Study On Mixing Process And The Method Of Quality Inspectiong Of Premixture Of Low Density Ablative Materials

With the development of aerospace technology,there is an increasing demand for thermal protection materials on the surface of spacecraft.A large number of ultra-thin wall hollow fillers and chopped fibers are added to the premixture of the new low-density ablative materials.The uniformity of these reinforcing materials directly affects the properties of ablative materials,and the existing mixing equipment cannot achieve the desired mixing effect.In this paper,the mixing process of premixture is studied,and the special high-efficiency mixing equipment for premixture is developed.At the same time,the method of quality inspection of premixture is studied for the shortcomings of quality inspection of premixture.Based on the dispersion characteristics of ultra-thin wall hollow fillers and chopped fibers in high-viscosity resins,a new type of mixing equipment for premixture was designed.The planetary agitation method and the twist frame blades was selected.By analyzing the influence on the mixing effect,the ratio of rotation to revolution is 32:17,and the phase angle of the two blades is 90°.The mixing process was simulated by Poly flow.The results show that the material is spirally ascending during the mixing process,and the mixing effect of the mixing blades is uniform.The mixing equipment for premixture has been prepared and tested.The mixing efficiency,mixing uniformity and ultra-thin wall hollow filler breakage rate meet the requirements of use,and the equipment has been accepted and put into use.This paper proposes the use of image processing technology to detect the dispersion uniformity of reinforcing materials.First,a microscopic image of the material is obtained through a microscope,and then the image is subjected to filtering and threshold segmentation processing to extract target information.Finally,the uniformity of the reinforcement material is quantitatively characterized by the combination of histogram and kl-divergence operator.Based on this,an image detection system is built.According to the multi-stage powder packing theory,the premixture pile-up model was established,and the theoretical density calculation method suitable for the premixture of low-density ablative materials was obtained.In view of the fact that the premixture needs compaction during density detection,the pressure bearing performance of the premixture is studied to obtain a critical pressure to ensure that the material is compacted without damage to the ultra-thin wall hollow filler.On this basis,the filling compaction device was designed.The high-precision ball screw and displacement sensor were used to realize the automatic measurement of the bulk volume,and the density detection system for premixture was established.The completion of the project lays a foundation for batch,continuous,standardized production and promotion of low-density ablation materials,and has certain guiding significance and high practical value.