Erosion Rate of Random Short Carbon Fibre/Phenolic Resin Composites: Modelling and Experimental Approach

Amodel is introduced to describe the erosion rate of random short carbon fibre composites exposed to high speed hot gas flow. A mathematical equation is derived to calculate the erosion rate of the composite using combined solution of the heat conductivity, filtration and kinetic equations of reactions which occur simultaneously in a pyrolysis process. The fibre orientation distribution density function has been employed to determine the mechanical erosion of the composite as well as its chemical erosion and to evaluate the fibres angles with respect to their flow direction. The model describes composite erosion rate as a function of composite surface temperature, hot gas pressure head applied on the material and the thermo-physical properties of the fibres and resin. The DSC and TGA techniques have been employed to measure the ablation kinetic parameters. The thermal conductivity coefficients of the composites have been obtained by Cussons thermal conductivity apparatus. To examine the validity of the results obtained by the model, a series of experiments were carried out using short carbon fibre/phenolic resin composite samples in an oxyacetylene torch. The results obtained from the model are totally in accordance with the experimental data collected from the oxyacetylene flame tests. This model can be effectively used in the design of thermal protection shields, for both material selection and calculation of the materials thickness.