Nonlinear Electro-Mechanical Impedance Spectroscopy for Comprehensive Monitoring of Carbon Fiber Reinforced Composite Laminates

This paper presents a Nonlinear Electromechanical Impedance Spectroscopy (NEMIS) methodology for the comprehensive monitoring of carbon fiber reinforced composite (CFRC) laminates. This method can obtain structural impedance spectra and capture nonlinear ultrasonic features for damage detection, combining the merits of the conventional EMIS and the nonlinear ultrasonic techniques. A comparative illustration between the conventional EMIS and NEMIS is presented. Various damage types and damage mechanisms of CFRC laminates are reviewed. Numerical investigation on a reduced-order 1-D Contact Acoustic Nonlinearity (CAN) model are conducted to demonstrate the chirp-induced nonlinear features. Furthermore. a finite element (FE) model is established to verify the feasibility of the NEMIS for damage detection. The macro-scale damage types are modeled by the changes of material properties, while the incipient damage like delamination is simulated by setting the contact interfacing condition between the laminate debonding areas. Correspondingly, the chirp-based impedance spectra are employed to detect the macro-scale damage via the deviation of resonance peaks, while the nonlinear features, such as higher harmonics and wave modulation are utilized to monitor the delamination. Two damage indices are developed to quantify the severity of both the macro and incipient damage. This paper finishes with conclusion and suggestions for future work.