Nonlinear guided waves to characterize damage in glass fiber reinforced plastics (FRPC)

Sensitivity of nonlinear acoustic methods to the presence and the evolution of micro-damage has been proven in various studies on a wide range of materials (composites, concrete, rocks, etc.). This sensitivity is due to the relationship existing between the elastic properties of the above-mentioned materials and the created strain during the passage of the acoustic disturbances. In nonlinear resonance experiments, where a single mode is considered, this observation has been proposed to explain the decrease in resonance frequency as a function of the dynamic strain. Thereby, the hysteretic parameters corresponding to the elastic modulus as well as damping are determined for a single frequency. In this work, we propose a guided wave approach to determine and corresponding to a GFRP taken at intact as well as damaged states. By changing the bending modes, and are determined as function of frequency. In addition, the dispersion of the generated guided wave’s velocity has also been determined as a function of strain. Experimental results reveal interesting correlations between velocity variations and excitation amplitude.