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Tech Hour

Tenue au feu des composites

Etude des comportements thermique et mécanique de composites aéronautiques soumis au feu

27/02/2018

ORGANISATEURS TECH HOUR TENUE AU FEU DES COMPOSITES

TENUE AU FEU DES COMPOSITES

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FORMAT ET DÉROULÉ

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Étude des comportements thermique et mécanique de composites aéronautiques soumis

au feu

B. VIEILLE1, A. COPPALLE2, Y. CARPIER1, E. SCHUHLER2, F. BARBE1

1 Groupe de Physique des Matériaux, UMR 6634 CNRS2 CORIA, UMR 6614 CNRS

Université et INSA Rouen, avenue de l’Université, 76801 St Etienne du Rouvray, France

[email protected]@coria.fr

Tech’Hour NAE, 27 février 2018

Introduction ConclusionsFire exposure Mechanical behaviorGeneralities Numerical simulation

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IntroductionIntroduction ConclusionsFire exposure Mechanical behaviorGeneralities Numerical simulation

Competition fuels innovation: what materials for tomorrow’s aircrafts?

Introduction

3

A few examples of TP-based composites parts in aeronautics

What about high-temperatureapplications ?

[Maruszczak, 2007]



Physical and chemical decomposition mechanisms [Guillaume, 2013]

4

Case of a thermosetting producing char Case of a thermoplastic


Fire

Crack

Pore

Fibre Fibre + matrixDelamination

Pyrolysis front

Schematic of the reaction mechanisms in fiber-reinforced polymer composites subjected to fire

5

6

Critical case: Nacelle’s fire of an aircraft’s engine[Bartlett, 2001]

Very few studies on the behavior (thermal degradation, mechanical) of TP-basedcomposites after or during fire exposure[Sorathia, 1993][Mouritz, 2006]

Collaboration

Fire + Mechanics: a multi-physics and multi-scales workComparative study between PPS (TP) and Epoxy (TS)-based composites

Project DECOLLEfunded by the institute CARNOT ESP (Energy & Propulsion Systems)


Singapour Airlines, juin 2016

Orenair, février 2016

7


Composite materials behaviour under fire conditions + mech. loading

GPM (Groupe de Physique des Matériaux)TP-based composite laminates for high-temperature applications

Fatigue, impact, damage tolerance, fire behavior PhD of Yann Carpier

CORIA (COmplexe de Recherche Interprofessionnel en Aérothermochimie)European Project AircraftFire (http://www.aircraftfire.eu)Projet Surface, collaboration with Airbus

Interaction fire/composite structures PhD of Eliot Schuhler

Question:What about the interaction heat / fire / physical-chemical-mechanicalbehavior ?

8


Introduction

9


Introduction

10


Introduction

11


Introduction

Presentation outlineGeneralities Aeronautics context What materials ? Experimental procedure

Fire exposure Cone calorimeter

ATG + Lamp furnacePropane-flame burner

Mechanical behavior under fire exposurePost-fire testingCombined testing

Numerical simulationCorrelation between temperature distribution and matrix thermal degradation

Conclusions and perspectives12


Generalities Aeronautics context What materials ? Experimental procedure







ContextThermoplastics (TP) composites: a promising material for aeronautics

Parts of aircraft engine’s nacelle : service temperature = 120°CProject TOUPIE (2006-2009)

Bulhead14

High-performance thermoplastic resins (e.g. PEEK, PPS,…)

Pros

Recyclable

Cons

Tg lower than TS

Reversible process Softens with heat

Low-cost processes possible : Welding, Stamping, …

Potential poor adhesion at the fiber/matrix interface

Shorter autoclave cycle times Lower mechanical properties

Good fire resistance

Impact Tolerance

Fairing


What materials ?

15

Are TP composites eligible in aeronautics : weight / price / certification ?

Materials 7 plies pre-preg laminates Matrix :

PolyPhenylene Sulfide PPS (Ticona) 5 HS carbon fibers satin weave

(Toray T300 3K 5HS) Fibers volume fraction 50%

Stacking sequences : Quasi-isotropic : fiber-dominated responseAngle-ply : matrix-dominated response

Main Objective Influence of fire exposure on the behavior (tensile and compressive) of

C/PPS woven-ply laminates ?

