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Correlation coefficient between the peak heat release rate (PHRR) and the average heat release rate (AHRR) for the different types of fibre composite materials This table corresponds to the data plotted in Fig. 5.

Figure 5 Correlation coefficient between the peak heat release rate (PHRR) and the average heat release rate (AHRR) for the different types of fibre composite materials This table corresponds to the data plotted in Fig. 5.

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Details of the composites, reinforcements and resin matrix Table 1 was calculated as a percentage of the initial specimen mass. of the material is below the pyrolysis temperature of the organic matrix. Following this induction period, there is a rapid rise in the heat release rate due to the combustion of volatiles, in this case mainly low molecular weight hydrocarbons, near to the composite/fire interface. Following the peak heat release rate (PHRR), the HRR decreases progressively with time due to the formation and thickening of a surface char layer that slows the decomposition reaction rate in the underlying material. The HRR also declines as a result of the declining resin content in the sample. Eventually the heat release rate becomes negligible, as the last of the resin matrix is decomposed.
Details of the composites, reinforcements and resin matrix Table 1 was calculated as a percentage of the initial specimen mass. of the material is below the pyrolysis temperature of the organic matrix. Following this induction period, there is a rapid rise in the heat release rate due to the combustion of volatiles, in this case mainly low molecular weight hydrocarbons, near to the composite/fire interface. Following the peak heat release rate (PHRR), the HRR decreases progressively with time due to the formation and thickening of a surface char layer that slows the decomposition reaction rate in the underlying material. The HRR also declines as a result of the declining resin content in the sample. Eventually the heat release rate becomes negligible, as the last of the resin matrix is decomposed.
Fig. 1. The cone calorimeter used to measure the fire reaction properties. Fig. 3 presents typical HRR curves at 50 kW/m* for vinyl ester composites reinforced with polyethylene and aramid fibres. These curves are very similar in profile to those with other polymer matrices (ie. epoxy, phenolic). The curves for the polyethylene and aramid composites are substantially different from each other and from the profile shown in Fig. 2 for the non-combustible fibre composite. The curve of the composites reinforced with polyethylene shows an initial peak in heat release rate, and this is attributed to the decomposition of fibres close to the surface. The second
Fig. 1. The cone calorimeter used to measure the fire reaction properties. Fig. 3 presents typical HRR curves at 50 kW/m* for vinyl ester composites reinforced with polyethylene and aramid fibres. These curves are very similar in profile to those with other polymer matrices (ie. epoxy, phenolic). The curves for the polyethylene and aramid composites are substantially different from each other and from the profile shown in Fig. 2 for the non-combustible fibre composite. The curve of the composites reinforced with polyethylene shows an initial peak in heat release rate, and this is attributed to the decomposition of fibres close to the surface. The second
Fabrication conditions of the composite specimens profile to that presented in Fig. 2. The heat release rate was substantially higher for composites with a polyester, vinyl ester or epoxy matrix, compared to those with a phenolic matrix. The HRR results for the composites reinforced with glass fibres are presented in Brown and Mathys [13].
Fabrication conditions of the composite specimens profile to that presented in Fig. 2. The heat release rate was substantially higher for composites with a polyester, vinyl ester or epoxy matrix, compared to those with a phenolic matrix. The HRR results for the composites reinforced with glass fibres are presented in Brown and Mathys [13].
Fig. 2. Typical heat release rate curve for a non-combustible fibre composite. The curve is for a woven glass/vinyl ester composite tested at the heat flux of 50 kW/m*. larger peak 1s Caused by the combined heat release trom the fibres and matrix. The polyethylene fibres at the surface release heat before the polymer matrix because of their lower pyrolysis temperature. UHMW polyethylene begins to decompose in an inert atmosphere at about 290 °C whereas the decomposition temperature of the vinyl ester matrix is about 350 °C [22,23]. The aramid curve in Fig. 3b shows an initial peak due to decomposition of the polymer matrix near the hot surface, followed by a small second peak also due to the polymer matrix near the surface. As opposed to the polyethylene fibres, the aramid reinforcement has a higher pyrolysis temperature (T=500 °C) than the vinyl ester, and therefore the matrix releases heat before the fibres [24]. A third broad peak is observed in the heat release-time profile, and this is due to decomposition of both the polymer matrix and aramid fibres. It is also seen that the heat release rates for the composite containing aramid fibres is, on average, much lower. This is because the decomposition of aramid yields a much lower amount of flammable volatiles than polyethylene fibres. Based on the mass loss data
Fig. 2. Typical heat release rate curve for a non-combustible fibre composite. The curve is for a woven glass/vinyl ester composite tested at the heat flux of 50 kW/m*. larger peak 1s Caused by the combined heat release trom the fibres and matrix. The polyethylene fibres at the surface release heat before the polymer matrix because of their lower pyrolysis temperature. UHMW polyethylene begins to decompose in an inert atmosphere at about 290 °C whereas the decomposition temperature of the vinyl ester matrix is about 350 °C [22,23]. The aramid curve in Fig. 3b shows an initial peak due to decomposition of the polymer matrix near the hot surface, followed by a small second peak also due to the polymer matrix near the surface. As opposed to the polyethylene fibres, the aramid reinforcement has a higher pyrolysis temperature (T=500 °C) than the vinyl ester, and therefore the matrix releases heat before the fibres [24]. A third broad peak is observed in the heat release-time profile, and this is due to decomposition of both the polymer matrix and aramid fibres. It is also seen that the heat release rates for the composite containing aramid fibres is, on average, much lower. This is because the decomposition of aramid yields a much lower amount of flammable volatiles than polyethylene fibres. Based on the mass loss data
Fig. 4. TGA curves for the (a) polymers and (b) organic fibres.
