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

2. EXPERIMENT / SIMULATION
Aim: Understanding and modeling
the multi-scale behavior
of materials
Model identification (coupons)
and validation (mock-ups)
EXPERIMENT / SIMULATION
INTERACTIONS

3. Testing
machines
Tested
objects
Strains
obtained by:
experiment?
computation?

4. Material
Model and identification
Shear test
Conclusion

5. Some applications of Sepcarb®

6. Needled laminates [Cavalier]
HR Carbon Fibers
HM Carbon Fibers
Needled laminates [Cavalier]
Novoltex®
Skinex®
Multirex®
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 of
continuous or non-continuous HR Carbon fibers
Preform manufacture (Stacking + Needling)
Carbonization
Pyrolysis (>1000°C)
Chemical vapor infiltration

7. Plane preforms made of non-continuous fibers Unidirectional layers
“C/C reinforced laminate”
Layers of continuous fibers “X”
Carbon preform +
Carbon matrix
stacked
+“needled”
and/or
Layers of non-continuous fibers “Y”
Some preforms …
Plane preforms made of non-continuous fibers
Needling
Unidirectional layers
Satin layers

8. Multirex® family Meso-undulations Macro-undulations No-undulation
satin layers
unidirectional plies
10 mm
Macro-undulations
(scale: n plies)
~1.5 mm
~3 mm
Meso-undulations
(scale: ply)
1.5 mm
0.5 mm
No-undulation
(scale: coupon)

9. Tension/compression tests at 0° and 45° on a [0y,90y]n satin
Multirex® behavior
Linear in continuous fiber direction
Tension/compression tests at 0° and 45° on a [0y,90y]n satin
Stress (MPa)
Non linear for tension test in non-continuous fiber direction
Non linear for 45° test

10. Model for a family of materials
Identification
procedure
Validation on a set of composites
Uniaxial tests
Biaxial tests
Displacement and strain field measurement

11. Material
Model and identification
Shear on C/C Composites
Conclusion

12. Model designed for a family of materials brittle (rupture of fibres)
Damage meso-model
Meso-constituents
Layers of continuous fibers
Layers of non-continuous fibers
Models
“X”
2 damage parameters: d2 and d12
Transverse tension ≠ compression
“Y”
3 damage parameters: d2 and d12
+ d1 (in fiber direction)
Fiber direction tension ≠ compression
Hybrid laminate
Model designed for a family of materials
Kinetics of damage:
gradual or
brittle (rupture of fibres)

13. Anisotropic damage theory [Lad 83]
State: damaged material strain energy
mechanism?
“crack opening”
“crack closure”
< a > +: positive part of a
a°: initial value of a
di = piecewise constant (meso level)
Kinetics:
Associated forces:
“Energy-release rate”
Effective stress
d1 ( , , )
d12 or 2 ( , b )
Mechanisms: friction and incomplete-closure of cracks
Plasticity model with isotropic hardening
Inelasticity

14. Elastic longi. and transverse energy
Elastic parameters: 2 tensile tests on a hybrid [0x,90y]n
Damage kinetics: 2 tensile tests on a [0y,90y]n satin
Elastic shear energy
Hyp: no change in d1
45° tension test
d12(Yd12 ) kinetics
Elastic longi. and transverse energy
0° tension test
Hyp: d12 and d2 linked
d1(Yd1 ) kinetics

15. Laminate 0y 90y Loading d1 d12 d2 Plies Plastic strains
0° tension test on a [0y,90y]n satin
Stress (MPa)
Test
Simulation
Mean L. Strain (%)
Mean T. Strain (%)
Simulation tool:
classical laminate theory
in the non-linear field

16. Material
Model and identification
Shear test
Conclusion

17. Comparison between experiment/simulation
[0y,90y]n C/C Composites
Biaxial tests
Comparison between experiment/simulation
Uniaxial tests
Heterogeneous
strains
Gages
Strain fields
CORRELILMT
[Hild, Périé & Coret, 1999]

18. Video digital camera + ICPCI bus + PC
Tensile machine
CARDAN joint
Long distance microscope
CCD video
camera PC
C/C specimen
Resolution :
> 1Mpixels
Coding :
8-12 bits
File format :
.bmp,
.tiff,
.jpeg…
Interchangeable lenses
Digital camera
Argentic camera or video camera + scanner
Scanning Electron Microscope ...

19. Principle of image correlation
Displacement
Scale of study:
(only depends on magnification and pattern)
micro
0.4mm
meso
Macro

20. Principle of correlation: displacement of 1D signal
x+A x g g g g f x d
Correlation product: g*f
(FFT) ) ( * g
FFT f = x
d-A d
d+A

21. Algorithm: CORRELILMT
Reference image (t0)
Deformed image (t)
Choice of ZOI
Pixel correlation
Extraction of
Displaced zone
Windowing
FFT correlation + interpolation
Sub-pixel displacement increment
FFT shift of displaced zone
Convergence?
Total displacement
New zone?
Strain computation
Reference ZOI
Shifted ZOI
Yes DV DU
FFT Correlation
(precision: pixel)
Max.
Sub-pixel displacement (dU,dV) No
Yes No

22. Shear test on [0y,90y]n C/C Composite (SEPCARB®)
Fibres
100 mm
10 mm
Macro-undulation
(random distribution)

23. Optical strain field measurement
ASTREE: Triaxial testing machine
Image Acquisition
Control

24. Boundary conditions: displacements
Specimen: plate
Boundary conditions: displacements
Loading (elastic FEA)

25. Validation of geometry:
shear damage in a ply
FEA + Damlam [Clu 01]

26. Surface displacement field
Gauges
Artificial
speckle
Experimental boundary conditions
x 30

27. 8-bit signal - Size of ZOI: 64 pixels - ZOI shift: 32 pixels
DIC
Gauge
0.2%
Strain (%)
Time (s)
Practical Precision (strain)
~10-4

28. Material heterogeneities ?
Strain field
Displacement field
N°1
Material heterogeneities ?
N°6
N°11
CORRELI2D
FEA
Boundary conditions

29. Shear damage d12 CORRELI2D Damlam Strain: Damage: Ply Ply CORRELI2D
Coupling
CORRELI2D
FEA
Damlam
Strain:
Damage:

30. Fiber damage d1 CORRELI2D Damlam Strain: Damage: Ply Ply CORRELI2D FEA
Coupling
CORRELI2D
FEA
Damlam
Strain:
Damage:

31. Brittle failure

32. Distributed shear damage (YET THERE ARE DEFECTS)
Displacement field measurement (CORRELILMT)
Experimental
strain field
(CORRELILMT)
Computation (FEA) of strain field with
experimental
boundary
conditions
Evaluation of damage state: Damlam
Distributed shear damage
(YET THERE ARE DEFECTS)
Onset of
fiber damage ?
Brittle failure

33. Material
Model and identification
Shear on C/C Composites
Conclusion

34. Specific identification procedure Model implemented in Damlam
Meso model
1 stacking sequence
2 meso constituents
Specific identification procedure
Model implemented in Damlam
Mock-up design

35. Multiaxial experiment (mock-up)
Displacement field measurement
Experiment / Simulation coupling
Experiment interpretation
by using the material model

36. Inverse identification
Understanding and modeling
the multi-scale behavior
of (composite) materials
Measurement of
fields (DIC)
(texture = tracer)
Numerical
simulations
Control of
test
Real-time simulation
Inverse identification
Multi-scale
measurement
Resolution of CCD cameras