Thermochemical erosion and thermophysical properties of phenolic resin/carbon fiber/graphite nanocomposites

The main objective of this work is an experimental investigation and an analytical modeling of ablation and to analyze the thermophysical properties of nanocomposites based on novolac resin/short carbon fiber/graphite nanocrystalline powders in oxyacetylene flame test. The composite consisting of 40wt.% carbon fiber was prepared as reference sample of which matrix was modified with three different percentages (6, 9 and 12wt.%) of nano-sized graphite powders as reinforcement. Ablation is calculated by mass balance equation. Some parameters in the ablation modeling are evaluated by simultaneous thermal gravimetric analysis technique. Results of this work show that ablation rates decrease by the addition of graphite powders. The theoretical ablation rates are 33-38% less than the experimental data analyzed by oxyacetylene flame tests. This difference is reasonable because the effect of fluid stream force of oxyacetylene flame that causes the thermomechanical erosion of the surface is omitted in theoretical calculations. Therefore the model only calculates thermochemical erosion. Also, the thermophysical properties change due to heating is analyzed. Moreover, in nanocomposite with 9wt.% graphite nanopowders, the rate of ablation and thermal diffusivity coefficient decreased by 10% and 50%, respectively, and thermal stability increased by 12% compared to the reference sample.