Research On Composite Material Defect Detection Based On Planar Capacitance Sensor

With the continuous optimization of aircraft structure and the continuous progress of carbon fiber reinforced composite material preparation technology,carbon fiber reinforced polymers has been widely used in the aerospace field due to its good performance such as fatigue resistance,corrosion resistance,high temperature resistance,light weight,etc.However,in the production process of the composite materials,due to the influence of technology,production environment and other factors may lead to defects in the production of the materials;in the process of using the composite materials,Due to the lightning,high temperature and other weather reasons may cause the material aging cracking and other problems,or in the process of service to produce impact injuries,etc.For aerospace and other fields with high safety requirements,these small damages will directly threaten the life safety of personnel.Therefore,the study of defect detection technology for composite materials is particularly important.Planar capacitive sensors have been widely used to achieve nondestructive detection of defects in composite materials based on the capacitive edge effect.In this paper,we study the detection theory involved,sensor optimization design method,and feasibility verification by finite element modeling simulation based on the planar capacitive sensor detection technology,and build an experimental system for nondestructive detection of constructed composite material defect samples.Studies in the article are as follows:(1)Optimal design of the planar capacitive sensor.Based on several important indicators for evaluating the performance of planar capacitive sensors,t the sensors were modeled in the simulation software COMSOL Multiphysics to study the effects of the sensor electrode area,electrode spacing,electrode aspect ratio and shielding electrode structure factors on the sensor performance.The structural parameters of the sensor were optimized for the characteristics of the actual detection object.(2)Simulation experiments are designed for analysis.After discussing the relationship between the dielectric constant distribution and the varying capacitance value,sweeping experiments are designed in the simulation software COMSOL Multiphysics to demonstrate the feasibility of the planar capacitance sensor for defect detection,followed by the design of defects of different sizes and depths to investigate the quantification effect of the planar capacitance sensor on the size of the defect of the object to be detected.(3)Design measurement experiments for verification.The experimental platform is built based on impedance analyzer,and the constructed composite material defect samples are subjected to fixed-point defect detection,and control experiments are conducted in the simulation software to further verify the feasibility of experimental defect detection quantification using this method based on the comparative analysis of experimental results.