Fig. 4. TGA curves for the (a) polymers and (b) organic fibres.
Fig. 5. Plot of AHRR against PHRR for the composites and their combustible fibres and resins.
Fig. 5. Plot of AHRR against PHRR for the composites and their combustible fibres and resins.
Fig. 6. Plot of AHRR against PHRR for the aramid composites tested at different incident heat fluxes.
Fig. 6. Plot of AHRR against PHRR for the aramid composites tested at different incident heat fluxes.
Fig. 7. Plot of AHRR against PHRR for the composites reinforced with woven glass fibres tested at different incident heat fluxes.
Fig. 7. Plot of AHRR against PHRR for the composites reinforced with woven glass fibres tested at different incident heat fluxes.
Fig. 9. Plot of average SEA against AHRR for the composites. a general linear increase with heat release rate in Fig. 9, although the rate of increase is much lower for the composites containing polyethylene fibres. Presumably this is because of the higher heat release rate due to the increased yield of flammable volatiles from both the polyethylene fibres and polymer matrix. Table 4 shows the linear correlation coefficient values between SEA and the peak and average heat release rates. The linear correlation coefficient values for the glass, carbon and polyethylene fibre composites are above 0.88, indicating that the heat release rate of these materials has a strong relationship to smoke density. It is believed that this relationship exists because the endothermic decomposition The dependence of smoke density on HRR for composites with non-combustible fibres was investigated further by analysing published smoke data for other types of composite reinforced with glass or carbon fibres. Fig. 10 presents a compilation of our smoke data with data by Sorathia [6] for various types of thermoset and thermo- plastic matrix composites. Despite some scatter (particu- larly for the glass/BMI), there is a general increase in SEA with AHRR, with a correlation coefficient of 0.78.
Fig. 9. Plot of average SEA against AHRR for the composites. a general linear increase with heat release rate in Fig. 9, although the rate of increase is much lower for the composites containing polyethylene fibres. Presumably this is because of the higher heat release rate due to the increased yield of flammable volatiles from both the polyethylene fibres and polymer matrix. Table 4 shows the linear correlation coefficient values between SEA and the peak and average heat release rates. The linear correlation coefficient values for the glass, carbon and polyethylene fibre composites are above 0.88, indicating that the heat release rate of these materials has a strong relationship to smoke density. It is believed that this relationship exists because the endothermic decomposition The dependence of smoke density on HRR for composites with non-combustible fibres was investigated further by analysing published smoke data for other types of composite reinforced with glass or carbon fibres. Fig. 10 presents a compilation of our smoke data with data by Sorathia [6] for various types of thermoset and thermo- plastic matrix composites. Despite some scatter (particu- larly for the glass/BMI), there is a general increase in SEA with AHRR, with a correlation coefficient of 0.78.
Fig. 8. Plot of AHRR against PHRR for a wide variety of glass and carbon reinforced composites containing thermoset or thermoplastic resins
Fig. 8. Plot of AHRR against PHRR for a wide variety of glass and carbon reinforced composites containing thermoset or thermoplastic resins
This table corresponds to the data plotted in Fig. 9. Linear correlation coefficients for smoke specific extinction area (SEA) against the heat release properties for the different types of fibre composite materials
This table corresponds to the data plotted in Fig. 9. Linear correlation coefficients for smoke specific extinction area (SEA) against the heat release properties for the different types of fibre composite materials
Fig. 10. Compilation of data showing relationship between average smoke specific extinction area and average heat release rate for various thermoset anc thermoplastic matrix composites reinforced with non-combustible fibres. The gas products released by a decomposing composite depend on the chemical nature of the organic constituents, oxygen availability, and the temperature of the fire. Tewerson and Macaione [32], for example, have shown that polyester matrix composites can release a mixture of gases that include CO, COs, low molecular weight organics such as propylene, benzene, toluene and styrene, and organic ring compounds including aromatic C—H and aromatic C—H-O. As another example, phenolic laminates yield, in addition to water, CO, CO», toluene, benzene and various aromatic compounds. While the types and amounts of the gas products can vary between materials, all polymer composites release CO and CO; [5,6,15,19,29,32]. CO is a major safety concern because it is lethal at a relatively low concentration, with human death occurring within one hour at a concentration of about 1500 ppm. Babrauskas [3] suggests that the yield of CO Fig. 12 shows that the average yield of CO, gas is not as strongly related as the CO yield on the heat release rate. The CO, yields for all the composites fall within the limits of ~ 1-2 kg/kg, and appear to be independent or only weakly related to the heat release rate. This seems to indicate that the mechanisms controlling the CO, yield are complex
Fig. 10. Compilation of data showing relationship between average smoke specific extinction area and average heat release rate for various thermoset anc thermoplastic matrix composites reinforced with non-combustible fibres. The gas products released by a decomposing composite depend on the chemical nature of the organic constituents, oxygen availability, and the temperature of the fire. Tewerson and Macaione [32], for example, have shown that polyester matrix composites can release a mixture of gases that include CO, COs, low molecular weight organics such as propylene, benzene, toluene and styrene, and organic ring compounds including aromatic C—H and aromatic C—H-O. As another example, phenolic laminates yield, in addition to water, CO, CO», toluene, benzene and various aromatic compounds. While the types and amounts of the gas products can vary between materials, all polymer composites release CO and CO; [5,6,15,19,29,32]. CO is a major safety concern because it is lethal at a relatively low concentration, with human death occurring within one hour at a concentration of about 1500 ppm. Babrauskas [3] suggests that the yield of CO Fig. 12 shows that the average yield of CO, gas is not as strongly related as the CO yield on the heat release rate. The CO, yields for all the composites fall within the limits of ~ 1-2 kg/kg, and appear to be independent or only weakly related to the heat release rate. This seems to indicate that the mechanisms controlling the CO, yield are complex
Fig. 11. Plots of AHRR against the average CO yield for the composites.