Service temperature = 120° >/

Warp Weft

Tg (°C) Crystallinity (%)

C/PPS 107,07 ± 0,82 26,7 ± 1,76

[Blond, 2011]Matrix-richareas


Experimental procedure

16

Fire exposure tests: cone calorimeterHeat flux: 20 – 30 – 40 – 50 kW/m² (anisothermal)Exposure time: 1-2-5 minLamp furnace (isothermal)Thermogravimetric analysis

Post-fire mechanical testing:Boeing anti-buckling fixture


Conecalorimeter

Specimen

[Rivallant, 2014]

Tensile tests specimens

Compressive tests specimens

17


Experimental procedureFire exposure: study at different scales

Large scale pool fire

‘Aircraft fire’ burner

Propane

Developed standard test

Kerosene

Propane

18


Experimental procedureFire exposure: experimental set-up

Premixed burner (propane or propylene)Sample size :5 cm

Features:

Parameter Setting:Heat flux at the stagnation point: 100 to 200kW/m2Burner exit temperature : 830 to 1172 °C

Diagnostics during tests:- Weight sensor: Mass Loss Rate MLRThermocouplesVideo camera

- IR camera (backside)- Flow velocity (PIV)

‘Aircraft fire’ burner

The heat flux on the sample:- Measured with a fluxmeter

19


Experimental procedureFire exposure: Propane (Aircraft Fire) burner

Same heat fluxes and temperature at the material surface Reduced cost (sample 4x4 cm2) More information: not only pass/fail test Burning rate (HRR) proportional to MLR Pyrolysis time, Peak of MLR, Burning time, mean burning time, etc… Larger number of tests More working parameters (Heat fluxes, Pressure, Load, thickness…








GPM Eircap

Fire exposure: cone calorimeter

21

Comparison of changes in temperature during fire-exposure [Vieille et al, 2015]

High heat fluxes (30-40-50kW/m²) above the pyrolysis range

Composite degradation leads to changes in thermal conduction: insulation layer =char formation ?


Fire-exposed surface Unexposed surface

-230°C

-86°C


22

TGA under N2 and O2 (10 K/ min at a flow rate of 35 ml/ min)

Thermal decomposition kinetics of C/PPS [Vieille et al, 2014]

Under N2: onset of pyrolysis (Td 500°C)

Under N2: significant mass loss occurs (about 20%) between 500 and 600°C

Under O2 : two-step decomposition (carbon fibers degradation)


Onset of carbonfibers degradation

= °

Thermal decomposition kinetics of C/PPS

Analysis of decomposition gases + TGA Infra-Red coupled

Physico-chemical mechanisms

Fire exposure: cone calorimeterIntroduction ConclusionsFire exposure Mechanical behaviorGeneralities Numerical simulation

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Changes in macroscopic fire-induced damaged areas [Vieille et al, 2016]



20kW/m² 30kW/m² 40kW/m² 50kW/m²

Fire

-exp

osed

sur

face

Une

xpos

ed s

urfa

ce


25

What about the fire-induced damage mechanisms ? [Vieille et al, 2016] Fi

re-e

xpos

ed s

urfa

ceU

nexp

osed

sur

face

Estimation of delaminated areas by C-scan inspections


20kW/m² 30kW/m² 40kW/m² 50kW/m²


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What about the fire-induced damage mechanisms ?

[Vieille et al, 2016]


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Changes in macroscopic fire-induced damaged areas [Vieille et al, 2016]



20kW/m² 30kW/m² 40kW/m² 50kW/m²

Extensive delamination

Heat flux

Fire-exposed surface

Unexposed surface2 mm

Intralaminarfiber/matrix debonding


28

Changes in laminates micro- and meso-structures: SEM Observations


Virgin 20kW/m² 30kW/m² 40kW/m² 50kW/m²


29

SEM observations of carbon fibres surface in C/PPS laminates (40kW/m²)

Redistribution of melted PPS matrix within the carbon fibers network: maintains a partial cohesion [Vieille et al, 2015]

Protection of the carbon fibres against oxidation


Fire exposure: lamp furnace

30

Isothermal behavior (lamp furnace)

Objective: degradation law E=f(T)what is applied to the materials?


