This paper describes the development and validation of a rapid internal defect detection method for multilayer composite components. Coplanar array capacitive imaging is based on electrical capacitance tomography, in which all electrodes are arranged in a single plane. The coplanar array capacitive sensor system is based on the capacitive edge effect and reconstructs the dielectric distribution in the sensitive area by measuring the capacitance of the sensor. A 4 × 3 array of coplanar electrode sensors is established and used to image the defects in the inner layers of multilayer composite components. Using a 3D model of the sensor and the sensitivity field, the variation pattern of the sensitivity field is analyzed. By placing different objects into the sensitivity area of the system, changes in the dielectric constant can be observed. Multilayer composite components with void defects are placed in the measurement area for defect detection. The dielectric distribution is visualized by reconstruction algorithms from the capacitance data and sensitivity field data. The results show that the imaging system based on a coplanar array capacitive sensor can reproduce the location of defects and realize the nondestructive testing of complex multilayer composite components.
We present here a new design of ion blower based on bipolar corona discharge of needledielectric-needle configuration. With the help of the dielectric plate, the new ion blower can endure higher voltage before spark than the traditional bipolar corona discharge, with the similar discharge characteristics and current-voltage curve. The high operating voltage provides a much greater ionic wind velocity compared with the traditional needle-to-needle corona. The neutral ionic wind can reach as far as 0.45m with a velocity of 0.2m/s. This feature is very helpful for eliminating mechanical rotating components in the design of ion blowers, so that the size of ion blower can be greatly compressed and the noise significantly reduced, which is more suitable for electrostatic elimination in small areas and some specific scenarios. The design of self-balancing regulation unit can effectively monitor the charged characteristics of mixed ion wind and make corresponding adjustments to ensure the neutrality of positive and negative discharge. This new ion blower has an excellent performance, including an offset voltage of ±5V, a short discharge time of 5s or less at distance of 20cm.INDEX TERMS Ion blower, ionic wind, bipolar corona discharge, needle-dielectric-needle.
The defect detection of thermal protective structures is of great significance in ensuring the safe flight of aircraft. In this paper, a dynamic measurement method based on the planar capacitance sensing principle is proposed to solve the problem of detecting defects in the adhesive layer of large-area thermal protection structures. This paper analyses the principle of capacitive sensing and establishes a planar array capacitive dynamic detection system. The dielectric distribution of the structural components to be measured is obtained at different locations by moving the array of electrode sensors regularly. To obtain the dielectric distribution information of the complete structure, the dielectric distribution at adjacent locations is spliced and fused. To achieve the precise location of the overlapping areas in the image to be fused, an image alignment method based on coordinates is adopted. The experimental results show that our proposed method can detect defects in the adhesive layer of large-area thermal protection structures and achieve complete visualization of the adhesive layer.
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