COMPARISON OF FLAMMABILITY AND FIRE · PDF file11.03.2015 · comparison of flammability and fire resistance of carbon fiber reinforced thermoset and thermoplastic composite materials

COMPARISON OF FLAMMABILITY AND FIRE

RESISTANCE OF CARBON FIBER REINFORCED

THERMOSET AND THERMOPLASTIC COMPOSITE

MATERIALS

Jianping Zhang , Michael Delichatsios , Talal Fateh,

B. Karlsson

FireSERT , University of ULSTER

FireSERT

FIRE SAFETY ENGINEERING RESEARCH AND TECHNOLOGY

2

Key research equipments (1)

Large-scale

20MW Cone calorimeter Large scale fire

resistance furnace

(3×3×4m)


Intermediate-scale (Cone, UFA, SBI, ISO room, etc)

Cone calorimeter Universal flammability

apparatus (infra-red)

Universal Flammability

Apparatus (UFA)


Micro- and small- scale for milligram samples (thermal and toxicity

analysis)

mg samples TGA, DSC, MDSC,

FTIR, ATR, etc

Thermal degradation,

specific heat, heat of

pyrolysis, toxicity,

residue strength

Inputs for modelling

large-scale tests

Overall design

Sampling points

Unheated distance 205mm

(based on ATS furnaces – 28” long with 24” heated length)

FireSERT

FIRE dynamics and MATERIALS LAB ( FML)

UNIQUE: FROM NANOSIZE TO 20 MW FIRES

NANOCOMPOSITES

(XRD, TEM, SEM)

INTRINSIC

FLAMM.

PROPERTIES

(TGA, FTIR, MDSC,

UNIV. FLAMM.

APPARATUS,)

LARGE SCALE

(20MW)

MATERIAL AND

CFD MODELLING

FOUR PHD STUDENTS, TWO POSTDOCS AND

THREE ENGINEERS

Major projects: FIRENET (EU) FAÇADE FIRES (EPSRC, Japan)

PREDFIRE NANO (EU) Industrial R&D , HFFRs, AIRCRAFTFIRES

Contact: [email protected]

AircraftFire Project Fire risks assessment and increase of passenger survivability

FP7 EASN Project - EU Grant Agreement n° 265612

2011 - 2014

www.aircraftfire.eu

The AircraftFire project

Presentation and Main Results

Characterisation of the fire performance of composite materials (physical/chemical/thermal flammability and burning

properties) for aircraft design and fire safety analysis (modelling)

Recommendations for efficient industrial technologies

Modelling of the cabin fire growth and passenger evacuation

Development and validation physical models correlated to the evolution of the fire scenarios,

AcF Research Objective

March 26th, 2014

Througlife,

Papenburg

10

Evaluation of fire threats and passenger survivability in new generation of aircrafts

Aluminium is substituted by flammable composites for decorative panels, hull, wing, cowling, structure, etc.

The fire threat can significantly increase due to… The flammability of materials in high temperature environment The toxicity of the smokes The total aircraft fuel load

With impact on the fire development and the passenger evacuation

Higher energy supply for avionics and electronics fire risks (ignition,…)

11

CAA, Airbus, EADS March 26th, 2014

Througlife,

Papenburg

The fire threat in new generation of aircrafts

12

Outline

Introduction

Testing for carbon fiber composite materials

Comprehensive flammability/toxicity evaluation

Flammability and toxicity parameters

Detailed flammability properties for modeling

Pyrolysis model

Back surface temperature for fire resistance

Towards large scale modelling

Conclusions

12

Introduction

Manufacturers of polymers or flame retardants or composites are constantly looking for improvements in their formulations for improving people safety and property protection.

Flame retardants or intumescent paints or carbon fibers are commonly used to prevent or delay the ignition of polymers and to reduce the intensity of the fire and prevent burn through. Unfortunately, they may also introduce new hazards such as an increase in the toxicity of combustion gases or in smoke production and, over longer periods, create environmental and toxicological hazards owing to disposal (e.g., brominated FRs).

