Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 1

ANALYSIS OF A SHEAR TEST ON A C/C COMPOSITE BY USING

DIGITAL IMAGE CORRELATION AND A DAMAGE MODEL

J.-N. Périé, S. Calloch, C. Cluzel and F. Hild

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 2

Aim: Understanding and modeling the multi-scale behavior

of materials

Model identification (coupons)and validation (mock-ups)

EXPERIMENT / SIMULATIONINTERACTIONS

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 3

Testing machines

Tested objects

Strains obtained by:experiment?computation?

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 4

Material

Model and identification

Shear test

Conclusion

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 5

Some applications of Sepcarb®

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 6

Unidirectional or woven plies

of ex-PAN fibers

(preoxyded)+

Ex-PAN fiber mat

(preoxydised)

Unidirectional or woven plies of HR Carbon

fibers +

Ex-PAN fiber mat

(preoxydised)

Yarns, unidirectional or woven plies

ofcontinuous or

non-continuous HR Carbon

fibers

Preform manufacture (Stacking + Needling)

CarbonizationPyrolysis (>1000°C)

Chemical vapor infiltration

Novoltex® Skinex® Multirex®

Needled laminates [Cavalier]HR Carbon Fibers

HM Carbon Fibers

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 7

Carbon matrix

stacked +“needled”

Layers of continuous fibers “X”

Layers of non-continuous fibers “Y”

and/or

“C/C reinforced laminate”

Carbon preform +

Some preforms …Plane preforms made of non-continuous fibers

NeedlingNeedling

Unidirectional layers

Satin layers

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 8

satin layers

10 mm

Multirex® family

Macro-undulations(scale: n plies)

~1.5 mm~3 mm

unidirectional plies

No-undulation(scale: coupon)

Meso-undulations(scale: ply)

1.5 mm0.5 mm

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 9

Tension/compression tests at 0° and 45° on a [0y,90y]n satin

Non linear for tension test in non-continuous fiber direction Non linear for 45° test

Linear in continuous fiber direction

Multirex® behavior

Str

ess

(MP

a)

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 10

Model for a family of materials

Uniaxial tests

Displacement and strain field measurement

Validation on a set of

composites

Identificationprocedure

Biaxial tests

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 11

Material

Model and identification

Shear on C/C Composites

Conclusion

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 12

Meso-constituents

Layers of continuous fibers

1

2

Layers of non-continuous fibers

1

2

Models

“X”

2 damage parameters: d2 and d12

Transverse tension ≠ compression

“Y”

3 damage parameters: d2 and d12

+ d1 (in fiber direction)

Transverse tension ≠ compressionFiber direction tension ≠ compression

Hybrid laminate

Kinetics of damage:gradual or

brittle (rupture of fibres)

Model designed for a family of materials

Damage meso-model

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 13

y y

E D y 1

2

11

2

E 1 y 0 ( 1 d 1 y

)

11

2

E 1 y 0

22

2

E 2 y 0 ( 1 d 2 )

22

2

E 2 y 0

2

12 y 0

E 1 y 0

11

22

12 2

2 G 12 y 0 ( 1 d 12 )

State: damaged material strain energy

di = piecewise constant (meso level)

mechanism? “crack opening” “crack closure” : positive part of °: initial value of

Mechanisms: friction and incomplete-closure of cracks

Plasticity model with isotropic hardening

Inelasticity

Anisotropic damage theory [Lad 83]

Kinetics:

Associated forces:

“Energy-release rate” Effective stress

Y d i

E

D

d i

˜ d1 ( , , )

d12 or 2 ( , +b )Yd1

Yd12

Yd2

Yd1

Yd12

Yd2

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 14

Elastic parameters: 2 tensile tests on a hybrid [0x,90y]n

Damage kinetics: 2 tensile tests on a [0y,90y]n satin

Elastic longi. and transverse energy

d12(Yd12 ) kinetics

d1(Yd1 ) kinetics

Hyp: d12 and d2 linked

0° tension test

Elastic shear energy

Hyp: no change in d1

45° tension test

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 15

0° tension test on a [0y,90y]n satin

Laminate0y 90y

Loading

d1

d12

d2

Plies

Plastic strains

Stress (MPa)

