Ablation properties of C/C composites with various needled preforms prepared by isothermal chemical

The ablation properties of C/C composites with four difierent needled preforms prepared by isothermal chemical vapor infiltration(ICVI), which are super-thin mat lay-up, 0°/90°weffless fabric lay-up, 0°/45°weftless fabric lay-up and 0°/45°twill fabric lay-up.were quantitatively evaluated by performing the ablation tests with an engine torch.And their ablation discrepancies were analyzed according to the surface characteristic, porosity and thermal diffusivity. The results show that the 0°/45°weffless composite has a fiat eroded surface with no obvious macroscopic pits. Its thickness and mass erosion rates are decreased by about 46.8% and 34.8%.25.0% and 27.5%, and 17.5% and 19.4%compared with those of the mat, the 0°/90°weftless and the 0°/45°twill composites, respectively. The ablation properties are mainly controlled by the thermo-chemical effect (oxidation), and a liRle by the thermo-mechanical effect (mechanical denudation). Theneedling fiber bundles play an important role in accelerating the ablation process and resulting in the heterogeneous ablation.