Existing test methods (such as LOI, UL-94, burn through tests ) assess the ignition and flame spread of a material without considering any toxicity effects

Also, most of these methods ranks materials in groups thus does not differentiate the material behaviour inside a given rank

13

Introduction (ctd)

This paper presents a simple method to characterize the fire performance and toxicity of polymers using parameters deduced from micro (TGA) and small-scale (Cone calorimeter) tests, namely

Fire spread and growth parameter

Smoke parameter

Toxicity parameter

Mass residue

Heat release rate for thermally thin materials

14

Literature review (Numerical modelling)

Two types of methods have been developed for the prediction of fire spread due to pyrolysis/burning of combustible materials: Firstly, purely thermal models for upward flame spread have

been used, with input data from the Cone Calorimeter, to predict flame spread in large scale and the resulting heat release rate.

Secondly, more fundamental work has been carried out using CFD (computational fluid dynamics) models and pyrolysis models to predict fire growth.

15


16


It is desirable and cost effective to be able to assess the flammability of materials by means of small scale-tests before new formulations progress in large-scale production of products made out of these materials;

This can be achieved by combining experiments with CFD modelling; but performing CFD modelling including deducing all the required material properties is very time consuming;

In this work, we developed, based on measurements, a set of fundamental parameters that can characterize and compare the flammability and toxicity of materials

17

Key flammability properties 2

These properties are determined using a combination of: TGA

TGA-FTIR

MDSC

Cone calorimeter

Universal flammability apparatus (UFA)

Two stage tube furnace

A numerical model describing the pyrolysis of materials that form char upon degradation


Fire spread and growth parameter

Smoke parameter

Toxicity parameter

Mass residue

Heat release rate for thermally thin materials

19


Fire spread and growth parameter = square of peak heat release rate divided by time to ignition

This parameter is proportional to FIGRA as measured in SBI

20

ignt

PHRR 2

ignSBIt

PHRR

t

QFIGRA

2

max

max


Smoke parameter = smoke yield / effective heat of combustion

The product of the smoke parameter and the fire growth parameter is proportional to the SMOGRA measured in SBI

21

𝑦𝑠/∆𝐻𝑐

c

s

c

s

ignH

y

t

Q

H

y

t

PHRRSMOGRA

max

max

2

~~


Toxicity parameter = the ratio of the effective heat of combustion of the fire retarded polymer to the effective heat of combustion of the neat polymer.

In the case where the polymer weight percentage is different for different formulations, the following should be used

22

polymerneatc

polymerFRc

H

H

_,

_,1

1 −∆𝐻𝑐 𝑜𝑓 𝐹𝑅 𝑓𝑜𝑟𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛

∆𝐻𝑐 𝑜𝑓 𝒏𝒐𝒏 𝐹𝑅 𝑓𝑜𝑟𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛×

𝑤𝑡% 𝑜𝑓 𝑝𝑜𝑙𝑦𝑚𝑒𝑟 𝑖𝑛 𝒏𝒐𝒏 𝐹𝑅 𝑓𝑜𝑟𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛𝐹𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝑚𝑎𝑠𝑠 𝑝𝑦𝑟𝑜𝑙𝑦𝑠𝑒𝑑 𝑖𝑛 𝒏𝒐𝒏 𝐹𝑅 𝑓𝑜𝑟𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛

𝑤𝑡% 𝑜𝑓 𝑝𝑜𝑙𝑦𝑚𝑒𝑟 𝑖𝑛 𝐹𝑅 𝑓𝑜𝑟𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛𝐹𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝑚𝑎𝑠𝑠 𝑝𝑦𝑟𝑜𝑙𝑦𝑠𝑒𝑑 𝑖𝑛 𝐹𝑅 𝑓𝑜𝑟𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛


Mass residue = how much of the initial material is left behind as residue after combustion.

This is not significant for fire spread and growth but it can

provide the amount of total fuel load in a fully developed fire.

Values for this parameter are not presented in this paper but are included in other publications for the materials examined in this work.

23


Heat release rate for thermally thin materials = maximum mass loss rate in Nitrogen (appropriately normalized by the initial mass and heating rate) In TGA multiplied by the heat of combustion in the Cone Calorimeter

24

rateHeatingHdt

dm

mc

initial

/1

max

Materials and experiments

Experiments were performed in a Cone Calorimeter for sample exposed to an external heat flux of 50kW/m2.

In parallel, experiments of the same formulations were performed in TGA /FTIR/ATR/ tube furnace but only results from TGA at 10 °C/min in Nitrogen are employed in this paper.

