Study On Defect Detection And Optimization For Aeronautical Composite Materials Based On Planar ECT

Composite materials have many excellent properties such as fatigue resistance,corrosion resistance,high temperature resistance and light weight.Therefore it was widely used in aerospace,military industry and other fields.Composite materials change their structure and properties during manufacturing and use.External environmental factors also have an impact on it.In the aerospace industry,in order to ensure the safety of aircraft flight,damage and defect detection of composite materials is required to ensure its quality.The development of electrical capacitance tomography has become a new type of non-destructive testing technology,which has the advantages of strong adaptability,fast speed and low price.Based on the edge effect of the capacitor,ECT can detect the damage inside the composite and make it visible.This paper optimizes the aerospace composite material detection technology based on planar ECT.The structure and related parameters of the sensor are optimized by simulation,then the performance of the sensor is verified through experiments.This paper mainly discusses from the following aspects:(1)Determine sensor-related performance metrics for planar array electrode sensors.Analyze the influence of the structural parameters of the electrode plate on its performance index,such us the electrode plate,such as the shape of the plate,the aspect ratio,the spacing,and the shielding layer,etc.The results show that reduction of aspect ratio and spacing of rectangular plates can improve the measurement sensitivity of the sensor.Adding a shield reduces the dynamic range of capacitance measurement and improves the uniformity of sensitivity distribution.Considering various indicators,a set of optimization parameters is obtained: the aspect ratio of the plates is at the range of 1-2,the plate spacing is 0.3cm,and the inter-electrode shielding width is 0.2cm.(2)Simulation modeling was performed using COMSOL multiphysics simulation software to compare the two-dimensional,three-dimensional sensitivity distributions and the difference of full field capacitance of sensors before and after optimization.The results show that the full field capacitance difference and sensitivity of the optimized sensor are improved.The uniformity of the sensitivity distribution is the best at a level 0.7cm above the distance sensor,and the simulated imaging effect is also the best at this level.Different types of defectswas reconstructed in planar ECT by MATLAB using different image reconstruction algorithms.The applicability of different algorithms in planar ECT is evaluated by comparing image correlation coefficients and image errors.(3)Experimental tests were carried out on a data acquisition system based on STM32 to detect the adhesive defects of composite materials.According to the imaging effect and capacitance data analysis,compare the sensitivity,penetration depth and detection accuracy of sensors before and after optimization for the detection of adhesive defects.The experimental results show that the optimized sensor improves the accuracy of defect detection,and the detection depth is best in the range of 0.5cm-0.7cm.