Thermal, ablation and mechanical properties of carbon-phenolic composites reinforced with zirconia coated graphene nanoplatelets

The present experiments have been conducted to investigate the thermal, ablation and mechanical properties of carbon/phenolic (C-Ph) composites loaded with zirconia (Zr) coated graphene nanoplatelets (Gnp) hybrid filler. The Zr/Gnp hybrid filler was synthesized by sol-gel technique and C-Ph composites were fabricated using hand layup method. The thermal stability was investigated by thermogravimetric analysis and it was significantly improved with the addition of Zr and Zr/Gnp hybrid filler to pure C-Ph composite. The ablative properties were studied under oxy-acetylene flame torch tests at a heat flux of 2100 kW m(-3). TheC-Ph/Zr/Gnp0.5 composite sample exhibited lower linear and mass ablation rates compared to pure C-Ph composite. The surface morphology of post-ablated composite samples was characterized by scanning electron microscopy. It was shown that the Zr/Gnp filler produced bubble-like structure around the C-fibers, which prevented the oxidation of fibers. Finally, the mechanical properties of C-Ph composites were investigated through three-point bending tests as per ASTMD7264 standard. The flexural strength and modulus of C-Ph composites loaded with hybrid filler increased about 30% and 54% compared to the pure C-Ph composite.