FAA Round Robin III Analysis

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INTERNATIONAL AIRCRAFT
MATERIALS FIRE TEST WORKING GROUP
ROUND ROBIN TEST III DATA
ANALYSIS


Khang D. Tran, Ph.D.,

Sr. Scientist

The Mexmil
Company, Santa Ana, California, USA.
June 2001
The
International Aircraft Materials Fire Test
Working Group Meeting
Sedgefield, Stockton-on-Tees, Cleveland, United
Kingdom, 27-28 June 2001

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ACKNOWLEDGEMENTS
The Mexmil Company Mr. David Indyke,
Materials Technology Manager, Mexmil Co.
Mr. Tim Marker, Project Manager, The FAA.
Mr. Johns Brook, Director of Research,
International Aero Inc.
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INTRODUCTION Purpose To analyze
data obtained from the burn-through round
robin test III for aircraft thermal/acoustical
insulation blanket. Date 09/2000 -
02/2001 Participants 8 Labs (A,
B, C, E, F, G, I, J) Burning
configuration Burner type P (Park)
Igniter position 10-12 oclock (Lab B at 1230,
Lab C at 10). Turbulator-Nozzle distance 3.75
in. (Lab C at 3.94) Calorimeter manufacturer
V (Labs A and G M) Thermocouple manufacturer
(Labs A, G, I, J X Labs B, C, E, F T) Air
Velocity Meter O (Lab C X) Fuel Jet A
Samples Fabricated by The Mexmil Company.

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ROUND ROBIN III MATERIALS
Blanket Blanket
Thickness Blanket Barrier
Estimated Approx. Approx. ID
Construction per Layer
Density Material Failure
Fiberglass Barrier
(inch)
(lb/ft3) Mode and
Required Required


Time (yds2) (yds2)
A 2 Layer Fiberglass 1.0
0.6 N/A
Burnthrough 214 0


(30-40 sec) B 2
Layer Fiberglass/ 1.0
0.42 Nextel Exceed Heat 214
107 Nextel
Paper
Paper Flux Limit


(gt300) C 2 Layer Orcobloc
1.0 0.6
N/A Burnthrough 0
214 OPF

(240) D
1 Layer Fiberglass/ 1.0
0.42 Pre Ox Burnthrough
107 107 1
Layer Pre Ox- 3/16
7 PAN Felt (190)
PAN Felt (7641) E 1 Layer
Fiberglass/ 1.0/0.15 0.42/15
Basofil/ Burnthrough 107
214 2 Layer Basofil/

Aramid (205) Aramid Felt
(4759R)
Felt F 1
Layer highloft 0.5
0.83 N/A Exceed Heat
0 107
aramid/inorganic
Flux Limit


(230)
Notes
thlt 0.5 in
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FLAME TEMPERATURE
PROFILE
(observed from the burner)
LAB
A

Temperature F
B
1149 C
A
C
1093
E
TEMPERATURERANGE PROPOSED
F
1038

G
I
982
E
J
927
1804
Thermocouple Number
Temperature T of each thermocouple was averaged
over 6 calibrations for all labs. The
difference ?T is as large as 214 F between
flames from Lab A and Lab E.
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FLAME TEMPERATURE-FRONT HEAT FLUX
CORRELATION
Heat Flux (Btu/s.ft2)
2 ?Q 0.8 Btu/s.ft2 ?Q/Q 3
G
I
A
C
J
F
B
E
Temperature (F)
- In the temperature range of 1800-2000 F, data
from 6/8 labs showed that the front heat
flux-flame temperature relationship is linear.
- A front heat flux in the (14-16 Btu/s.ft2)
range could be generated when the average
flame temperature is in the range of (1875-1950
F). - A 5 variation of flame temperature (T2-
T1)/T1 yields a heat flux variation (Q2-
Q1)/Q1 as large as 25.
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INTAKE AIR VELOCITY FLAME TEMPERATURE
CORRELATION
Average Intake Air Velocity (ft/min)
Temperature (F)

Intake air velocity
2?V 100 ft/min
Temperature
2?T 20 ºF
G B C I F J
A E
Lab
Intake air velocity as recorded by each lab was
plotted in the increasing order (blue dots). The
corresponding flame temperature was then
correlated (green dots). The graph showed that an
increase of in-take air velocity V about 70
ft/min could yield a flame temperature increase
of 100 F.
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TEST CELL TEMPERATURE - FLAME TEMPERATURE
CORRELATION (1)
Flame temperature (ºF)
Test cell temperature (ºF)
170
145
120
95
70
Calibration/Test
Flame Temp.(F)
TC Temp. (F)
Data from from one lab showed that the flame
temperature varied in accordance with the test
cell temperature variation.

