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H. Najmi et al.
the primary HRR peak, two additional HRR peaks are observed (Fig. 6). The peak
observed just after the primary peak represents thermal degradation of the honeycomb structure. In order to describe the final HRR peak in case of composite, CH 4
concentration and HRR are plotted in Fig. 9. In the first phase of this experimental
study, it is confirmed that the amount of CH 4 released during the honeycomb decomposition is negligible. It (CH 4 ) is mainly observed in case of laminate and paint
decomposition therefore CH 4 concentration is used in Fig. 9. The first two CH 4
peaks represent the decomposition of paint and laminate present at the top of the
composite. While the final peak of CH 4 concentration rises just after the final HRR
peak similar to the laminate decomposition case. Also, the back face temperature
measured at that time corresponds to the decomposition of methylene bridges. This
confirms that the final HRR represents the decomposition of laminate present at the
bottom of the composite. At the end of the final test, thickness of the composite is
reduced to 7 mm from the initial thickness of 13 mm.
It should be noted that in all the test cases, a major part of CO emission is observed
after the flame out, representing char decomposition. This occurs at a sufficiently high
temperature which is about 580–650 °C. It seen that with the addition of a layer the
CO emission is delayed (see Fig. 7). This is probably due to the increase in thickness
which retards the increase in back surface temperature (Fig. 10) and hence char
decomposition is delayed.
The total mass loss percentage in composite is about 45% (see Table 3). If the
average mass loss percentage of P.L.H (59%) and laminate (29%) is estimated, it is
around 44% which is very similar to the total mass loss of the composite. This allows
us to conclude that the addition of a laminate at the back of P.L.H assembly does not
Fig. 9 Evolution of heat release rate, CH 4 concentration and back face temperature for composite
H. Najmi et al.
the primary HRR peak, two additional HRR peaks are observed (Fig. 6). The peak
observed just after the primary peak represents thermal degradation of the honeycomb structure. In order to describe the final HRR peak in case of composite, CH 4
concentration and HRR are plotted in Fig. 9. In the first phase of this experimental
study, it is confirmed that the amount of CH 4 released during the honeycomb decomposition is negligible. It (CH 4 ) is mainly observed in case of laminate and paint
decomposition therefore CH 4 concentration is used in Fig. 9. The first two CH 4
peaks represent the decomposition of paint and laminate present at the top of the
composite. While the final peak of CH 4 concentration rises just after the final HRR
peak similar to the laminate decomposition case. Also, the back face temperature
measured at that time corresponds to the decomposition of methylene bridges. This
confirms that the final HRR represents the decomposition of laminate present at the
bottom of the composite. At the end of the final test, thickness of the composite is
reduced to 7 mm from the initial thickness of 13 mm.
It should be noted that in all the test cases, a major part of CO emission is observed
after the flame out, representing char decomposition. This occurs at a sufficiently high
temperature which is about 580–650 °C. It seen that with the addition of a layer the
CO emission is delayed (see Fig. 7). This is probably due to the increase in thickness
which retards the increase in back surface temperature (Fig. 10) and hence char
decomposition is delayed.
The total mass loss percentage in composite is about 45% (see Table 3). If the
average mass loss percentage of P.L.H (59%) and laminate (29%) is estimated, it is
around 44% which is very similar to the total mass loss of the composite. This allows
us to conclude that the addition of a laminate at the back of P.L.H assembly does not
Fig. 9 Evolution of heat release rate, CH 4 concentration and back face temperature for composite