| Flexible insulation materials have great application potential in the field of aerospace.this subject combines quartz fiber flexible insulation felt with fiber plain cloth through full thickness suture technology,so that it has a neat surface for easy to transport and installation and has good high temperature heat insulation performance and reusable performance.Different preparation parameters were designed to investigate the effects of the layers of plain cloth,the thickness of needled felt and the density of suture on the thermal conductivity and thermal insulation properties of the material,and the optimized process parameters were selected.On this basis,the compressive resilience and thermal fatigue performance were further studied and analyzed,and the compressive resilience mechanism and thermal fatigue mechanism of the material were analyzed and summarized,to provide theoretical guidance for the reusable cycle evaluation of the material under actual working conditions.The main contents include the following aspects:(1)The quartz fiber needled felt was selected as the core,the quartz fiber cloth was used as the surface material and the quartz fiber bundle as the stitching thread to prepare the suture sandwich felt insulation material through the full thickness puncture suture technique.27 groups of insulation materials were designed according to three different preparation parameters including surface layer,core layer thickness and suture density.(2)The thermal conductivity of 27 groups of materials was tested and analyzed.It was found that there is no interaction between the material factors.The thermal conductivity of materials increased with the increase of surface layers and decreased with the increase of core layer thickness,while the suture density had no significant influence on the thermal conductivity of materials.(3)The control variates were used to test the back temperature of materials,and the curve of the back temperature with time was obtained,which directly reflected the high temperature insulation performance of the material.The thermal insulation performance of the material is getting better with the increase of the number of surface layers and core layer thickness,while the suture density has no significant effect on the actual thermal insulation performance of the material.After comprehensive analysis,2layers of surface layer,23 mm of original thickness of core layer and 5×15mm of suture density were selected as the optimized process parameters.(4)Single and cyclic compression resilience tests were carried out on the optimizing materials to obtain the compression performance curves and resilient rate data.Further analysis of the compression resilient mechanism of materials shows that the compression process can be divided into three stages: The first stage mainly compresses the air in the needled felt on the surface of the material and the core layer,and the compression load increases linearly.In the second stage,the fibers in the material slip and the compression load is at an increasing speed.In the third stage,the material is gradually compacted,and the compression load increases rapidly in a small strain.With the increase of the number of compressions,a part of the material has permanent deformation,which affects the overall density of the material.In general,the stitched sandwich felt insulation material has good compression resilience.(5)After the material is placed in a high temperature environment of 400-1000℃for 2 hours to accelerate its thermal fatigue,the thermal conductivity and back temperature of the material are tested.The test results show that the overall structure of the material does not change after high temperature heating,so the thermal conductivity is basically unchanged.However,the decomposition of surface treating agent on quartz fiber leads to the weakening of thermal radiation during thermal assessment,so the back-temperature data is higher than the data before. |
PDF Full Text Request