Test

Simulation

Mean L. Strain (%)Mean T. Strain

(%)

Simulation tool:classical laminate theory

in the non-linear field

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 16

Material

Model and identification

Shear test

Conclusion

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 17

[0y,90y]n C/C Composites

Uniaxial tests

Biaxial tests

Comparison between experiment/simulation

Heterogeneousstrains

Gages Strain fields

CORRELILMT

[Hild, Périé & Coret, 1999]

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 18

Video digital camera + ICPCI bus + PC

Resolution :> 1Mpixels

Coding : 8-12 bits

File format :.bmp,.tiff,

.jpeg…

Interchangeable lenses

Digital camera

Argentic camera or video camera + scanner

Scanning Electron Microscope ...

Tensile machine

CARDAN joint

Long distance microscopeCCD video

camera

PC

C/C specimen

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 19

Principle of image correlation

Displacement

Scale of study:(only depends on magnification and pattern)

t0 t

icro

0.4mm

meso Macro

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 20

Principle of correlation: displacement of 1D signal

x

dd-A d+A

Correlation product: g*f

d

fg g gg

x+Ax

g

Signal

dxgfxgf )()())(*((FFT)

)()()*( gFFTfFFTgfFFT

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 21

Choice of ZOI

Pixel correlation

Extraction of Displaced zone

WindowingFFT correlation + interpolation

Sub-pixel displacement incrementFFT shift of displaced zone

Convergence?

Total displacement

New zone?

Strain computation

Algorithm: CORRELILMTReference image (t0) Deformed image (t)

Reference ZOI Shifted ZOI

V

U

FFT Correlation(precision: pixel)

Max.

Sub-pixel displacement (U,V)

Yes

No

No

Yes

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 22

Shear test on [0y,90y]n C/C Composite (SEPCARB®)

10 mm

Macro-undulation(random distribution)

100 mm

Fibres

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 23

ASTREE: Triaxial testing machine

Image Acquisition

Control

Optical strain field measurement

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 24

Loading (elastic FEA)

Specimen: plate Boundary conditions: displacements

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 25

Validation of geometry:shear damage in a ply

FEA + Damlam [Clu 01]

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 26

Gauges

Artificialspeckle

Surface displacement field

Experimental boundary conditions

x 30

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 27

8-bit signal - Size of ZOI: 64 pixels - ZOI shift: 32 pixels

Practical Precision (strain)~10-4

DIC

Gauge0.2%

Strain (%)

Tim

e (s

)0.2%

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 28

CORRELI2DCORRELI2D

FEAFEA

Displacement fieldStrain field

N°11N°6N°1

Material heterogeneities

?Boundary conditions

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 29

Ply PlyShear damage d12

CORRELI2D

CORRELI2D

Damlam

Strain:

Damage:

CORRELI2D

FEA

Damlam

Strain:

Damage:

Coupling

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 30

Ply Ply

CORRELI2D

FEA

Damlam

Strain:

Damage:

Fiber damage d1

CORRELI2D

CORRELI2D

Damlam

Strain:

Damage:

Coupling

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 31

Brittle failure

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 32

Displacement field measurement (CORRELILMT)

Experimental strain field

(CORRELILMT)

Computation (FEA) of strain field withexperimental

boundaryconditions

Evaluation of damage state: Damlam

??

Brittle failure

Distributed shear damage

(YET THERE ARE DEFECTS)

Onset of fiber damage

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 33

Material

Model and identification

Shear on C/C Composites

Conclusion

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 34

Meso model

Specific identification procedure

1 stacking sequence2 meso constituents

Model implemented in Damlam

Mock-up design

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 35

Experiment / Simulation coupling

Displacement field measurement

Multiaxial experiment (mock-up)

Experiment interpretation by using the material model

Applications of Optical Techniques

Analysis of a shear test on a C/C composite by using digital image correlation and a damage model 36

Understanding and modeling the multi-scale behaviorof (composite) materials

Measurement of fields (DIC)

(texture = tracer)

Numericalsimulations

Control oftest

Real-time simulation

Multi-scalemeasurement

Resolution of CCD cameras

Inverse identification