Fig. 11. Plots of AHRR against the average CO yield for the composites.
Fig. 12. Plot of AHRR against the average CO yield for the composites. The relationship between the peak heat release rate and the peak yield rates of CO and CO, gases from the composites was also investigated. A strong correlation between the PHRR and peak gas yields for CO and CO, was observed for both the woven glass and chopped glass fibre composites. For example, Fig. 13 shows that the peak yields of CO and CO, increased at a linear rate with the PHRR for the woven glass composites. In this material, the PHRR is a measure of the maximum rate of thermal decomposition of the polymer matrix. It is to be expected that the maximum It is interesting to note, however, that the linear correlation coefficient values in Table 5 for the composites with non-combustible fibres are positive whereas the values for the composites with combustible fibres are negative, suggesting that for these materials a reduction in the CO,
Fig. 12. Plot of AHRR against the average CO yield for the composites. The relationship between the peak heat release rate and the peak yield rates of CO and CO, gases from the composites was also investigated. A strong correlation between the PHRR and peak gas yields for CO and CO, was observed for both the woven glass and chopped glass fibre composites. For example, Fig. 13 shows that the peak yields of CO and CO, increased at a linear rate with the PHRR for the woven glass composites. In this material, the PHRR is a measure of the maximum rate of thermal decomposition of the polymer matrix. It is to be expected that the maximum It is interesting to note, however, that the linear correlation coefficient values in Table 5 for the composites with non-combustible fibres are positive whereas the values for the composites with combustible fibres are negative, suggesting that for these materials a reduction in the CO,
Linear correlation coefficients for (a) CO and (b) CO, yields against the heat release properties for the different types of fibre composite materials This table corresponds to the data plotted in Figs. 11 and 12. Table 5
Linear correlation coefficients for (a) CO and (b) CO, yields against the heat release properties for the different types of fibre composite materials This table corresponds to the data plotted in Figs. 11 and 12. Table 5
Fig. 13. Plot of PHRR against the peak yields of CO and CO) gases from the woven glass composites. Table 7 gives the linear correlation coefficients between the ignition time and the PHRR and AHRR values, and for
Fig. 13. Plot of PHRR against the peak yields of CO and CO) gases from the woven glass composites. Table 7 gives the linear correlation coefficients between the ignition time and the PHRR and AHRR values, and for
Linear correlation coefficients for ignition time against the heat release properties for the different types of fibre composite materials This table corresponds to the data plotted in Fig. 14. Table 7
Linear correlation coefficients for ignition time against the heat release properties for the different types of fibre composite materials This table corresponds to the data plotted in Fig. 14. Table 7
Linear correlation coefficients for the peak yields of CO and CO, gases with the peak heat release rates for the different types of fibre composite materials This table corresponds to the data plotted in Fig. 13. Table 6
Linear correlation coefficients for the peak yields of CO and CO, gases with the peak heat release rates for the different types of fibre composite materials This table corresponds to the data plotted in Fig. 13. Table 6
Linear correlation coefficients for total mass loss against the heat release properties for the different types of fibre composite materials This table corresponds to the data plotted in Fig. 15.
Linear correlation coefficients for total mass loss against the heat release properties for the different types of fibre composite materials This table corresponds to the data plotted in Fig. 15.
Fig. 15. Plots of AHRR against total mass loss for the (a) combustible fibre composites and (b) non-combustible fibre composites
Fig. 15. Plots of AHRR against total mass loss for the (a) combustible fibre composites and (b) non-combustible fibre composites
Fig. 16. Plots of (a) PHRR against peak mass loss rate and (b) AHRR against average mass loss rate for the composites
Fig. 16. Plots of (a) PHRR against peak mass loss rate and (b) AHRR against average mass loss rate for the composites
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