Elastic property and airtightness of ceramic fiber baseline seals with elastic elements

The baseline seal structure is widely used in the thermal protection of aircraft due to its excellent thermal insulation and stability. However， prolonged exposure to high temperatures and heavy loads in service can easily lead to permanent deformation of the seal， limiting its reusability. In this study， elastic elements woven from GH4169 alloy wires are used to fabricate ceramic fiber baseline seals with different internal filling structures， such as loose fiberfill， unidirectional fiber tow， and braided fiber bundles. The effects of the cotton core filling structure， compression cycles， and heat treatment of the elastic elements on the elastic property of the seals are investigated. The results show that as the compression level increases， the recovery ratios of the seals with the three filling structures decrease to varying degrees. When the compression level reaches 30%， the seal with the loose fiberfill structure exhibits the highest recovery ratio of 95.93%. As the number of compression cycles increases， the recovery ratio of the seal decreases. After standard heat treatment of the elastic elements， the peak load of the elastic elements at a 60% compression level decreases from 451.25 N/m （untreated） to 196.25 N/m， while the recovery ratio of the seals increases from 77.87% to 87.78%. Theoretical calculations and experimental analysis of the seal’s tightness reveal that as the pressure difference increases， the leak rate of the seal rises. The experimental values of the leak rate are higher than the theoretical values， and the tightness of the seal is influenced by its elastic property and the insulating cotton core.