Improvement of ablation and heat shielding performance of carbon fiber reinforced composite using graphite and kaolinite nanopowders

Abstract

The main objective of this work was to prepare nanocomposites based on novolac resin/short carbon fibers having appropriate mechanical properties and the ideal thermal and ablative properties. In order to evaluate the thermal and ablative properties a composite consisting of 40 wt% carbon fiber was prepared as reference sample which its matrix was modified with three types of reinforcements, including micron-sized kaolinite, nano-sized kaolinite and graphite powders. Filler concentrations in the kaolinite nanocomposites and graphite nanocomposites were 6, 9 and 12 wt% and in the micron-sized kaolinite filled composite was 20 wt%. The investigation and measurement of thermal properties were made by TGA, hot plate and oxyacetylene flame tests. The three-point bending test was performed to measure the mechanical properties of the samples. The obtained results showed that the addition of micron-sized kaolinite although led to an increase in the thermal properties but impaired the mechanical properties dramatically. Substitution of micron-sized particles by nanometer-sized particles improved thermal properties and also prevented the severe reduction of mechanical properties, and thus, maintained them in an ideal state. Addition of 9 wt% nanographite particles increased thermal stability by 12 % compared to the reference sample. Moreover, in nanocomposite with 9 wt% graphite, the rate of ablation and thermal diffusivity coefficient decreased by 10 and 62 %, respectively.