We have established the variability (uncertainty) in our apparatus to be a number between 3-5% for individual measurements.

25


26

ACF1, type 1: epoxy (thermoset) +carbon fiber(~70%)

ACF2 , type 2 :epoxy ( thermoset) +carbon fiber(~70%)

ACF6 PEEK ( thermoplastic) +carbon fiber (~70%)

ACF7 , type 3 : epoxy (thermoset) +carbon fiber (~70%)

NOTE : exact composition has not been provided being

prorietary

GLOBAL FLAMMABILITY PARAMETERS

FOR THE COMPOSITE MATERIALS

27

FLAME SPREAD AND SMOKE

28

ACF7

29


30

Materials PHHR tig

Fire

growth

parameter

smoke

yield

CO

yield

CO2

yield THRR TML HoC

Initial

mass

Final

mass Residu

e

Units

kW/m2 s kW2/m4-s g/g g/g g/g MJ/m2 g kJ/g g/kJ g g %

ACF1-1 194.8 49 774.43 0.0627 0.03690 1.263 33.75 18.66 18.09 0.00347 64.1 45.44 70.89

ACF1-2 194.1 49 768.87 0.0652 0.04590 1.277 33.71 17.86 18.87 0.00345 64.1 46.24 72.14

ACF1-3 213.2 47 967.11 0.0762 0.04560 1.337 33.38 16.9 19.75 0.00386 64.4 47.50 73.76

ACF1-

AVE 200.7 48.333 836.80 0.0680 0.04280 1.292 33.61 17.807 18.90 0.00359 64.2 46.39 72.26

ACF2-1 314 65 1516.86 0.0878 0.05920 1.469 28.51 16.52 17.26 0.00509 60.9 44.38 72.87

ACF2-2 355.1 73 1727.34 0.0844 0.06140 1.52 28.85 16.36 17.63 0.00479 60.8 44.39 73.07

ACF2-

AVE 334.55 69 1622.10 0.0861 0.06030 1.4945 28.68 16.44 17.45 0.00494 60.8 44.39 72.97

ACF6-1 103.2 121 88.02 0.0451 0.04940 1.383 28.09 15.71 17.88 0.00252 63.4 47.69 75.22

ACF6-2 128.4 128 128.80 0.0483 0.04280 1.39 31.15 17.46 17.84 0.00271 66.7 49.26 73.83

ACF6-

AVE 115.8 124.5 108.41 0.0467 0.0461 1.3865 29.62 16.585 17.86 0.0026148 65.06 48.48 74.53

ACF7-1 336.8 66 1718.70 0.1705 0.06420 1.69 34.66 16 21.66 0.00787 61.0 45.00 73.77

ACF7-2 352.5 63 1972.32 0.1448 0.05030 1.75 30.99 14.12 21.95 0.00660 61.0 46.88 76.85

ACF7-

AVE 344.65 64.5 1845.51 0.1577 0.05725 1.72 32.825 15.06 21.81 0.00723414 61 45.94 75.31


31

ys (g/g)

0.00 0.05 0.10 0.15 0.20

PH

RR

2/t

ig

(k

W2/m

4-s

)

10

100

1000

10000

ACF1

ACF2

ACF6

ACF7

ACF1-Pprime

ACF3

ACF9-1

ACF9-2

ACF1 (2mm)

Flame spread parameter versus smoke yield


32

ys/HoC (g/kJ)

0.000 0.002 0.004 0.006 0.008 0.010

PH

RR

2/t

ig

(k

W2/m

4-s

)

10

100

1000

10000

ACF1

ACF2

ACF6

ACF7

ACF1-Pprime

ACF3

ACF9-1

ACF9-2

ACF1 (2mm)

Flame spread parameter versus smoke parameter

COMPARISON WITH OTHER

POLYMERS

33

THERMALLY THIN PARAMETER

34

TGA and DTG curves at 10 oC/min for ACF1,ACF2,ACF7 (

different epoxy thermoset carbon fiber composites) and

ACF6 ( PEEK thermoplastic carbon fiber composite).

