Effect of thickness on the ignition behaviour of carbon fibre composite materials used in high pressure vessels

This paper presents a fundamental approach to assess the time-to-ignition data from solids, based on an experimental programme for assessing flammability parameters of a carbon fibre reinforced polymer (CFRP) used for storage and transport of hydrogen gas. Two different thicknesses representative of real end-use conditions, 4.9 and 29 mm, were tested using the Cone Calorimeter. The ignition temperature for the particular CFRP has been established within the range [314, 349] °C, and the nominal thermal inertia within [1.00E+06, 1.07E+06] W2·s·K-2·m-4. The ultimate aim is to assess the applicability of classical ignition theory and in particular the assumption of semi-infinite behaviour of the solid. The analysis is based on an analytical model derived from the one-dimensional solution of the heat transfer problem in a semi-infinite solid domain, and a comparison with classical time-to-ignition correlations. Additionally, a finite-difference heat transfer model is used to evaluate the deviation in the time-to-ignition data between experimental data arising from samples of different thickness, and also to study the error included in the assumption of null net (conductive) heat flux
typically considered for the critical heat flux for ignition. To conclude, recommendations for rigorous analysis of time-to-ignition data from solids are given based on the proposed methodology.