Experimental Investigation on Thermal Degradation …
559
Table 1 Description of materials and assemblies used in two different phases of an experimental
study
S.No
Heat flux
First phase
Second phase
Materials
Assemblies
1
50
kW/m 2
Paint
Paint + Laminate
(P.L)
2
Laminate
Paint + Laminate + Honeycomb
(P.L.H)
3
Honeycomb
Paint + Laminate + Honeycomb + Laminate
(Composite)
decomposition in the case of different assemblies (i.e. Phase 2 study). After that, in
the second phase, three different assemblies (Cf. Table 1) are made by using phase
one materials (i.e. laminate, honeycomb, and paint) and tested at the same heat flux.
The results of the second phase demonstrate how the thermal decomposition gets
affected with the addition of layers (i.e. material) and also allows the comparison of
various decomposition parameters in case of different assemblies.
3 Results and Discussion
At first, as described above, in order to understand the decomposition process of
materials separately, each constitutes of the multilayer material (i.e. paint, laminate,
and honeycomb) is tested individually at the incident flux of 50 kW/m
2 . It is evident
from Fig. 4 that thermal decomposition of paint and laminate occurs in one step
while the honeycomb structure decomposes in two steps (see HRR curves in Fig. 4).
In case of all three materials (i.e. paint, laminate, and honeycomb), CO 2 emission
coincides with the HRR curve due to the method used in HRR calculations which is
primarily based on the CO 2 emission during the combustion [14]. In order to compare
different gaseous emissions with respect to HRR and back surface temperature, some
of the lower emission values are multiplied by the factor of 10 and 100. The modified
gaseous emissions are indicated in the respective legends of the figure. In case of
paint, CH 4 and CO emissions are observed at the same time. Whereas in the case of
laminate, CO is observed at the time of ignition and at the end of the decomposition process while a single peak of CH 4 is observed at the end of the HRR peak. In
the case of laminate, CH 4 emission corresponds to the decomposition of methylene
bridges while release of CO 2 and CO at the start of the ignition represents the decomposition of the resin. Sudden rise in CO emission at the end of the decomposition
corresponds to the char decomposition which is usually observed at 600 °C. In the
case of honeycomb structure, the CH 4 emissions are very negligible and observed
after the end of the primary decomposition for a very brief time. CO emissions are
observed corresponding with HRR peak and as peak back surface temperature is
attained, the sudden increase in CO emission corresponds to char decomposition.
559
Table 1 Description of materials and assemblies used in two different phases of an experimental
study
S.No
Heat flux
First phase
Second phase
Materials
Assemblies
1
50
kW/m 2
Paint
Paint + Laminate
(P.L)
2
Laminate
Paint + Laminate + Honeycomb
(P.L.H)
3
Honeycomb
Paint + Laminate + Honeycomb + Laminate
(Composite)
decomposition in the case of different assemblies (i.e. Phase 2 study). After that, in
the second phase, three different assemblies (Cf. Table 1) are made by using phase
one materials (i.e. laminate, honeycomb, and paint) and tested at the same heat flux.
The results of the second phase demonstrate how the thermal decomposition gets
affected with the addition of layers (i.e. material) and also allows the comparison of
various decomposition parameters in case of different assemblies.
3 Results and Discussion
At first, as described above, in order to understand the decomposition process of
materials separately, each constitutes of the multilayer material (i.e. paint, laminate,
and honeycomb) is tested individually at the incident flux of 50 kW/m
2 . It is evident
from Fig. 4 that thermal decomposition of paint and laminate occurs in one step
while the honeycomb structure decomposes in two steps (see HRR curves in Fig. 4).
In case of all three materials (i.e. paint, laminate, and honeycomb), CO 2 emission
coincides with the HRR curve due to the method used in HRR calculations which is
primarily based on the CO 2 emission during the combustion [14]. In order to compare
different gaseous emissions with respect to HRR and back surface temperature, some
of the lower emission values are multiplied by the factor of 10 and 100. The modified
gaseous emissions are indicated in the respective legends of the figure. In case of
paint, CH 4 and CO emissions are observed at the same time. Whereas in the case of
laminate, CO is observed at the time of ignition and at the end of the decomposition process while a single peak of CH 4 is observed at the end of the HRR peak. In
the case of laminate, CH 4 emission corresponds to the decomposition of methylene
bridges while release of CO 2 and CO at the start of the ignition represents the decomposition of the resin. Sudden rise in CO emission at the end of the decomposition
corresponds to the char decomposition which is usually observed at 600 °C. In the
case of honeycomb structure, the CH 4 emissions are very negligible and observed
after the end of the primary decomposition for a very brief time. CO emissions are
observed corresponding with HRR peak and as peak back surface temperature is
attained, the sudden increase in CO emission corresponds to char decomposition.