The Experiental Research Of Paste Defects Detection About Heat Shield And Substrate

The supersonic aircraft need flying in high speed for a long period of time in the atmosphere, but the thermal environment caused by the air impact friction is extremely bad, and the plane surface temperature is quite high. To ensure the safety of the fuselage, heat must be prevented effectively to an internal diffusion. Heat insulation performance of Ceramic fiber heat shield is improved obviously, and it has been able to meet the requirements of the supersonic aircraft’s thermal insulation after decades of development. Ceramic fiber heat shield use space special viscose, using special technology bonding together with the fuselage. Under the impact of the high-speed airflow, it must ensure that the glue is firm and will not be overturned, however, Due to the error of the production process, paste defects often appear, which cause all sorts of catastrophic accidents. Therefore the paste defects must be tested and evaluated effectively. At present, the paste defect detection is mainly divided into the defect detection of debonding and sticky strength testing, in this paper, the research is mainly aimed at recognition problems of the bonding defects, providing a rapid and effective method to guide the operation of engineering practice. In addition, this paper analyzed the stress distribution of different bonding defect component adhesive layer with the ANSYS finite element simulation, and studied the Bonding defects on the influence of bonding strengthIn this paper, to study the issue of material internal sound velocity, analyze the material composition and ratio based on energy spectrum test. To judge material possible failure mode qualitatively and study the attenuation of stress wave in material internal analyzed the anisotropic characteristics, pore characteristics and caking characteristics of the materials by SEM electron microscope scanning in order to judge qualitatively the potential failure mode. Analyze the strength of the material and the basic mechanical properties such as elastic properties and deformation characteristics through compression test, providing the basis for the impact of the shock echo experiments. Using nuclear magnetic resonance(NMR) technology, the basic physical properties such as porosity of materials is analyzed. And through the nuclear magnetic resonance tomography, the microscopic damage of the compression specimens is analyzed.On the basis of understanding the basic performance of the material, using impact echo detection technology to detect paste defects of the heat shield material and the substrate. In the process of specimen making, the bonding defects were set, by studying the difference of the defective point and zero defect point signal to determine whether there is paste defects. At the same time, setting up different sizes of paste defects, in order to study the identify defects precision of the shock echo detection technology, in the process of detection. And using MATLAB wavelet analysis technology to analyze the collected time domain signal, obtained the basic rule of the bonding defect area signal and no bonding defect area signal.Finally, the paper uses finite element analysis software ANSYS to study the effects of defect size and adhesive bonding defect position on viscose layer stress distribution.