Comparison of anti-ablation performance of phenolic resin composites with different fiber contents

The influence of fiber content on the anti-ablative properties of phenolic resin composites is investigated in this paper. The study is conducted in response to the need for performance optimization of anti-ablative thermal protection materials used in ultra-high-speed flight vehicles. Functional gradient composites are prepared by RTM (Resin Transfer Moulding) process, which consist of 2.5D woven structural anti-burnout layer composites with fiber contents of 45 %, 50 % and 55 %, and fiber cloth/fiber mesh tire insulation layer composite material. The properties of the four materials are compared, showing that density, thermal conductivity, and specific heat capacity are slightly increased with higher fiber content. At the same time, thermal stability is significantly enhanced as fiber content rises. In particular, the residual carbon rate of the 55 % fiber content composite reaches 94.1 %, which is 5.54 %, 9.62 % and 21.69 % higher than that of the 50 %, 45 % fiber content and insulation layer materials, respectively. In addition, the tensile and flexural properties of the materials gradually improve with the growth of fiber content, which is attributed to the better bonding ability between the fibers and the resin matrix, thus demonstrating greater anti-ablative effects. The SiC ceramic fused cladding layer is generated on all the composites after ablation. With elevated fiber content, the conform ability of the materials is improved in wind tunnel ablation tests, and the formation of gully structures is effectively suppressed. As a result, the anti-ablative performance of the materials is further enhanced. Specifically, the mass ablation and linear ablation of the composite with 55 % fiber content are only 6.27 % and 13.04 % of the initial mass and thickness, respectively. The anti-ablative performance of the material is not only strengthened by the increase in fiber content, but heat transfer is also effectively slowed down, and the insulation ability of the material is significantly improved.