Thermo-Chemical and Mechanical Coupled Analysis of

G. PINAUD

ASTRIUM SPACE TRANSPORTATION, F-33165 St. Médard-en-Jalles, France

Thermo-chemical and mechanical coupled analysis of swelling charring and ablative

materials for re-entry application

5th Ablation Workshop, Feb. 28th – Mar. 1st 2012, Lexington, Kentucky

G. Pinaud - 5th Ablation Workshop, Feb. 28th – Mar. 1st 2012, Lexington, Kentucky - 2

OUTLINE

Outline

AstriumNorcoat Liege

Phenomena overview and model

Experimental validationNumerical simulation

ConclusionAstrium

Norcoat Liege

Phenomena overviewAerothermodynamicsConductive heat transferPyrolysisAblationSwelling

Experimental validation

Numerical simulation

Conclusions & perspectives


AstriumAstrium: part of EADS, a global leader in aerospace and defence

Astrium

Norcoat LiegePhenomena overview and modelExperimental validation

Numerical simulationConclusionAstrium Space

TransportationThe European

prime contractorfor civil and

military spacetransportationand manned

space activities

RE-ENTRY SYSTEM &

TECHNOLOGY DEPARTMENT

ISS servicing

Thermal protection systems for

interplanetary probes

Interplanetary exploration


A material: Norcoat LiegeAstrium

Norcoat LiegePhenomena overview and modelExperimental validationHarvest of cork bark

From tree "Quercus suber"to

space

Stockpiling

drying of bark

Grinding

in granules

Mixing- Curing

Phenolic Resin Additives

NL sheets

NL molding

Back cover of ARD

Beagle2 Heat-shield


PHENOMENA OVERVIEW & MODEL

Close up view on a side cut of the heat shield

Astrium

Norcoat LiegePhenomena overview and modelExperimental validation

Numerical simulationConclusion


Aero-shell

Free stream flow

Boundary layer

Thermal protection material

Astrium

Norcoat LiegePhenomena overview and model:Side view


Conclusion



Free stream flow

Boundary layer

Convection

Radiation

Surface shear

Computation of the viscous boundary layer heat transfer:

convective heat fluxshock radiationwall shear stressequilibrium and non equilibrium

air chemistry

Astrium

Norcoat LiegePhenomena overview and model:Aerothermodynamic


Conclusion


Internal Convection Mutual Radiation


Boundary layer

Hea

t con

duct

ion

Computation of the conductive heat transfer in the material:

standard Fourier's lawmaterial state (density) default

linear dependency

Astrium

Norcoat LiegePhenomena overview and model:Conductive heat transferExperimental validation

Numerical simulation

Conclusion


[ ]cvv λλαλλ −−=

cv

v

ρρρρα

−−

=


Boundary layer

Under heating, organic material compounds start to degrade:

kinetics of the pyrolysis approached by multiple Arrhenius law

momentum conservation of the gaseous products follows Darcy's law for porous media ( and perfect gas law)

Astrium

Norcoat LiegePhenomena overview and model:Pyrolysis (1/2)


Conclusion


Decomposition gas blowing

Dec

ompo

sitio

n

Virgin

Pyrolysis

Charred

PKm Pg ∇−=&

T E M P E R A T U R E : [K ]

MA

SS

LOS

S:[

%]

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

T G A : 5 K /m in2 A rrh e n iu s la w s: 5 K /m inT G A 2 0 K /s2 A rrh e n iu s la w 2 0 K /sT G A : 5 0 K /s2 A rrh e n iu s la w 5 0 K /s

( ) [ ] ( ) RTE

Ni

Ncv

Nvii

iiii eA −−− −−= χρρρχ 111&

∑=

Δ−=

Narrhii

v

i

v

t,1

.1)( χρρ

ρρ


Enthalpy of pyrolysis gas supposed at thermal and chemical equilibrium with charred material

Extrapolation at low temperature to keep constant endothermal heat of pyrolysis

Using quasi-steady state assumption for pyrolysis gas advective heat term

Astrium

Norcoat LiegePhenomena overview and model:Pyrolysis (2/2)


Conclusion


Chemica

l equ

ilibriu

m regim

e

Extrapolation

at constant ΔHpyroCV

NLCNLVgazpyro

NLgazpyro

THTHPTHPTH

THPTHPTH

CV

ρρρρ

−

−−=Δ

−=Δ

)()(),(),(

)(),(),(

)),((),(

PTHmt

PTHgaz

ggazg

&∇<<∂

∂ρ


Boundary layer

Surface material is removed by:heterogeneous chemical reactions

(oxydation with temperature dependent rate)

Heat of ablation taken into account

mechanical spalation under shear stress

Astrium

Norcoat LiegePhenomena overview and model:Ablation


Conclusion


Virgin

Charred

Original surface

Heatshield surface

Ablation

)( wcc Tfm =&

)( wcc THH Δ=Δ

),( wwmm Tfm τ=&


Boundary layer

Volume expansion generated by:in-depth structural and chemical

decomposition initiated by heat transfer

internal pyrolysis gas product pressure in cork cell

Prismatic cork cells membranes are made of 2 main molecules:

SuberinLignin

responsible for flexbility and rigidity

Astrium

Norcoat LiegePhenomena overview and model:Swell (1/3 )


Conclusion


Virgin

Charred Original surface

Heatshield surface

Swelling

Temperature increase triggers mass

exchange between the 2 structural molecules

cells wall become more brittle


Astrium

Norcoat LiegePhenomena overview and model:Swell (2/3 )


