Improved Performances of SiBCN Powders Modified Phenolic Resins-Carbon Fiber Composites

The effect of SiBCN powder on properties of phenolic resins and composites was analyzed. Compared with phenolic resins, the thermal stability of SiBCN powder modified phenolic resins (the SiBCN phenolic resins) by characterization of thermogravimetric analysis (TGA) improved clearly. It was found by X-ray photoelectron spectroscopy (XPS) that reactions between SiBCN powder and the pyrolysis product of phenolic resins were the main factor of the increased residual weight. TGA and static ablation of a muffle furnace were used to illustrate the roles of SiBCN powder on increasing oxidation resistance of SiBCN powder-modified phenolic resin–carbon fiber composites (SiBCN–phenolic/C composites), and the oxidative product was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). For SiBCN–phenolic/C composites, the occurrence of oxidation reaction and the formation of protective crust contributed to improving oxidative resistance. The result of the oxygen-acetylene test showed that the linear ablation rate (LAR) and mass ablation rate (MAR) of phenolic resin–carbon fiber composites reduced from 0.052 ± 0.005 mm/s to 0.038 ± 0.004 mm/s and from 0.050 ± 0.004 g/s to 0.043 ± 0.001 g/s by introducing SiBCN powder, respectively. The mechanism of ablation resistance after the introduction of SiBCN powder was investigated. The high melt-viscosity of SiBCN powder caused SiBCN powder to remain on the surface of composites and protect the internal resins and carbon fibers. The oxidation of SiBCN powder and volatilization of oxide can consume energy and oxygen, thus the ablation resistance of SiBCN–Ph composite was improved.