Post-buckling behavior of thin-walled damaged laminates

3DEXPERIENCE Conference Design, Modeling and Simulation19 – 21 Nov. 2019

Post-buckling behavior of thin-walled damaged laminates underCompression-After-Impact loading

Hamburg University of Applied Science (HAW Hamburg)

Aurelio Jose Olivares-Ferrer, Markus Linke

3DEXPERIENCE Conference Design, Modeling and Simulation|19 – 21 Nov. 2019

1. Introduction

2. Problems

3. Solution approach

4. Results

5. Conclusions

OUTLINE

2


1. Introduction

2. Problems


4. Results

5. Conclusions

OUTLINE

3


Composites in the Aeronautical industry

4

Optimize structures by reducing weight:

Thin-walled laminates

Structural components mainly use:

Carbon Fiber Reinforced Polymers (CFRP)

Excellent mechanical properties, such as:

• Specific strength

• Specific stiffness

But, CFRP laminates have a main drawback:

Low impact strength

1. INTRODUCTION


1. INTRODUCTION

5

Aircraft receive lots of impacts during their lifeMainly low-energy impacts caused by:

• Ground operation (main cause)

• Runway debris

Barely Visible Impact Damage (BVID)

Internal 3D damage patterns:

• Delaminations

• Matrix cracks


1. INTRODUCTION

6

(Delaminations projected view)

X

YThe most widely used because:

• Projected view of delaminations (2D)

• In-airfield application

Internal damage detection

Non-Destructive Testing (NDT) techniques

Ultrasonic Sensing


Compression-After-Impact (CAI) tests on laminated flat plates

1) Impact test (damaging the samples at a controlled energy)

2) Inspection test (dimensioning the damage size)

3) CAI test (residual strength)

7

Check the residual strength of laminates with BVID

Simply Supported

Clamped

1. INTRODUCTION

3DEXPERIENCE Conference Design, Modeling and Simulation|19 – 21 Nov. 2019 8

OBJECTIVE: Get more knowledge about failure mechanisms of CAI test of

thin-walled CFRP laminates with BVID

By creating finite element models with Abaqus software

1. INTRODUCTION


1. Introduction

2. Problems


4. Results

5. Conclusions

OUTLINE

9


The FE model of CAI test of thin-walled laminates must face:

Laminate modeling

2. PROBLEMS

Laminate modeling strategy and material definition

• Plies and interfaces.

• Damage initiation criteria for intra- and interlaminar failure modes.

• Damage evolution models for intra- and interlaminar failure modes (material non-linearities).


Laminate modeling

Global buckling

YX

Z

2. PROBLEMS

Post-buckling behavior

• In thin-plates, the buckling load is lower than the compression failure load of an ideal straight plate.

• Plates can bear higher loads than the buckling load.



ZX

Laminate modeling

Global buckling

Initial geometrical imperfection

2. PROBLEMS

Geometrical non-linearities

• Permanent deformations in the plate due to the previous impact.

• Influence the post-buckling behavior.



Laminate modeling

Global buckling


Internal damage

Y

X

2. PROBLEMS

Modeling strategy of the initial damage

• Only a 2D projected view of the delaminated area known.

• Unknown damage pattern in the through-thickness direction.

• Model initial delaminations.



ZX

Laminate modeling

Global buckling


Internal damage

Y

X

YX

Z

2. PROBLEMS



1. Introduction

2. Problems


4. Results

5. Conclusions

OUTLINE

15


Geometry and boundary conditions

a = 120mm

b = 90mm

Simply SupportedClamped

Original CAI test Simplification used in the models

3. SOLUTION APPROACH

Y

X

a = 120mm

b = 90mm

Y

X


• Physical thickness is needed to model interfaces between layers.

• Continuum shell elements for the laminate layers.

• Cohesive elements for the interfaces.

• Connection between layers and interfaces with shared nodes.

Laminate modeling

Layers modeling strategy

Equivalent Single Layer (ESL)

Layer-Wise (LW)

Cross-section Zoom-in

Layers Interfaces

Y

Z

Layer 1

Layer 2

.

.

