Research On Damage Detection System Of CFRP Laminates Based On EIT

In recent years,carbon fiber reinforced polymer(CFRP)has been increasingly used in aerospace,industrial applications and civil life due to its high strength and stiffness/weight ratio.However,CFRP laminates inevitably cause structural defects or damage during manufacturing and use,which leads to a decrease in the safety of material use.Therefore,it is essential to monitor the occurrence and development of damage through effective detection techniques.Since CFRP laminates have electrically conductive properties,structural defects or damage can cause changes in the spatial distribution of electrical conductivity.Electrical impedance tomography(EIT)is a structural health detection technique based on the distribution of conductive media.Compared with other commonly used structural health nondestructive testing methods,EIT has the advantages of low cost,non-invasiveness,non-ionization,high time resolution,and simple structure.Therefore,the application of EIT method in the damage detection of CFRP laminates has become one of the hotspots of scholars at home and abroad.This topic uses the EIT method to do the following research on the damage detection of CFRP laminates:(1)The EIT electrode structure,excitation mode and reconstruction algorithm for anisotropic CFRP laminates were investigated.The shock,delamination and crack damage models of CFRP laminates were established by COMSOL software,and the three-dimensional field space potential distribution information was obtained by finite element analysis.In order to improve the image reconstruction effect of EIT technology on anisotropic composite damage,the embedded electrode is used to realize the effective collection of CFRP laminate internal information.At the same time,the traditional electrode excitation mode is improved,the independent measurement data is effectively increased,and the sensitive field is alleviated inhomogeneity;In addition,an improved image reconstruction algorithm based on L1 regularization is proposed to improve imaging speed and image resolution while ensuring stable operation of the algorithm.(2)Establish an embedded 16-electrode EIT hardware system based on a digital multimeter.The system mainly includes a sensor unit,a data acquisition and processingunit,and a host computer image reconstruction unit.After testing,the system designed by this subject is stable and has good channel consistency.The position and size of single-hole and double-hole damage of CFRP laminates were detected by EIT system.The results show that the image reconstruction of damaged materials is good,which proves the feasibility of EIT method in structural damage detection of carbon fiber reinforced composites.