MEMS vibrometer: Dynamic modeling of multimodal inertial transducers

Guided ultrasonic wave-based structural health monitoring utilizes propagating elastic waves to identify, locate, and characterize damage within aviation structures. Fiber metal laminates, which are composite materials made by layering metal sheets with fiber-reinforced polymers, combine the high strength of composites with the ductility and impact resistance of metals. However, structural health monitoring methods suitable for these materials have to be developed, allowing to monitor also the inner laminate layers. Therefore, laminate-embedded MEMS vibrometers have been introduced recently. Due to the quasi-free operation of these inertial sensors, they are directly sensitive to the displacement induced by propagating guided ultrasonic waves. However, the multimodal excitation of the sensor's core resonator, when exposed to ultrasound bursts, leads to a pseudo-nonlinear sensor response, which is attributed to the spectrum of guided ultrasonic waves and their interference with higher harmonics of the continuum resonator. The transfer behavior of the sensor can be improved by implementing electrical mode suppression. This research involves analytically modeling the continuous resonator with multiple aggregated resonators, numerically simulating sensor responses to 100 kHz ultrasound bursts, and using a laser scanning micro vibrometer setup for experimental validation, providing a deeper understanding of MEMS vibrometer dynamics for ultrasonic monitoring and demonstrating their applicability.