Study On Preparation And Properties Of Carbon Fiber Composites With Oxidation Resistance And Thermal Conductivity

Thermal management systems(TMSs)are important for the long-term performance of a variety of aerospace applications in harsh environments.Heat resistant materials(HRM)are one of the core materials in a TMS because it can withstand high temperatures without undergoing degradation or oxidation.Carbon fibre(CF)reinforced SiC matrix composites(CF/SiC)are widely used as HRMs because of their low density,high strength and high heat resistance.However,the anisotropic structures,the weak bonding between the CF and the matrix and the low thermal conductivity in the through-thickness direction(k?)limit its practical application in TMS.In this paper,entangled carbon nanotubes(ECNT)and vertically aligned carbon nanotubes(VACNTs)were grown on the surface of CF fabrics to form ECNT@CF hybrid and VACNT@CF hybrid by chemical vapour deposition.The CF/SiC,ECNT@CF reinforced SiC matrix composite(ECNT@CF/SiC)and VACNT@CF reinforced SiC matrix composite(VACNT@CF/SiC)composite were prepared through the precursor impregnation and pyrolysis(PIP)method.The interfacial compatibility between the CF and the PCS was significantly improved by the VACNTs on the CFs due to the strong capillary attraction of the VACNT arrays with the porous surface.The good interfacial compatibility results in uniform coating of SiC on the VACNT@CF after pyrolysis and improves the density of the composites.VACNT@CF/SiC shows the maximum density of 2.04 g/cm~3 after 15 PIP cycles.The VACNT@CF/SiC composite exhibits high flexural(248.62 MPa)and compressive strengths(416.20 MPa),which are 14.75 and 30.74%higher than those of the CF/SiC,respectively.Owing to the strong interfacial bonding,the VACNT@CF/SiC exhibits superior oxidation resistance than the ECNT@CF/SiC and the CF/SiC.The VACNT@CF/SiC exhibits the highest value of k?,16.80 W/(m?K),much higher than that of the CF/SiC(7.94 W/(m?K)),due to the presence of thermally conductive pathways in the dense structure.Infrared thermal imaging spectroscopy confirmed that the VACNT@CF/SiC composite shows a fast and efficient heat transfer in the through-thickness direction compared to the ECNT@CF/SiC and the CF/SiC composites.The VACNT@CF/SiC composite with a combination of properties such as high thermal conductivity,high strength,and high oxidation resistance is a potential candidate for HRMs in TMSs.