load introduction into aerospace structures€¦ · load introduction into aerospace structures ......

Load Introduction into Aerospace Structures Dr. Tamas Havar,

Airbus Group Innovations

Symposium 5th anniversary of Institute of Carbon Composites

POC: tamas.havar@airbus.com

Introduction

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Investigated Composite Load Introduction Structures in Aircraft

CFRP Rear Link

A340 CFRP Spoiler

Composite

4-Bar Linkage

Flap Support

CRFP Flap Load Introduction Rib

Innovative Flap Load Introductions

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Flap

LIR

Aircraft Structures:

• Continuous development of aircraft structures

• Increased use of composite materials

• Composites currently used in frame structures

• Metallic Load Introductions

High Lift System – Composite Flap:

• Composite skin with stringers

• Composite ribs and Spars

• Except metallic load introduction rib

Aim: Innovative composite design for Load Introduction Rib (LIR)

A330 / A340

Innovative Flap Load Introductions

Aim of Project:

• Redesign of metallic LIR => innovative composite LIR

• Requirements:

• Equal design space, attachments,…

• Load transmission from flap track into flap

• Resistance against temperature, humidity, chemicals,…

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Composite Flap

Metal - LIR

Flap Structure

Project Goals:

• Innovative composite design (No black metal!)

• Low manufacturing costs

• Low weight

• High robustness => low maintenance costs

Composite LIR

Project Team:

• Airbus Group Innovations

• Airbus (Lead)

• Airbus Helicopter

• Airbus Defense and Space & Premium AEROTEC

• IVW Kaiserslautern

Innovative Flap Load Introductions

New Composite Textile Preform Design

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

DS Rib

DS Bracket

LIR FS Attachment

SL Attachment

RL Attachment

RS Attachment

Innovative Flap Load Introductions

Design Process

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Modification of

exist. Flap FEM

New Design of

LIR (CAD)

New FEM

Model of LIR Integration of

LIR Model in

Flap Model

Integration of

Rivets

Part C

Part B

Part A

Application of

Loads

Analysis of

Stresses

Innovative Flap Load Introductions

3D Sizing with effects of defects

• Plies milled (Waviness => too thick)

• Fiber orientation taken from pre-form

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3

Results of Analysis

• Successful Sizing of LIR

• Few critical points

• Local small Reserve Factors (RF) dependent on load case

•Fiber compression S11min

•Matrix tension S22max

• No critical delaminations calculated S12, S13 und S23

• No matrix crack at gusset fillers

1

2 2

1 2

3

Innovative Flap Load Introductions

Manufacturing (Airbus Helicopters)

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Preforming of Parts

• Automated NCF Cut Out

• Positioning of Load Introduction

• Draping of Rib Layers

• Precompatcting

• Adding of Reinforcement Layers

• 3D Stitching of Edges

• 3D Cutting of Edges

• Automated Pre-form QS

Innovative Flap Load Introductions

Manufacturing (Premium Aerotec)

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Infiltrated Parts

• LIR with CFRP Lugs

• 3D Reinforcement

• Drive Ribs

• Drive Bracket

• Pi Profiles

• FS-Attachments

• Aux Spar

Innovative Flap Load Introductions

Manufacturing (Airbus)

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Assembly

• Shortening of A340 OB Flap

• Reinforcement of Lower Skin

• Assembly of LIR

• Assy. DS Rib and Bracket

• Assy. Clamping Ribs

Top View Bottom View

Innovative Flap Load Introductions

Validation (Premium Aerotec)

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Testing of 5 Critical Load Cases

•Testing of Flap with integrated LIR

• BVID (Barely Visible Impact Damage)

• VID (Visible Impact Damage)

• NDI after Damages

• Static Loads partly with EKDF

• Fatigue Loads with LEF

BVID + NDI VID + NDI

Fatigue Phase, LEF 1,15 Damage Tolerance

Phase

3 Actuators 80 Strain gauges

Innovative Flap Load Introductions

Validation (Premium Aerotec)

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Finished Testing

• Small Delamination of Gusset Filler of DS Bracket

• Possible Delamination in inner LIR Radius

• Loads were carried despite small damages

• Fatigue Testing without further damages

Innovative Flap Load Introductions

Summary LIR

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Design and Sizing

• New Innovative Composite Design of Flap Load Introduction Rib

• Ability to analyze complex 3D Composite Parts

• Integration of effects of defects into sizing

Verification

• Verification with Risk Reduction Articels Spring Back etc.

