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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)
Key research equipments (2)
Intermediate-scale (Cone, UFA, SBI, ISO room, etc)
Cone calorimeter Universal flammability
apparatus (infra-red)
Universal Flammability
Apparatus (UFA)
Key research equipments (3)
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
Flammability and toxicity parameters
16
Flammability and toxicity parameters
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
Flammability and toxicity parameters
Fire spread and growth parameter
Smoke parameter
Toxicity parameter
Mass residue
Heat release rate for thermally thin materials
19
Flammability and toxicity parameters
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
Flammability and toxicity parameters
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
~~
Flammability and toxicity parameters
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
Flammability and toxicity parameters
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
Flammability and toxicity parameters
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
Materials and experiments
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
Materials and experiments
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
Materials and experiments
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
Materials and experiments
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
Flammability and toxicity parameters
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
Results and discussions
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
Results and discussions
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?