MEMS Vibrometer for Structural Health Monitoring Using Guided Ultrasonic Waves

Area of Science:

• Materials Science
• Mechanical Engineering
• Nanoscience

Background:

• Structural health monitoring (SHM) is crucial for lightweight composite materials.
• Guided ultrasonic waves (GUWs) are effective for SHM in composites.
• Integrated sensors are needed for GUW detection in fiber metal laminates (FMLs).

Purpose of the Study:

• To develop a robust micro-electro-mechanical systems (MEMS) vibrometer for integrated SHM.
• To ensure the sensor maintains structural and functional compliance within FMLs.
• To demonstrate the vibrometer's capability in detecting GUWs for SHM applications.

Main Methods:

• Fabrication of a silicon-based piezoresistive transducer encapsulated with glass lids.
• Utilization of femtosecond laser ablation and established pressure sensor fabrication processes.
• Experimental determination of eigenfrequencies using an optical micro vibrometer setup.
• Testing on a customized rig to record GUW packages.

Main Results:

• The MEMS vibrometer is sensitive to high-frequency displacements from structure-borne ultrasound.
• The sensor operates effectively between its first and second eigenfrequencies.
• Application-relevant GUW packages at 100 kHz were successfully recorded at a distance of 0.2 m.

Conclusions:

• The developed MEMS vibrometer is suitable for integrated SHM in FMLs.
• The sensor demonstrates reliable detection of GUWs for structural integrity assessment.
• This technology advances the monitoring capabilities for composite structures.