In this work, the Zirconia (Zr) particles were coated with graphene nanoplatelets (Gnps) using the wet chemical synthesis process and sintered at 500°C and 900°C. At sintering temperature of 900°C, the Zr coated with 0.25 wt% Gnp fillers exhibited better oxidation resistance. Thus, the carbon epoxy (C‐Ex) composites containing Zr/Gnp, 0.25 wt%, were fabricated by the hand‐layup technique. The prepared composites were characterized by scanning electron microscopy, thermogravimetry analysis (TGA), flexural, and ablation tests. The C‐Ex composites modified with Zr/Gnps fillers showed significant improvement in thermal stability and flexural strength compared with the pristine sample. The composite containing 0.25 wt% Zr/Gnp filler reduced the mass ablation rate to 23%, whereas back‐surface temperature was decreased to 170°C compared with pure C‐Ex composite. The surface morphology of ablated composite samples revealed that the Zr/Gnp produced char droplet spheres on the carbon fibres, which prevented the further oxidation of the matrix and thus improved the ablative performance.

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In this study, an effort has been made to improve the mechanical, thermal, and ablation performance of carbon-phenolic (C-Ph) composites. The ZrO 2 , SiC, and ZrO 2 /SiC hybrid fillers were synthesized using sol-gel method followed by individual incorporation into C-Ph composites. The thermal stability and flexural strength of these C-Ph composites were analyzed using thermogravimetry analysis and three-point bending test, respectively. A significant improvement in the flexural strength and modulus of the reinforced C-Ph composites was observed and also exhibited the higher thermal stability. The oxyacetylene flame test was conducted to measure the ablation behavior of these filler reinforced C-Ph composites under a heat flux of 4.0 MW/m 2 for 60 seconds. ZrO 2 /SiC0.5 reinforcement in the C-Ph composite decreased the linear and mass ablation rates by 46% and 22%, respectively when compared with pure C-Ph composite. The surface morphology analysis revealed that the burnt composite covered with the ZrC ceramic phase and SiO 2 bubble-like structure, which could have improved the ablation resistance of composites. These results were found well within the acceptable range when using the surface energy dispersive spectroscopy and X-ray diffraction analysis. K E Y W O R D Sablation behavior, carbon fiber, flexural strength, nano silicon carbide, thermal stability

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