Composites Testing and Model Identification Châlons-en-Champagne, 28 January 2003 Z. JENDLI*, J....

Composites Testing and Model Identification Châlons-en-Champagne, 28 January 2003Composites Testing and Model Identification Châlons-en-Champagne, 28 January 2003

Z. JENDLIZ. JENDLI*, J. FITOUSSI*, F. MERAGHNI** et D. *, J. FITOUSSI*, F. MERAGHNI** et D. BAPTISTE*.BAPTISTE*.

*LM3 UMR CNRS 8006. ENSAM Paris.

**LMPF-JE 2381. ENSAM Châlons en Champagne.

Micromechanical analysis Micromechanical analysis of strain rate effect on damage of strain rate effect on damage

evolution evolution in discontinuous fibre reinforced in discontinuous fibre reinforced

compositescomposites


advantages advantages of SMCof SMC composite materialcomposite material

good strength/weight ratio manufacturing process devoted to large series high-energy dissipation with a diffuse damage.

Passengers safety

Structures lightweight

Manufacturing and productivity.

Interaction

Manufacturing ↔ mechanical behaviour

CONTEXTCONTEXT


Industrial requestsIndustrial requests

Overall mechanical behaviour prediction under dynamicOverall mechanical behaviour prediction under dynamic loading.loading.

Inaptitude of current dynamic behaviour laws for the structuresInaptitude of current dynamic behaviour laws for the structures calculation in composite materialscalculation in composite materials Insufficiency of the phenomenological approaches currently used.Insufficiency of the phenomenological approaches currently used.

Development of multi-scaleDevelopment of multi-scale approaches.approaches.

Material microstructure integrationMaterial microstructure integration

Physical description of damage mechanisms.Physical description of damage mechanisms.

CONTEXTCONTEXT


Behaviour stages

Damage threshold and accumulation

Experimental analysis (at micro and Experimental analysis (at micro and macroscopic scales) macroscopic scales)

AIMSAIMS

Visco-elastic

Visco-damage.

Behaviour modelling using a multi-scale approachBehaviour modelling using a multi-scale approach

Analysing effect in the Analysing effect in the SMC-R SMC-R damagedamage( ( ) )..

( = 10-4 – 400 s-1 )


Interrupted high-speed tensile tests.Interrupted high-speed tensile tests.

In-situIn-situ tensile tests. tensile tests.

SEM observations.SEM observations.

Damage mechanisms experimental investigationDamage mechanisms experimental investigation

MODELING COMPOSITEMODELING COMPOSITE DYNAMIC BEHAVIOURDYNAMIC BEHAVIOUR

Introduction of sIntroduction of strain rate effect in a micromechanical modeltrain rate effect in a micromechanical model

Prediction of the Prediction of the dynamicdynamic m mechanicalechanical behaviour and its interaction with behaviour and its interaction with

the composite microstructure.the composite microstructure.


MATERIALMATERIAL

SMC-R26 compositeSMC-R26 composite

Sheet Molding Compound-Random.glass E/polyester, discontinuous fibres 26%.

Hydraulic high speed tensile test Hydraulic high speed tensile test machinemachine

20 m/s, piezo-electric load cell 50 kN

Performed strain ratesPerformed strain rates

-1-1-4s400s 10

TESTS PARAMETERSTESTS PARAMETERS

EXPERIMENTAL EXPERIMENTAL INVESTIGATIONSINVESTIGATIONS


Strain rates effects on the Strain rates effects on the SMC-R mechanical SMC-R mechanical

characteristicscharacteristics

The composite macroscopic response is widely The composite macroscopic response is widely affected byaffected by

Minor variation of the anelastic slope as a function of the strain rateMinor variation of the anelastic slope as a function of the strain rate

Insensitivity of the Young’s modulus to strain rate increaseInsensitivity of the Young’s modulus to strain rate increase..

( ).

0 0.5 1 1.5 2 2.5

150 s-1124 s-123 s-110 s-10.022 s-1

0

40

80

120

160

(

MP

a)

(%)

8 103

9 103

1 104

1.1 104

1.2 104

1.3 104

1.4 104

1.5 104

10-2 10-1 100 101 102 103

E (

MP

a)

d/dt (s-1)




20

30

40

50

60

70

80

10-4 10-3 10-2 10-1 100 101 102 103

th

resh

old

(MPa

)d/dt (s-1)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

10-4 10-3 10-2 10-1 100 101 102 103

d/dt (s-1)

th

resh

old

(%)

The first non-linearity The first non-linearity Damage Damage thresholdthreshold

is considerably delayed in term of strain and is considerably delayed in term of strain and stress. stress.




80

90

100

110

120

130

140

150

160

10-4 10-3 10-2 10-1 100 101 102 103

ul

timat

e (M

Pa)

d/dt (s-1)

0

0.5

1

1.5

2

2.5

10-4 10-3 10-2 10-1 100 101 102 103

d/dt (s-1)

ul

timat

e (M

Pa)

Behaviour accommodation when increases the Behaviour accommodation when increases the strain ratestrain rate :

Steady rise of the ultimate strain (38 %)

Maximum stress increases considerably.


