Study On Airtight Properties Of Three - Dimensional Braided Quartz Fiber Heat Sealant

In order to meet the urgent requirements of thermal sealing materials in aerospace frontier field,3D braided Quartz fiber preforms was introduced as thermal seals. With flexibility of quartz fiber and compression rebound properties of three-dimensional fabric,different parameters seals were designed. According to the seals compression rebound performance standards, the tests were studied. This article analyze the effect of different parameters on the seals and provide a theory basis for the application of the seals. The results are as follows:(1) Based on the air permeability performance analysis of 3D braided structure, different structures, different fiber volume content of the sample can meet the air permeability performance requirements of thermal sealing materials, when the compression rate is 10% and 20%, air permeability significantly reduced with fiber volume content of the sample increasing; 3D braided structure and 3D 4-directional exhibit more excellent air permeability performance compared to the 3D 5-directional structure.(2) 2D braided structure and 3D braided structure has reached the performance requirements of thermal sealing materials. Compression ratio at 10% and 20%, due to Lack of links between surface structure and the core yarn,the 2D braided structure has large pores and uneven; On contrast, the air permeability performance of 3D bradied structure is more excellent, more suitable for thermal sealing material structure selection requirements.(3) Air permeability of 3D braided thermal sealing materials structure of the sample reduced with the increase of the compression ratio, the compression rate is 10%, the internal pores of the air permeability fabric along the channel is still relatively smooth; Compression ratio of 20% sample substantially closed internal porosity, only a portion of gas through tiny pores between the fibers penetrate; when the compression rate is increased to 30%,the sample showed significant shear deformation and fragmentation of the matrix, the specimen failure.(4) By comparing the air permeability material with the test results that the annular strip specimen sample under compression rate fixed, and the pressure increases, along with a corresponding increase of air permeability.(5) According to the flow resistance of the model under different conditions,pressure and compressibility of air permeability based on Kozeny-Carman equation establishment found the air permeability of 3D braided thermal seals depends on the amount of thermal seal material properties and porosity of the material itself; The way of air permeability is divided into two categories, in the design of the model,the choose of parameter variables according to the characteristic of the braiding material and the change of gas channel.(6) Air permeability test of 3D braided preform results showed the structure can be directly used as a high temperature sealing material of spacecraft with rational design.