35

We

igh

t (%

)

70

75

80

85

90

95

100

Temperature (oC)

200 300 400 500 600 700 800

We

igh

t lo

ss

ra

te (

%/m

in)

-5

-4

-3

-2

-1

ACF1

ACF2

ACF6

ACF7

Thermally thin parameter

36

(𝟏

𝒎𝒊𝒏𝒊𝒕𝒊𝒂𝒍× 𝒎𝒂𝒙

𝝏𝒎𝝏𝒕

)

𝒉𝒆𝒂𝒕𝒊𝒏𝒈 𝒓𝒂𝒕𝒆× ∆𝑯𝒆𝒇𝒇

ys/HoC (g/kJ)

0.000 0.002 0.004 0.006 0.008 0.010

PH

RR

2/t

ig

(k

W2/m

4-s

)

10

100

1000

10000

ACF1

ACF2

ACF6

ACF7

ACF1-Pprime

ACF3

ACF9-1

ACF9-2

ACF1 (2mm)

DETAILED FLAMMABILITY PROPERTIES

AND PYROLYSIS MODEL

37

Material

s Thickness

Critical

heat flux Diffusivity Conductivity Density

Specific

heat

Ignition

temperature HoC

Heat of

pyrolysis

mm kW/m2 m2/s W/m-K kg/m3 J/kg-K K kJ/g kJ/g

ACF1 4.12 13 0.8X10-7 0.236 1480 1993 697 19 =0.2

ACF2 3.95 11 1.9X10-7 0.52 1550 1860 668 18 = 0.2

ACF6 4.16 31 1.9X10-7 0.38 1480 1366 860 18 =1

ACF7 4.16 11 1.9X10-7 0.51 1420 1890 658 22 = 0.2

Material

s ys yco Residue

Average

MLR

Average

HRR

Stoichio.

Ratio, S a

Smoke point

height b

Activation

energy, Ea

Pre-expon.

Factor,

Ln(A)

Reaction

order, n

g/g g/g % g/m2-s kW/m2 mm kJ/Mol s-1

ACF1 0.0680 0.0428 72.26 Fcn( ) c Fcn( ) c 6.3 9.05 149 21.4 1

ACF2 0.0861 0.0603 72.97 17 300 6.0 6.83 169 26.1 1

ACF6 0.0467 0.0461 74.53 6.5 120 6.0 12.59 261 32.3 1

ACF7 0.1577 0.0573 75.31 11 250 7.3 4.44 160 24.7 1

38

Deduced effective ignition and thermal properties of ACF1, ACF2, ACF6 and ACF7.

PYROLYSIS MODELS FOR DIFFERENT

FORMULATIONS

39

40

One of the objectives of this paper is to develop a simple model that can be incorporated in

CFD models for full scale modelling. In this work, it is found that the heat flux ratio between

the heat flux assuming that there is no carbon fibre layer (4

ignextTq ) and the actual heat

flux between the carbon fibre layer and the virgin layer ( erfaceq

int ) can be related to the depth of

the material pyrolysed in the following three cases:

a) Heat flux ratio increases linearly with the pyrolysed depth (ACF1) independent of the

heat flux, as found for typical charring materials

b) Heat flux ratio increases non-linearly with the pyrolysed depth independent of the

heat flux (ACF2 and ACF7)

c) Heat flux ratio initially increases linearly the pyrolysed depth but then remain nearly

constant independent of the heat flux (ACF6)

PREDICTIONS

41

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0 50 100 150 200 250 300 350 400 450 500

Mas

s lo

ss ra

te (g

/s)

Time (s)

ACF1

70kW/m2

30kW/m2

EXPERIMENTS

42

INSULATED BACK SURFACE TEMPERATURE AND NET HEAT FLUX

43

44

50kW/m2

Time (s)

0 100 200 300 400 500 600

Back s

urf

ace t

em

pera

ture

(oC

)

0

100

200

300

400

500

600

700

ACF1

ACF2

ACF6

ACF7

45

After 100 s , ignition starts and the net heat flux into the solid can be estimated for the slope

of temperature histories , the mass remaining ( 45 g over an area of 0.01 m2) and the specific

heat of carbon fibers C= 0.5kJ/kg K . This net heat flux is equal to 4.5 *0.5* 300/200 = 3.4

kW/m2. This heat flux will be imposed on the insulated material behind the fuselage. We

expect and have shown ( for heat fluxes up to 75 kW/m2) that same proportional reduction of

the imposed heat flux ( by 90 %) occurs at higher imposed heat fluxes and therefore, no flame

through or flame spread will occur behind the fuselage.

