Active Health Monitoring of Thick Composite Structures by Embedded and Surface-Mounted Piezo Diagnostic Layer

• Published in: Sensors (Basel, Switzerland) Vol. 20; no. 12; p. 3410
• Main Authors: Feng, Tianyi, Bekas, Dimitrios, Aliabadi, M. H. Ferri
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 17.06.2020; MDPI
• Subjects: Aeronautics; Aircraft; Amplitudes; Carbon; Circuits; Composite materials; Composite structures; Diagnostic systems; Epoxy adhesives; Impact damage; laser doppler vibrometer; Manufacturing; Mechanical impedance; Methods; Sensors; structural health monitoring; temperature influences; thick composites; Vibration meters
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s20123410

An effective approach for an embedded piezo diagnostic layer into thick composite material is presented. The effectiveness of the approach is assessed in comparison to the surface-mounted layer. The proposed manufacturing alleviates difficulties associated with trimming edges of composites when embedding wires. The Electro-Mechanical Impedance technique is used to access the integrity of the piezoelectric sensors bonding process. Comparisons of ultrasonic guided waves are made between embedded and surface-mounted diagnostic layers and their penetration through and across the thickness of the composites. Temperature influences with the range from −40 °C up to 80 °C on embedded and surface-mounted guided waves are investigated. An investigation is carried out into the relationship between amplitude and time-of-flight with temperature at different excitation frequencies. The temperature has significant but different effects on amplitude and phase-shift of guided waves for the embedded layer compared to the surface-mounted layer. A Laser Doppler Vibrometer is used to identify the blue tack and impact damage. Both embedded and surface-mounted layers are shown to be an effective means of generating detectable wave scatter from damage.