Effect of Orders of Scattering in Linear Grating of Fibrous Reinforced Composites Using Resonance Ultrasonic Spectroscopy

In this paper, resonance ultrasonic spectroscopy is employed to evaluate a linear grating of fibrous composite materials. The ultrasonic longitudinal wave scattering from the embedded linear grating in an elastic matrix is simulated using finite element method. To involve the frequency effects of the measurement system, the modified short-pulse method of isolation and identification of resonances (MIIR) is employed to calculate the resonance modes and frequencies of the elastic fibers. The conformity conditions of the obtained results from analytical methods and the short pulse MIIR method are then investigated, including various orders of scattering. The FE-based resonance ultrasonic spectroscopy method is employed to investigate the behavior of the backscattered resonance spectrum for a linear grating of two fibers embedded in an epoxy matrix and evaluate the effects of grating structure and measurement system. The obtained results show that, due to the second-order of scattering, variation of the transducer position with respect to the linear grating of fibers can shift the detected resonance frequencies.