APPLICATION TO LARGE SCALE SITUATIONS:

BURNING RATE IN THE SBI EXPERIMENT

46

47

Time (s)

0 200 400 600 800 1000 1200

HR

R (

kW

)

0

30

60

90

120

EXP Test 1EXP Test 2Burner HRR = 30kWIntegral model

Comparison of the predicted HRR of Flaxboard in SBI by a numerical

model and the experimental data using the calculated flammability

properties

CONCLUSIONS

Comprehensive flammability/toxicity evaluation


Detailed flammability properties for modeling

Pyrolysis model

Back surface temperature for fire resistance

Towards large scale modelling

48

Thanks for your attention!

Any questions?

TOXICITY PARAMETER WHEN IT SHOWS A DIFFERENCE

50

PG1

PG2

PG3B

PG4

0.0

0.2

0.4

0.6

0.8

1.0

Toxicity assesment based on effective Heat of combustion

Inefficiency of combustion

PG1

PG2PG3B

PG4A

0

10

20

30

40M

ass left (

wt%

)

Percentage of initial mass left after tests in Cone calorimeter at 30kW/m2

PG1

PG2

PG3B

PG4A

0

1

2

3

4

5

Mass le

ft (

-GF

)

Percentage of initial mass left after tests in Cone calorimeter at 30kW/m2

Mass of Glass fibres was substracted

Results and discussions

Fire growth and smoke parameters (all formulations)

54


Toxicity parameter (all formulations)

55

Page 56 World Rescue Challenge 2012

Heat release parameter for thermally thin conditions calculated as

(𝟏

𝒎𝒊𝒏𝒊𝒕𝒊𝒂𝒍×𝒎𝒂𝒙

𝝏𝒎

𝝏𝒕)

𝒉𝒆𝒂𝒕𝒊𝒏𝒈 𝒓𝒂𝒕𝒆× ∆𝑯𝒆𝒇𝒇, where 𝒎𝒊𝒏𝒊𝒕𝒊𝒂𝒍 is initial mass of sample (mg),

𝒎𝒂𝒙𝝏𝒎

𝝏𝒕 is peak mass loss rate (mg/s) and ∆𝑯𝒆𝒇𝒇 is effective heat of

combustion (kJ/g) taken from Cone calorimeter


Heat Release Rate for thermally thin materials (PBT+GF and PA66+GF)

57

Conclusions

Five parameters were deduced based on micro- and small-scale tests in order to characterize ignition and flammability behaviours of any material, namely, fire spread and growth parameter, smoke parameter, toxicity parameter, mass residue and heat release rate for thermally thin materials

These parameters (except mass residue which is not relevant in this work) were applied to polymers fire retarded with brominated fire retardants (BFRs) or halogen free fire retardants HFFRs) and it is found that:

In terms of fire growth and smoke parameters (i) base polymers have the highest fire growth parameter but with minimum production of smoke, (ii) BrFRs reduce the fire growth parameter but increase the smoke production considerably and (iii) HFFRs achieve similar and smaller fire growth parameter but with less smoke production compared to BrFRs.

58

Conclusions

In terms of the toxicity parameter, BrFRs have highest inefficiency of combustion because of their strong gaseous action, whereas HFFRs have higher combustion efficiency because they mostly act in the solid phase by modifying the char formed on the surface of the polymer.

In terms of the heat release rates at thermally thin conditions, PBT+GF and PA66+GF formulations behave differently, where the formulation containing BrFRs has the lowest value for PBT+GF whilst the highest for PA66+GF. The opposite behaviour by PA66+GF is due to the fact that brominated PA66+GF has a maximum mass loss rate about twice that of neat PA66+GF. This result demonstrates the limitation of TGA data which is obtained under thermally thin condition as opposed to real burning conditions where the material behaves as a thermally thick material as typically found in the Cone Calorimeter tests.

59

60

61

Acknowledgements

The authors acknowledge the EU for financially supporting the ENFIRO project under Grant No 226563 and AircraftFire Project under Grant No 265612. The authors also thank Mr M McKee and W Veighey for helping with the Cone experiments.

62

Thanks for your attention!

Any questions?

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COMPARISON OF FLAMMABILITY AND FIRE · PDF file11.03.2015 · comparison of flammability and fire resistance of carbon fiber reinforced thermoset and thermoplastic composite materials