Repair

Process

-

Digitized

Geometry

for

Tooling

Generation (Hard Patch)

- Digitized

Geometry

for

Documentation

-

Automated

Milling/Grinding

of Scarf

for

Minimization

of Human Factor

- Automated

Milling/Grinding

of Scarf

forMaintenance

Time Reduction


DLR - Design Concept

Removal of Damage / ScarfingLaserscanning

of 3D-Surface

Scanning

by

Perceptron

V5 Laserscanner:Absolute Precision: ~45μm

ATOS 3D-Scanning System

Manufacturer: GOM

*

*Source: EADS

or


DLR - Design Concept

Virtual Design of RepairSurface

reconstruction

in CATIA V5

Design of Scarf

by

parameterized

Construction

Pointcloud Triangulation Real-Surface

Scarf-DesignParameter Input Machining

Data


Aligning

of 3D-Data

Preparation of Damaged Area for Bonded Repair

Focussing

of 3D Data on relevant RegionReduction

of 3D-Data DensityTriangulation

of 3D-Point CloudReconstruction

of real GeometryChecking

of deviationDesign of Tapered

Repair

based

on real 3D-Shape

DLR – Machining Concept

Damage

Removal by

Milling

of StructureStructure

prepared

for

Patchrepair

Process

demonstrated

on unstiffened

Panel

Automated

Positioning

andBonding of Repairpatches

Process

demonstrated

on unstiffened

Panel


Hard-Patch

Repair

Characteristik- Bonded

repair- Cured

Patches- Automation of Process- One Sided Access only

Hard Patch RepairRepair

Concepts

Machining

of Scarf

-

Laserscanning

of Surface- Surface

Reconstruction


Data- Milling

of Scarf

(3-Axis or

7-Axis)


Concept

Advantages

- Assembly

Possible

from

One Side

-

Improved

Mechanical

Performance via Double Lap

Joint

- Improved

Safety

via Double Lap

Joint


Hard Patch Repair

Hard Patch Repair ConceptMaximum of 3 Repair

Patches

(outer

Patch

optional)

Inner Patch

Inserted

via Elliptic

RepairholePositioning

of Centre and Outer

Patch

Aligning

by

Middle

Patch

and Two

Drill HolesClosing

of Drill Holes

by

Two

Blind Rivets


Hard Patch Repair

Hard Patch Repair3D-Demonstrator

CNC-milled

Scarf

Based

on Scanned

Surface

Hard Patch

Repair

with

Inner

and Centre Patch

Hard Patch

Repair

withInner, Centre, and

Outer

Patch


Infusion Repair

-

Infusion of Positioned

Preform- Cobonding

of Patch

and Adhesive- One Sided Access only- Low Assembly

Tolerances

Infusion-Patch

Repair

Repair

Concepts

Machining

of Scarf

-

Laserscanning

of Surface- Surface

Reconstruction


Data- Milling

of Scarf

(3-Axis or

7-Axis)


Concept

Advantages

-

Easy Repair

Process

via Infusion

of Patch

- No Patch

Tooling

necessary

-

Flexible Patch

for

Repair

of Double Curved

Structures

- High mechanical

Performance

- One Sided Access only

necessary


Cobonding Infusion Repair ConceptBonding of Filler

Plate

Insertion of Film AdhesiveInsertion der Preform

(with

Overplies)

Single Sided VacuumbaggingInfusion of PreformCo-Curing

of Adhesive

and Patch

Infusion Repair

Preform

Grundplatte(AL oder GFK)

StructurePatch


Infusion Repair

Evaluation of Mechanical PerformanceCoupon Specimen

EN6066

Easy ManufacturingEasy Testing

(1-Axis Tension)

Testing

of Scarf

not

AdhesiveQuantative

Evaluation of Joint

Surface

Analytic

of Break Surface

Patch

Parent

Adhesive

Void

Overply End of Adhesive

Parent

Standard Set of

En6066 Coupons


Infusion Repair

Evaluation of mechanical PerformanceARAMIS

Evaluation of Surface

StrainfieldStrain

Gauges

for

Local

Strains

0°/90°

0°/90°90°

/0°

90°

/0°+45°/-45°

+45°/-45°

-45°/+45°

-45°/+45°

-45°/+45°

25kN 35kN


Infusion Repair

Detail TestingQuantification

of Geometry

Influence

Scarf

Angle, Elliptic

RepairsEvaluation of Repair

Process

Verification

of Doubler

ConceptsValidation of Patch

Lay-Up

Ply-by-Ply

/ Cupped

MaterialsDry

Fabrics

e.g. G0926, G1157 (Hexel)

Dry

NCF from

Saertex

(Biax)Resin: RTM6 (Hexel), LY (Huntsman) Adhesive: FM300 (Cytec), Hysol

EA 9596 (Henkel)


Infusion Repair

Microscopic EvaluationCobonding

Good Bond Line, no VoidsHard Patch

(State-of-the-Art)

Good Bond Line, some

Voids

Mechanical Evaluation (Coupon)Infusion Repair

has equal

Mechanical

Performance compared

to Hard Patch

About

80% total Load Recovery

has been

achievedundamaged

State-of-the-Art

DLR-Concepts

Load Recovery

ParentBond Line

Patch

Bond LinePatch

Parent


Infusion Repair

3D-Infusion Repair Process Demosntration

Cocured

Patch

CNC-milled

Scarf

based

on Scanned

Surface


Summary

DLR is certified for changes on our own aircrafts (EASA part 21,25) e.g. on our Do228, Dassault Falcon, Airbus A320

State-of-the Art lacks a Bonded Repair Solution for Primary Structures to overcome „Designed for Bolted Repair“- Design-Rule

Repair ist strongly driven by Certification Requirements

Design and Machining Concept improves Repair Quality, Documentation and allows Process Automation as well as new Geometries

Infusion Repair reduces Process Complexity for curved Parts drastically by equivalent mechanical Performance


Outlook

Development of Repair Method for Certification Process

Development of Process Chain for Automated Repair Process

Demonstration of a Full Automated Repair Process on a CertifiedAircraft Structure

Inflight Testing of Repair


Thank you for your Attention!


Contact Data

Expert Repair: Dirk Holzhüter

Phone: 0531 295 2319

Email: [email protected]

Expert Joining: Dr. Axel Fink

Phone: 0531 295 2308


Expert Manufacturing: Michael Hanke

Phone: 0531 295 2303


Head of Department Composite Design: Dr. Christian Hühne

Phone: 0531 295 2310


Abschlussworkshop CFK-Rumpf NG

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