Determination of optimal combination of pumping and probing inputs in vibro-acoustic modulation for sensitive BVID detection of CFRP

Abstract

In this work, the potential of using defect resonance-based vibro-acoustic modulation (VAM) spectroscopy to determine pumping and probing frequencies to maximize the nonlinear VAM response of carbon fiber reinforced polymer (CFRP) plates is investigated. An integrated 3D finite element (FE) model which implements the barely visible impact damage (BVID) due to impact force and the loading of ultrasonic signals is proposed. Based on this model, the scaling subtraction method (SSM) is used to determine the low-frequency global plate resonance that leading strongest defect excitation for pumping input (GPRpump) and high-frequency local defect resonance for probing input (LDRprobe). A scanning laser Doppler vibrometer (SLDV) is adopted to experimentally validated the proposed numerical methodology. Then, the maximum response amplitude (MRA) of nonlinear VAM response is proposed to evaluate the influence of defect resonance on the nonlinear VAM response. The numerical and experimental results are in good agreement and show that MRA of the VAM sideband can be improved when the GPRpump frequency is taken as the pumping input and the LDRprobe frequency is taken as the probing input, respectively. The best BVID detection effect is obtained when the pumping input of the VAM test is selected as the GPRpump frequency and the probing input is selected as sum or difference of the GPRpump frequency and LDRprobe frequency.