Visual inspection of CFRP laminates based on EIT

Electrical Impedance Tomography (EIT) is an emerging method for monitoring damages in carbon fiber reinforced polymer CFRP composites. This paper presents a method of detecting the shape and position for the damages of anisotropic CFRP laminates based on EIT with embedded electrodes. According to the boundary values of voltage change collected from the electrodes, the conductivity distribution map of the material is reconstructed to assess the damage condition. In order to improve the quality of reconstructed images, a new modified residual norm steepest descent (MRNSD) algorithm is applied to reconstruct the conductivity distribution. Moreover, the EIT test system is built for experimental verification. The experimental results verify both the feasibility and effectiveness of the proposed method.

I. Introduction

CFRP are increasingly applied for aerospace, auto industry and wind energy structures due to their high stiffness-to-weight ratio, high specific strength, corrosion resistance and fatigue resistance. However, CFRP matrix composites are prone to intralaminar matrix cracking and interlaminar delamination failure due to the brittle nature of the matrix material [1]. CFRP material may be impacted during its life cycle.And fiber fracture is a more serious defect type, because most structures are loaded by the fibers themselves. Therefore, the damage types of CFRP laminate usually include crack, delamination, broken wire and impact.