Experimental study of the burning behaviour of a commercial carbon fibre composite material used in high pressure vessels

This paper presents an analysis on the charring rate experienced by a commercial CFRP material used to construct composite pressure vessels for hydrogen storage and transport applications. An experimental programme using the Cone Calorimeter apparatus explored the effect of incident heat flux, sample thickness and rear face boundary condition on the charring rate, which is critical to the residual mechanical strength under fire conditions. Samples measured 100 mm by 100 mm, with thicknesses of 4.5 mm and 29 mm. Mass loss was determined for each thickness and at heat fluxes between 15 and 80 kW·m. Two back boundary conditions were used: ceramic insulation and an aluminium block, representing bounds on heat loss. A method to estimate the CFRP charring rate is proposed based on mass loss rate measurements and the assumption that the material does not shrink after pyrolysis. Characteristic times of surface oxidation are found to be much longer than those for charring and pyrolysis. Initial peak charring rates are found within the range of 1.5-2.3 mm·min for heat fluxes up to 80 kW·m. Reasonably steady charring rates of below 0.5 mm.min only occur with back face heat losses, with a secondary peak for insulated cases