ACP04

Material description

Material ID: ACP04

Material type: Predominantly organic composition rich in aromatics, such as cellulose-based and/or phenolic polymers.

Polymer: Cellulose and phenolic binder (100%)

Additives (fire retardants, fillers or traces of inorganic elements): Traces of other elements (<1%)

Core thickness: 2.76mm

Thickness of single metal skin: 0.51mm

Table 1. Estimated mass concentration of compounds.

Compound	Mass Concentration (%)
Cellulose and phenolic binder (-)	100
Traces of calcium (Ca)	<1
Traces of sodium (Na)	<1
Traces of potassium (K)	<1
Traces of sulfur (S)	<1
Traces of silicon (Si)	<1

A. Material composition identification

A.1 Attenuated total reflection – Fourier transform infrared spectroscopy (ATR-FTIR)

Table 2. FTIR compound identification.

Identified Compounds
Cellulose and phenolic binder (-)

Figure 1 . FTIR spectra: Absorbance percentage versus wavenumber from the sample.

Figure 2. FTIR spectra: Absorbance percentage versus wavenumber from the sample and the identified compounds.

A.2 Energy Dispersive X-Ray Fluorescence (EDXRF)

Table 2. Inorganic elements and their mass concentration identified with EDXRF.

Element	Mass Concentration (%)
Ca	<1
Na	<1
K	<1
S	<1
Si	<1

Figure 3. EDXRF spectra. Counts vs energy. Identified elements are shown as vertical lines.

B. Thermogravimetric analysis

Table 3. Mass fraction of residue after thermal decomposition.

Condition	Fraction of mass residue at 800°C
Non-oxidative (nitrogen)	0.38
Oxidative (air)	0.03

Table 4. Temperature and amplitude of main peaks in non-oxidative conditions.

Peak ID	Temperature peak (°C)	Amplitude of peak (°C^-1)
Peak 1	343	5.58 x 10^-3
Peak 2	413	1.52 x 10^-3

Table 5. Temperature and amplitude of main peaks in oxidative conditions.

Peak ID	Temperature peak (°C)	Amplitude of peak (°C^-1)
Peak 1	337	5.18 x 10^-3
Peak 2	451	7.65 x 10^-3

Figure 4. Normalised mass (solid line) and derivative of the normalised mass (dashed line) in 150 ml min^-1 of nitrogen and a heating rate of 20°C min^-1.

Figure 5. Normalised mass (solid line) and derivative of the normalised mass (dashed line) in 150 ml min^-1 of air and a heating rate of 20°C min^-1 .

. Gross Heat of Combustion

Table 7. Gross Heat of Combustion individual results for sample.

Trial	ΔH_c [kJ g^-1]
Trial 1	22.72
Trial 2	22.65
Trial 3	23.01
Average	22.79
Std dev	0.19

D. Ignition parameters

Table 8. Summary of ignition parameters for sample.

Critical heat flux for ignition	Ignition temperature	Total heat transfer coefficient of losses	Apparent thermal inertia
q̇″_cr [kW m⁻²]	T_ig [°C]	h_r [W m^-2 K^-1]	kρc [kW² m^-4 K^-2 s]
20.40	433	44.50	0.728

Figure 6. Time-to-ignition vs incident radiant heat flux for samples.

E. Burning behaviour

Table 9. Summary of key burning behaviour metrics.

Heat flux	Test	Time to ignition	Fraction of mass residue	Peak heat release rate	Total energy released
q̇″_inc [kW m^-2]		t_ig [s]	m_res [-]	q̇″_p [kW m^-2]	Q_t [MJ m^-2]
35 kW m^-2
	Test 1	78	0.09	173.50	52.10
	Test 2	91	0.24	212.79	63.95
	Avg	84	0.17	193.15	58.02
50 kW m^-2
	Test 1	39	0.04	243.59	58.37
	Test 2	67	0.12	270.20	109.87
	Avg	53	0.08	256.90	84.12
60 kW m^-2
	Test 1	33	0.02	237.45	64.70
	Test 2	-	-	-	-
	Avg	33	0.02	237.45	64.70
80 kW m^-2
	Test 1	-	-	-	-
	Test 2	-	-	-	-
	Avg	-	-	-	-

Figure 7. Normalised mass loss over time for samples tested with 35, 50, 60 and 80 kW m^-2.

Figure 8. Heat release rate per unit area over time for samples tested with 35, 50, 60 and 80 kW m^-2.

Table 10. Effective Heat of Combustion individual results for sample.

Test	ΔH_c [kJ g^-1]
35 kW m^-2 (Test 1)	16.75
35 kW m^-2 (Test 2)	23.06
50 kW m^-2 (Test 1)	17.19
50 kW m^-2 (Test 2)	34.08
60 kW m^-2 (Test 1)	18.51
60 kW m^-2 (Test 2)	-
80 kW m^-2 (Test 1)	-
80 kW m^-2 (Test 2)	-
Average	21.92
Std dev	7.24

F. Flame Spread

Table 11. Minimum heat flux for flame spread rate and minimum flame spread rate for sample.

Orientation	q̇″_min.spread [kW m^-2]	V_f.min [mm s^-1]
Horizontal	10	0.40
Vertical	3	1.20

Figure 9. Lateral flame spread rate versus heat flux.

Figure 10. Vertical flame spread rate versus heat flux.

Figure 11. V_f^-1/2 as function of q̇″_ext in horizontal configuration.

Figure 12. V_f^-1/2 as function of q̇″_ext in vertical configuration.

Table 12. Flame spread parameter results for sample.

Orientation	Trial	(^kρc_p⁄_Φh²)^¹⁄₂ [m^³⁄₂ s^¹⁄₂ kW^-1]	Φ [kW² m^-3]
Horizontal	1	5.17	13.75
Horizontal	2	1.983	91.42
Vertical	1	-	1000
Vertical	2	-	1000