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TEST CELL TEMPERATURE - FLAME TEMPERATURE
CORRELATION (2)
Flame temperature (ºF)
2?T 20 ºF
Test cell temperature (ºF)
The cell temperature was plotted in the
increasing order. The above graph showed that,
above 100 F, the flame temperature increased
with increasing cell temperature. This behavior
was not obvious if the cell temperature is
smaller than 100 F. Indication is that a
burn-through test should begin only when the cell
temperature had returned to the ambient
temperature.
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RELATIVE HUMIDITY AND FLAME TEMPERATURE
Relative Humidity ()
Flame Temperature(ºF)
2050
2?H 6
2000
1950
2?T 20
F
1900
1850


1800
E B
C G J F
I A
Lab
Flame temperature was plotted along with
increasing humidity for each lab. Data does not
show convincingly that the relative humidity
affects flame temperature. For 6 labs from E to A
(EBGJFA), the flame temperature increased with
increasing humidity while for 4 labs from C to I
the variation is reverse.
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FLAME TEMPERATURE AND BURN-THROUGH TIME
CORRELATION (Graph 1)
Burn-through time (s)
D
C
?t/t 5-10
E
A
Lab
E I B G
F J C A
Average burn-through time for 4 sample materials
A, E, C, and D by 8 labs was plotted versus
increasing flame temperature. For A and E
samples, 6 over 8 labs obtained burn-through time
data that is in agreement with temperature
variation. For C and D samples, 4-5 labs
obtained consistent data.
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FLAME TEMPERATURE AND BURN-THROUGH TIME
CORRELATION (Graph 2)
Temperature (ºF)
2?T 20 ºF (?T/T0.5 )
CURRENT RANGE
2?Q 0.8 (?Q/Q 3 )
Lab
E I B G
F J C A
The flame temperatures for all labs were plotted
in the increasing order to correlate with
burn-through time data. 6/8 burner set-ups
generated flame temperature in a pretty narrow
range (1850-1950 F).
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EFFECT OF MATERIALS
COMPOSITION VARIATION The shape of the heat
flux curves Q k f(?T) is a characteristic of
materials composition . The rear heat flux
curves of samples A, E, C, and D as independently
recorded by Labs F, I, and J were utilized to
examine the effect of materials composition
variation. Below are heat flux graphs for
sample E2 and A2 by labs F, J, and I where
(1) the E2-signals were zero for 50 seconds,
then started increasing. Burn-through occurred
with a sharper increase of the rear heat flux at
around 95-110 s. (2) the A2-signals increased
smoothly from nearly zero to 0.7 in t 20-25 s,
indication of a near burn-through.
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HEAT FLUX CURVES OF SAMPLES E2 BY LABS F,
J, AND I
Heat Flux (Btu/ft2s)
(Ja)
(Fa)
(Jb)

(Fb)
Time (s)
(Ja and Jb) SAMPLE E2 - LAB J, burned through at
110 s. (Fa and Fb) SAMPLE E2 - LAB F, burned
through at 95 s
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SAMPLE E2 - LAB I
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SAMPLE A2
Data from LAB I
(Fa)
(Ja)
Data from LABs F and J
Burned- through
(Jb)
(Fb)
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EFFECT OF THE TEST CELL VENTILATION CONDITION
A strong vertical ventilation stronger vertical
air flow ---gt longer burn-through time. A poor
vertical ventilation slower vertical air flow
---gt faster burn through
Ventilation alters the turbulent nature of the
flame, both spatially and temporally
FLAME MODELS UNDER DIFFERENT VENTILATION CONDITION
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EFFECT OF MATERIALS SHRINKAGE
For some kinds of sample blanket the vertical
clamps cannot hold specimens tightly on the frame
during the fire. The specimen was shrunk
and/or blown towards the calorimeters. 1/ a
failure due to an exceeding heat flux resulting
from a nearer distance between the hot
surface of the blanket and the rear
calorimeter. 2/ an increase of burn-through time
due to a longer distance between the burner
cone and the blanket.
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CONCLUSION
(1) The temperature-front heat flux
relationship by 8 labs indicate that, within a
15 error, flame temperature is directly
proportional to the flux.
(2) The average flame temperature required for
generating a heat flux in the range of
14-16 Btu/s.ft2 in the range of 1875-1950 F.
(3) A 5 variation of average temperature (T2-
T1)/T1 could yield a heat flux variation
(Q2- Q1)/Q1 as large as 25. This could cause a
significant difference in burn- through
time. Therefore, the allowable fluctuation of the
average temperature should be 50 F (2.6)
instead of 100 F (5) (1900 50 F instead of
1900 100 F ). (4) Factors need to be
controlled The in-take air velocity, the
cell temperature, the test cell ventilation, and
the shrinkage of materials. Effect
of humidity is not evident. (5) Heat flux curves
indicated that materials composition variation in
samples may not be a significant factor
affecting the burn through results.