Research On CFRP Non-destructive Testing System Based On Scanning Electrical Impedance Measurement

With the rapid development of aerospace industry,various new composite materials emerge as the times require.Compared with the traditional metal material,the carbon fiber composite material has many advantages such as light weight,high strength,large hardness and so on.It is widely applied in the field of aviation materials.Composite materials are used widely and inevitably damaged at the same time,which seriously endangers the flight safety of aircraft.In order to improve flight quality and predict the residual life of materials effectively,nondestructive testing of composite materials has become a focus.Electrical impedance measurement is a special and efficient measurement method compared with the current non-destructive testing technology.The nondestructive testing method has the advantages such as non-invasion,no radiation,fast response,low cost and so on.Considering the electrical conductivity of carbon fiber composites,the scanning four-terminal structure is designed based on the principle of electrical impedance detection to realize the damage scanning detection of material structure.The main work and results of this paper are as follows:Firstly,the scanning four-electrode sensor is built with COMSOL software.According to the electrical characteristics of anisotropic materials,two kinds of excitation measurement modes are proposed,and the damage model is simulated to realize the reconstruction of scanning images.In contrast to the two excitation modes,the effect,sensitivity,measurement dynamic range,relative image error,relative coefficient and other parameters of the typical damage of the carbon fiber composite material are obtained,and the optimal excitation measurement mode is obtained.Secondly,we build a scanning four-electrode electrical impedance detection system based on LCR table,compile the LabVIEW visual interface the control core,realize the instruction transmission of the singlechip system through serial communication,complete to switch to the four-electrode excitation and measurement and float;In addition,the electrical impedance data detected by LCR table is uploaded to the LabVIEW visual interface of the host computer through USB,and the real-time display and data preservation are realized.Finally,the scanning electrical impedance measurement system is tested to detect the damage position,shape and size of carbon fiber composites,and the damage shape position is described by the experimental results.At the same time,the scanning detection effect of different electrodes of the diameter is compared,and the better electrode is obtained according to the imaging result and the data.