0

2

4

6

8

10

0

50

100

150

200

250

0 200 400 600 800

Force (kN)

Tem

péra

ture

(°C)

Temps (s)

Détermination E référence

Temps nécessaire à l’équilibre thermique

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Isothermal behavior (lamp furnace)

Objective: degradation law E=f(T) T<Td (=450°C): high degree of retention of longitudinal stiffnessWhat about E at T>Td ?


0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 100 200 300 400

E/E 0

moy

en

Température (°C)

TraverseExtensoTgTm


32

Modelling of macroscopic thermal degradation [Mahieux, 2002]


Themal degradation law E=f(T)

= − exp −

+ exp −

Extension to the case of fire-exposure: thermal decomposition= failure of chains primary links

= − exp − + ( − ) exp − + é é exp −


33


Results: comparaison between C/Epoxy and C/PPS composites

Average (a) residual mass, (b) mass loss rate (MLR)

Backside temperature: (a) carbon/epoxy samples, (b) carbon/PPS samples

Fire exposure: flame burner

Propane burner

[PhD E. Schuhler]

Char + Matrice 20% Fibres 40%

Porosité 40%

Flamme 1mm

Fire exposure: flame burnerIntroduction ConclusionsFire exposure Mechanical behaviorGeneralities Numerical simulation

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Changes in macroscopic fire-induced damaged areas

[PhD E. Schuhler]

C/Epoxy106kW/m²

90 secondes


35

Changes in macroscopic fire-induced (propane burner) damaged areas

1mm

Flamme

Char + Matrice 7% Fibres 16%

Porosité 77% C/PPS106kW/m²

90 secondes


36

An important point: the flow velocity of the impinging hot jet- Convective heat exchange between the impinging jet and the composite- Analysis of the radiative flux contribution- Important to know the flow velocity to provide up-scale results

H

Particle Image Velocimetry (PIV)


37

Results: the flow velocity in the impinging hot jet

UV

U V


38

Work in progress: kerozene burner at laboratory scale Same strategy and same advantages as for the propane burner

Same heat fluxes and temperature at the material surface Reduced cost (sample 4x4 cm2) Detailed measurements Larger number of tests More working parameters (Heat fluxes, Pressure, Load, thickness…

standard testslaboratory tests

However with a radiative flux more important equivalent to the nextgen burner: 100-200kW/m2 – 1100°C


Fire exposureCone calorimeterATG + Lamp furnacePropane-flame burner





Post-fire testing at high temperature

40

Influence of prior fire conditions on tensile behaviors in service (120°C)


Quasi-isotropic [+/-45°]7

-35%-30%

-47%

-50%


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Influence of prior fire conditions on compressive behavior in service (120°C)

Fire conditions: 20 – 30 – 40 – 50 kW/m² for 2 minQuasi-isotropic laminates

Similar evolution of tensile and compressive properties

More detrimental -80% vs -30% on strength-60% vs -35% on stiffness


-80%

-60%


42

What about the damage mechanisms under compressive loading ?


20kW/m² 30kW/m² 40kW/m² 50kW/m²


43



20kW/m² 30kW/m² 40kW/m² 50kW/m²


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Microscopic buckling at woven-ply level

Delamination and global plastic buckling at laminates level



45

What about the damage mechanisms under compressive loading?