• Verification of Preforming Abilities of all Parts

• Curing of Load Introduction Ribs with VAP Process

• QS of finished Parts

Validation

• Integration of LIR in existing A340 outbaord flap

• Fatigue and damage tolerance Testing

Over 25% Weight Reduction

Over 5% Cost Reduction

Further Investigations

CFRP Lug Sizing Rules

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CFRP Lug Sizing Rules

Motivation

• Increased use of composites in current high-lift lightweight designs

• Mostly extensive testing needed for new structural components

• => Costly: most critical several load cases are to be tested

• There are only few guidelines / designers experience

• More general approach from specific part towards common design

guidelines for high-lift structures are needed

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Comparison between FEA and Test for Composite Lugs

0

50

100

150

200

250

300

350

400

450

500

1.2 1.4 1.6 1.8 2 2.2

Radius Ratio ra/ri

Fo

rce

[kN

]

FEA: QI FF

Test: QI FF

Test: QI IFF

FEA: QI IFF

Fiber Failure

Inter-Fiber Failure

Aim: General Design Rules for Lugs and Loops

CFRP Lug Sizing Rules

Approach

• Analysis of composite load introductions

(analytical and FEA)

• Validation of composite lugs and loops

• First Ply Failure / Residual Strength

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Failure Load Verification of Laminates with Lug

under 0° Loading

Test vs. FEM and Analytical Calc.

0

50

100

150

200

250

300

350

400

450

500

1,3 1,4 1,5 1,6 1,7 1,8 1,9 2

Ratio of Radius: ra/ri [ ]

Fail

ure

Lo

ad

[K

N]

Test-Lug-Failure

FEM-Lug-Failure

Analyt-Lug-Failure

Test-Lug-Non Linear

FEM-Lug-First Failure

Analyt-Lug-First Failure

Parameter study at 0° Loading

Lug vs. Loop (with and without inner ring)

0

100

200

300

400

500

600

700

1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2

Ratio of Diameter: Da/Di [ ]

Fail

ure

Lo

ad

[K

N]

FEM-Loop-Innerring-Failure

FEM-Loop-Failure

FEM-Lug-Failure

Test-Lug-Failure

0° Loading:

Loops better performance:

=> Fiber in load direction

Lugs low performance:

=> Fiber cut in load direction Parameter study at 90° Loading

Lug vs. Loop (with and without inner ring)

0

50

100

150

200

250

300

1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2

Ratio of Diameter: Da/Di [ ]

Fail

ure

Lo

ad

[K

N]

FEM-Loop-Innerring-Failure

FEM-Loop-Failure

FEM-Lug-Failure

90° Loading:

Loops low performance:

=> Matrix in load direction

Lugs low performance:

=> Fiber partly in load direction

CFRP Lug Sizing Rules

Progressive Failure Analysis of Lugs and Loops

=> AIM: Virtual Testing of Composite Lugs and Loops

• Damage Initiation using 3D Puck

• Damage evolution: failure mode dependent

– Gradual softening for inter-fiber fracture

Stiffness degradation (not E║) depending on failure mode

– Instantaneous degradation for fiber fracture, representing total structural failure

• Coupling of Fortran subroutine (including 3D Puck and degradation scheme) within every

incremental calculation of nonlinear simulation

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Analysis at every integration point

Evaluation in layers possible FF

IFF,

IFF,

0n

0n

CFRP Lug Sizing Rules

Scientific Approach (by Carolin Werchner)

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0

1000

2000

3000

4000

5000

6000

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Increments

Sh

ea

r m

od

ulu

s G

12 [

N/m

m2]

IFF FF

softening factor h degraded shear modulus G12

Verification of gradual and instantaneous

stiffness degradation

Comparison Strain Distribution:

Test vs. FEA

Test FEA

Comparison Fracture Mode

Very good qualitative accordance

But strong calibration needed

(mesh dependency etc.)

0

0.2

0.4

0.6

0.8

1

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Increments

So

fte

nin

g f

ac

tor

h

IFF FF

Further Investigations

Next Applications

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Next Applications

Basis: Composite 4 Bar Linkage Flap Support

• Replacement of metal carriage

• Full Composite Linkage System

• Linkages

• Brackets

• Linkages mostly as composite loops

• Lugs: thick laminate load introduction

• Failure case reduction:

• No jam of carriage

• Linkages with bearings

• Maintenance reduction

• No ball bearings

• Self lubricant bearings

• Major weight reduction

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

WingFlap

Metal Track Rear Link Kinematics

Composite 4 Bar Linkage Kinematics

Next Applications

Innovative High Lift Systems for Future Aircraft

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Airbus Group Innovations – Tamas Havar - 5th Anniversary LCC

Questions?

Thank You!

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