.Layer N

Interface 1

Interface 2...Interface NX



Laminate modeling

Materia models

Layers

Interfaces

• Elastic behavior: Traction-separation law

• Damage initiation: Quadratic nominal stress criterion

• Damage evolution: Energy based

• Mixed mode: Benzeggagh-Kenane

• Softening: Linear

• Laminate: [ 0w, 0, 90, 0, 90, 0, 90 ]s

• Layers: 12 unidirectional (UD) and 2 woven (W)

• Damage initiation: Hashin’s criteria

• Damage evolution: Energy based

• Softening: Linear



Post-buckling behavior

An initial perturbation is required to allow the geometrical non-linear behavior

Linear buckling

Post-buckling

• Shapes of the buckling modes.

• The permanent deformation due to the impact is approximated by the first buckling mode.

• The perturbation is added by an initial geometrical imperfection.

• This imperfection is induced in the mesh through the scaled shapes of the buckling modes.

• The same mesh created in the linear buckling model must be used.


Experimental measurement

FE model approximation

Source: Olivares-Ferrer, A. J., et al (2019)


Y

X

Y

X


Initial damage modeling

Interfaces

Initially undamaged

Initially damaged

• Only initial delaminations are considered.

• Interfaces are divided into two zones.

• Damage idealization based on ultrasonic scans.

• Elliptical damage shape idealization.

X

Y

X

Undamaged

Damaged

Interfaces



Simulation procedure

Solver

Static Riks

Explicit Dynamics

• Higher computation time.

• A mass scaling factor must be used to reduce the calculation time.

• Verification needed with implicit calculations (Riks).

• Lower computation time.

• But it has problems with delamination growth.

• Useful for verifying the explicit simulation without considering the interfaces (delaminations).



1. Introduction

2. Problems


4. Results

5. Conclusions

OUTLINE

22


Different through-thickness damage pattern idealization

23

Undamaged

Damaged

X

Cylindrical pattern

y

z

DelaminationUndamaged interfacePly

Conical pattern

y

z

Undamaged

Conical

Cylindrical

267

183219

0

40

80

120

160

200

240

280

1

Failu

re S

tress

[Mpa

]


31% 18

%

4. RESULTS


Imp=0.1mm Imp=0.4mmImp=0.2mm

269

215

267219

264

228

0

50

100

150

200

250

300

Undamaged Damaged

Failu

re S

tress

[Mpa

]

24

Different magnitudes of the geometrical imperfection

4. RESULTS

Shape of the geometrical imperfection


X


4. RESULTS

beff/2 beff/2

b

y

z

Stress distribution comparison (𝛔𝛔𝐏𝐏 = 𝟏𝟏𝟏𝟏𝟏𝟏 𝐌𝐌𝐏𝐏𝐌𝐌)

400200

0-200

Ply

Stre

ss, 𝛔𝛔

𝟏𝟏𝟏𝟏[𝐌𝐌𝐏𝐏𝐌𝐌

]

-400-600-800

600

Y Coordinate, 𝐲𝐲 [𝐦𝐦𝐦𝐦]-50 -10 0 10-20-30-40 20 30 40 50

Damaged

beff/2beff/2

Undamaged

Interaction between global buckling and local delaminations

Middle section

σP

σPx



1. Introduction

2. Problems


4. Results

5. Conclusions

OUTLINE

26


5. CONCLUSIONS

27

• The creation of a finite element model that considers post-buckling behavior, initial geometricalimperfection, initial damage and intra- and interlaminar damage evolution is feasible with ABAQUSsoftware.

• A better understanding of the CAI test with thin-walled laminates is being possible through the investigationof these models.

• Further research still can be performed with the CAI models in order to improve the prediction of itsbehavior.


1. Olivares-Ferrer, A. J., Linke, M., García-Manrique, J. A. (2019) Influence of geometric imperfections and internal damage patterns of thin-walled laminates on failure in Compression-After-Impact testing, Procedia Manufacturing.

REFERENCES

3DEXPERIENCE Conference Design, Modeling and Simulation19 – 21 Nov. 2019

MANY THANKS

Questions?

CONTACT DETAILS:

Aurelio Jose Olivares-Ferrer

E-mail: [email protected]

HAW Hamburg University of Applied Science

mailto:[email protected]

Documents

Post-buckling behavior of thin-walled damaged laminates