In-situ analysis of damage mechanisms (Acoustic Emission) Localization, acoustic signature, classification Compression + heat flux (50kW/m²)


Forc

e (k

N)

Time (s)

Class 1 : Thermal decomposition

Class 2 :Matrix cracking

NoesisClassification

Mechanical response

Class 3 :Delamination

Combined testing

46

Influence of critical service conditions: loading + calorimeter Project CARNOT ESP DECOLLE

Développement d’une plateforme d’Etude du COmportement mécanique au feu de composites thermopLastiques pour L’aéronautiquE


Mac

hine

hyd

raul

ique

d’e

ssai

s m

écan

ique

s

Hotte extraction fumées

Calorimètre régulé

Montage de fixation

éprouvette

Combined testing

47

Influence of critical service conditions: tension + calorimeter (40 kW/m²)


Combined testing

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Influence of critical service conditions: compression + calorimeter


Combined testing

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Combined testing

50



Influence of creep stress (q=50 kW/m²)

Influence of thermal flux (σ=17,4 Mpa)

Strong competition between mechanical and thermal mechanisms (compression, thermal expansion, pyrolysis…)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0 500 1000 1500 2000 2500Lo

ngitu

dina

l str

ain

(%)

Time (s)

30 kW/m²40 kW/m²50 kW/m²

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0 500 1000 1500 2000

Long

itudi

nal s

trai

n (%

)

Time (s)

σ=0.25 σuσ=0.50 σuσ=0.75 σu

Combined testingIntroduction ConclusionsFire exposure Mechanical behaviorGeneralities Numerical simulation

Influence of critical service conditions: compression creep + calorimeter

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52

Exposed face Opposed face



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= +

( ) =( )

= 1 −

= 1 −

Strong thermal / mechanical coupling

What about the agression by an

impacting flame?

Technologicalbottle-neck

50kW/m²…. Far fromcritical conditions

Side view



54


Influence of critical service conditions: compression + fire-exposure?

Key point for plane manufacturers

Development of adapted characterization means

Two scales:

Industrial : kerosen flame burnerNextgen certified ISO/FAA

Temperature = 1100°C 80°CHeat flux = 116 10 kW/m² very complex mechanical

loading

Laboratory : kerosen or propane flame burnerTemperature = 1150°CHeat flux = 116 -200kW/m² possibility of mechanical loading

55

Simulation of thermal conduction

57

Correlation between temp. distribution and matrix thermal degradation


0

50

100

150

200

250

300

350

400

450

0 50 100 150 200Te

mpé

ratu

re (°

C)

Temps (s)

Face avant (exp.)Face avant (simu.)Face arrière (exp)Face arrière (simu.)

Simulation of thermal conduction

58

Correlation between temp. distribution and matrix thermal degradation


Thermally-degraded area

Pyrolisis range for C/PPS

Simulation of thermo-mechanical resp.

59

2-Dimensional meso-macro F.E. analysis (Z.SET)

Two material phases are considered: matrix and fibers

Thermally-induced matrix degradation: Stiffness is decreased to zero and thermal conductivity is increased to very high values

Thermal problem: transient thermoelastic + boundary value problem

= ( ,T).div( ( )), ∀ ∈ Ω

where ( ,T) )= ( ,T),T . ( ,T)

is the diffusivity coefficient .

with ( ,T) conductivity coefficient,T volumic density

( ,T) thermal heat capacity

Heat transfer is governed by the Fourier law:

= − ( ,T) ( ) where heat flux imposed at the surface


Quasi-isotropic laminates subjected to 30kW/m² for 2 min

Preliminary approach : 10000 tetrahedral elements

Weak coupling between thermal and mechanical phenomena

Matrix-richareas

Laminates’ geometric model

Simulation of thermo-mechanical resp.Introduction ConclusionsFire exposure Mechanical behaviorGeneralities Numerical simulation


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Simulation of thermo-mechanical resp.

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2D Temperature distribution and matrix degradation

Von Mises effective stress : stress concentration at the crimp


Laminates’ geometric model Meshing (154399 triangular elements)




Post-fire behavior at high-temperatureTensile testsCompressive tests




Conclusions and perspectives

63


Towards the certification of TP composites for aeronautics applications

What about the worst case scenario? Development of an

experimental platform

Normalized flame :

Temperature =1100°C 80°CThermal flux =116 10 kW/m²

Numerical modelling : phase transition growth of porosities Propane or

kerozen burner

Thanks for your attention !Questions ?

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