Conclusion


At higher temperature:cell membrane thickness becomes

thinner (mass loss)membranes start to stretchmembranes break-off

Considering:Volume phenomenonThermo-chemically decomposition linked mechanical expansionnon-elastic expansion

choice of an Arrhenius kind law for the strain rate evolution:

Temperature °C

1500

2000

2500

( ) [ ] ( ) RTE

Ns

Ncv

Nvst

ssss e−−− −−∝∂ χρρρε 111


Astrium

Norcoat LiegePhenomena overview and model:Swell (3/3)


Conclusion


Swelling numerically treated by a staggered coupling scheme involving :

Amaryllis for the thermal and ablative response

Mecano for the mechanical response

Supervisor as the interface and the synchronisation of the chore modules

Need to implement A.L.E (arbitrary Lagrangian Eulerian ) solution in Mecano to take into account for the mesh deformation (due to ablation) sent by AmaryllisT,ρ, ,P,X exchange at every time step and are used to solve for the stress and strain

( )

( )⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

+−Δ−=

=∂∂

=

=+

LagrangianEulerian,,,

, and

0

tot

,

iijijij

klijkliji

i

ijij

PTFT

TCxPf

f

χραδεε

ερτ

τ

iχ


EXPERIMENTAL VALIDATIONObservation of swelling under various environment

Radiative furnaceFlat plate configurationMax cold wall heat flux: ~500 kw/m2

Duration : ~ 80 s Inner face thermocouple

Inductive plasma torch: CometeStagnation point configurationMax cold wall heat flux 800 kW/m2Internal thermocouple

Arcjet plasma: SimounAir/CO2 atmosphereMax cold wall heat flux 1.8 MW/m2Duration: ~60 sThermocouple plugsLaser recession

Astrium

Norcoat LiegePhenomena overview and model:Experimental validation



TIME: [s]

WA

LLD

ISP

LAC

EM

EN

T:[%

]

0 100 200 300 400 5000

10

20

30

40

50

Measures

Swell timeline

EXPERIMENTAL VALIDATIONRadiative furnace

Perspective view of the specimen during exposure to radiative heat flux

Astrium



Initial thickness

T=0 s T=22 s T=74 s T=100 s

Post-test direct measurements

Specimen sheet before test

Specimen sheet after test

Final thickness


EXPERIMENTAL VALIDATIONComete inductive plasma torch

Astrium



TIME: [s]

WA

LLD

ISP

LAC

EM

EN

T:[%

]

0 50 100 150 200 250 300 350 400 450 500-10

-5

0

5

10

15

20

Measures

T=0 s T=150 sT=45 s

Heat flux ~800 kW/m2

Specimen before test

Specimen after test

Comparison of surface scanned geometry

before/after test

Post-test direct axial

measurements

Strong lagged swelling effect on thickness

Recession

Expansion


EXPERIMENTAL VALIDATIONSimoun arc-jet plasma test

Astrium



Specimen before test Specimen after test

Cross section:

Charred, pyrolysis and virgin layer

Top view of the sample at thermocouple plug

location

T IM E : [s]

WA

LLD

ISP

LAC

EM

EN

T:[%

]

0 50 100 150 200

-70

-60

-50

-40

-30

-20

-10

0

10

M easures Laser AM easures Laser B

Pla

sma

shut

dow

n

S atu

ratio

nLa

ser

Recession

Expansion

Laser tracked surface motion

Due to high convective exchange coefficient, recession is dominating expansion


NUMERICAL SIMULATIONSurface kinetic rebuilding including

Surface chemical recessionSurface mechanical recessionVolume swelling

Astrium



TIME:[s]

WA

LLD

ISP

LAC

EM

EN

T:[m

]

0 50 100 150 200-0.012

-0.01

-0.008

-0.006

-0.004

-0.002

0

0.002

MeasuresLaserAMeasuresLaserBSimulationP

lasm

ash

utdo

wn

Satu

ratio

nLa

ser

TIME:[s]

WA

LLD

ISP

LAC

EM

EN

T:[m

]

0 50 100 150 200 250 300 350 400 450 500-0.002

-0.0015

-0.001

-0.0005

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

MeasuresSimulation

TIME:[s]

WA

LLD

ISP

LAC

EM

EN

T:[m

]

0 100 200 300 400

0

0.0005

0.001

0.0015

0.002

0.0025

MeasuresSimulation

Optimization of the ablation law, and the swelling Arrhenius law parameters to fit the surface motion, density gradient and thermal thermocouple history


CONCLUSIONNew development in Amaryllis and Mecano were successfully applied to model the behavior of a cork based Thermal Protection Material including:

conductive heat transferchemical decomposition (pyrolysis) kinetics and energychemical and mechanical ablationthermally-generated volume swelling

For cork based material, ablation and swelling cannot be dissociated in model rebuilding. Lagged effects of swelling must be considered for checking the reliability of post-test direct measurements

Samcef modules enable full coupling between thermal, thermo-chemical and mechanical response

various industrial issues when coupled thermal and mechanical loads play an important rule could be treated

Astrium




CONCLUSION & FUTURE

Future model will focus on 2D orthotropic swelling material properties

Design a specific instrumentation for in-depth characterization of swelling phenomena

Astrium



Temperature field Density field

Documents

Thermo-Chemical and Mechanical Coupled Analysis of