Damage analysisDamage analysisINTERRUPTED DYNAMIC INTERRUPTED DYNAMIC

TENSILE TESTTENSILE TEST

Correspondence between ligament and

force

Ligament (mm)

Force (N)

7 822

10,5 1059

12 1089

13,5 1314

14,5 1511

15 1635

15,5 1721

16 1842

The specimen geometry is a bar with dimension 36*6,5*2,7 mm3

The fuses material: PMMA (Poly Methyl Methacrylate) Fragile elastic behavior.

Specimen/fuseIntermediate fixing

Ligament

SMC-R specimen

Mechanical fuse


Macroscopic damage analysis Macroscopic damage analysis

Macroscopic damage vs. total strain for three strain rate values01

E

ED

D

Damage initiation is considerably delayed in terms of strain thresholdsDamage initiation is considerably delayed in terms of strain thresholds

Critical damage level : insensitive to the strain rate effect.Critical damage level : insensitive to the strain rate effect.

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 0.5 1 1.5 2

20.5 s-18 s-13 s-1D

mac

rosc

opic

(%)

D_critical

0 0.5 1 1.5 2 2.50

20

40

60

80

100

120

Interrupted high-speed tensile tests

Strain (%)

Str

ess

(MP

a)


Strain rate Strain rate increase:increase:

Delayed damage Delayed damage thresholdthreshold

Decreased damage Decreased damage growth speed.growth speed.

Microscopic analysis results Microscopic analysis results corroboratecorroborate those those obtained at the macroscopic level.obtained at the macroscopic level.

Fibre-matrix interface damage descriptionFibre-matrix interface damage description

d_micro = fv_debonded / fv d_micro = fv_debonded / fv total. total.

Overall behaviour Overall behaviour accommodationaccommodation

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 0.5 1 1.5 2

0.0002 s-18 s-120.5 s-1

d m

icro

scop

ic

(%)

_ult

Microscopic damage analysis Microscopic damage analysis


Global dGlobal damage growth in term of micro-cracks lengthamage growth in term of micro-cracks length(including matrix and interface damage)(including matrix and interface damage)

Delayed damage thresholdDelayed damage threshold Decreased damage growth speed.Decreased damage growth speed.

0 100

1 103

2 103

3 103

4 103

0.2 0.6 1 1.4 1.8

0.0002 s-18 s-120.5 s-1

L (

µm

)

(%)

Microscopic damage analysis Microscopic damage analysis

l1

l2


CONCLUSIONCONCLUSION

Strain rate effects :Strain rate effects :

Insensitivity of the material elastic properties.

Delayed damage threshold.

Decreased damage growth speed.

Accommodation of the overall behaviour leading

to an increase of the ultimate characteristics.

Integration of the experimental findings to set up physical Integration of the experimental findings to set up physical damage modelling.damage modelling.

Prediction of Prediction of elastic visco-damagedelastic visco-damaged behaviour. behaviour.

Viscosity effects Viscosity effects on the fibres-matrix on the fibres-matrix interfaces damage.interfaces damage.


THE ENDTHE END

☺☺


Experimental investigationExperimental investigationSpecimen optimised Specimen optimised geometry :geometry :

L1= 6 mm, L2 = 80 mm, L3 = 30 mm, R = 7 mm, e=3

mm

Evolution of the longitudinal stress for a test calculated at 200/sEvolution of the longitudinal stress for a test calculated at 200/s

homogeneoushomogeneous

constantconstant


Contrainte= f(Déformation) à 1m/s

0

20

40

60

80

100

120

0 0,5 1 1,5 2 2,5

déformation (%)

Cont

rain

te (M

Pa)

7mm

10,5mm

13,5mm

14,5mm

15,5mm

15mm

1ms à rupture

Experimental Experimental MethodologyMethodology

Analysis on the two scales of materialAnalysis on the two scales of material

Macroscopic analysisMacroscopic analysis Microscopic analysisMicroscopic analysis


MULTI –SCALESMULTI –SCALESMODELLINGMODELLING

MatériauMatériauHomogène Homogène EquivalentEquivalent( )

.

MatrixMatrixPolymer or Polymer or

MetallicMetallic

FibresFibresArchitecture, Architecture,

Geometry, Geometry, quantity, ...quantity, ...

damagedamageMicro discontinuitiesMicro discontinuities

Mori Tanaka’s approachMori Tanaka’s approachEschelby inclusion theory Eschelby inclusion theory

Behaviour law Visco-elastic

.

PROCESSPROCESS Probabilistic approachesProbabilistic approachesWeibull, Monte Carlo, ...Weibull, Monte Carlo, ...

Local criterionLocal criterion

Pr =1 - exp[(0202m

(0 0 m) = f ( ).

Experimental investigationExperimental investigationInterrupted dynamic testsInterrupted dynamic testsSEM and ultrasonic testsSEM and ultrasonic tests

Damage growth D=f (Damage growth D=f (

Composites Testing and Model Identification Châlons-en-Champagne, 28 January 2003 Z. JENDLI*, J....

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Transcript of Composites Testing and Model Identification Châlons-en-Champagne, 28 January 2003 Z. JENDLI*, J....